Seminar 14 expectations

McGann answers

Diagnosis

1. If the skeletal resistance is severe on the LOWER incisor of a growing class III patient, and a

lower lingual corticotomy is planned, then what changes if the patient grows more or less than

predicted?

If the patient grows more than predicted, then the mandible moves more forward than

expected and to avoid edge-to-edge or anterior crossbite, the lower incisor must be positioned

further back, with more skeletal resistance relative to the lingual cortical bone. The corticotomy

is needed more than ever.

If the patient has less DHG than expected, then the lower incisor does not need to be positioned

as far back, and there is less skeletal resistance. The patient may now not need the planned

corticotomy.

2. If RHG moves the maxilla forward 6mm, what is the effect on the DHG?

The DHG is less”nearly” by the amount that A point moves forward, since DHG is RELATIVE to A

point. There is not an exact 1:1 relationship of maxillary drift forward to mandibular

enlargement since growth is progressing at an angle, the McGann angle (angle between

maxillary length and mandibular length lines).

3. When do you use Li torque in the upper incisor of a class III case.

When the upper incisors starting inclination is retroclined and you want to be sure that the

upper incisor moves as far forward as possible, OR if there is risk of the upper incisor detorquing

(upper arch extraction or spaces to close). The retraction limit then either pushes the upper

incisor crown forward or maintains its position as the forces are closing spaces.

4. At what age and under what circumstances is lower 8 enucleation considered in the lower

arch?

IF you plan to distalize the lower arch, then this is limited by the presence of the lower 7s and

8s. This is the same in the upper arch when you say there is “posterior crowding”. The lower 8 is

the obvious choice to extract if given a choice of the 7 or 8, since the lower 8s usually erupt into

a mesial-lingual inclination and rotation when the 7s are removed. The lower 7 then is allowed

to erupt further distal, into the space previously occupied by the 8s.

At age 8 or 9, there is a radioleucency for the lower 8 “buds”. When these are removed, there

is an opening on the occlusal surface OR to the lingual. Use a surgical spoon to scoop out the

tooth buds. There is NO BONE to remove or grind, no teeth to section.

Then, the 8s start to calcify, as with the case shown below at age 10. At this stage, the crown

may be a “disc” and to remove the disc you may use a hemostat to grab the disk and break it

with a twist. The disc may be too large to be removed through the hole.

After the stage below, when the full crown is calcified, the extraction becomes very difficult

since sectioning the crown is almost impossible as it rolls around in the socket. Bone then needs

to be removed until the hole is large enough to remove the crown. (case 977)

5. How do you do a lower 8 enucleation?

Make a vertical incision to the disto-buccal cusp tip, then reflect the flap to expose the

underlying bone and tissue. Be especially careful not to damage the lower 7 follicle. Identify the

lower 7, then moving more posterior, find the location of the lower 8. With a surgical spoon,

scoop out the follicle and then hopefully the crown. At age 8-9, the crown will look like the white

of a hard boiled egg, with approximately the same consistency. The follicle will be darker blue.

Usually the incision is held together by the tongue so no sutures are needed.

6. When and how is it possible to distalize the lower arch in class III cases.

The lower arch is no different than any other group of teeth. It can be moved as a unit with the

proper force application. The line of force should be parallel or slightly below the occlusal plane,

the amount of force should be approximately 150-200 grams per side, and there must be

posterior space to move the arch back. Once the force is applied, then it is only a matter of time

for the biologic process of moving teeth to do its work. In the anterior, retracting the lower

incisors can be resisted by the lingual cortical bone. In moderate skeletal resistance situations,

using the dental vto or ceph vto prediction of the final lower incisor position and inclination,

bone remodeling can be expected with less than 150 grams per side of applied force. If there is

severe or extreme skeletal resistance, then it is best to do the Distalization in 2 steps, first

retracting the lower 3-7 first, then using the corticotomy assisted retraction of the lower incisors.

The reason not to do the corticotomy for retracting the entire arch is that the cortical bone will

be healed before the intended tooth movement is completed.

7. What line of force should you use if you want ZERO intrusion or extrusion as you retract the

upper anterior segment with zygoma buttress supported coils, and why?

Experience as shown on dental overlays has shown that a 5-10 degree angle is needed from

the occlusal plane “up” on the upper anterior segment to retract it straight back at “zero”

extrusion/intrusion. This is to compensate for the normal extrusion of the upper incisors that we

normally observe during orthodontic retraction. Below notice there is a coil from 7-KH and then a

second coil from the zygoma buttress. The combined line of force is approximately 10 degrees.

