All ofthe following are advantages ofthe indirect method of bondingbrackets to a tooth over the direct method EXCEPT one.

Which one is the CXCEPIIOM

. Reduced chair-side time

. \Iore precise location ofbrackets possible in the laboratory

. Controlled thickness ofthe resin between the tooth and the bracket interface

. Less technique sensitive

. Easier clean-up during bonding and de-bonding

. Better visualization inlab (especially Jbr lingual brackets)

1

Coprighr O 2011'2012 Dental Decks

*** The indirect bonding technique is more complex and technique sensitiv€ and requir€s extra precautions

The procedure involves the following steps:1. An accumte impression with alginate is tak€n and poured up with orthodontic model stone to be used as

a working model.2. Vertical lines arc draM on the teeth to aid in bracket placement and a separating media is aPplied.

3. The brackets are then loaded with a filled resin paste and cured.

4. After its initial set, individual positioning of a ffay with siiicone is prepared by applying it over the brack-

eted teeth on plaster model.5. This whole set-up th€n is placed in warm water to dissolve the separating media

6. Th€ silicone tray is then removed from the plaster model with brackets embedded in it.7. Brackets are cleaned under running watff making sure that pads have cured resin.8. Enamel is etched, conditioned and unfilled resin is applied. Unfilled resin is also applied to cued resin

on the base of the bracket pads.

9. The silicone tray with embedded brackets is then positioned on the teeth being bonded and held in posi-

tion till the initial set ofthe unfilled rcsin is reached.

f. The conhol of"tfrsh" (e&ess of resin) not only makes clean up easy but also the controlledthickness ofit accurately expresses the built-in prescription ofthe appliance.2. Also, in situations where visibility is a problen (e.g., linqpal appliance), this technique is al-

most always employed.

lmportent:l. All orthodontic appliances obey Newton's Third Law: There ir in equel and opposite rcaction to everyrction.2. For each appliance, the sum ofthe forces and the sum ofthe moments acting on it sum to zero.

3. T,?es ofappliances. Equal and opposite forc€s: an elastic band stretched between two brackets produces equal and oppo_

site forces (the sum ofthe forces equals zero).. One.couple applirnces: inserted into a bmcket at one end and tied as a point contact at the other

end. A couple is produced only at the engag€d end. The sum of the forces is zero.. Two-couple appliances: inserted into a bracket at each end. Both a couple and a force are produced at

each end. The magnihrde ofthe couple is largest at the end closer to the bend in the wire The sum oftheforces is zero.

ORTHODONTICS

All ofthe following are functional appliances trXCfP? one.Which one is the EXCEPTIO-M

. Frankel

. Bionator

. Clark's Twin Block

. Herbst

. Activator

. Quad-Helix

2

Copyrighr e 201l'2011 - Dentel Decks

Appliances

1. The photograph shows a maxillary fixed bilateral space maintain€r. This t)?e ofspace maintainer also is known as a:

2. Iftroth primary canines were present, which ofthe following space maintain€r(s)could be used in plac€ of this appliance that cannot be used in this case?

. Distal shoe

. \ance appliance

. Lin-eual holding arch

. Hawley retainer

. Band and loop (bilaterul)

coplrlhr 2000-200.1 Unilcriry ol $'x\hngron All nght rc*ncd.Ac.c$ ro IhcAdar ofPc.lirdc Dcnlisrry isaorcmcd by rlicensc. UnaulhoriT.d acccs or toFoducton E fo.b'ddcn wrhoutihc lrnor sntcn Fft'\non ofrhc Unive6ir-v of$xshineton Forinfomrton. co.ra.r I c.nscalN $ash,n gton cdr

3

Copq'ghr a<l 20ll :012 Dcntal D.cks

*** This frxed appliance, consists of4 helices (2 onterior and 2 posterior). Essettially, this appli-ance is used for posterior cross-bite cases with a digital-sucking habit.

Functional appliances are by definition ones that change the posture ofthe mandible, holding itopen or open and forward. Stretch ofthe muscles and soft tissues creates pressures transmitted tothe dental and skeletal struchrres, moving teeth and modifying growth. They are used to treatClass II malocclusions,

Functional Appfian ces (in biet - Cl^ssified asi

. Tissu€ borne: The Frankel functional appliance is the only tissue bome functional appliance,which serves to expand the arch by "padding" against the pressure ofthe lips and cheeks on theteeth and postures the mandible forward and downward.

. Tooth borne:. Activator: advances the mandible to an edge-lo-edge position to induce mandibular growthfor the correction ofClass ll malocclusion. The maxillary teeth arc prevented from eruptingby the acrylic shelfwhile mandibular posterior teeth are free to erupt. This improves the deep

bite seen in Class II cases.. Bionator: similar to the activator in function but its design is a himmed-down version oftheactivator to make it more comfortable to wear. Herbst appliance: it can be fixed or partially removable. A metal rod and a tube-telescopicapparatus is attached bilaterally to the maxillary first molars and mandibular first premolars.This helps to posture the mandible forward and induce growth. Jasper modified the applianceby replacing the tel€scopic apparahrs with a flexible plastic open coil spring.. Twin block appliance: the two-piece acrylic appliance postures the mandible forward withhelp ofocclusally inclined guiding planes and bite blocks. The vertical separation ofthejawsis also configured by the height ofthe bite blocks. It postures the mandible forward to inducegrowth for correction ofClass lI malocclusions.

Note the small acrylic button thatwill restagainst the palatal tissue with thc Nanceappliance. Some clinicians object

to the button since it can create tissue irritation. Thc Nance applianc€ is used in situations where premature biltt-

appliarce, in ahis casc a maxillary removable bilaleral spacc maintainer Note: Rcmovablc appli-anccs arc not commonly uscd bccaus€ ofproblcms *ith thc appliancc not bcing wom and

tbc frcquen( incidcncc of breakage and loss.C.9!xOr :ooc?0rx Unilesii_! of Wdhingron. All nghB rcaded Ac6 b dr n,las ol P.n'ahc Dc.iisrry is gotm.d by ! licN Uuu'T?L a.tu o_TlrodLchon F fortidd.

' rirhau' dr pnn trn1-

adms'on or $. UDseFir-w of wEhingo.. For inroD8rioa Fnk:l,@?l u *6hingr.n edu

Other appliances:. Lower lingual arch: may be fixed or rernovable and is effective in maintaining mandibular leeway space whilestill allowing horizontal and vertical growlh changes jn thc positions ofmolars and incisors.. Lip bumper: is a removablc appliancc uscd in growing children to create and save thc space necessary to ac-

commodate the adult teeth without extraction. The lip bumper hamesscs thc nahrml forces ofthe muscles sur-

rounding thc lowcr teeth to broaden and lenglhen thc dcntal arch. By keeping lhe lip pressurc away fiom thc lowc.front teeth, the longuc prcssuro is allowed to gradually move the ftont teeth forward to "unravel" or align the

crooked teeth- The constant prcssure ofthc lower lip against the front pad of the lip bumpcr exerts a force to gen-

tly push thc molar leeth backward. The lip bumpcr will gradually "strctch" thc dental arch to makc room for thc

crupting adult tccth.

This photograph shows two band and loop space

maintaincrs, an example ofthc bilatoral usc offixcdunilateral band and loop space maintaincrs- These

arc vcry common types ofunilateml spacc mam-taineis, and they often are used bilaterally.

c.p"iehr 200G200a Un,veNq ofwBhingon All ngtu rcsrye'1. Acc6sto n\. ads of Pcdiatic Dlrlsy is e@o.d by a lrm. LrMurh.riz.d .c-ces or rqlrcdudim is foftiddm without rhe pnn Mftn p.mism. ot seU.ileKny of warhingio.. For inldmarid, o.tu. hc.Ne{,lu msh'n8

. Anchorage

. Traction

. Both anchorage and traction

. Neither anchorage or traction

1Coplrighr O 201l-2012 - DenlalDecl6

. Lingual archwires

. Whip-spring appliances

. Palate-separating devices

. Frankel's appliances

. Edgewise mechanisms

. Light-wire appliances

Coplright O 201 1-201 2 - Denral Decfts

*** Anchorage is used to maintain space. Tmction is used to create space.

Headgear is used to modiry growah ofthe maxtlla, to dislalize (retracl, or protract maxillary teeth, or to rein-force anchorage.

Headgear is an orthopedic appliance that allows orthodontists to:. Control growth of facial structures. Use various designs (cervical pull, straighl pull, high pull, awl reverse pull). Use with gowing patients

Headgear components:. Force applied to first molars that are banded via a facebow with a headcap or a neckstrap for anchorage. Facebow: Outer bow dillerent lenglhs

lnner bow sized, connects to the maxillary molars. Headstraps: Cervical and high pull

Optim!l usage of headgear:. wom rcgularly lor 10-12 hours per day, minimum is 8 hours per day. Normally, orthodontists suggest l4 hours/day. Crow,th hormone released in lhe early evening. Ideal to place headgear aftcr dinner not before bedtime

llagnitude oI Force:. Ideal amount offorce for onlropedic changes is 250450 gm per side. Ideal amount offorce for teeth movement is 100-200 gm per side. \losl mo\emenr lhrough intermrnent forces. Ilyalinized bone around molars. \lobilit-Y ofmolars is normal

\ote: One ofthe greatest advantages ofusing extraoral anchomge fl.e., headgear) is that it permits posterior

mo\ement ofteetb in one arch without adversely disturbing the opposile arch.

*** Frankel's appliancc is a removable functional appliance and is employed in cascs of ab-

noll]'j,al (h.r-peracti|e) soft tissue pattems.

Fixed orthodontic appliances offer controlled tooth movement in all 3 planes ofspace. Exam-ples i[clude: lingual archwire, fixed space maintainen, palate-separuting devices, the edgewise

mechanism, light-wire appliances as well as other fixed appliances (i.e., tv'int'ire appliance,

writersaI appliance).

Important: Removable orthodontic appliances are generally rcstrictcd to tipping teeth. Ex-amples include;

. Attached removable appliances

l. Active appliances. Extra-oral traction devices: head gears, face masks, chin cups. Lip bumpers. Active plates: Schwartz appliance, antedor spring aligners. Vacuum formed appliances

2. Passive appliances. Bite planes, occlusal splints, retainers

. Loose removable appliances: functional appliances, functional jaw orthopedic appliances

i ' -. . .- l. For an orthodontic appliance to be effective in tmnslating the roots of teeth, it

/ Not€d. must be capable of exerting a torque.'&g 2. Remember: The 4 basic components of fixed appliance include: bands, brackets,

archwires, and auxiliaies (elastics or ligatures to hold the archwire in brackets).

3. Whip-spring appliances are used to de-rotate one or two teeth.

4. One ofthe easiest mov€ments to accomplish is tipping incisors mesially.

. stainless steel

. Beta titanium

. Nickel-titanium

. Vitalium

6coplright @ 20ll-2012, Denlal Decks

. The Begg appliance

. The edgewise appliance

. The universal appliance

. None of the above

7

Copright O20ll-2012 - Dental D€ck

The prop€rties ofan ideal wire material for orthodontic purposes can be described largely in terms ofthe fol-lowing criteria. It should possess: (1) High strenglh (2) Low stifliess (3) High working range and (4) Highformability

In addition, the material should be weldable or solderatrle, so that hooks or stops can be attached to the wire.Loops and helices are incorporated into archwires to increas€ the activation range.

St.inless steel wires are very popular because oftheir good mechanical properties, excellent corrosion resist-

ance, and low cost. Tle ry?ical formulation for orthodontic use has l8% chromium and 8% nickel.Note: Stainless steel exhibits the highest modulus ofelasticiry frltlresr/ and lowest springback.

Nickel-titanium alloys offer a highly desirable combination of a very low modulus ofelasticity and an ex-tremely wide working range.

Beta titanium wires are also known as TMA (tilanium-molybdenum d//o', wires. They offer a highly desir-able combination ofstrength and springiness (i-e., excellent resilience) and reasonably Sood formabiliry

Note: Each of the major elastic properties (i.e., strength, stillness/springiness, and range) is ^ffected

by a

change in the lenglh and cross section ofa wire. Doubling the length of a wire decrease its strength by half,makes it I times less stiff, and gives it 4 times the range. Similarly, when lhe diameter of a wire is doubled,its strength is increased by 8 times, its stifiness by 16 timcs, and its working range is decreased by half.R€member: Strength: Stiffness x Range

\€r] important: Deleteious €ff€cts oforthodontic forcel

. Effects on the pulp: light forces should have little ifany effect on the pulp; loss ofvitality is very rare

but has been seen in teeth that are moved with unusually hearry force. Note: Endodontically treated teeth

are more prone to root resorption when orthodontically moved.. Effects on root structure: root resorption is a potential side effect ofonhodontic movement; healy con-tinuour forces have more potential to crcate rcot tesorption than do light forces. Areas ofresorption ofbothcemenrum and dentin ofthe root tend to fill in with new cementum so that the original form ofthe root is

retained. \ote: Only ifthe attack on the root suface produces large def€cls at the apex that ev€ntually bc_

come separated fiom the root surface is repair ofthe damaged root impossible.. \tobilit! ofteeth: moderate mobility occurs and resolves with the completion of the.apy.. Pein: usually occurs within a few hours ofinitiation of force application and lasts for 2 to 4 days.. Tissue inflammation; usually results liom poor oral hygiene.

