Seminar- Tooth Prep CLass II Amal

7/31/2019 Seminar- Tooth Prep CLass II Amal

1/44

CLASS II CAVITY PREPARATION FORSILVER AMALGAM


2/44


3/44

PRINCIPLES OF CAVITY

PREPARATIONS OF CLASS II INTIAL TOOTH PREPARATION

1.OUTLINE FORM AND INITIAL DEPTH

2.PRIMARY RESISTANCE FORM3.PRIMARY RETENTION FORM

4.CONVINIENCE FORM

FINAL TOOTH PREPARATION

1.REMOAL OF ANY REMANING ENAMEL OR DENTIN.2.PULP PROTECTION

3.SECONDARY RESISTANCE AND RETENTION FORM

4. PROCEDURE FOR FINNSHNG THE ENAMEL WALLS


4/44

DEFINATION :AS PLACING THE PREPARATORY MARGINS IN

POSITONS THAT THEY WILL OCCUPY IN FINAL PREPARATION

EXCEPT FOR FINISHING ENAMEL WALLS AND MARGINS.

1. OUTLINE FORM

a)SIZE OF CARIES CONE IN ENAMEL TO THAT IN DENTIN,AND THEIR

RELATIVE SIZE TO THAT OF UNCLEANSABLE PROXIMAL AREA.

i)Forward decay: in which the caries cone is less than the sizeof the proximal uncleasable area.

ii)Bacward decay: in which caries cone in dentin is less than

The proximal uncleansable area.

FACTORS


5/44

iii)BACKWARD DECAY: in which the caries cone in dentin exceedsthe size of both enamel and uncleansable area.

B)EXTENSION FOR CONVENIENCE OR ACESS:in molars and premolars with proximal lesions, the occlusal surface or part of it

Should be included in cavity preparation for access purpose.

C)LOCATION AND CONDITION OF GINGIVA:the most protected area of the proximal surfac is just below the gingival sulcus.

And outline of the cavity is placed 0.5mm below the contact area.


6/44

D)CONDITION OF MARGINAL RIDGE: if marginal ridge is not involved,proximal cavity

preparation and even separate proximal and occlusal cavity preparation could be madewith intact marginal ridge.

E)CONVEXITY OF THE PROXIMAL SURFACES: the more convex the surfaces the widerthe embrasures. Less will be the required extention of the cavity preparation outline.

F)LOCATION AND EXTENT OF THE CONTACT AREAS AND THEIR RELATION TOTHE MARGINAL RIDES,EMBRASURES AND GINGIVA:

is the relation between contact area,marginal ridge,embrasures and gingiva.

G)MODIFY FACTORS INFLUENCING OUTLINE FORM:

i)masticatory load ii)plaque index iii)cariogenic factors

iv)esthetics v)tooth position


7/44

2.RESISTANCE FORM DEFINATION: AS THE SHAPE AND PLACEMENT OF THE

PREPARATION WALLS THAT BEST ENABLE THERESTORATION AND TOOTH TO WITHSTAND ,WITHOUTFRACTURE ,MASTICATORY FORCES PRINCIPALLY IN THE

LONG AXIS OF THE TOOTH.

A) OCCLUSAL LOADING AND ITS EFFECTS: during centric and excursivemovements of the mandible, both the restoration and tooth structure areperiodically loaded separately and jointly.

the loading situation and their stress patterns are in following patterns.i)a small cusp contacts the fossa away from thethe restored proximal surfaces,in proximo-occlusalrestoration at centric closure.


8/44

ii)A large cusp contacts contacts the fossa adjacent to theRestored proximal surface.

iii)The occluding cuspal elements contact facial and lingualtooth structure .

iv)Cuspal elements occlude or disclude via facial or lingualgroove of restoration.


9/44

DESIGN FEATURES FOR THE PROTECTION OF THE MECHANICALINTEGRITY OF THE RESTORATION:

i) ISTHMUS: is the junction between the occlusal part of a restorationand the proximal,facial,lingual parts.

mechanical and photoelastic analyses of stress occuring due to loadingrevels three things.

a) the fulcrum of bending occurs at the axio-pulpalline angles.

b) stress increase closer to the surface of arestoration,away from the fulcrum.

c) tensile stresses predominate at marginal ridgearea of proximo-occlusal restoration.


10/44

-A theoretical solution might be to increase amalgambulk at the axio-pulpalLine angles.placing the stresseaway from the fulcrum.