On the final overlay, the upper incisor moved straight back without extrusion or intrusion. (case

1029)

8. Explain the significance of an exploratory flap to examine bone remodeling palatal to the

upper incisor in the maxillary overlay in case 1029?

The exploratory flap clearly showed the presence of bone covering the roots of the incisors. This

means that bone “remodeling” exists, and is not bone “resorption” where the roots would be

exposed.

9. Explain what might cause “bunching” of palatal tissue, and why this might be important to

correct with perio surgery. (case 1029)

There was definite palatal cortical bone remodeling in this case and the appearance of

bunching of tissue could have been the remodeling of tissue and bone adjacent to the incisors.

But the risk is that the palatal tissue did NOT remodel, that the tissue is bunched up instead, the

fiber elasticity being a possible retention problem as the tissue re-establishes the starting incisor

position after the brackets are removed.

A WEDGE of tissue was removed to relieve the palatal tissue elasticity, similar to an extraction

space fiberotomy, and at the same time the flap raised to examine the underlying palatal cortical

bone and roots. The roots of the incisors were covered with “remodeled” bone.

10. Why is an exploratory flap to examine bone remodeling preferred over the tool of CBCT (cone

beam CT scans)?

3D scans are not accurate when examining THIN bone, less than 0.5mm thick. Bone this thin

appears to be not present on a CBCT scan. Note below the two different filters to examine the

CBCT scan to not clearly show the bone covering the roots of the incisors (a different case than in

the last question).

11. What are your options if you prematurely lose the first bicuspid extraction space before

correcting the incisor protrusion?

a) Extract 6s if the 8s are present to replace the extracted 6s

b) extract another set of bicuspids, the molars contacting the cuspids

c) distalize both upper and lower arches.

NONE of these are good solutions, with patient management becoming difficult as you ask

for either more teeth to be removed or the placement of skeletal anchorage. It is better to

avoid this problem by aggressive molar anchorage planning, accurate diagnosis, and

identifying cases that may need multiple extraction at the start of the case.

12. Describe crown lengthening diagnosis and the procedure to reduce gingival display.

To enhance the appearance of the smile, lengthen the visible clinical crowns of the upper

anterior teeth, and/or reduce gingival display, a crown lengthening procedure can be done.

There needs to be a good band of attached gingiva in the area of the intended surgery. An

incision is made in the attached gingiva and in the facial sulcus and papilla. The band of

attached gingiva is thrown away.

Next, the full thickness flap is reflected to the piriform rim and denuding most of the

attachment to ANS. These muscles will reattach at a more inferior level as the reflected flap is

repositioned (stretched) to the bone margin by mattress type sling suturing.

The bone is recontoured and scalloped where it is bulbous with 2mm of cementum exposed at

the crest of the teeth. Below right is after 5 weeks healing.

13. Explain the various definitions of “dentofacial orthodontics”.

a) Provide a service beyond simply straightening teeth

b) Provide a service beyond straightening teeth and correcting bites to class I

c) To Do something beyond “orthodontics”, the definition of that term is established by the

extent of work provided by the specialty

d) To spend more time, skill, and energy to save the patient restorative work,

e) To accept a case with known extended treatment time, such as a 2-phase mixed dentition

treatment.

f) A growth management case with estimated or individual growth predictions

g) Cases with maximum and moderate-maximum anchorage, since the specialty generally

closes extraction spaces with sliding mechanics, moderate anchorage

h) Changing the vertical to ‘raise the smile’

i) To change the facial features by the altering the underlying tooth positions.

14. When should a gingival graft be done before starting orthodontics.

When there is a lack of a SEAL between the oral environment (non sterile) and the underlying

tissues (sterile). This is usually a band of attached gingiva, but the appearance of attached

gingiva can be present with the attachment still missing from the tooth and underlying bone.

15. Explain what you need to do when using a lower cuspid in the lower lateral incisor position

a) Level the cusp tip to an incisal edge

b) Reduce the size of the cuspid mesial-distal to be approximately the size of the lateral incisors

(or leave an occlusion that is slightly class II in the posterior).

c) It is NOT needed to thin the lingual as on upper cuspids

d) It is NOT needed to extrude the lower cuspid to level the tissue as is needed on the upper

16. Explain how to close a lingual flap after lower lingual corticotomy.

Starting with the midline suture that was placed before reflecting the lingual flap to mark the

starting point of the closure, push the “dull” end of the needle through the contact between the

central incisors. Then back again under the wire on the next embrasure, push the ‘dull’ end of

the needle to the lingual and “grab” the lingual flap at that location. In the pictures below, top

left, the needle is pushed between the same teeth, under the archwire, withOUT penetrating the

labial papilla…you can now see the SLING that will hold the lingual flap from the facial surface of

the central incisor.