To overcome the dcficiencies ofthe bbon arch (trhich was an eotlier Angle appliance) Angle reoriented the

slot from vertical to hoizontal and inserted a rectangularwire rotated 90 degr€es to the orientation it had with

the ribbon arch, thus the name "edgewise." The dimensions ofthe slot were altered to 0.022 x 0.028' and a

0.022 x 0.028 precious metalwire was used. These dimensions allowed excellent control of cro"{'n and rootposition in all three plan€s ofspace.

The contemporary edgewise appliance has evolved far from the original design while retaining th€ basic prin-

ciple of a rcctangular wire in a rectangular slot. Major steps in the evolution of cdgewise appliances in-

clude:. Automatic rotNtional controli this is accomplished either by using twin brackets on the labial surface,

or single brackets with extension wings that contact the arch wire to conffol and correct rotations.. Horizontal control: this is accomplished by varying the relative thickness ofth€ bracketbase for teeth ofdifferenr thickness. Note: In the original edgewise appliance this was accomplishedby applying first-orderbends ,liliolitgual bcnd! in the arch wire.. ltlesiodistal tip control: is accomplished by angulating th€ bracket or bracket slot to provide the proper

tipping movement lor each tooth. Note: In the original edgewise appliance this was accomplished by ap-

pll ing second-order bends langled bends) rn the arch wire.. Torque: is accomplished by having the bracket slots inclined to compensate fbr the inclination ofthe fa-

cial surface..\-ote: [n the original edgewise appliance this was accomplished by applying third-order bends(r'aning btist in segments ofeach rcctangular arch rire) in the

^rah \Nie.

Brackets are the attachments through which forces are appliedto the teeth and they allow the placement

of arch* ire and other accessodes to b ng about the desircd tooth movement. The brackets most com-

monly used are the Edgewise brackets - single and double edgewise- and the Begg brackets. Edgewise

b.ackets have an archwire channel which is rectangular in cross-section, with the largest dimension hor-

izontally. These brackets can also be us€d with round cross-section archwires. The slot sizes commonly

used are 0.022 inch 10.JJ md) and 0.018 inch (0.45 hm).Thebftcket has tie-wings on opposite sides ofthe archwire slot for engaging a ligature that is used to bind the archwire to the bracket.

Thc Begg bracket has a narrow slot wh€re an archwire is looscly fitted and held in place with a locking pin.

Unlike the Edgewise brackets, these Begg brackets can only be used with round cross_seclion archwires.

The Hawfey retainer (shoren l)elow) is the most common retainer inorthodontics because it can use the palate for anehorage.

copynsbr 1000 200.1 unxcniry of r ,$hriSron

An r€hs fs.nrd Acc.s rod'eAdlsof Pcdf r'ctldldry is govmcd by rli.cnsc Unaurhorizcdacccs or i.produdioi 't forbidd.n vahout rh.pnor Minen p€mi$ior ordi! Unilen y ol\lishi',Fon For infomarion. .onhd licens@-uqash

. Both the statement and the reason are correct and related

. Both the statement and the reason are correct but NOT related

. The statement is corlect, but the reason is NOT

. The statement is NOT correct, but the reason is correct

. \EITHER the statement NOR the reason is corect

An actiye {inger spring of a removable appliance usually touches thetooth with a point contact. What is the most likely type of tooth

rnovement produced in this situation?

. Extrusion

.Intrusion

. Translation

9

Cop)riShr@ 20ll 2012 Dental Decks

*** Multiple appliances can use the palate for anchorage. The true reason that the Hawley re-tainer is the most common is because ofthe varietv ofbenefits it has and can have when usedproperly.

The palatal coverage ofa removable plate like a Hawley retainer makes it possible to incor-porate a bite plane lingual to the upper incisors to control the bite depth. This design consid-ention is important for ary patient who once had an excessive overbite. This palatal coverage(agylic) is the major source of anchorage in th€ Hawley appliance,

A Hawley retainer can be made for the upper or lower arch. The lower retainer is somewhatfragile and may be difficult to insert because ofundercuts in the premolar region. Note: Apa-tient may have difficulty pronouncing linguoalveolar consonants for a few days after re-ceiving a maxillary Hawley appliance until the tongue adapts to the palatal covemge.

llajor components of a remoyable appliance:

l. Retentiv€ component: retains the appliance in function: consist olvarious clasps. Thebest example is Adam's crib.2. A framework or baseplate: usually acrylic. This provides anchorage.3. Tooth-moving elements: typically either springs or screws.

'1. Anchorag€ component: resists force ofactive components (e.g., Acrylic base-plate).5. -{ctive components or tooth moving components: springs, screws or elastics.

lndications for removable appliances:. Retention after comprehensive treatment. Limited tipping movements. Gronth modification during the mixed dentition

\ote: Components ofanchorage can also bing about (desired or undesired) toothmovements.

The best method for tipping maxillary and mandibular anterior teeth is with linger springs. These fin-gcr springs are attached to a removable appliance. Tte most common problems associated with these

simple removable appliances are lack ofpatient cooperation, poor design leading to lack ofretention, and

improper activation. An undesimble common side effect ofa finger spring is the tendency for the rootapex to move in the direction opposite from the crcwn.

Z-springs can also be used but they deliver excessively heary forces and lack rang€ ofmotion.

Important: Ma,\illary incisor rotation is not commonly treated during the stage of mixed dentition. Itis best teated after all permanent teeth have efl)pted (earll permanent dentition). This is usually ac-

complished with a simple removable appliance. Howevet ifthe incisor is in crossbite, it should be cor-rected as soon as possible (while il is erupling).

r' - , -, Lwhen using buccal coil springs to try and regain space by pushing a tooth mosially or dis-

,.:Note{ii tally, be careful because what commonly occurs is rotation of that tooth instead of actual

i;,r::,,,,,':: movement.*tt 2. Th" fo."" generated in the spring is directly proportional to the distance (d) that an ortho-dontic spring is deflected and the radius (r) ofthe wire. It is inversely propo(ional to thelength ofthe spring.

Precisely: Fct

Exc€ssile orthodontic force used to move a tooth may: (l) Cause hyalinizatio'l (necrcsis) of the PDL mem-

brane; (2) Cause undermining resorption; (3) Crush the periodontal ligament

Importanti Pe.iodontal disease dudng orthodontic therapy is preventable and is controllable and inconrinuous studies affer orthodontic therapy has been completed, it has bcen shown that under the prop-

erly controlled regimen oftreatment the destruction to the periodontal tissues ofthe teeth is not accen-tuated to a statistically significant degree as great€r than that which occurs during the same intedm\r'ithout orthodontic therapy. Note: When a patrent (young or old) )s in active orthodontic heatment andthe gingiva is inflamed. the dentist should encourage better oral hygiene. It may be useful to recommendthe use ofwater irrigation devices to help flush food debris away from the brackets.

d14l3

ORTHODONTICS

Prior to direct bonding,

Prior to placing bands,

is used as an etching agent.

is used as an etching agent.

. Nothing; 35-50% unbuffered phosphoric acid

. 35-50% unbuffered phosphoric acid; nothing

. Nothingt l0-l5% unbuffered phosphoric acid

. 10-15% unbuffered phosphoric acid; nothing

10

Copyflghr C 20ll 2012 DenlalDecks

ORTHODONTICS

An example of a maxillary permancnt central incisor in crossbite is shown.In order to treat this condition properly, the dentist should do what?

copFlhr 1000tr,04 unircrrq ol $hsh

Adas of redrahc D.'triry f 3.v!rrd h),alrc.is! Umurhoi,Tr'lrc.c$orrFroductroi R forbiddcr $irhoDr lh. prio.{.ftcnFm,isnon ofl h. unnt^fyof !\k!hrigooFor rnromdio...on'ad l,.hi.r4u.q:h

. Do nothing until all permanent teeth have erupted

. Surgically reposilion the central inclsor

. Correct the condition immediately with a simple appliance

. Place a maxillary expander

11

Coplaight C 20ll-2012 - Dental Decks

*** When placing bands, eitherglass ionomerorzinc phosphate cements are used and do not require etching.

The tooth surface must not be contaminated with saliva, which promotes immediate remineralization, untilbonding is completed; otherwise re-etching is required. Topicalfluoride should not be used before etching be-cause fluoride decreases the solubility ofenamel. Remember: After etching, the tooth surface should have a

frosted appearance. Note: 37% phosphoric acid is the most commonly used etching agcnt.

lndications for using bands instead ofbonded brackets:. To provide better anchorage for greaier tooth movement. For teeth that will need both lingual and labial attachment. Teeth with short clinical crowns. Tooth surfaces that are incompatible with successful bonding

Cementation ofbands: Glass ionomer cements (resin or non-resin based) because oftheir fluoride releasingprcperties and retentive strenglbs are fast replacing Zinc phosphate cement. The cold slab is used for mixingregardless olwhich ofthe two cements is used ("liozen slab technique '). This allows the addition ofa greater

amount ofpowder into th€ cement liquid and thus produces a stronger cement.

Important: Anchorage is the word used in ofihodontics to mean resistance to displacement. The " anchor-age vafue" ofany tooth is roughly equivalent to its root surface area fu'hich is the same os its periodontal lig-ame t area). Dilferent anchorage situations include:

. Reciprocal tooth movem€nt: is produced when two teeth or resistance units of equal size are movedagainst each other and move the same amount toward or away iiom each other.. Reinforced anchorage: is accompl ished by adding additional teeth to the unit to di stribute the force overa larger rcot surface ar€a in the anchorage unit. Not€: Another method for reinforcing anchonge would beto add an exffaoml force such as headgear or interarch elastics,. Stationary anchorage: displacement ofanchor teeth can b€ minimized by ananging the force system so

rhat anchorteeth must movebodily (translation) ifat all, wbile movement teeth are allowed to tip. This ap-proach is called "stationary anchorage.". Corticrl anchoruge: anchor teeth roots are moved into cortical bone whichresorbs more slowly than does

medullary bone. This situation may be encountered at an old extraction site, it can be almost impossible toclose such an extraction site, because tooth movement is slowed to a minimum as the roots encounter cor-tical bone along the resorbed alveolar ridge.. Implants for rochorrg€: implanls can serve as anchorage for holding or moving teerh. The implant f/r/drle/ \r'ill not move because it has no PDL.

Ideally, this anterior crossbite should be corrected before it reached the occlusal plane (vhile il !'aserupting). The rnost probable etiologic factor for this happening is prolonged retention ofthe primary

maxillary incisors.

Cross-elastics from the maxillary lingual to the mandibular labial can be used to conect a single-tooth

crossbite. A maxillary removable appliance can also be used. When elastics are used to move teeth they

should be attached directly to the appliance components.

-{nterior crossbite, particularly crossbite of the incisors' is mrely found in children rvho do not have a

skeletal Class IIIjaw relationship. A crossbite relationship ofone or two anterior teeth, however, may

derelop in a child who has good facial proportions. The maxillary lateral incisors tend to erupt to the lin-glal and may become trapped in that location, especially in the presence ofscvere crowding. In this sit-

uarion. extmcting the adjacent primary canines usually leads to spontaneous corection ofthe crossbite.

Ir is important to evaluate the space situation before attempting to correct any antedor crossbite. If enough

space is available to accomplish the movement, a maxillary removable appliance is usually the best

mechanism to concct a simple anterior crossbite that requires a tipping movement.

Remember: Anterior crossbite in a primary dentition usually indicates a skelet.l growth problem.

Note: The permanent antcrior tooth that is most often atypical in size is the maxillary lateral incisor

Elastics are available as rubber bands, elastic thread, and formed shapes for specific purposes. They are

used to move teeth, to ligate archwires to brackets, for intermaxillary traction, and for separation. Elas-

tics are aiways attached to bmckets and archwires, never around a naked tooth.. Cl.ss I elastics (intramdxillary)r nsed for traction between tceth and groups of teeth within the

same arch.. Class II elastics (in termaxillary\: :js]'J,ally are wom from a tooth in the anterior part of the ma,{illa(i.e., the petlnd ent canine) to a looth located in the posterior part ofthe mandible fi.e.,jirst perma'nent molar).Usedto correct Class II malocclusion.. Class III elastics (irtemaxillary)r usually are wom from a tooth in the posterior part ofthe max-

illa (i.e., the pennanentjirst molar) to a tooth located in the anterior part ofthe mandlble (i.e., per-manent canine).Vsed to improve the overjet in an edge-to-edge or ante.ior crossbite situation.. Crossbite elastics: are wom from the lingual ofonc or more maxillary teeth to the buccal ofone ormore teeth in the mandible to helD correct crossbites.

. The first statement is true; the second statement is false

. The first statement is false; the second statement is true

. Both statements are true

. Both statements are false

12

Cop!.righr O 201 l-2012 - Dental Decks

Which of the following may cause extrusion of the marillarylirst molars which can cause an open bite?

. Straight-pull headgear

. Reverse-pull headgear

. Cervical-pull headgear

. High-pull headgear

13

CopFight O20ll-2012 - Dental Deck

Orthodontic forces can be treated mathematically as vectors. When mor€ than one force is applied to a tooth,the forces can be combined !o determine a single overall resultant. Forces can also be divided into componentsin order to determine effects parallel and perpendicular to the occlusal plane, Franlfort horizontal, or the longaxis ofthe tooth. Forces produce eith€r translation (bodib movement), rotation, or a combination oftransla-tion and rotation, depending upon the relationship ofthe line ofaction of the force to the center of resistanceoftbe tooth. The tendency to rotat€ is due to the moment ofthe force, which is equal to force magnitude mul-tipliedby the perpendicular distance offhe lin€ ofaction to the center ofresistance. The only force system lhatcan produce pure rctation (a mome t *-ith no netforce) is a cottple, which is two equal and opposite, non-

coflinear but paralfel forces. The movement of a tooth (or a set of teet ) can be described through the use ofacenter ofrotation. The mtio between the net moment and net force on a toolh (M/F ratio) \nith reference to thecenter ofresistance determines the center ofrotation. Since most forces are applied at the bracket, it is neces-

sary to compute equivalent forc€ systems at the center ofresistance in o.der to predict tooth mov€ment. Agraph ofthe M/F ratio plotted againsi lhe c€nter of rotation illusirates the precision rcquired for controlledtooth movement.