-bring the axio-pulpal line angles closure to the surface

-combination of both ie increasing the amalgambulk near the marginal ridge ,while bringing theaxio-pulpul bulk near the marginal ridge.


11/44

ii) MARGINS: four designs features should be observed.

a)butt-joint amalgam tooth structure.

b)leave no frail enamel at the cavo surface margins.

c)remove flashes of amalgam on tooth surface adjecent to amalgam margins.

d)tooth structure should not be at an occcluding contact area

either with opposing teeth either in centric or excurssive mand.

movements.

iii) CUSPS AND AXIAL LINE ANGLES:

a)amalgam bulk should be 1.5mm in all three dimensions.

b)each portion of restoration should be immobilized by retentive

modes.


12/44

C) amalgam should be seated on a flat floor.

Box shape cavity will provide flat pulpal floor. a)that will prevent restoration movements ,where as rounded

floor b)is conconductive to restoration rocking action providedby wedging force,resulting in splitting of the tooth.


13/44

3.RETENTION FORDEFINATION:IS THE SHAPE OR FORM OF CONVENTIONAL

PREPARATION THAT RESIST DISPLACEMENT OR REMOVAL

OF RESTORATION BY TIPPING OR LIFFTING MOVEMENTS.

A)PROXIMAL DISPLACEMENT OF ENTIRE RESTORATION: in this pic. The obliquely applied force vertical component V and horizontal

componenent H will try to seat the restoration .but H will tend to rotate therestoration proximally across axis X.

B)PROXIMAL DISPLACEMENT OF PROXIMAL PORTION: C)LATERAL ROTATION OF RESTORATION AROUND (PULPAL AND GINGIVAL) FLOORS: D)OCCLLUSAL DISPLACEMENTS:


14/44

4.CONVINENCE FORM IS THE SHAPE OF PREPAPRATION THAT

PROVIDES ADEQUATE

OBSERVATION,ACCESSIBILITY AND EASE OFOPERATIVE PROCEDURES.


15/44

SECONDARY RESISTANCE AND RETENTION FORM:

After any remaning pit ,fissure, infected dentin or old restoration isremoved. pulp protection has been applied additional resistance and

retention features are necessary for preparation. The sec. resistance and retention form are of two types.

a)mechanical preparatory features

b)treatment of preparation walls with etching, priming and adhessivematerial.

A)mechanical features: i)retentive locks, grooves,coves

ii)slots

iii)boxes

in final tooth preparation involves resistance of remaning

tooth structure against fracture from oblique forces andrestoration of restorative material against fracture..


16/44

Grooves for secondary retention may be placedhorizontally or vertically.

Horizontally placed grooves may be SLOTS or Coves

Vertically placed grooves may be LOCKS (in case of directrestoration) and retentive GROOVES (in case of indirectrestoration).


17/44

BOX-ARE OF TWO TYPES:

i)Internal box:prepared in dentin with four vertical

surrounding wallsJoining a floor with definate line and point angle&their min.

size is 2mm.

ii)external box: these are box shaped prepations opening to

the axial tooth surface with three, four or five surroundingwalls and floor.

They can be proximal , facial or lingual.


18/44

I)RETENTIVE LOCKS

i)Position : refers to axio-facial and axio-lingual line angles of initialtooth preparation.(0.2 axial to DEJ)

Retetive locks should be placed 0.2 inside DEJ.

ii)translation: to the direction of movement of the bur.

iii)depth: refers to the extent of translation (ie 0.5mm into gingivalfloor)

Iv)occluso-gingival orientation: tilt of bur which dictates occlusalheight of locks.


19/44

FOUR CHARACTERISTICS OF RETENTIVE LOCKS

a)Occlusal view of MO prepara-

Tion before placement of retent-Ive locks.b)Proximal view of MO prepara-Tion

c) And d) position,translation &Depth.

e) &f) occluso gingivalOriantation.


20/44

II)RETENTIVE GROOVES

Are horizontally () as well as vertically placed.

.is made with a no.1/4 burs are prepared intoOcclusoaxial and gingivoaxial line angles

(0.2mm) inside the DEJ or 0.3-0.5mmInside the cemento_enamel cavosurface margins.

.the depth of these grooves is one half the diameter of bur head.Ideally the direction of occlusal groove is slightly more occlusal than axial

And the direction of an gingival groove would be more gingival than axial.


21/44

III)COVES:

Are vertically placed retentive feature.