Continue the same through each contact until you get to the last tooth, and then use the

LOOP as the end to tie the KNOT on the facial surface of the last tooth. This is a “continuous

Mattress suture.

Go back to the other side and do the same from the next tooth from the midline to the most

posterior extension of the flap.

IP Appliance:

17. When is the “D” variation used in class III cases in the upper arch and when should you use

“Roth” on the upper 6s? Why not use tipD?

The “D” variation does NOT have any “distal offset”, meaning that the archwire will be

parallel to the facial surface of the molar and the molar will be rotated more MESIAL-PALATAL

than you are accustomed to seeing in class I or II occlusions. This is a benefit in NON

EXTRACTION upper arches when you want the molar to consume more archlength, pushing 5-5

more forward. **note that this variation was used in standard edgewise and the orthodontist

compensated by making a ‘bayonette’ bend in the archwire to rotate the molar mesial-buccal.

The molars upper and lower do not fit together as well without a distal offset or bayonette bend,

but this is a small compromise to help the effort in the [smaller] upper arches in class III cases.

When the upper arch is a [bicuspid] extraction arch, then the Roth prescription gives the best

fit with the lower molar AND the Roth Rx typically leaves a mesial inclination to the upper 6s,

serving to push 5-5 more mesial.

TipD would NOT be good in a class III non extraction or extraction arch since this is tipping

back the crown, making the upper more retracted than the lower arch.

It should be noted that if you start phase I with a non extraction preliminary diagnosis and the

“D” variation, and then change to extraction, then the appliance needs to be re-evaluated, and

that includes the molar buccal tubes.

Mechanics:

18. Explain what happens to the line of force when T loops are activated at the same time that

zygoma coils are active to the T loop.

The force is now being applied from multiple sources, one at zero degrees (the coil between

the teeth) and the other from a more superior location. IF there is equal forces from each, the

NET line of force is half way between the two. As the teeth move and the T loop force rapidly

decays, the line of force moves ‘up’ until it is at the zygoma buttress supported coil when the T

loop reaches its original passive state. Since the T loop can generate very high forces, the line of

force can be near zero to as high as the zygoma coil, variable according to where the T loop is in

the deactivation process.

19. Explain why there can be EXCESS force when a T loop and zygoma coil are both applied at the

same time and what the consequences can be.

The amount of force is cumulative, the total felt by the teeth is the sum of the zygoma plus T

loop generated forces. T loop forces are typically 250grams per side with 1mm of activation at

the vertical leg, and can be easily 300-500 grams per side with over-activation. Add this to 200-

250 grams from the zygoma supported nitie closed coil and the forces now are excessive. No

tooth movement, necrosis, and pain can be the result. Either of these forces is sufficient, there is

no need to use both.

In the optimum force curve for biologic efficiency, the amount of force where teeth may stop

moving is at approximately 300 grams. Yes, the force is distributed amongst the root surface

area in the segment, so four incisors could need 1200 grams to reach these levels, but remember

that the T loops and coils are also forces per side, and must be added together. There is no

reason to approach these numbers, even after corticotomy surgery where we are trying to move

the bone segment with the teeth.

20. How much force should be applied to an upper 2-2 segment after upper lingual corticotomy.

What are the choices to deliver this force.

I have recommended 200 grams per side if upper 2-2 corticotomy and 250 grams per side if

upper 3-3 corticotomy. This is only after years of estimating forces applied to teeth and tracing

overlays after corticotomy.

The choices to deliver this force are

a) T loops reactivated every 2-3 weeks to keep the forces from dropping to bone remodeling

levels (0.5mm of T loop activation). 1-1.5mm of vertical leg separation is sufficient on this

schedule.

b) OR, zygoma buttress supported nitie or stainless steel coils. Nitie coils have a longer range of

activation, for the same force applied, requiring less reactivation of the coil. Same as the T

loops, avoid the bone remodeling force of less than 150 grams. In general, see the patient

every 8 weeks and reactivate the amount of distal ends cut.

21. Why do we not activate KH loops by cinchback activation to retract incisors? Excess force,

molars advance. (case 732)

The Keyhole loop delivers MORE force per 1mm activation at the vertical legs since there is

less wire in the loop (less flexible). The upper molars then tend to move forward as the forces are

now in the “optimal” tooth movement range for both the anterior and posterior segment. In the

example below, the space 2-3 was closed, but the cuspid moved forward from class I to class II

2mm.