Principles of Biomechanics in Fixed Orthodontic Appliancesl. Forc€: is a load applicd to an object that will tend to move it to a different position in spac€- A force has

magnitude, point ofapplication, and direction. Therefore, forces are r€presented and treated mathemati-

cally as vectors.. C€nter ofresistance: a point at which aesistance to movement can be concentmted for mathematic analy-sis. In single-rooted teeth, the center ofresistance is on the long axis ofthe tooth one-third to one-halfthe'!\ ay ftom the alveolai crest to the apex. [n multirooted teeth it isjust apically to the furcation. Note: A forcerhrough the center ofr€sistance causes all points ofthe tooth to move the same amount in the same direc-don. Tlris RDe ofmovement is called translation or bodily movement.. Rotation: occurs when a force is applied away from the center ofresistatce. Thc potential for rotalion is

rermed a moment. Note: A force, applied by a bmcket that does not act through the center ofresistance,causes rotation ofa tooth. This tendency to rotate is measured in moments and is calledthe momentoftheforce.. C ou ple: is rwo equal and oppos ite, noncol inear but paral lel forces. Thc result of applying two forces inlhis \r'ay produces pure rotation without translation, Note: Couples are usually applied by engaging awirein an edgewise bracket slot.

Cervical-pull headgear consists of a cervical oeck strap (as ahchorage.) and a standard facebow in-serting into the headgear tubes of the maxillary first molar aftachments The objeotives of treatment

with these types ofheadgear are to rcstrict anterior growth ofthe maxilla and to distalize and erupt max-

illary molars. A major disadvantage of treatment using cervical headgear is possible extrusion of the

maxillary molars. Likely results include: opening the bite, first molars will move distally and forward

growth ofthe maxilla will decrease. Indications: Class II malocclusions with deep bite

High-pull headgear consists ofa high-pull headstrap and a standard facebow inserting into the headgear

tubes ofthc maxillary fi.st molar attachments. The objectives oftreatment with these typcs ofheadgear

ar€ restriction ofanterior and downward maxillary gowth and/or molar distalization and control ofmax-illary molar eruption.These types ofheadgear have a more direct effect on the anterior segmcnt ofthea{ch. Indications: CIass II malocclusions. with increased vertical dimension and minimal overbite.

Straight-pull headgear is similar to the cervical-pull headgear. Howevet this appliance places a force

in a straight distal direction from the maxillary molar Like cervical-pull headgear, the indications are

Class II, Division I malocclusions (wlen bite ope i g is undesirable).

Reverse-pull headgearunlike all ofthe otherheadgears above, has an extraoral component that is sup-

ported by the chin, cheeks, forehead or a combination ofthese structures. [t consists of two pads that rest

on the soft tissue ofthese structurcs. These pads are connected to a midline framework and are adjustable.

Side effects include downward and backward rotation of the mandible. Indications: Class lll maloc-

cllJsions (\rhere protraction ofthe maxilla is desirable).

Chin ctp (chin capl ar€ devices to utilize cxtra-oral traction to restrain or alter mandibular growth. In-dications: Class II maloccltJsions (due to excessive mandibular powth).

Side Effects of Headgear:. Unwanted extusion forces on maxillary molars f4p-ically found with cervical headgear) will cause themandible to move inferiorly and posteriorly. Negates Class II correction. May cause distal tipping ofmolars

Timing ofAny Headgea. Treatment:- Females:.8.5-10.5 years old

- Males.9.5-11.5 years old

. Deviated midline in the absence ofa functional shift

. Mild crowding of lower permanent incisors

. Two deciduous molars nearly in crossbite

. Posterior crossbite with a functional shift

14

coplright @ 20ll-20 t2 - D€nbl Decks

. Posterior crossbite after prolonged thumb sucking

. Class lI, Division I malocclusion

. Anterior crossbite in mildly prognathic children

. Ar anterior open bite after prolonged thumb sucking

15

coplright O 201 I -20 12 - Denhl Decks

Posterior crossbite:. Should be corrected as soon as possible. Should be thoroughly diagnosed as to whether it is ofa dental, functional or skeletal origin. Ma) be corrected with nalatal expansion. May be associated with a mandibular shift

It is important to correct poste or crossbites (which are related to lhe t|ansverse plane ofrpdcel and mildanterior crossbites in the first stage oftreatment, even ifthe permanent first molars have not yet cruptod. Se-

vere anterior crossbites, in contrast, are usually not corrected until the second stage ofconventional treat-ment,

Important: The most common rype ofactive toolh movement in the primary dentition is to correct a poste.rior crossbite frrarrverse problem).

Maxiilary or palatal expansion appliances are used to correct trrnsverse discrepancies by skeletal expansionofthe midpalatal suture. Appliances to correct crossbites:

. Hyrax appliance: is the most commonly used tlpe ofappliance for rapid expansion /r.5 ,tnt/dql.lt cor-sists ofa hymx screw held in place with a wire framework that is attached to several upper ieeth with ce-

mented bands. The screw is activated by at least 0.25 mm daily forre qudrler turn).. Haas appliatrce: is both tissue and tooth-bome and has an extensive amount ofpalatal acrylic wltich acts

on the palatal mucosa. [t consists ofbands that are cemented on maxillary first premolars and first molars.T*o acrylic pads with a midline jackscrew are connected to the rest ofthe appiiance.. Harrley-type removable appliance with a jack screw: can bc uscd for mild poste.ior crossbites in chil-dren.. Quad-hefix, W-arch: these consist ofhealy stainless steel wire with fonr (quad-helix) or three (ty arch)hcljces rhat are incorporated to increase the range and flexibility. Tlley can be us€d to corect unilateral orbilareral crossbites and for corecting rotated molars.. Transpalatal arch AP,4): is a thin wire that goes across the roofofthe mouth from first molar to firstmolar. TPA is used to maintain expansion in the molars. An omega loop is tlpically included making the ap-pliance useful in rotating and widening the molars.

Remember: A skeletal crossbite, as contnsted with afunctional crossbite, usually demonstmtes a smoolh clo-!ure !o centric occlusion.

Prolonged sucking habits often produce a mildly narrow maxillary arch and a ten-

dency toward bitateral crossbite. Children with this condition usually shift the mandible

to one side on closure to gain better function, which can guide permanent molars, or later,

premolars into a crossbite relationship.

A young child who has a tendency toward a Class III malocclusion will have end-to-end

contact ofthe primary incisors. A true anterior crossbite in the primary dentition is quiterare because mandibular growth lags behind maxillary growth. The primary incisors wear

down rapidly, and an anterior shift ofthe mandible to escape occlusal interferences rarely

occurs until the permanent incisors begin to erupt. A pattem of anterior displacement ofthe mandible may develop when the permanent incisors come into contact, however' pro-

ducing an anterior crossbite ftom the shift.

. .. l. An anatomic crossbite (skeletal), as contrasted with a functional crossbite\ote*. (y6y thumb sucking), usually demonstrates a smooth closure to centric occlu-'-A::. sion.

2. A functional crossbite is usually caused by thumbsucking and does notdemonstrate smooth closure into CO.3. A corrected anterior crossbite is best retained by the normal incisor rela-tionship that is achieved through treatment (the overbite), not appliances.

4. Class III relationships are more prevalent in Asian populations, whereas

Class II relationships are more commonly found in whites of northern Euro-pean descent.

5. Reverse overjet, suggesting a Class III malocclusion, is much less frequentthan Class II in the U. S. population.

. The first statement is true; the second statement is false

. The first statement is false; the second statement is true

. Both statements are true

. Both statements are false

't6

Coptrighr O 20ll-2012 'Denial Decks

. Anterior open bite

. Crossbite

. Expanded maxillary arch

. Proclination ofthe maxillary incisors

. Retroclination of the mandibular incisors

. A Class II malocclusion

17

Cop)'righr O 201l-2012 - Dental Decks

. Both the statement and the reason are correct and related

. Both the statement and the reason are correct but NOT related

. The statement is correct, but the reason is NOT

. The statement is NOT correct, but the reason is correct

. NEITHER the statement NOR the reason is correct

18

Cop)'right O 20ll-2012 - D€ntal Deks

. Prognathic; retrognathic; Class II

. Retrognathic; prognathic; Class III

. Prognathic; prognathic; Class I

. Retrognathic; retrognathic; Class I

. Prognathic; prognathic; Class II

. Retrognathic; retrognathic; Class II

't9

coplrighr o 20ll-2012 - Dental D€cks

. Dental cast aralysis

. Facial profile analysis

. Photographic analysis

. Full face analysis

. Long anterior facial vertical dimensron

. Anterior open bite

. Tendency to Class III malocclusion

. Greater maxillary-mandibular plane angle

20

Coplyighr O 201 I '2012 - Dental Deckj

21

Cop)right O 201| -2012 - Dental Decks

The facial profile analysis delineates the same information as that obtained throughlateral cephalometric radiographs. The difference lies in the detail obtained through thelatter method, however, the former is considered a vital diagnostic technique for primaryevaluation. It is a quick and simple (also cheap) technique which readily gives thefollowing information:

1. Anteroposterior position/proportion ofthejaws relative to each other2. Lip posture (competent/incompetant) and incisor prominence3. Vertical facial proportions4. Inclination ofthe mandibular plane angle

Note: Within the lower third of anterior face height the mouth should be about one-thirdofthe way between the nose and the chin.

Important: The most stable area from which to evaluate craniofacial growth is the an-terior cranial base.

,- '-.'. l. There is a significant difference in esthetics and cephalometric values among; No&gf racial and ethnic groups.i&;*& Z.Individual cephalometric measures, by themselves, should not be used to

make a diagnosis. They should be used to explain or support a diagnosis based

on all the data required to make a diagnosis.3. Cephalometric measures in themselves are usually not considered problems,

but what they indicate m ybe (i.e., prognathic mandible, small maxilla,Jlaredincisors, elc.).4. In treatm€nt planning: impacted teeth are usually a high priority; withinocclusal problems, interarch relationships usually take priority over intra-archrelationships; habits (i.e., thumbsucking, brttxism, elc./ should also be consid-ered.

The mandibular plane angle can be visualized clinically by placing a mirror handle orother instrument along the border ofthe mandible.

Important: A flat mandibular plane angle correlates with short anterior facial verti-cal dimensions (height) and anterior deep bite malocclusion.

The angle between the mandibular plane (Go-Me line) and the maxillary plane flN,t-PNSline) rs called the maxillary-mandibular plane angle (MMPA).lts normal value is:

27'(+/- 4"). The greater value indicates a longer anterior face height.

There is also an interaction between face height and the anteroposterior position of the

mandible; all other things being equal, a long face predisposes the patient to Class IImalocclusion. a short face to Class III malocclusion.

What is needed so that soft tissues are clearlyvisible on a lateral cephalometric radiograph?

. Adjustment in kilovoltage

. Adjustment in milliamperage

. A soft tissue shield

. A hard tissue shield

. Nothing must be done to make soft tissues visible

22coplright (] 201I ?012 Doral Deck

n--J

23CoDright O 201l-2012 - Denbl Decks

Identify the Frankfurt-Ilorizontal plane and thenumbered points it uses for its origin.

The lateral head radiograph (cephalometric x-ray) must be compared with the "nor-mal" lateral radiographs form an accepted norm. Linear and angular measurements are

obtained utilizing known anatomical landmarks in the lateral head radiography ofthe pa-tient. These measurements are then compared with those considered within normal lim-its and in that way enable the orthodontist to assess aberration in the dentition and jawstructures, which result in malocclusion.

Aaalysis ofcephalometric radiographs is not limited to the hard structures such as boneand teeth, but also includes measurements of soft tissue structures such as the nose, lipsand soft tissue chin.

Superimposition in longitudinal cephalometric studies is generally on a reference planeand a registration point. This will best demonstrate the groMh ofstructures furthest fromthe plane and the point. The most stable area from which to evaluate craniofacial growthis the anterior cranial base because ofits early cessation ofgrowth.

Cephalometrics is useful in assessing tooth-to-tooth, bone-to-bone and tooth-to-bonerelationships. Serial cephalometric films can show the amount and direction of gro{th.

),Iote: A lateral cephalograph usually shows magnification with up to 7-8olo magnificationconsidered acceptable. The resuldng double shadows are traced and the average is used

for measurements.

Cephalometric studies show that, on the average:. The maxilla, during growth, is translated in a downward and forward direction. llandibular growth stops after maxillary gowth

*** The Frankfort-Horizontal plane is constructed by drawing a line connecting porion (4)

and orbitale (8), This has been adopted as the best representation ofthe natural odentation ofthe skull.

l. Bolton (Bo): highest point in the upward curvature of the retrocondylar fossa ofthe oc-

cipital bone.2.Basion (Ba):,lowest point on the anterior margin olthe foramen magnum, at the base ofthe clivus.3. Articulare (,4r): the intersection of three radiographic shadows, the inferior surface ofthe cranial base and the posterior surfaces ofthe necks ofthe condyles of the mandible.4. Porion (Po): midpoint ofthe upper contour ofths metal ear rod ofthe cephalometer.