Class III cavity

Is given when less retention is needed.

Similar shape to that of groove except is smaller in length. Placed more inscisally.

Depth is 0.25 -0.3mm


22/44

IV)SLOTS:

Given in older patients with gingival

ression.exposing cementum.

Root surface caries. Gingival depth(0.75-1mm) if noenamel is present

And(1 -1.25mm) ifmargin is in enamel.

If occlusal margin is in enamel the axial depth is 0.5mm inside DEJ.

External walls should form 9o-degree cavosurace angle.

The lingual walls should face facially to aid in condensation ofamalgam.

Retentive groove prepared into occluso-axial and ogingivoaxail lineangles0.2mm into DEJ or 0.3 to0.5mm inside cemental cavosurfacemargin.


23/44

DESIGNS OF CAVITY PREPARATION CLASS II DESIGN I:

INVOLVEMENT:proximal and occlusal surfaces.

INDICATIONS: a)moderate large size lesions with similar sized

occlusal lesions. b) undermined marginal ridge.

C)caries cone necessitate cavity width of the inter cuspal distance.

GENERAL SHAPE:

occlusally-similar to class 1, design 1 or 2.dove tail only on one side.

Proximally-inverted trancated cone.

LOCATION OF MARGINS:

Occlusal portion-similar to class1,design 1 or 2

Proximal portion-f &l margins are placed in


24/44

in corresponding embrasures.

-tip of explorer should pass freely.

gingival portion:

gingivally margins are located in occlusal portion of the gingival sulcus.isthmus portion: f & l margins at isthmus are located on the inclinedplanes of corresponding cusps and remaning portion of marginal ridge.

INTERNAL ANATOMY:

Occlusally: similar to class 1, design 1 or 2.

Proximally:m-d section:

-if gingival margin is located on cementum it should be scraped fromCavosurface.-gingival floor is flat.


25/44

Gingival margin is located in gingival third of proximalsurface,the gingival floor will be 2-planed. Inner dentinalplane at rt angle to long

Axis of the tooth and outer enamelo-dentinal planefllowing the direction of enamel rods.

If gingival margin is located at middle 3rd in young&incompletly errupted teeth 1 plane

Retention locks (st at the AF &AL line angles of isthmus).


26/44

CLASS II,DESIGN II (MODERN DESIGN) Involvement:

proximal and occlusal surfaces.

Indications:

a)moderate- small sized proximal lesions

b)occlusal lesions not exceding the width of th of inter cuspal

distance. General shape:

Occlusal portion: similar to class 1 design 1 &sometimes little dove tail.

Proximal portion:

Unilateral inverted truncated cone In upper teeth lingual inverted truncated cone only.


27/44

In lower teeth buccal inverted truncated cone only.

This feature is done on the functional cusp only. Location of margins:

Occlusal portion:

Similar to class 1 design 1

Proximal portion:

Gingival margins may be located anywhere on proximal surface.

Isthmus:

F & l margins are separated by not more than 1/4th of inter cuspaldistance.

Reverse cure- (sweeping curves of the facial &lingual marginsocclusally will reverse in isthmus to include contact area.


28/44

Internal anatomy:

Occlusal portion:similar to class 1 design 1

Proximal portion:

M-d cross section:

Similar to conventional design

All line angles rounded with exception of gingivo-axial line angle keptsharp to stabilize the restoration.

Preparation modification:

In tapered teeth(bell shaped) in which facial and lingual retentivegrooves are placed.


29/44

CLASSII, DESIGN III (CONCERVATIVE DESIGN) Involvement:

primarily proximal ,very little occlusal not beyond triangular fossa.

Indication: a)decay in proximal surface only & occlusally sound.

Restoration subjected to minimal loading.

General shape:

Inverted truncated cone located proximally. The tip involves involves part of adj. occlusal triangular fossa.


30/44

Location of margins:

Occlusally:

Occlusal inclined plane of the involved marginal ridge.

F & l margins are very limited.

Proximally:

Similar to modern design.

internal anatomy:

M-d cross section- i)Gingival floor: if in gingival 3rd- 3 planes(inner dentinal, transitional,

outer enamelo-dentintinal plane)

ii)in middle 3rd-2 planes(inner dentinal &st plane)

F-l ross section-shows axial walls to be convex.


31/44

CLASS II, DESIGN IV(SIMPLE DESIGN):

Involvement:proximally only.