In the clinical setting, it is also confusing to have some KH loops activated and others only used

for attachment of coils and elastics. Therefore, we do NOT activate KH loops as a closing loop. If

you want a closing loop, then use a machine made T that you know the forces with known

treatment responses.

22. What happens AFTER all the [extraction] space is closed and zygoma coils remain attached to

the archwire loop.

The entire upper arch may distalize, depending on the force applied (150 grams per side will do

this) and the resistance of the palatal cortical bone and posterior crowding. If the incisors

cannot retract, or retract more slowly, the VERTICAL vector will become more evident and the

incisors will INTRUDE.

In line of force planning, it is common to get a treatment response from zygoma coils with

more intrusion than expected from the actual line of force due to resistance to the horizontal

force.

23. Explain why the line of force should be calculated from the alignment vto and how to do that.

The retraction with zygoma supported coils does NOT START until the teeth are aligned and a

19x25ss rectangular archwire is in place. In cases with significant anterior crowding, this

starting point for the incisors can be a much more forward position.

In cases with anterior crowding, you may want to make a copy of the alignment vto to record

the starting point of the incisor retraction (leave the ‘final’ incisor) and then move the “start’

incisors to the estimated final positions on the “ceph vto”. THEN turn on the grid to determine

how many millimeters of incisor retraction and intrusion are needed.

In the example below, the starting incisor position (white arrow) advanced during the

alignment to the red tooth on your right. The ‘starting’ incisor (green) is moved back to fit the

lower incisor. The distance the upper incisor needs to be retracted is from the more forward

‘aligned’ position, not the starting position.

24. Explain why the upper incisor should be at the retraction limit before the [upper lingual]

corticotomy is done.

If the upper incisor is more proclined than the retraction limit, then the forces applied by the T

loop or coils will TIP the incisor instead of moving the incisor at the same inclination (bodily

movement). The corticotomy is not needed for tooth tipping, only for bodily movement. During

the time it takes to get the incisor to the retraction limit, where bodily movement starts, the

cortical bone cut has healed, the procedure is ineffective.

25. What is tooth movement like after the corticotomy heals? How long do you have for

corticotomy assisted incisor retraction?

I Learned from doing overlays on hundreds of corticotomy cases, the tooth movement changes

to near what it would be without corticotomy after 3 months of healing, possibly extended with

a more consistent skeletal anchorage supported coil force…4-5months maximum.

Without a corticotomy, the incisors

a) tip back (detorque), even beyond the retraction limit due to archwire (loop) flexibility,

rotating around the intersection of the cortical bone and the root.

b) Extrude, [ increasing deep bite]

c) Generally do not retract.

26. What happens when deep bite is predicted on the dental vto and no skeletal anchorage is

used to control the vertical?

a) The Mandible swings open to clear the incisor collision, increasing class II and less chin

b) The posterior teeth finish in class II dental with no anterior overjet

c) The patient may experience TMD symptoms from the mandible being forced back

d) Posterior open bite as the incisors collide, with significant finishing wire bends and vertical

elastics to get the teeth [back] together.

e) Difficulty in closing spaces on the upper incisors as the collision with the lower incisors and

brackets push the upper incisors forward.

27. What happens if there is an incisor collision (deep bite) during retraction (space 2-3) and the

patient is skeletal closed bite? Is that different than skeletal open?

Mandible cannot swing open, since the muscles of mastication are tight, so the mandible is

forced back, and/or the upper incisors cannot retract, the [2-3] space does not close. Eventually

the upper molars must move forward to close the space.

In skeletal open, the mandible swings open, making edge-to-edge incisors and posterior open

bite in the bicuspids.

28. Explain why Ron Roth did not have lingual inclined cuspids like we see when using a Roth type

cuspid torque.

Ron Roth Used 21x25 instead of 19x25. Just like the incisors, there is a round wire range and

limits (retraction and advancing) where the archwire engages the sides of the bracket slot. The

“retraction” limit would be the limit of LINGUAL crown inclination. The advancing limit would be

where the crown tips to the buccal. 19x25 and 21x25 have a different retraction limit. Just like

on the upper incisors, the Li bracket torque compensates for the difference in the archwire “wire

spin”. Roth 21x25 = Li 19x25.

29. How can an expanded archwire cause slow cuspid retraction in 2-step mechanics.

The root is forced into the buccal cortical bone, creating anterior cortical anchorage. If the

molar cannot move forward, then the cuspid is slow to retract.

30. Explain how an archwire stop during cuspid retraction can give you the false impression that

the cuspids are retracting.