5. Spheno-occipital synchondrosis (SO): junction between the occipital and basisphenoid

bones.6. Sella /S): midpoint of the cavity ofsella turcica.7. Pterygomaxillary fissure (Przr): point at base of fissure where anterior and posterior

walls meet.

8. Orbitale for: lowest point on the inferior margin ofthe orbit.9. Anterior nasal spine (lNS): tip ofthe anterior nasal spine.

10. Point A fsabsprrale/: innermost point on contour ofpremaxilla between anterior nasal

spine and incisor tooth.Il.PointB (Suplamentqle)| ifi.€rmost point on contour ofmandible between incisor toothand bony chin.12. Pogonion fPog): most anterior point ofthe contour ofthe chin.13. Menton (Me): most inferior point on the mandibular symphysis, the bottom ofthe chin.14. Gonion (Go): lowest most posterior point on the mandible with the teeth in occlusion.15. Nasion fNa): anterior point of the inte$ection between the nasal and frontal bones.

Important: The most stabl€ point in a growing skull from a cephalometric standpoint iss€lla turcica, the center ofthe pituitary fossa in the cranial base.

mal-r€lstionships in s growing child, the orthodontist can get themost Yduable information from:

. A wrist-hand radiogaph

. Height-weight tables

. Presence ofsecondary sex characteristics

. Stage ofdental development

21Coprighr O 201 l'2012' Denral Decks

Coptrisht 2000.2004 Uuv.nity of wrd,i.sron Allrisbt r6ded Acc.s b theArlis of Pediadc Dcnhsry $ govemed by a hceGeUn.ulhonrcd.ccs or rcprcdud,m is fd.f iddcn wInoui rhe pno. \riftcn p€mission ofrhe UnikBity of w$hngion. Ior inromatoo. con

dd: l'.65.!9u.sa\hington edu

25Cop}{ight O 20ll-2012 'Denlal Decks

The anomaly depicted in the plcture below is called a*** Be as specilic as possible.

Abo think about the treatment options for this anomaly.

The physiologic age or developmental age can be judged by finding out the skeletal devel-opment. The wrist-hand radiograph offers the best aid for this purpose. By looking at the os-sification and development ofthe carpal bones ofthe wrist, the metacarpals ofthe hands andthe phalanges ofthe finge$ the orthodontist can have an idea about the cbronology ofskele-tal development. Comparing the overall pattem observed in the hand-wrist radiograph, withage standards in a reference atlas, does this. Important: Dental age refers to the state of den-tal maturation.

Rememb€r: The ulnar sesamoid or hamate bones are considered as landmarks to obtain an

estimate ofthe timing ofthe adolescent growth spurl Wrist-hand radiographs in the dentaloffice can be obtained by using a standard cephalometric cassette and dental x-ray.

The state ofphysical maturity or skeletal development co-relates well with the jaw groMh.fthodontists use this information to predict how much jaw growth can be expected.Note: After sexual maturity much less growth is expected and therefore growth modificationis not attempted.

Remember: Hand-wrist radiographs are less useful in evaluating whether growth has stoppedor is continuing (patient's position on growth curve). Seial Cephalometric radiographs are

used for this pupose.

A midline supemumerury tooth (mesioderu) in the mandibular arch is shown. Mesiodens usuallyoccur in the maxillary arch. However, you will see them occasionally in the lower arah. Note thecrowding of the mandibular permanent incisors. Extraction of the m€siodens is the heatment ofchoice. Important For the best therapeutic result, orthodontic treatment to close the space may be

necessary.

A midline supernumerary toolh (mesiodens) is present. Note thatthe maxillary right permanent cenhal incisor is (slightry rctated,and that the direction ofthe roots ofthe central incisors is moreflared. The cerhal incisors most likely were deflected from theirnormal paths of eruption by the mesioderc. The mesiodensshould be extracted.

To localize a supemumerary tooth or impacted tooth and its re-lationship to other teeth, you should take two or rnore periapical

x-rays at different angles and an occlusal view film.

Coorieh 20{o 2004 Uniydny ofwahin8loD. All nshb6d.d Aas lo lh€ Ad,s of Pedi.tic D€nriry is eovcrn d by.lien$. Ulluiioiz.d @s or rprodxrion is

fdbiddm enhour thc pno. widd p.mision offi. univdiry of Wshinghn. Fo. inf{lruio'! co.i.cli li

CotFghr 2a0G20Ol UnileGiry of Wahinsron. all risht lt3d.d A€s b $. Arla orPrdi.ttc Ddristryii sovo.d by r licre. U.rutfnizcd aacs or rep'tdcrioD is foi'iddf, wil])out iE prtd qino pmisidofd. Univm'ty of wGhinclon, Fd infom.rio, co.ilct li.6g@uv8ri4rd.cd!

Conditions associated with multiple supemumerary teeth:. Gardener's syndrome . Down's syndrome. Cleidocranial dysplasia . Sturge-Weber syndrome

Note: Oligodontiay'absence ofone or more teeth, is more common in females than males. It is oftenassociated with smaller than averaee tooth-size ratio.

. Primary canines

. Primary first molars

. Permanent first premolars

. Primary second molars

Cop''righl O 20ll-2012 - Dental Decks

. Band

. Complete crown preparation and fabrication

. Complete crown lenglhening procedure

. Separate

. Upright

27

Cop)'.aghr O 201 | '2012 ' Dent.l Drcks

Serial extraction is the orderly removal of selected primary and permanent teeth in a pre-determined sequence. It is indicated primarily in severe Class I malocclusion in themixed dentition that has insullici€nt arch length. This procedure primarily benefits chil-dren who demonstrate an arch-length discrepancy.

Stages in serial extraction: The primary canines are the first to be removed, followed bythe primary first molars, and then the permanent flrst premolars (usually). Six to fifteenmonths is the interval between extractions. To aid in support and retention during thistime, a lingual arch should be used in the mandible and a Hawley appliance in themaxilla. This is usually followed by full orthodontic treatment. Note: The key to success

is extraction ofthe first premolars before the permanent canines erupt.

In serial extraction procedures, concems about eruption sequence are usually related tothe eruption pattern of the permanent rnandibular canines and first premolars.Note: After extraction ofthe maxillary first premolar in a serial extraction procedure, themaxillary canines path of eruption will usually be downward and backward.

Remember: Severe arch space deficiency in the p€rmanent dentitton (over l0 mm) willalmost always require extractions to properly align teeth.

A common dental condition that can benefit from orlhodontic treatment prior to prosthetic

treatment is the long-term loss ofa rnandibular permanent lirst molar. The loss ofthefirst molar results in tipping, migration and rotation of the adjacent teeth into the edentu-

lous space. Note: The best way to upright a second molar that had drifted mesially is by tip-ping its crown distally and opening up space for a pontic to replace the missing first molar,

rather than attempting to move the second molar mesially to close the space.

Important: A high mandibular plane angle is one ofthe most significant complications ofmolar uprighting, because if the molar is uprighted unsuccessfully, it can lead to an in-creased open bite and loss ofanterior guidance.

A normal angulation ofa molar is desirable since it:. Improves the direction and distribution of occlusal forces. Decreases the amount oftooth reduction required for parallelism ofthe abutrnents. Decreases the possibility of endodontic, periodontic or more complex prosthodontic

procedures.Increases the durability ofthe restorations, due to better force distribution. Irnproves the periodontal environment by elirninating plaque-retentive areas. Improves the alveolar contour. Imoroves crown-to-root ratio

. Distal shoe on "T"

. Band and loop on "T"

. Removable partial denture

. No space maintenance is needed

20

Cop)'righr @ 201 I '2012 - Dental Decks

. Tipping

. Translation

. Pulling

. Extrusion

. Intrusion

. Torque

. Rotation

29Coplright O 201l-2012 - Dental D€ck

l. Ifa permanent first molar is extracted on a child tlefore the eruption ofthepermanent second molar, the best approach is to allow the eruption of the

second molar and the mesial drifting to occur naturally. This will fill in the space

most of the time.2. A space maintainer can be removed as soon as the permanent tooth begins

to erupt through the gingiva. (See picture below).3. The most reliable indicator ofreadiness of eruption of a succedaneous tooth(and the need for a space maintainer) is the extent of root development deter-

mined by radiographic evaluation. No space maintainer is required if eruptionofthe succedaneous tooth is imminent.

Very important:l. The most rapid losses in the A-P distance ofthe ach is usually due to a mesial tip-ping and rotation of the permanent first molar after rernoval of the primary second

molar.2.When the primary second molar is lost, always maintain space until the arival of the

second nremolar.

This photograph demonstrates a tooth partiallyerupting between the wires ofa space maintainerThe space maintainer now can be removed.

Copltght 2000 2001 Untueniit of Wdhlngton All rishts N.fr.d Acccs to rhc ArldofPcd$tic D.n.s!a is goremed by a li.frs. Un rhor;.d a.c$i d rctoducrion is

fodiddcn $nhout !h. tnor rrittm psmkion or rh. Univdi.y orqlshirglon For infomation, conhd liccns(4u Kshine1on.edu

The optimal force levels for orthodontic tooth movement should bejust high enough to partially but not com-pletely occlude blood vessels in the periodontal ligament. Both the amount of force delivered to a tooth and

also the area ofthe periodontal ligament overwhich that force is distributed are important. The PDL response

is determined not by force alone, but by force petunit area, or pressure.

Thc periodontal lig|ment is a well-organized connective fibrous tissue andremodels significantly during or-

thodontic movement. Under normal physiologic conditions, the PDL is rich in collagen fibers organized to re-

sist the forces ofmastication.Important: On th€ side toward which the tooth is being moved, youwill find "osteoclastic activity" that re-

sult in bone rasorption. This is called the pressure ot compression side. on the side ofthe root from whichthe tooth moves, you will find "osteoblastic activity" that rcsults id bone apposition. This is called the ten-sion side.

Types oftooth movement that can be accomplished with orthodontics:L Tipping: the crown moves in one direction while the root tip is displaced in the opposite direction due

to rotation or pivoting ofthe tooth around the axis ofresistance or axis of rotalion (localed somewhere inthe apical o e-thitd of the root). This $eates two areas of compression and tension. Most readily accom-plished with a removable appliance. Accomplish€d most easily with Nnterior incisor teeth.

2.'Ir^nslsJtioln (bodily movement): a force lhrough the center ofresistance causes all points ofthe tooth to

move the same amount in the same directioD. This Bpe ofmovemcnt is called translrtion orttodily move-ment. This creates one area ofcompression aad one arca of tension. Very difficult to accomplish.3. Ertrusiotr: displacement ofthe tooth from the socket in the direction oferuption.4. Intrusion; movement into the socket along the long axis ofthe tooth. Very dillicult to accomplish.5. Torque: controlled root movement labiolingually or mesiodistally while the crown is held relativelystable (mesial-distal root movenlent is also termed "uprightingr.6. RotAtion: the only force system that can prcduce pure rot.tion fd moment with no netJbrce) is

^ aotr-

ple, which is two equal and opposite, noncolinear but parallel forces. Recuning tooth rotations after ortho-

dontic cofiection occur because ofthe persistence of the elastic supracrestal gingival fibers (mainly freegingival and transseptal.fbels). Importsnt: Need adequrte retention to prevent rclapse.

Crown movement occurs when a force is applied at the bracket and a small couple is also applied to paniallynegate the tipping ofthe crou'n caused by the force. The center ofthe rctation is at the root apex.

Root movement occurs when a forc€ is applied at the bracket and an even larger couple is applied to more thannegate the tipping of the crown caused by the force. The center of rotation is at the crown of the tooth.

. The first slatement is true; the second statement is false

. The first statement is false; the second statement is true

. Bolh statements are true

. Both statements are false

30

CoplriSht O 20ll 2012 ' De.talDecks

. Allow for reorganization ofthe gingival and periodontal tissues

. Minimize changes due to growth

. Maintain teeth in unstable conditions

. All ofthe above

31

Coplrighr O 201 I -20 12 - Denral Decks

One of the most importart aspects of orthodontic therapy is retention. After malposedteeth have been moved into the desired position, they must be mechanically supporteduntil the hard and soft tissues have been thoroughly modified

-both in structure and in

function -to meet the demands of the new position. Once the desired occlusal results areachieved and the hard tissues are in normal function, the next step is to maintain or tomodify the soft tissues in the retention phase. Important: Most clinicians believe thatthe collagen fibers in the supra-alveolar tissue are signifrcantly responsible for the re-lapse oforthodontically rotated teeth as well as the redevelopment ofspaces between or-thodontically moved teeth.

Remember: Collagen fibers are the primary components ofthe attached gingiva. Whenteeth are orthodontically moved, the fibers stretch like rubber bands to adjust to the newposition. However, like rubber bands, they have a strong tendency to retum to theirformer position, pulling teeth with them as they go.

The circumferential supracrestal fibrotomy is a minor surgical procedure. A simpleincision in the sulcus is made to the crest of the bone. This incises all of the collagenfibers that are inserted into the root ofthe tooth. By cutting the collagen fibers, two thingsare accomplished:

1. Eliminate the polential for relapse due to collagen fiber retraction.2. Allow new fibers to form that will help retain the tooth in its new position.