Indications:

a) decay restricted to contact area b)diastema or adj.tooth is missing

c)affected tooth is rotated or inclined

General shape:

No specific design.

Assumes a trapizoidal/rhomboidal shape.


32/44


If there is no proximally contacting tooth (diastema)there is nolocation of margins

If gingival margin is apical to contact area the occlusal and & gingivalmargins will be in gingival embrasures..

Facial and lingual margins in facial and lingual embrasures.

Occlusal and gingival margins in occlusal and gingival embrasures.

Internal anatomy: Facial - lingual cross section-axial wall is flat to slightly

convex .


33/44

CLASSII, DESIGN V

Involvement:part of proximal surface with very little acess on facial and lingual

surfaces.

Indications: two shapes

Shape A-

Facial and lingual access will not have dove tail.a)small-medium sized proximal lesion.

b)Marginal ridge intact

c)Does not involve contact area

d)Gingival embrasures not accessiblee)Will have four well formed walls with retentive grooves on their

opposing sides.


34/44

Shape b

Facial and lingual acess will have locking feature in form of dovetail,unilaterally cut in occlusal direction.

a)med-large size proximal lesions

B)cavity will not have four walls.

General shape:

.no specific shape

May apper trapizoidal/elliptical Facial and lingual part will be if shape-a (box or rectangular shape-b

(one sided dove tail)


35/44


Gingival margins in gingival embrasures.

Occlusal margins in occlusal embrasures just apical tocontact area.

Facial and ingual in corresponding embrasures.


36/44

CLASS II,DESIGN VI

Involvement: occlusal,proximal and part of the facial and lingualsurfaces.

Indications: a) cusp length is double or more in width.

b)cusp is missing or undermined.

c)badly broken down tooth.

General shape:

occlusal and proximal parts similar to design 1 or 2

facial and lingual part rectangular in outline.


37/44


Occlusal and proximal similar to design 1 or 2

Facial and lingual portions in areas at or occlusal to the height of con

tour of facial and lingual surfaces. Donot place margins in grooves

If margins comees near groove include in cavity preparation.

In areas apical to the height of contour facial and lingual surfaces.withpartial mesio distal replacement of a cusp, the margins should not

end at the cusp tip .it should be located mesial or distal to it.if marginscome near the groove involve the groove in cavity .


38/44

internal anatomy:

Occlusal and proximal similar to design 1 or 2.

Rules to prepare a cusp:

i)Cusp to be replaced or reduced by 1.5-2.0 mm from opposing cuspalelements more on fuctional cusp.

ii)Cusp cut flat in form of table which is right angle to the cavo surfacemargins.

iii)in multiple junction rounded.


39/44

CLASS II, DESIGN VII

Involvement: shape -A

Shape-a: junction between the class 2 and class 5 via proximal crossing

the axial angles.General shape:

Occlusal portion similar to design 1.

Proximo-facial and proximo lingual portion if unilateral will be L-SHAPED.

If bilateral will be T-SHAPED .shape B: junction between the class II and classV

is through the occlusal via the buccal and lingual

grooves.


40/44

General shape:

occlusal and proximal portions similar to design 1 or 2.

Facial and lingual portions have inverted T-SHAPE


41/44

CLASS II ,DESIGN VIII

Involvement:two or more surfaces of endodontically treted tooth thatdoes not require posterior retention.

Indications:a)a tooth has sufficient pulp chamber to accomudate retaning self

resisting amalgam bulk.

b)The post endodontic pulp chamber has two opposing intact walls.

c)Tooth contains sufficient large root canals to accomulate amagam at its

occl.1/3rdD)Foundation is neede for reinforcing restorations.

General shape: similar to design 6


42/44

Internal anatomy:

rules to arrive to the final product.

i) excavate entire pulp chamber and any residual root canal filling.

Bare the dentin exposed. ii) large root canal that can accommodate an amalgam 1.5mm should

have root canal filling removed to 3-4 mm depth.

iii) if possible square up surrounding walls.

iv)in bulky portions of surrounding walls cut flat ledges to receive

occlusal loading.


43/44

REFERENCES OPERATIVE DENTISTRY - MARZOUK

ART & SCIENCE OF OPERATIVE DENTISTRY( STURDEVANTS)


44/44

THANK YOU

Date post:	04-Apr-2018
Category:	Documents
Upload:	shakeel-ahmad
View:	239 times
Download:	0 times

Seminar- Tooth Prep CLass II Amal

Documents