If molars move forward, then the incisors move forward with the stop on the archwire (the

stop connects the molars to the incisors when the molars move forward). This creates a space 2-

3, but it is NOT due to cuspid retraction, instead it is from incisor advancement. The molars are

moving forward to close the 4 space and now you have an “extraction” space from 2-3, the

incisors round tripping to finish at the start position.

In the example below, how do you know if the space 2-3 was not created by the incisors

moving forward, away from the cuspid OR the cuspid moving back away from the incisors?

Same with the bicuspid, how do you know that the bicuspids did not move forward to meet the

cuspid OR the cuspid moved back into the first bicuspid extraction space to meet the bicuspid. I

know, you will say the occlusion will tell you…looking at the change from class II to class I cuspid.

Yes, that is true, assuming the lower molars are not also moving forward!

31. What is the usual problem when molars become “hypermobile” and what do you do about it?

The problem is too much force on the hypermobile tooth (teeth). This can be from the opposing

occlusion (traumatic occlusion) or from the application of headgear or elastics. The VERTICAL

force is usually the problem, seen when you use more than one class II elastic to a lower molar,

or when a bracket is bonded too gingival.

The action to take includes:

1. Evaluate bracket position and change as needed

2. Discontinue the [elastic] force and give the tooth a rest, reevaluate the forces applied to the

tooth(reduce the force) and try to distribute to other teeth in the arch

3. Remove the band or step down the archwire to remove the tooth from occlusion with the

opposing teeth.

32. What is the usual problem when ALL the teeth become hypermobile during fixed orthodontic

treatment and what do you do about it?

It is fortunately very rare to have ALL the teeth “hyper” mobile (“2” mobility or more), but I have

had this 1-2x before. The problem here is the general tight muscles putting too much force on

the teeth that are now undergoing changes in the supporting bone through orthodontics. There

may be bruxing or clenching of the teeth.

Action to take includes:

1. Document the mobilities and hopefully you had documentation at the start (adult patient)

2. Take a full mouth x-ray survey to evaluate the bone surrounding the teeth and to establish a

good baseline to monitor for bone loss.

3. Lighten the forces on the teeth through the archwires and elastics/coils.

4. See the patient more frequently (1x per month) to monitor changes, taking a new set of x-

rays every 3-4 months to confirm the bone is holding up under the stress

5. Make a soft night guard over the top of the brackets to be worn at night or when

clenching/bruxing happens

6. Possibly discontinue treatment early as the teeth are not tolerating the orthodontic

treatment

7. Do not ignore the problem, as this is where you can get into trouble.

33. What can the problems be if a cuspid does not retract [on one side] and what should you do

about it? What are the chances of a cuspid being ankylosed?

The chances are very low that the cuspid is ankylosed. The things to check are,

a) If there is a ‘kink’ in the archwire preventing the tooth from sliding along the archwire

(change to a new straight archwire)

b) If the force is too much or too little (get a new nitie closed coil, stop using elastics)

c) If the cortical bone is interfering at the root or a constricted extraction space (if an expanded

archwire, change to an archwire to maintain, if the root is into the buccal cortical bone, then

change to Li torque).

d) If the opposing occlusion is preventing the tooth from retracting (grind the occlusion or even

remove the [lower] bracket temporarily)

e) If the tongue is protruding into the extraction space, blocking the path of the cuspid

retraction (bond cleats to the lingual on either side of the extraction space)

f) If nothing works, then make a sectional T loop (6-3) to retract the cuspid by cinchback

activation, removing friction. But a T looped archwire in half, then contour as needed,

bending the archwire ‘in’ mesial to the cuspid or bend it ‘up’ mesial to the cuspid so it will

not slide through the bracket slot. Add gable bend 10 degrees distal to the loop to counter

tipping, insert the sectional archwire and cinchback with NO MORE than 1mm activation at

the vertical legs. Reactivate in 4-6 weeks.

Growth Prediction

34. What does selecting the dental vto from dentalcad do for us when making a growth

prediction?

This Eliminates the need to incorporate model measuring and the lateral ceph since the VTO

incorporates both of these. Growth and growth management can be easily “added” to any

treatment represented in the dentalcad list of VTO predictions.

35. Explain the differences in dentalcad manipulations when using the estimated system versus

the individual system of growth prediction.

In the estimated system, we make a ‘growth adjusted ceph” to reference all the possible

treatments to. This accounts for DHG only.

In the individual system, where the molars and jaws are all predicted, in addition to DHG, the

growth adjustment is made in Growth management software to make the final line drawing

dental vto.

36. Explain how changing the years of treatment, ending at T2, can influence your treatment

decision.