\ote: Post-orthodontic circumferential supracrestal fibrotomy is most often performed ona rotated maxillarv lateral incisor.

difficult aspects ofthe entire treatment process. Retention is necessary in orthodontics forthe following reasons:

l. The gingival and periodontal tissues are affected by orthodontic tooth movementand require time for reorganization when the appliances are removed.2. Changes produced by growth may alter the orthodontic treatment result.3. The teeth may be in an inherently unstable position after the treatment, so that thesoft tissue pressures constantly produce a tendency for relapse.

In the last situation, gradual withdrawal ofan orthodontic appliance is ofno value. Theonly possibilities are accepting relapse or using permanent retention. Fortunately, onlythe first two reasons apply to most orthodontic patients, and maintaining the position ofthe teeth until remodeling ofthe supporting tissues is completed and growth has essentiallyceased allows a stable orthodontic result without further retention.Note: Retention is accomplished with either fixed or removable retainers.

Remember:. The corection ofan anterior crossbite is easily retained after orthodontic correctionby the overbite achieved during treatment.. Supracrestal fibers are commonly associated with relapse following orthodontic ro-tation ofteeth.

l. Significant reorganization ofthe PDL occurs in 3 to 4 months, and full-timeretention is critical during this time.2. Part-time retention is recommended up to a year and often longer

Maintainins the treatment result followins orthodontic treatment is one of the most

. Endochondral bone formation; with

. Intramembranous bone formation; without

. Both endochondral and intramembranous bone formation; with

. Both endochondral and intramembranous bone formation; without

32

Coplright O 20ll-2012, Dental Decks

. Interstitial grorth only

. Appositional growth only

. Both appositional and interstitial growth

. Degenerative changes into bony structures

Copyright O 201 1-2012 - Denral Decks

In the cranial vault, the growth process is entirely the resuit ofp€riosteal activity at the surfaces ofthebones. Remodeling and growth occur primarily at the pcriosteumlincd contact areas between skullbones, the skeletal sutures, but periosteal activity also changes both the inner and outer Jurfaces oftheseplateJike bones. Although the majority ofgrowth in the cranial vault occu^ at the sutures, thcre is a

tendency for bone to be removed from the inner surface ofthe cranial vault, while at the same timenew bone is added on the exterior surface.

In contrast to the cranial vault, the bones (i.e., elhmoid, sphenoid, ond occipitdl rores/ ofthe cranialb.se are formed initially in cartilage and are later transformed by endochondral ossi{ication to bone.

As ossification procc€ds, bands ofcartilage called synchondroses remain between the centcrs ofossi-fication. These important growth sites are the synchondrosis between the sphenoid and occipital bones,

or spheno-occipital slnchondrosis, the intersphenoid synchondrosis, between the two parts ofthe sphe-

noid bone, and the sphenoethmoidal synchondrosis, between the sphenoid and ethmoid bones- Even-tually, these synchondroses bccome inactive. Note: The bones ofthe cranial base are not affected to a

great degree by growth ofthe brain (siace lhey are endochondral bones).

,'-...., 1. After age 6, the greatest increase in size ofthe mandiblc occurs distal to the lirst molars,

,t!{ote{t 2.The condyle ofthe mandible grows by proliferation of cartilage.3. The chief factor in thc formation ofthe alveolar process is the eruption of teeth',1. Arch lengrh space for the eruption of pemanent mandibular second and third molars is cre-

ated by resorption at the anterior border ofthe ramus.5. At birth the greatest dimension ofthe face is width.6. After a tooth has bcen moved from one position to another, thc resulting bone is transi-tional bone.7. The dependencc oftooth development and tooth eruption upon growth ofbone and bones

is considerable.8. Grow1h ofthe cranial base generally precedes growth ofthejaws.

Important: Mandibular growth is in the downward and forward directions. Growth in the condyle in-

creeses lhe anterior-posteior (downward and fo' **(td patlern ofg|orlr, dimension ofthc mandible.

*** Which is grorvth by the addition ofnew layers on those previously formed.

Bone formation begins in the embryo whete mesenchymal cells differentiatc into either fibrous

membrane or cartilage. This leads to two paths ofbone development:

1. Intramembranous ossification is so called becausc it takcs place in mcmbranes of connec-

tive tissue. Osteoprogenitor cells in the membrane differentiate into osteoblasts: a collagen ma-

trix is lbrmed which undergoes ossification.\ote: The maxilla and mandible as well as the cranial vault are lbrmed lhis way

:. Endochondral ossification is how the remainder ofthe skeleton fornrs and takes place withina hvaline cartilage modef. Cartilage cells are replaccd by bone cells (osleocytes rcplace choh-

drocr 1es;. organic matrix is laid down and calcium and phosphate are deposited. This type ofos-sification is principally rcsponsible for the formation ofshort and long bones. Note: The cthmoid,

sphenoid and occipitalbones lbones of the cranial base) form this way.

L The growth ofthe cranial vault occurs almost entirely in response to growth ofthe\otcs brain. Remember: The bones ofthc cranial base are not affccted to a great degree by

.-.,,.._, growth ofthebruilr' lsince thqt are endochondral bones).

2. Growth ofthe cnnial base is primarily the result ofendochondral growth and bony

rcplac€ment at the synchondroses, which have independent growth potential.

3. The greatest period ofcranial growth occurs between birth and 5 years ofagc.4. ln fetal life , at about the third month, the head takes up almost 50% ofthe total body

length. At birth, the head is 30% ofthe body. In the adult, the head repres€nts about

l2% ofthe total body lenglh -all

ofthese changes, which are part ofthe normal growth

pattem, retlect the "cephalocaudal gradient of gro\ryth."

5. In determining a patient's skeletal growth pattem, the most important factor is hered-itv.6. Remodcling ofbone occu.s on both endosteal and periosteal surlbces.

7. Remodeling ofbone rcsults in the histologic structurcs called osteo[s.8. Deposition and resorption may not occur in cqual amounts.

. Apposition

. Sutural expansion

. Interstitial growth

. Endosteal remodeling

31Coplrishr O 20ll-2012 - D€nbl Decks

. Both the statement and th€ reason are correct and related

. Both the statement and the reason are correct but NOT related

. The statement is correct, but the reason is NOT

. The statement is NOT correct, but the reason is correct

. NEITHER the statement NOR the reason is correct

Coplright @ 201l-2012 - Denral Dect!

Grofih ofcartilage occurs in two ways:l. Appositional by the recruitment of ftesh cells, chondrcblasts, from perichon&al stem cells and the ad-

dition ofnew matrix to the surface.

Note: The perichondrium consists ofa fibrous outer layer and chondroblastic inner layer2. Interstitial by the mitotic division of, and deposition ofmore matrix around, chondrocytes already es-

tablished in lhe cartilage. Examples ofsites that gow by interslitial growth include the mandibular condyle,nasal septum and spheno-occipital synchondrosis.Notei The "V" principle ofgrowth is illustrated by the maDdibular condyle.

Importanti Cartilagc tissue is pressure tolerant and able to providc flexible suppon b€cause it is avascularand contains an intacellular matrix ofproteoglycans.

Growth of bone:.Appositionat below the covering periosieal layerofbone- Periosteum consists ofa fibrcus out€r layeranda cellular inner layer ofosteoblasts, which Iay down bone. Bccause ofits rigid structure, interstitial growth

is not possible.*** Do not confus€ bone growth with bone formrtion. Bone foms by cither endochondral ossification or in-tmmembranous ossifi cation,

It is a truism that grollth is strongly influenced by gcnetic factors, but it can also be significantly allectcd bythe environment, in the form ofnutritional status, degee ofphysical activity. health or illness, and a number

of similar factors. Thre€ major theories havc atlcmpted to explain the determinants ofcraniofacial growth:

l. Bone, likc othcr tissues, is the primary determinant ofits own growth-2. Cartilagc is the primary determinanr ofskeletal growrh, while bone responds secondarily and passively

J. The soft lissue matrix in which the skeletal elem€nts are embedded is the primary determinant of grow1h,

and both bone and cartilage are secondary followers. Note: This theory is kno\Mr as the functional matrixtheory.

T}e major difference in the theories is the location at which genetic control is expressed. The first theory im-plics rhar gcnetic control is expressed directly at the level ofthe bone, and therefore its locus should be the pe-

riosteum. The second theoryor cartilage theory suggests that genetic control is expressed in the cartilagc, whilcbone responds passively to being displaced. This indirect control is called epig€netic' The third theory as-

sumes gcnetic control is mediated to a large extent outside the skeletal system and occurs only in response to

e srsnal from other tissues.

The bone ofthe alveolar prccess exists only to support the teeth. Ifa tooth fails to erupt, alveolar bone neverforms irl that area; and ifa tooth is extracted, the alveolus resorbs after the extmction until finally the alveolarridge completely atrophies.

The space betwe€n the jaws into wbich the teeth erupt is gene.ally considered to be provided by growth atth€ mandibular condyles (especially the moldlt. The condyle is a major site of vertical growth in themandible. Many arguments have been made about the condyles function in mandibular gron'ih. Most author-iiies agree that sofFtissue development carries the mandible forward and downward, while condylar growthfills in thc resultant space to maintain contact with the base ofthe skull.In infancy, the ramus is located at about the spot wh€re the primary fir$ molar will erupt. Progressive poste-

rior remodeling creates space for the second primary molar and then for the sequential eruption ofthe perma-nent molar teeth. More often than not, however, this growth ceases before enough space has been created foreruprion oflhe third permanent molat which becomes impacted in the ramus. Note: After age 6, the great-elt increese in size ofthe mandibl€ occurs distal to the first molars.

Irnportlnt: In contrast to the maxilla both endochondral and periosteal aclivity are important in growth oftbe mandible. Cartilage covcrs the surface ofthe mandibular condyl€ at the TMJ. Akhough this cartilage is

not like rhe cartilage at an epiphyseal plate or a synchondrosis, hlperplasia, hypenropht and endochondralreplacem€nt do occur there. All other ar€as ofthe mandible are formed and grow by direct surface appos!tion and remod€ling.

Remember: Gro\\,th ofthe mandible occurs at the mandibular condyle and along lhe postedor sudace oftheramus. Tte body ofthe mandible grows longerby periosteal apposition ofbone on its posterior surface, whilerhe ramus grows higher by €ndochondral replacement at the condyle accompanicd by surfac€ remodelinglon the onterior surface oflhe ramus).

.. To summarize the growth ol the maxilla and mandible:

. rda, 1. Growth ofrhe maxilla and its associated structurcs occurs from a combination of growth at su-

';e; tures and direci remodeling ofthe surfaces ofthe bone.

2. The maxilla is translated downward and forward as the face grows, and new bone fills in at the

sutures. Growth ofthe surrounding soft tissues s€ens to be important.3. Grow'th ofthe mandible occurs by both endochondml proliferation at the condyle and apposi-tion and resomlion ofbone at surfaces.

4. The mandible is translated in space by the g.owth ofmuscles andother adjacent soft tissues and

fiat addition of new bone at the condyle is in response to the soft tissue changes.

. Palate

. Tuberosity

. Incisor

. Zygomatic

. Late mandibular growth

. Pressure from third molars

. Maxillary tooth-size excess

. Trauma

. An oral habit he must have

36CoplriShr O 201 | '2012 - D€ntal D€.ks

Cop'.right O 201l-2012 - D€ntal Drcks

The bony maxillary arch lengthens horizontally in a posterior direction. Bone has been de-

posited on the posterior-facing cortical surface ofthe maxillary tuberosity. Resorption oc-

curs on the opposite side ofthe same cortical plate, which is the inside surface ofthe maxillawithin the maxillary sinus.

lmportant: The maxilla develops postnatally entirely by intramembranous ossification.Since there is no cartilage replacement, growth occurs in two ways: (l) by apposition ofboneat the sutues that connect the maxilla to the cranium and cranial base and (2) by surface re-modeling.

,-'-- ,.. l. The maxilla migrates downward and forward away from the cranial base and

l$ote$j undergoes significant surfac€ remodeling. This surface remodeling includes re-'k; sorption of bone anteriorly and apposition of bone inferioriy.

2. Much ofthe anterior movement ofthe maxilla is negatedby anterior resorption,and downward migration is augmented by inferior apposition ofbone.3. As growth of sunounding soft tissues translates the maxilla downward and for-ward, opening up space at its supedor and postedor sutural attachments, new bone

is added on both sides ofthe sutur€s.4. As the maxillary tuberosity grows and lengthens posteriorly, the whole maxillais simultaneously carried anteriorly.5. The amount of forward displacement exactly equals the amount of posteriorlenglhening.

The counterparts to the bony maxillary arch development include:. The nasomaxillary complex. The anterior cranial fossa. The palate. The body ofthe mandible

Thc cunent concept is that late incisor crowding develops as thc mandibular incisors, and perhaps the

entirc mandibular dentition, move distally relative to thc body ofthe mandible late in mandibular growth.

Late incisor crowding does occur in individuals with no third molars at all, and so the presence ofthescteeth is not a c tical variable

-the extent oflate mandibular growth is a critical variable.

Cephalocaudal gradient of growthi simply means that there is an axis of increased growth extendingfrom the head toward the feet. When the facial growth pattem is vierved against the perspective ofthccephalocaudal gradient, jt is not surprising that the mandible, being further away from the brain, tends

to gro$ more than the maxilla, which is closer. Remember: The mandibl€ can and does undergo moregro$th in rhe late teens than does the maxilla.