The more years you select, the more DHG, the more molar movements, and the more growth

management manipulations are possible, increasing the chances of obtaining a non-extraction

treatment decision and/or the best dentofacial treatment decision.

37. Describe why we still need the concepts of over-estimation and under-estimation in the

individual growth system, and how these are applied.

Even though the individual growth prediction system should be more accurate than an

estimated system, it will never completely tell the future! It is still possible to under-estimate or

over-estimate the movements of jaws and teeth.

In class II cases, if DHG is over-estimated, then mechanics must make up the difference, and

the case is more difficult than expected. If under-estimated, then the case is easier than

expected with less ‘mechanics’ needed to get to the full correction.

In class III cases, if DHG is over-estimated, this is good and the case is easier. If under-

estimated, this can be catastrophic as the case becomes much more difficult and possibly a

surgery case.

In the individual system, the molars, incisors, and jaws are all predicted and moving. Each

‘moving part’ will have the possibility of under-estimation or over-estimation. This can influence

the NET anchorage planning and the effectiveness of any growth management techniques

applied.

38. What does it mean to say that growth management is cumulative?

There are 4 elements or possible moving parts that can be manipulated with growth

management techniques and appliances. The total manipulation of the four, working towards

the eventual final treatment objective, are added together. In the example below for a class III

case, the enhancement of the maxilla and upper teeth, plus stopping the lower teeth and bone

from moving forward is all cumulative to correct the class III. If each is 1mm, then the total

growth management effect is +3mm.

39. Discuss what the percentile grower means in a growth prediction of class II cases

This is the ‘ranking’ of the patient within the total population studied in the growth sample. A

low percentile grower (eg. 10%) would expect to have the smallest DHG, a high percentile would

expect to have the most DHG in the population. Like being the tallest or smallest at a school.

40. Discuss what the percentile grower means in a growth prediction of class III cases

If the characteristics of the patient are pointing towards a high percentile grower, then this

type of patient may be more likely to need orthognathic surgery than a low percentile grower.

41. How do you determine if a class III case is a surgical case or an orthopedic-orthodontic case?

Determine from the prediction what the TOTAL mandibular length after growth will be and

determine if that is “excessive”. The large mandible would be the most common request for

surgery. Next, determine the total maxillary length after growth, which represents midface

deficiency. There can be a normal size mandible, but if the midface is VERY deficient, then the

lower face will ‘look’ too protrusive.

42. How does the growth management differ between a class III surgical case and a class III

orthopedic-orthodontic case?

In an orthopedic-orthodontic case, the correction of the dental occlusion to class I is

important, at the same time building out the midface for the best facial appearance (RHG and or

bone-anchored maxillary protraction).

In the surgical approach, no attempt should be made to correct the class III dental, as this will

be important to obtain the largest change at surgery, getting rid of the “class III look”. Efforts

can be helpful to

a) Build out the midface with RHG and bone anchored maxillary protraction

b) Establish the upper incisor at the Roth ideal inclination

c) Expand the maxilla with Rapid palatal expansion

d) Establish the lower incisor inclination at the Roth ideal…this will probably not be done until

the year before surgery as this is where the lower lip will look protruded and the anterior

crossbite will look the worse. Leave the retroclined lower incisor for now.

43. How can the POS Growth Management software help you determine if there is expected “late

growth” remaining in a teenage class III case.

CVM ‘growth’ ends at stage 5, and Wrist x-ray growth can be classified to stage 6 (McGann).

The growth study gathered untreated data to stage 6 in most cases, so you can input T1 as stage

4 or 5 and end after stage 6 to check for predicted late growth. This will add ‘magnitude’ and

percentile grower to the diagnosis.

44. Describe what is represented and what is important in the first individual growth prediction,

Alignment vto + untreated growth, using POS Growth management software.

This prediction will establish what “structures and teeth” are moving and what can be

potentially “managed” to treat the case [non extraction] and/or to obtain the best facial

esthetics. This prediction also sets the baseline for what moves without adding appliances (CHG

or RHG or zygoma ligation, etc.)

45. Describe how to make a growth management prediction to include cervical headgear in a class

II case. What changes can you expect for a patient who wears CHG?

In the drop-down box in class II cases (ONLY), cervical headgear is a possible selection for a

growth calculation. If you factor this into the selected [dentalcad] alignment vto, then this

prediction will show the what is expected to happen if the patient wears the headgear. This can

be compared to the alignment+untreated prediction to see if it is worth the effort to add this

appliance to the treatment plan.

Be looking for changes in Maxillary drift and upper molar drift. If there is a change in Maxillary

drift, you may also notice an increase in DHG.