Scammon's gronth curves point out four major tissue systems ofthe body and a percentage ofadultarainmenr at :0 years ofage. The curve for lymphoid tissue which reaches 200olo ofadult attainmentar or around age twelve. The lymphoid tissues then undergo a decrease in size until they reach 100% inadulrhood. The neural tissues reach about 90% oftheir adult attainment at roughly 9 yeaN ofage and

tinall) at age 20 are at adult attainment. General body tissue growth follows a direct line to age twentyand t-inally the getrital tissues begin their growth at puberty which is around agc fourteen.

Important:L The maxilla, follows a pattem closer to that or neural tissues than does the mandiblc.2. The mandible grows later and follows a pattem closer to that ofgenital tissues.

G.o$th velocity cunes show that groMh in height is very rapid after birth but decelerates quickly toa louer, more consistent level in childhood. Growth accelerates again around puberty before slowing and

vifually stopping at maturiry Key point: The timing of $owth spurts is important in orthodontics.

: - , .,. l The average peak growth for girls is around age 12, for boys it is around age 14.

,,Noteql' 2. Generally speaking, the earlier the growth spurt, the shorter the duration ofthe growth

-- .lun and the less overall the grourh will be.*' 3. Girls will generally start growth sooner, grow for a shorter amorult of time, and will growless than boys.4. Because of time and variability, chronologic age often is not a good indicator ofthe in-dividual's crowth status.

.78%

' 98o/o

. 49Yo

. Less than 25%

38CoDriglt @ 201| -2012 - D€nlal Decks

. The first statement is true; the second statement is false

. The first slatement is false; the second statement is true

. Both statements are true

. Both statements are false

Coplaighr O 201l-2012 - Dedtal Decks

*** It is prevalent in 49% of l1-year-old children.

The cause ofa median diastema could be anv ofthe followins:. A tooth-size discrepancy. A mesiodens. An abnormal frenum attachment. A normal stage ofdevelopment

The spaces tend to close as the permanent canines erupt. The greater the amount ofspacing, the less the like-Iihood that a maxillary central diastema will totally close on its own. As a general guideline, a maxillary cen-tral diastema of 2 mm or less will probably close spontaneously, while total closure of a diastema initiallyg€arer than 2 mm is unlikely. Note: lfthe space is 2 mm or less and the maxillary laterals are in a good posi-

tion, it is most likely the result ofa normal developmental proccss.

Ifit is caused by an rbnormal frenum, it is best to align the teeth orthodontically and then do a frenectomy.Usually this is not done until the permanenl caoines erupt.

Accepted methods ofclosing a diastema:. Using a lingual arch with finger springs. I srnr a Halrley appliance with finger springs. Using cemcntcd orthodontic bands with inter-tooth traction

\ote: Space closure is least likely to occur following early loss ofa primary maxillary central incisor.

1. In rhe United States, clefting ofthe lip and/or palate occurs in I of 700 - I,000 bifihs, making

\oL3, i! the most common craniofacial birth defect.' 2. The lip and primarJ- palat€ begin to develop at four to five w€eks gestational age. The two me-

_ '-' dial nasal swellings and the maxillary s$'ellings fuse io form the upper lip. Failure ofthis fusionrcsults in clcft lip. Clefts ofthe lip are more frequent in malcs. Cleft lip involvement is more fre-quent on the left side than the right.3.The secondary palate develops at approximately nine weeks dev€lopmental age. Tle pairedpalatal shelves arise from the iDtraoral maxillary processes. These shelves, originally in a verticalposition, reorientto a horizontal position as the tongue assumes a more inferior position. Thc palatal

shelvcs fuse with one another andwith the primarypalate anteriorlt which, in tum arises from the

fusion ofmaxillary and mandibular processes. Failure of fusion results in a cleft palatc. Clcftpalate is more frequent in females.

Rememb€r: The maxillary arch is slightly longer in length compared to the mandibulararch. The reason is the sum ofthe M-D diameter ofthe maxillary permanent teeth is ap-

proximately 128 mm, whereas the sum of the M-D diameter of the mandibularpermanent teeth is approximately 126 mm.

l.Permanent teeth move occlusally and buccally while erupting.\ot€ 2. Also, during active tooth eruption there is apposition ofbone on all surfaces

3.The grand design of the human face is the result of remodeling and dis-placement which interact to produce the final result.

4. Displacement and remodeling can occur in opposite directions.

5. The functional matrix theory (the 3rcl theory o the back oJ card #34)holds that:

r Qnft ticc,re ic nrim.. , --..-4ry. Bone is responsive to soft tissue. Deglrtrtion (mandibular function) influences mandibular growth. The soft tissues ofthe brain expand thus pacing growth ofthe flat bones

of the skull

6. The growth in width ofthejaws is generally completed before the adoles-

cent growth spurt begins.7. The growth in length ofthe jaws continues through the growth spurt.

. The first statement is true; the second statement is false

. The first statement is false; the second statement is true

. Both statements are true

. Both statements are false

40Cop)'dght O 20ll-2012 Denta! Decks

. Disking the distal of the primary first molar

.An appliance incorporating a finger spring to move the primary second molar mesially

. A brass wire placed between the primary second molar and permanent first molar

. Extraction ofthe Drimarv second molar

41

Coplrighl O 2011-2012 - Denhl Decks

*** The maxillary canine is the most commonly impacted tooth.

Failure ofa permanent tooth to erupt may cause damage to roots of other teeth and also

create a severe orthodontic problem. Orthodontic consultation is indicated when first ob-

served on an x-ray. An impacted canine or other tooth in a teenage patient can usually be

brought into the arch by orthodontic traction after being surgically exposed. In older pa-

tients, there is an increasing risk that the impacted tooth has become ankylosed. Even

adolescents have a risk that surgical exposure ofa tooth will lead to ankylosis.

In treatrnent planning for an impacted tooth, three principles should be followed:

l. The prognosis should be based on the extent of displac€ment and the surgicaltrauma required for exposure.2. During surgical exposure, flaps should be reflected so that the tooth is ultimatelypulled into the arch through keratinized tissue, not through alveolar mucosa.

3. Ad€quate space should be provided in the arch before attempting to pull the

impacted tooth into position.

It{ote: Research suggests the association of impacted canines with missing lateral incisors or shortened roots oflateral incisors. The distal aspect ol the root of lateral incisors

suides the eruotion ofcanines.

This separating device (brass wire) will cause the permanent first molar to be tippeddistally.

Ectopic eruption occurs when a tooth erupts in the wrong place. It is most likely to occurin the eruption of maxillary first molars and mandibular incisors. Its occurrence is much

more common in the ma"rilla and is often associated with a developing skeletal Class IIpattern. It is seen in about 2-6Yo of the population and spontaneously corrects itself inabout 60olo ofcases.

Ifthe eruption path ofthe maxillary lirst molar carries far too mesially at an early stage,

the permanent molar is unable to erupl and the root of the primary molar may be

damaged. The mesial position of the permanent molar means that the arch will be

crorvded unless the child receives treatment. Remember: This mesially inclined position

ofthe permanent molar makes it susceptible to decay. If it shows signs ofcaries, extract

the adjacent primary second molar immediately. The resultant space can then be

maintained as part of orthodontic treatment.

Ectopic eruption of mandibular lateral incisors, which occurs more frequently than

mandibular first molars, may lead to transposition ofthe lateral incisor and canine. A poor

eruption direction of the canine, sometimes leading to impaction, is observed often butusually is due to the eruption path being altered by a lack ofspace.

1. The time required to upright a molar can vary from:

2. The time required to stabilize the molar can vary from:

. 2-3 weeks

. l-2 months

. 2-6 rnonths

. 6-12 months

. 2-3 years

42Coplrighl aq 201l-2012 Denial Decks

ORTHODONTICS

Match the dental rrch relationships on the left withthe correct d€piction ofthe relationship on the right.

Normal occlusion

Class I malocclusion

Class II malocclusion

Class III malocclusion

Cop)riShr O 20ll-2012 - Dental Decks

*** A severely tipped molar or one that requires mesial movemmt to shorten the pontic space requires a longertreatment time.

A fixed edgewise orthodontic appliance is usually used for molar uprighting. The bracket slot size of0.022inch allows a wide mnge of wire sizes to be used. The altemate slot size is 0.018 inch, which can also uprightthe molar, but limits the wire sizes available. The tipped second molar should be banded because ofthe con-

siderable posterior masticatory forces produced can easily shear offbonded brackets.

Facts about molar uprighting:. A severely lingually tipped mandibular molar is more difficult to control and upright proP€rly.. Molar uprighting treatment in high angl€s cases will tend to result in excessive bite opening (increases

vertic a I d imens i on of occ lusion).. stebilization should lasi until the lamin{ durr and PDL reorganize. This ranges ftom approximately 2

months (simple uprightind to 6 monrhs (uprighting plus osseous s rgery, grafts, etc.).. Retention (slabilization) can be provided by an appliance or by a well-fitting provisional restoration,

which will stabilize the tooth positions. This will allow for reorganization ofthe PDL.

\ote: Slow progess in molar uprighting in an adult patient is most likely due to occlusal int€rf€rences.

When an orthodontic forc€ is applied lo a tooth, t\do scena os can develop depending on whether the force

is heavy or light:. Heavy force:

- lniti^l peiiod (from secoruls to weeks)t causes " hyalinization" (blood supplv is lost and results inn?crosis.) and "undermining resorptionn(osleoclasts atlackthe lanina dura ftom the underside ofthelamina dura). When this occun an inevitable delay in tooth movement occurs.

-Secondary period oftooth movement fdfer lhe above happens)t lhe PDL heals and there is second-

ary tooth movement. Note: It is best to Nvoid excessive orthodontic force.. Light force: the use ofliglt forces causes smooth continuous tooth movement without formation ofa sig_

nificamly hyalinized zone in the PDL. Osteoclasts attack the adjacent lamina dura, removing bone in theprocess of"fiontal resorption" which begins tooth movement. As a result teeth start to move earlier and

in a more physiologic way than do teeth subjected to hea\y forces.

Important: For a tooth to move, osteoclastic cells must be formed, which will remove bone from the area ad-jacent to compression ofthe PDL. Osteoblasts also must form newbone on the tension side, but the timing ofosteoclestiq not osteoblaslic, activify is critical.

Normal occlusion = C

The triangular ridge ofthe mesiobuccal cusp ofthe maxillary first molar articulates in the buc-

cal groove ofthe mandibular first permanent molar.

Classlmalocclusion=D

Class I malocclusion has the normal molar relationship but the incorrect line ofocclusion.

Class II malocclusion = A

Class II malocclusion has the mandibular molar placed behind or posterior to the maxillarymolar.

Class III rnalocclusion = B

Class III malocclusion has the mandibular molar olaced forwardmolar.

or anterior to the maxillary

. Lack of spacing in primary dentition

. Crowding ofpermanent incisors in mixed dentition

. Premature loss ofmandibular primary canines

. Larger than normal primary teeth

44Cop),right O 201l-2012 - De.tal D€cks

. Class I

. Class II, Division I

. Class II, Division 2

. Class III

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45Copyrighr e 201 I ,2012 - Dental Decks

There may be a dispropo.tion between the size ofthe maxilla and mandible or between the jaws and toothsize resulting in overcrowding ofteeth or i1r abnormal bite pattems. Supemumerary teeth, malformedteeth, impacted or lost teeth and teeth that eiupt in an abnormal direction may contribute to malocclu-sion. Less fiequent causes ofmalocclusion include habits such as thr-rmb sucking or tongue thrusting-

Signs of incipient malocclusion:. The lack ofinterdental spacing in the primary dentition. The crowding ofthe permanent incisors in the mixed dentition. The premature loss ofthe primary canines, particularly in the mandibular arch

; '., .. - l.The significance of the lack of sp.cing relates to the increased mesiodistal width of the

/Noae*lil Permanentteeth.

- - I 2. Arch perimeter does increase after eruption ofthe incisors. Howeveq it is a small increase

rn the maxilla, and essentially non-existent in the mandible. Therefore, the minimal arch

grofih does not usually contribute to further dental alignment.3.The premature loss ofthe mandibul.r primary canine reflects insuflicient arch size inthe anterior region. As such, the crowns ofthe lateral incisors, during eruption. impingc on

the roots ofthe primary canines causing them to resorb. When the canine is shed, the mid-Iine will shift in thc direction ofthe lost tooth. You will have lateral and lingual migration ofthe mandibular incisors.4. The maxillary anterior primary teeth are about 7570 ofthe sizc oftheir permanent suc-

cessors.

5. The mandibular anterior primary teeth are, on average, about 6 mm narrower mesio-

di\rally rhan lheir successors.

Rememberi An anterior crossbite in a primary dentition usually indicates a skelet.l growth problem.

At birth, the alveolarprocesses are covered by gum pads, which soon are segmented to indicate the sites

of lhe developing teeth (called gum pad stage). The maxillary arch is horseshoe-shaped and the gums

rend !o extend buccally and labially beyond those in the mandible; furthermore, the mandibular archis posterior to the maxillary arch when the pads contact.

Class II, Division 2 is a malocclusion in which the body of the mandible and itssuperimposed dental arch are also in distat relationship to the maxilla, and the molar and

canine occlusion are the same as Class II, Division I type. The distobuccal cusp ofthemaxillary first molar occludes in the buccal developmental groove ofthe mandibular firstmolar. and the maxillary canines occlude mesial to the mandibular canines. The big dif-ference between Division I and Division II is in Division II the maxillary laterals have

tipped labially and mesially.

Remember: Class II, Division I = maxillary incisors (centrqls qnd laterals) are in ex-treme labioversion. Anterior teeth are most likely to be fractured in children with this

n ne of mixed dentition malocclusion.

I . There is no set rule as to when a malocclusion should be treated. The age at

which it is treated depends on the problem involved.2. Malocclusions are more identifiable in children 7 to 9 years old because the

eruption of permanent incisors reveals tooth-arch length discrepancies.

. Dental open bite

. Skeletal open bite

. Dental cross bite

. Skeletal cross bite

46Coplright C 201l-2012, Dental Decks

\

. 5n. 45

.60; 35

. 70. ?5

47

Coplrighr O 201 1-201 2 - Dental Decks

The following factors are associated with chronic rrouth breathing:

. Narrow face

. Narrow oropharyngeal space

. Chronic rhinitis: inflammation ofthe mucous membranes ofthe nose

. Chronic tonsillitis

. Allergies

. Deviated nasal septum

Note: The earliest possible diagnosis ofthis open bite is essential because the conditionis not self-correcting and usually worsens with time. Anterior open bites can be classi-fied as a form of apertognathism (which neans open bite deJbrmity)

Classification of Human Occlusion (Angleb):. Cfass I: most common (about 70 o% of the populatior). The triangular ridge ofthemesiobuccal cusp ofthe maxillary first molar articulates with the buccal groove ofthemandibular first molar. The maxillary central incisors overlap the mandibulars. Maxil-lary canine lies between the mandibular canine and first premolar. Class I is associated

rvith an orthognathic (straigh) facial profrle where the nose, lips, and chin are harmo-

niously related. It is most commonly caused by a discrepancy between tooth structure

and the amount ofsupporting bone length.. Class II: less common (about 25 %r'). The mesiol:uccal cusp of the maxillary firstmolar falls approximately b€tween the mandibular first molar and the second premo-lar (the buccal groove of the mandibular first molar articulates posteriorly to the

mesiobucctl cusp of the maillary Jirst molar). The lowerjaw and chin may also ap-

pear small and withdrawn. The mandibular incisors occlude even more posterior to the

maxillary incisors so they may not touch at all. Maxillary canine is mesial lo mandibu-lar canine. Class ll is associated with a retrognathic (convex) facial profile.. Class III: the least common (less than 5 Zo). The mesiobuccal cusp ofthe maxillaryfirst molar falls approximately between the mandibular first molar and second molar.(the buccal groove ofthe mandibularfrst molar articulotes qnteiorly to the mesiobuc-

cal cusp ofthe marillaryfrst molar) The chin may also protrude like a bulldog's does.

The mandibular incisors overlap anterior to the ma"\illary incisors. The maxillary ca-

nine is distal to mandibular canine. Class III is associated with a prognathtc (concave)

facial profile.

Note: The nasolabial angle is the angle between the base of the nose and the upper lip,it should be perpendicular or slightly obtuse.

. SNA angle of> 84o

. SNB angle of< 78'

. ANB angle of < 4'

. None ofthe above

4A

Cop)'righl O 201l-2012, D€ntal Decks

. The first statement is true; the second statement is false

. The first statement is false; the second statement is true

. Both statements are true

. Both statements are false

49

Copyrigh O 20:l-2012 - Denral Decks

**x Remernber: An SNA Algle of> 84' indicates maxillary prognathism, An SNB angleof < 78' indicates mandibular retrognathism and an ANB angle of < 4' indicates a har-monious skeletal profile. Note: The ANB angle describes the relation of the maxillaryand mandibular denture bases.

Severe mdocclusion may compromise all aspects oforal function. There may be difficultyin masticating ifonly a few teeth meet, andjaw discrepancies may force adaptive alter-ations in swallowing. It can be difEcult or impossible to produce certain sounds in thepresence of severe malocclusion, and speech therapy may require some preliminary or-thodontic treatment. Referral to a speech therapist is helpful because both patient andparents are likely to benefit from the counseling. Even less severe malocclusions tend toaffect mastication, swallowing and speech; not so much by making the function impossi-ble as by requiring physiologic compensation for the anatomic deformity.

*** A concave profile is also termed prognathic. Although the maxilla can be termed

prognathic and/or retrognathic. when no clarification is given these tenns refer to the

mandible.

. 1. An orthognathic profile is one in which the nose, lips and chin are harmo-\otes niously related. This relationship is usually accompanied by a Class I dental

2. A prognathic profile is one in which rhe mandible is markedly forward ofthe maxilla giving a concave midfacial appearance. This is often indicative ofa Class III malocclusion. The maxillary incisors will most likely be tippedlingually.3. A r€trognathic profile is one in which there is a protruding upper lip or the

appearance of a recessive mandible and chin, or convex profile. The convex-

ity is due to the relative prominence of the maxilla compared to the mandible.The mandibular incisors will most likely be tipped forward. This relationshipis usually accompanied by a Class II malocclusion.4. As children mature their profiles become less convex.5. Speech is affected in severe malocclusions along with other oral fturctions(i.e., swallowing and mastication). For example, patienls with a skeletal Class

III malocclusion sometimes have difficulty pronouncing "f' and "v" soutds.

Important: A bimaxillary dentoalveolar protrusion means that in both jaws the teeth

protrude. This condition is seen in facial appearances in 3 ways: excessive separation ofthe lips at rest (rnco mpelence), severe lip strain @eeded to bring the lips into closure), and

prominence of lips in the profile view.

. Retrognathism only

. Overbite only

. Underbite only

. Overbite or retrognathism

. Underbite or prognathism

50Copright O 201l-2012 - D€nhl Deck

. Class I malocclusion

. Class II malocclusion

. Class III malocclusion

. Normal occlusion

51

CoplriSht O 201l-2012 - Dental Dects

Those malocclusions in which there is a "distal" relationshio ofthe mandible to the max-illa make up Class II.

Divisions of Class II malocclusions are as follows:. Class II, Division l: a distal relationship ofthe buccal groove ofthe mandibular firstpermanent molar to lhe mesiobuccal cusp ofthe maxillary first permanent molar alongwith the maxillary incisors (centrals and laterals) tn extreme labiovenion @rchuded).

. Class II, Division 2: a distal relationship ofthe buccal groove ofthe mandibular firstpermanent molar to the mesiobuccal cusp ofthe maxillary first permanent molar alongwith the maxillary laterals being tipped labially and mesially (sometimes actuallyoverlapping the centrals). The maxillary centrals are usually retruded somewhat.

*** Subdivisions: when the distoclusion occurs on one side ofthe dental arch only, the

unilateral distoclusion is referred to as a subdivision of its division. For example:

. Class II, Division I Subdivision: one side of the maxillary arch is in a Class II rela-tionship with its occluding mandibular quadmnt while the other side is in a Class I re-

lationship. The protruded maxillary incisors (centrals and laterals), maxillary overjet,and other anterior aberrations, are usually confined to one side ofthe maxillary arch.

Class III malocclusions arc those in which the body ofthe mandible and its superimposed dental

arch are in a mesial relationship to the skull base and maxilla. The maxillary first molar therefore

occludes distal to the mandibular first molar, while the maxillary canine is an exaggerated distal

relationship to the mandibular canine. The mandibular incisors are usually tipped lingually and

forward to the maxillary incisors. Also characteristic ofthe "true" Class lll malocclusion is the

prognathic mandible. Class III subdivision is a Class III relationship of the teeth on one side

$ ith a Class I relationship on the other side.

--\ pseudo-class III malocclusion is one in which the mandibular incisors are forward ofthe max-

illao incisors when in centric occlusion, however, the patient has the ability to bring the mandible

back $ithout strain so that the mandibular incisors can touch the maxillary incisors (this abilityis ofren considered diagt?o.ttlc). This type is therefore a milder form ofthe "true" Class Ill mal-occlusion and more amenable to conservative orthodontic novement than the "true" Class lll mal-

occlusion u,hich often requires sugrcal corection.

Different etiological factors have been suggested in pseudo-Class lll malocclusion:

Dental factors:. Ectopic eruption of maxillary central incisors. Prenrature loss of deciduous molars

Functional factors:. Anomalies in tongue position. Neuromuscular features. Naso-respintory or airway problems

Skeletal factors:. Minor transverse maxillary discrepancy

Notei It has also been suggested that these sequelae occur more frequently in subjects with a prog-

nathic mandible (ptimary cause) and the mandibular shift can be considered a functional (envi,o mehtal) factor, therefore the postnatal causative factors may not be the pnmary cause.

. Class I

. Class II, Division 1

. Class II, Division 2

. Class III

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52

CoplriSht O 201 I,20 12 , Dmtal Decks

. "True" Class III malocclusions

. "Pseudo" Class III malocclusions

. "Sunday bite"

. All ofthe above

Coplright O 201l-2012 - Dental Decks

In most cases Class II, Division 1 malocclusions, the body ofthe mandible and its su-perimposed dental arch are in a distal relationship to the maxilla and the ma,rillary inci-sors are usually in a labial axial inclination. In addition, the relationship ofthe maxillaryfirst molars and canines to their mandibular counterparts is such that the distobuccal cuspofthe maxillary first molar occludes in the buccal developmental groove ofthe mandibu-lar first molar and the maxillary canines occlude mesial to the mandibular canines. Be-sides the labial axial inclination ofthe maxillary incisors (overjet), various abenations inthe individual alignment ofthe teeth (for example, crowding) canbe superimposed uponthis class.

Remember: Class II, Division I Subdivision includes malocclusions, which have one

side ofthe maxillary arch in a Class II relationship with its occluding mandibular quad-

rant, while the other side is in a Class I relationship. The maxillary overjet or other ante-rior aberrations are usually confined to one side ofthe maxillary arch.

),{ote: Relative to a heterogeneous population, the incidence of malocclusion in a ho-mogeneous population generally is lower.

Mesio-occlusion 1Class III malocclusion) is an anteroposterior dentoalveolar relationship charac-terized by a more anterior position ofthe mandibular dentition compared to the maxillary dentition.Clinically. there are two types of mesio-occlusion. The first t,?e is considered to be a positionalform, as a result of a mesial displacement ofthe mandible into an anterior position and has beennamed in a different ways (pseudo, functional or apparent).The other form of mesio-occlusion isa truc skeletal Class lIL Thc characteristics ofthis malocclusion result from a combination ofskcle-lal and dentoalveolar features.

\ote: In order to ayoid the interference of teeth, a patient Inay adopt a jaw position on closure,\r hich is forward to normal. This may look like a Class III position in the absence ofa true skele-tal Class lll relationship. Hence termed 'pseudo Class lll malocclusion." In most cases they havean edge-to-edge bitc. Mandibular incisors are forward of maxillary incisors in centric occlusionbul the patient can bring the mandible back without strain so that the mandibular inciso$ touch themaxillary incisors.

T}le benefits attributed to the treatment ofpseudo-Class lll malocclusion in the mixed dentitionare:

. Preventing unfavorable growth ofskeletal components (infact, early treatment ofanteriorcrossbite can help lo ninimize adaptations that ate often seen in seyere late adolescent maloc-ch6iotl). Preventing functional posterior crossbite and habits, such as bruxism that can develop from an-tenor or posterior interferences. Gaining space for eruption ofcanines (lack of space could be catsed by retro-inclination ofupper incisors frequentlyfound in pseudo or Class III malocclusion). Avoiding the risk ofperiodontal problems to mandibular incisors caused by the traumatic oc-clusion due to the crossbite.

\ote: The "Sunday bite" is a term given to the forward postural position ofthe mandible whichis adopted by people with Class II profiles in an effort to improve their esthetics.

. Al abnormal flenum

. Uneven growth of the arches

. Mandibular incisor crowding

. Discrepancy between tooth size and supporting bone

51Cop)right O 201 I -20 l2 - Dental Deck

. Hereditary gingival fibromatosis

. Down's slndrome

. Rickets

. Hlperparathyroidism

Cop,.righr O 20ll-2012 - Dentaltr€cks

l{oted;.:.,- l

The cephalometric analysis ofthe Class I occlusion would indicate an ANB angle ofless than4 degrees signif ing a harmonious skeletal prohle and sagittal harmony between the maxillaryand mandibular dental arches. The most common cause ofClass I malocclusion is a discrep-ancy between tooth structue and the amount of supporting bone (length). Perhaps the mostprevalent characteristic ofClass I malocclusion is crowding (i.e., insulficient alveolar qrch

length to qccommodate all teeth in ideol alignment qnd in q good sqgittql position).

When a diagnosis is made that crowding does exist and this crowding exceeds 4 mm in themandibular arch, extractions are often required to attain an excellent, stable result. However,the decision whether to exftact teeth depends greatly on a space analysis performed on themandible. Th€ patient should be ref€rred to the orthodontist for this analysis.

In general:. when the space lacking is less than 4mm, in most cases it can be obtained by carefullystripping some interproximal enamel from each ofthe antedor teeth. A space deficiency exc€eding 4mm usually indicates extraction for correction of themalocclusion

l. Physiologic occlusion: although not necessarily an ideal or Class I occlusion, itis an occlusion that adapts to the stress of function and can be maintained indefi-nitely.2. Pathologic occlusion: cannot function without contributing to it's own destruc-

tion. It may manifest itselfby any combination of: excessive wear ofthe teeth with-out sufficient compensatory mechanisms,TMJ problems, pulpal changes rangingfrom pulpitis to necrosis and periodontal changes.