46. Describe how to make a growth management prediction to include Reverse headgear in a

class III case. What changes can you expect for a patient who wears RHG?

Select the alignment vto from dentalcad, then select from the growth management drop

down box “reverse headgear”. From the growth sub-study of patients that were confirmed RHG

wearers during their treatment, the calculations will add the significant difference compared to

untreated. Then look at the maxillary drift and upper molar drift increases, if any, compared to

the previous alignment+untreated prediction.

** although not on the prediction line drawing, the nose may get larger the amount of the

added maxillary forward movement (drift), as a midface effect.

47. Describe how to make a growth management prediction to include Zygoma ligation in a class II

case.

Select the alignment vto from dentalcad, then select from the growth management drop

down box “zygoma ligation”. The upper molar drift should stop, showing you the relation with

the lower molar which has moved forward by mandibular enlargement and lower molar drift.

You may want to increase the years of treatment and see what this does to the prediction,

utilizing a longer period of growth over more growth stages.

48. Explain how to add growth to a bicuspid extraction dental vto.

First make an alignment/untreated growth prediction to determine where the structures are

moving and the magnitude of DHG and molar movements. Save that project then start a new

project, selecting the extraction vto, without added growth, from dentalcad (there should be

some anterior overjet to be corrected). Make a “braces” growth prediction to confirm that this

is the anchorage planning (by the dots) you want.

If the picture does not look the way you want with the added growth, go back to dentalcad

adjust the upper and lower molar anchorage and repeat to get the final treatment decision

picture you want. The model measuring that was used to create that picture, will show you

how to close the extraction space.

49. Discuss why it would be important to know if there is predicted DHG after time T2, the end of

active orthodontic treatment.

The final [class I] Bite could be disturbed and/or the incisors recrowd due to a collision of the

incisors. With that information, you may want to extend the treatment time for better

stability.

Growth management

50. How can a lower lingual arch (LLA) work against growth management of a class II case.

The lower lingual arch can reduce the mesial migration of the lower molar, which assists in

correcting the class II molar relation to class I. Lower lingual arches should ONLY be used to

change an otherwise extraction lower arch (too much advancement) into a non extraction

arch.

**it should be noted that the lower lingual arch can move with the entire lower arch forward

drift. (see below)

51. What is the difference between using a LLA and lower molar ligation in the growth

management of a growing class III case

A lower lingual arch will maintain the space between 6-incisors, BUT the entire 6-6 dental arch

with the lower lingual arch can drift forward RELATIVE to the mandible (below)

With lower molar ligation, the molar is attached to the mandible, so the molar canNOT drift

forward RELATIVE to the mandible. The lower 3-4-5s naturally drift lingual unless pushed

forward by the molar. This makes lower molar ligation the preferred growth management

method.

52. What does the term “bone anchored maxillary protraction” refer to and when is this

considered in growth management?

This is a term created in articles published in 2011 and 2012 referring to skeletal anchorage

being secured to the zygoma and mandible to support a class III elastic force of 100 grams

initially to 250 grams after 3 months. The results have been a forward movement of the

midface, including cheekbones and the nose, which is not possible with surgical advancement

of the maxilla.

This “added” force application, directly to the maxilla instead of to the upper molars, is

considered to be beneficial in nearly all class III cases to build out the midface, reducing the

apparent prominence of the lower face.

In the McGann modification, an elastic is directed to the existing RHG from a zygoma bone

plate. This is in addition to the elastic from the molar to the bone facemask. When the

facemask is NOT being worn, then the class III elastic is added from the bone plate to the

lower dental arch, assuming there are brackets available to support the elastic.

The bone plate immediately above is an 8 hole plate with the last hole ‘cut’ to make a hook.

The “Bollard” plates used for protraction headgear have a very high materials cost ($800) plus

the surgery.

53. Why would the extraction of upper 6s be beneficial to the growth management of a class II

case?

IF one of the signals for the upper teeth to DRIFT forward comes from the lower teeth, then

the first molar and incisor coupling are obvious sources of interdigitation that could provide

such a signal, especially when eating. [note: the primary molars have “flat” occlusal planes

and thus are not good sources for inclined planes distributing forces]. Extracting the upper 6s

removes this interdigitation, allowing for DHG of the jaws without the upper teeth following

the lower.

54. What can we gain by zygoma ligation to the upper anterior teeth during a period of growth?

Stop upper molar and incisor movement forward, RELATIVE to the maxilla [in a class II case],

correcting class II dental. If the ligation is to the upper anterior teeth, this ligation can also

reduce the anterior vertical drift (down) of the incisors. The face including the lips, continue to

grow down but the upper incisors are not allowed to extrude, reducing excess vertical. If the

incisors never extrude (vertical maxillary excess), then there is no reason later to use piriform

rim coils to intrude them.

55. If you do NOT want to use brackets on the upper anterior teeth to support zygoma ligation,

(eg. Poor hygiene), then what choice do you have to ‘growth manage’ the upper molar from

moving forward?

17x25ss tie back to zygoma. Use the “pig” triple tube variation on the molar.

56. What can we gain by zygoma ligation to the upper molars during a period of growth?

Stopping the vertical drift of the upper molars, closing dental open bite and autorotation of

the mandible for a bigger chin. This works best when done along with lower molar ligation (for

vertical) to prevent the lower from extruding more to meet the upper. It is a good idea to

include a TPA from the molars to prevent the palatal cusps from dropping even though the

buccal of the molars are held ‘up’.

57. What are the negative growth management features of a lower utility arch in class II cases?

Tipping back the lower molars is working against correction of the class II molars. This

should be done only if the molar tipback is needed to change the lower arch from an extraction

arch to a non extraction arch.

58. What positive growth management features are there in lower utility arches in class II cases?

Uncoupling the incisors, allowing for the extra growth of the mandible to move the lower

teeth forward withOUT the upper teeth following.

59. Explain how clockwise rotation of the mandible from orthodontic mechanics can ‘kill’ the

advantages of DHG in a class II case.

When there is clockwise rotation of the mandible (occlusal plane), the Mandibular

enlargement is directed to the floor, vertically, instead of horizontally, so there is no correction

of the dental class II. Counterclockwise rotation is normal without treatment and favorable for

DHG.

**special note: this was the concept of the first significant predictor of DHG, the McGann

Angle (between the line for mandibular length and maxillary length). If the McGann angle is

zero (in theory since this is impossible in real life) then the DHG is the maximum as every

millimeter the mandible grows larger than the maxilla, there is 1mm of DHG. On the other

side of this theory, if the McGann angle is 90 degrees, then mandibular enlargement is not

contributing at all to DHG and the value will be negative as the maxilla moves forward but the

mandible does not.

60. Describe how to modify the dental VTO for auto-rotation of the mandible in an open bite case.

Intrude the upper molars, grid and screenshot to document how many millimeters of

intrusion is planned (coil length, reactivation, and palatal bar location from the palate)

Next, move the lower incisors and molars to fit with the upper teeth

Next, move the mandible and symphysis to the incisors,

For the autorotation, hold down the shift key and rotate the mandible “end point” back to

the original condylar head position. You will notice there is more chin.

Adjust the soft tissue.

61. How can you know if there is bone covering the roots after “bone remodeling” or not?

A CBCT 3D scan can look under the tissue at the bone covering the roots, BUT this method is

not very accurage for thin (less than 1/2mm) bone covering roots. Thin bone is not “seen” on

the scans. The other choice is an exploratory flap, enabling you to look visually at the presence

or absence of bone covering the roots.

**McGann did 3 of these and then determined that that was enough.

Practice management:

62. Give reasons why you should quote phase I+II total case fee at the start of a 7 year case versus

the reasons for quoting only a phase I fee, phase II to be determined later.

a) Quoting a total fee allows for the Parents can plan,

b) less Doctor time is spent at consultations in the transition from phase I to phase II, as the

financial arrangement has already been agreed to at the start of the case.

c) The payments are ‘cheaper’ payments if the treatment is longer, becoming more affordable

for the parents

d) no surprises, no second opinions.

63. Explain how to manage the patient/parent if a tooth needs endodontic treatment during

active treatment.

Hopefully you have documentation that the tooth was ‘dead’ before treatment started,

proving that the brackets did not cause the need for endodontic treatment! If not, then discuss

possible trauma and fractures to the tooth in the history prior to the start of treatment. If that

is negative, then the patient may think you caused the problem and therefore is not feeling

obligated to pay for the treatment. You may need to do the treatment complimentary!

64. Explain how to manage the patient when decalcification is noted upon deband.

Hopefully you have documentation of hygiene deficiencies in your charting, and best would

be documentation of the parent being informed either verbally or in writing of the lack of care

during orthodontic treatment. Photographs can also be used to show the plaque, but this

could also backfire on you as they then ask why you did not make efforts to remove it or tell

the parent this was happening. Informed consent of course has this risk listed, and that the

patient is responsible, but who reads the fine print, right? Practically, this is a difficult

situation, especially when there is a lot of restorative work to repair the damage.