3. Tooth movement caused by pathologic conditions is termed pathologic toothmovement.

*** This condition can result in the premature exfoliation of primary teeth

The generalized eruption failure or "primary failure of eruption" is caused by the failureofthe eruption mechanism itself. Bone resorption proceeds normally, but involved teeth

simply do not follow the path that has been cleared. The involved teeth do not erupt spon-

taneously and are not amenable to any orthodonlic recourse. This condition is rare.

The localized causes of failure of eruption or the delayed eruption of the teeth include:. Congenital absence. Abnormal position ofthe crypt. Lack of space in the arch (crowding). Supemumerary teeth. Dilacerated roots

Remember: Anodontia, diagnosed in a 5 year old child, primarily affects the growth ofthe alveolar bone fas opposed to the midface, maxilla, or mandible, etc.). *** The bone

ofthe alveolar process exists only to support the teeth. Ifa tooth fails to erupt, alveolar

bone never forms in that area; and ifa tooth is extracted, the alveolus resorbs after the ex-

traction until finally the alveolar ridge completely atrophies.

Atl ofthe following statements regarding the effect ofenvironmental influencesduring growth and development ofthe face, jaws and teeth are true

EXCEPT ongWhich one is the EXCEPTIOM

. Patients who have excessive overbite or anterior open bite usually have posterior teeththat are infra- or supra-erupted respectively

. A non-nutritive sucking habit leads to malocclusion only if it continues during the mixeddentition stage

. Negative pressure created within the mouth during sucking is not considered a cause ofconstriction of the maxillary arch

. "Tongue thrust swallowing" leads to an open bite

. "Adenoids" which lead to mouth breathing, cannot be indicted with certainty as an eti-ologic agent ofa long-face pattem ofmalocclusion because studies show that the maj-ority ofthe long-face population have no nasal obstruction

56

CoDrjght aq 20 I I 20 I 2 - Denral Declis

. In the maxillary arch, the primate space is located between the central incisors andlareral incisors

. In the maxillary arch, the primate space is located between the lateral incisors andcanines

.In the mandibular arch, the primate space is located between the canines and firstmolars

.ln the mandibular arch, the primate space is located between the lateral incisors andcanines

Coplright C 201l-?012 DenralDecks

"Primate spaces" in the primary dentition arefound in which TIYO locstions?

Recent studies indicate that "tongue tbrust swallowing" can not be blamed for an open biteas it was shown that there is no tongue-force on the teeth during swallowing even thoughthe tip ofthe tongue is placed forward.

The tendency to place the tongue forward between the teeth (in cases ofanterior open bite)appears to originate from the need to attain an oral seal during swallowing. So, the for-ward position ofthe tongue during swallowing is due to the arterior open bite, the re-verse is not true

-"A tongue thrust swallow therefore should be considered the result

ofdisplaced incisors, not the cause."

1. A sucking habit that is stopped prior to mixed dentition has not been shown

to lead to malocclusion.2. The negative pressure created within the mouth during sucking is not whatcauses the maxillary constriction. It is the force from the buccinator muscles

that does.

r** Spacing is normal throughout the anterior part ofthe primary dentition, but is most noticeable in these

t$o locations.

These primale spaces are normally present from the time the teeth erupt. Developmental spaces between the

incisors arc often present from the beginniDg, but become somewhat larger as the child gtows and the alveo_

lar processes expand. Generalized spacing ofthe primary teeth is a requireme[t for proper alignment ofthepermanent incisors. This slacing is most frequently caused by the growth ofthe dental arches.

If spacing is present, there is a possibility that dritting ofthe adjacent teeth will occur if there is a loss of a

primary incisor. However, if there is no spacing present and the primary anterior teeth were in contact before

the loss, a collapse in the arch after the loss ofone ofthe primary incisors is almost certain.

lmportrnt: This is not true in the case ofa lost permanent incisor. Space closure occun mpidly whether spac-

ing is present or not prior to the loss. Space maintenance would be indicated.

Remember: One ofthe most common cruses of malocclusion is inadequate space management followingthe early loss of primary teeth.

Primary dentition strge:. Starts with the eruption of the primary teeth and lasts until the first permanent tooth erupts. Boys prccede girls in total number of teeth erupted until I 5 months, then girls surpass boys and r€main

ahead throughout completion of the primary dentition. Tle mesiolingual cups ofthe maxillary molars occludes in the central fossae ofthe mandibular molars,

and the incisors are vertical, with minimal overbite and overjet. The mandibular second primary molarusually is somewhat wider mesiodistally than the maxillary giving dse, typically, to a flush terminalpleDe at the end ofthe primary dentition stage.. mefl the termiral plane is straight until the arival ofth€ first permanent mola$, the latter are usuallyguided into aD ideal end-to-€nd relationship considered "nomal" for whites in North America.. IDterproximal cavities, sucking habits, or the skeleial pattem may Foduce a 'step" mther than a flush ter-

miDalplane. Dist l step: the mandibular terminal plane is distal to the maxillary termidal plane. Mesial step: the mandibular terminal plane is mesial to the maxillary terminal plane

. Class relationships

. Step relationships

. Primitive relationships

. Occlusion relationships

. Tooth #22 is erupting distally

. Tooth #22 is erupting mesially

. Tooth #22 is erupting lingually

. Tooth #22 is erupting facially

58

Coplrighi O 201 I -20 12 - Dental Decks

59

CoplYiSh O 201 I '2012 - Dental Deck

The primary molar relationship shown in the figureabove is a mesial-step relationship, as the distalsurface of the lower second primary molar ismesial to the distal surface ofthe upper second pri-mary molar. The mesial-step molar relationship al-lows for the first permanent molars to erupt into a

normal occlusion immediately on eruption. Notethat the permanent nolars are in a normal Class Iocclusion.

This figure demonstrates the fl ush-terminal-planerelationship for primary molars. The distal surfaces

of the maxillary and mandibular second primarymolan are in an end-to-end relationshio.

In these cases (ie/ashlerminal-plane),the fiIst permanent molars do not erupt immediately intoa normal relationship. As you can see, the first permanent molars are in a Class Il relationship. TheClass II relationship usually is temporary until the second pdmary molars are lost and the perma-

nent nolars move into a Class I relationship. This occurs at approximately age ten or eleven and

is called the late mesial shift, Both the mesial-step and flush-terminal-plane relationships usuallyresult in the development of a Class I permanent molar occlusion, although the flush-terminal-plane relationship can result in a Class ll relationship ifthe late mesial shift does not occur An-other stcp relationship involves a situation where the distal suface of the mandibular primarysecond molar is located to the distal ofthe distal surface ofthe maxillary primary second molar.This is termed a distal-step relationship. In these cases, the permanent molars erupt into a Class llrelationship. lmportant: The terminal plane relationship ofprimary second molars detenninesthe future anteroposterior positions ofpermaneot firct molars.

Sometimes the permanent mandibular canines erupt facially relative to th€ primary canines.However, often they are right in line with the primary canines. Ifthere are problems in erup-tion. these teeth can be displaced either lingually or labially, but usually they are displaced labi-ally ifthere is not enough room to accommodate them within the arch.

.. , l. The mesial inclined plane ofthe primary maxillary canine articulates with the,\oto* distal inclined plane of the primary mandibular canine. This is the normal rela-'*aii' tionship.

2. In both the maxillary and mandibular arches, the permanent incisor tooth budslie lingual as well as apical (inferior) to the primary incisors. The result is a ten-dency for the mandibular permanent incisors to erupt somewhat lingually and in aslightly inegular position. This occurs even in children who have normal dentalarches and normal spacing within the arches.3. Permanent teeth normally move occlusally and buccally while erupting.4. Remember: The maxillary arch is sli glttly longer (approximately 128 mm) thanthe mandibular arch (approximqteu 126 mm )-

. The first statement is true; the second statement is false

. The first statement is false; the second statement is true

. Both statements are true

. Both statements are false

60

Copyright () 2011,201?, Denial Decks

. She is mixing up overbite and ovefet

. She is mixing up overbite and open bite

. She is mixing up overbite and negative ovedet

. She is mixing up her cartoon characters

6tCop)'rigbt O20ll-2012 - Dental Decks

*** There is typically more leeway space in the mandibular arch.

ImportsDt:l. The primary anterior teeth (ihcisots ahd canines) are narrower than their permanent successors

mesiodistally.2. The primary molars are wider than their permanent successors mesiodistally.*** This size di{ference has clinical significance. The diff€rence is called the leeway space.

The mandibular l€eway space avemges about 2.5 mm on esch side while the maxillary leeway space

averages about 1.5 mm on e.ch sid€. The important factor is that some space will be avaihble in theposterior palt ofthe mouth. This leeway space serves to at least accommodate the permanent canines,

which are generally larger than the primary canines.

During the canine-premolar transition period, the permanent first molars generally move mesiallyinto the leeway space after the primary second molars are shed, thus causing a loss in arch length.

Note: This is referred to as "the late mesial shift ofa permanent first molar."l On occasion, the permanent incisors "spread out" due to spacing. This is referred to as the

"ugly duckling stage"of development. With the eruption of the permanent canines, thespaces often will close. As a g€neral guideline, a maxillary central diastema of2 mm or less

will probably close spontaneously, while total closure ofa diastema initially geater than 2

mm is unlikely.2. The permanent dentition stage begins when the last primary tooth is lost.3. For the maxilla and mandible: Crowth in the width is completed first, then growth inlength, and finally glowth in height.4. Maxillary and mandibular arch widths increase and this is completed before the ado-

lescent growth spurt5. The dental arch perimeter (length) decreases a surprising amount during the late ado-

lescent and young adult periods due to the late mesial shift ofthe permanent molan into the

leeway space, the mesial drift tendency ofthe posterior teeth in general, and the lingual po-

sitioning of the incisors.6. Increases in the vertical height ofthe jaws and face continue until 17 or l8 in girls and

in the earlv twenties in bovs.

*** This is a common la)?erson mistake. Overjet is in the anterior-posterior dimension,rvhereas overbite is in the vertical direction.

Overbite is the vertical overlapping ofthe maxillary anterior teeth over the mandibular

anterior teeth. Overbite is generally is 10ok to 2jo/"but can vary up to 50olo.

Overbite(deep bite)

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Overjet

Overjet is the horizontal projection ofthe maxillary anterior teeth beyond the mandibu-lar anterior teeth (labial axial inclination of the maxillary incisors). Normal overjet is 2-3 mm.

. Mandibular first molars

. Maxillary first molars

. Mandibular incisors

. Maxillary incisors

Copldght O 201 I -20 12 - Dental Decks

. It is used to predict the amount ofcrowding after the permanent teeth erupt

. It determines space available vs. space required

. The analysis is based on a correlation oftooth size

. It is performed during the mixed dentition

. It is performed with a boley gauge, study models and a prediction table

. Analysis is done for each quadrant

Coplriglft O 201 1,2012 - Dental Deck

A mixed dentition an^lysis (transitional dentition analysis) detemines space available versus spacerequired. The analysis is based on a cofielation oftooth size; one may measure a tooth or a group ofteethand predict accurately the size ofthe other teeth in the same mouth.

In thc Moyers' mixed dentition analysis, the size ofthe unerupted canines and premoJars is predictedfrom knowledge ofthe siz,e (nesiodistal \|idth) ofthe mandibular incisors that have already erupted intothe mouth early in the mixed dentition. The maxillary incisors are not used in any ofthe predictive pro-cedures, since they show too much variability in size.

Notei The mandibular incisors are measured to predict the size ofmaxillary as well as mandibular pos-

terior teeth.

lf mandibular antcrior crowding is notcd during thc mixcd dcntition phase, thc most appropriate ap-proach to management is to take study models and perform an arch length analysis. This mandibular in-cisor crowding usually results from a tooth size-arch length discrepancy,

Mired dentition stage:. That period during which primary and permanent teeth are in the mouth together, the earliest indi-cation ofa mixed dentition consists ofthe prirnary dentition and the permanent mandibular firstmolars.. Supervision ofa child's development ofocclusion is most critical during this mixed dentition stage.. From a clinical point ofview, there are two very important aspects to the mixed dentition period:

L The utilization ofthe arch perimeter:. The adaptive changes in occlusion that occur during the transition from one dentition to another.

. The elveolar process is one ofthe most actively adaptable areas ofbone growth during the periodof Eansition between the dentitions. Therefore, it is an ideal time for most majo. orthodontic inter-\'ention.. \ormal characteristics ofthe mixed dentition stage: molar and canine relationships are Class l;lec$ay space is present; well-aligned incisors or up to moderate crowding ofthe incisors; proximalcontacts are tight.. The total leeway space is the important clinical consideration and the method ofutilization oftheleeway space is the key factor in th€ transitional dentition.

*** This is false; analysis is done for each arch.

Procedure for rnixed dentition analysis:

L \4easure the mesial-distal diameter ofthe mandibular incisors and add them together

2. Veasure the space available for the rrandibular incisors3. Subract # I from #2*** A negative number indicates crowding in the incisor region

-1. \leasure the space available lor the canine and premolars on each side ofthe arch

5. Calculate ftom the prediction table the size olthe canine and premolars

6. Subtract #5 from #4 on each side

""" Once again, a negative number indicates crowding

*** At this point, there will be 3 numbers:. The number for incisor crowding or excess space. The number for the right canine and premolar crowding or excess space. The number for the left canine and premolar crowding or excess space

*** Add the three numbers:. A negative number = crowding. A positive number = space

Note: For the maxillary arch, use the mandibular incisors to predict the size ofthe max-illary canines and premolars. Follow the same steps as described for mandibular teeth.