Cavity Designs For Amalgam Cavity Designs For Amalgam RestorativeRestorative

ContentsContents

IntroductionHistorical reviewDefinition of Cavity and Cavity preparationObjectives of cavity preparationsFactors affecting tooth preparationNomenclature of tooth preparationCavity classificationPrinciples of tooth preparations for amalgamPhysical , Biological and Anatomical considerations of cavity preparationArmamentarium Class l, ll , lll , lV, V Cavity DesignsTooth preparation for pin amalgam and bonded amalgam Recent concept of cavity design v/s old designConclusion References

Introduction Introduction

Historical BackgroundHistorical Background

1908-G. V Black father of operative dentistry Established principles of cavity preparation Dr. Arthur – developed instruments Charles .E.Woodbury – Cavity design (class lll ) Dr. wedelsteadt -- 1868* Dr. Jonathan Taft – bulky chisels Bur drill (1/32 to !/5 inch ) Hand pieces (foot engine ) Hand pieces (air driven ultraspeed )

Brief review of class ll Design

1908 - Black ‘s cavity 1924 –Prime 1951 – Markely 1972 – Rodda 1976 – Elderton / Granger

Cavity Cavity –– Defect in enamel or in enamel and Defect in enamel or in enamel and dentin resulting from the pathological process of dentin resulting from the pathological process of dental careis dental careis ( Acc Charbeneau ( Acc Charbeneau 3 Edition)3 Edition)

Cavity preparation Mechanical alteration of a defective, injured or

diseased tooth in order to best receive the restorative material which will reestablish a healthy state for the tooth including esthetic corrections where indicated, along with normal form and function (Sturvdent 4 Edition)

Acc Gilmore

Acc Charbeneau

• Objectives of cavity preparationObjectives of cavity preparation

Factors affecting tooth preparation General factors Diagnosis Dental anatomy Patient factors Conservation of tooth structure Restorative material factors

NomenclatureNomenclature

Cavity Line angle Point angle

Class l 8 4Class 2 11 6MOD 14 8Class lll 6 3Class lV 11 6Class V 8 4

Cavosurface marginCavosurface margin

Classification of cavityClassification of cavity

G.V .Black classification (Sturvdent 4 Edition)

According Class l – pit and fissure restoration

-Restoration on occlusal surface of

premolar and molars -Restoration on occlusal two thirds of

facial and lingual surfaces of molars -Restoration on lingual surface of maxillary incisors

Class ll –Restoration on proximal surfaces of posterior teeth

Class lll - Restoration on proximal surfaces of anterior teeth that do not involve the incisal angle

Class lV -Restoration on proximal surfaces of anterior teeth that do involve the incisal angle

Class V – Restorations on the gingival third of the facial or lingual surfaces of all teeth

Class Vl – Restoration on the incisal edge of anterior teeth or the occlusal cusp heights of posterior teeth

Class Vl - cavities on both mesial and distal proximal surfaces of bicuspids and molars when restored will share a common occlusal isthmus ( Acc charbeneau )

Modification of blacks original classification Modification of blacks original classification (Markely and bronner (Markely and bronner ) )

Class llClass ll – – Cavities on single proximal surfaces of Cavities on single proximal surfaces of bicuspids and molarsbicuspids and molars

According to number of surfaces According to number of surfaces involvedinvolved

Simple Compound Complex

Simple

Compound

New cavity of classificationNew cavity of classification Site 1. Pits fissures and enamel on occlusal surface of posterior teeth or other smooth surfaces such as Cingulum pits on anteriorSite 2. Approximal enamel immediately below areas in contact with adjacent teethSite 3. The cervical one third of the crown or,following gingival recession, the exposed root.

Acc Graham J mount (1997)

The four sizes of carious lesions Size 1. Minimal involvement of dentine just

beyond treatment by remineralization alone. Size 2. Moderate involvement of dentine.

sound,. That is, the remaining tooth structure is sufficiently strong to support the restoration .

Size 3. The cavity is enlarged beyond moderate.The remaining tooth structure is weakened to the extent that cusps or incisal edges are split,

Size 4. Extensive caries with bulk loss of tooth structure has already occurred.

Site1 ,size 0 Site1 ,size 1

Site1 ,size 2

Site1 ,size 3 Site1 ,size 3

Site2 ,size 0Site1 ,size 4

Site2 ,size 2

Site2 ,size 1

Site 2,size 2

Site 3,size 0 or 1Site 2,size 3

Site ,size 4 Site 3,size 2

Site 3,size 4

Site 3,size 3

Principles of tooth preparation for amalgam

• Initial stages • Final stages

- Out line form

Cavosurface margin

Resistance form

Reverse curve

Primary retention form

•Convenience form

•Removal of infected dentin Spoon excavator Round bur

•Pulp protection

•Secondary resistance and retention form

•Final procedure

Physical , Biological and Anatomical considerations

of cavity preparation

Physical considerationsStress bearing area anterior posterior

Weak areas

Applied mechanical properties

•Biological considerations

Irritating agents of tooth preparation

•Anatomical properties

Armamentarium used for cavity preparation

Basic instruments

330 245

Burs

Class l designs

Class l, design 1Class l, design 1

Caries penetration into dentin does not exceed 0.5-1mm

Width- I/4 intercuspal distanceLow caries index

Molar outline Premolar outline

General shape

Mesio distal cross section

Pulpal floor of Lower premolar

Class l, design 2Indication ; caries cones in dentin extend 1mm or more from the DEJ

Pulpal floors have different levels

Mesiodistal cross section

Class l, design 3

Indication ; in occlusal one to two thirds of facialand lingual surfaces of molars and on lingual surfacesanterior teeth of

General shape

Internal anatomy

Class l, design 4

Applied to molars involving their occlusal surfaces,the grooved part of the facial or lingual surfaces

--Pulpal wall elevated occlusaly--Use in mandibular first molar

Class l, design 5 :Class l, design 5 : IndicationsIndications Occlusal surface, most of the facial or lingual surface

involved Occlusal surface is not conducive to retention of

restoration

Location of margins In occlusal cavity mesial and distal margins located at Corresponding axial angles

Gingival margins –gingival third of the facial or lingual Surface

Pulpal floor – internal boxes (mesial third)

Mesio distal cross section

Class l, design 6 :Class l, design 6 :Includes occlusalIncludes occlusal surfaces of molars or surfaces of molars or premolars as well as portion of facial, premolars as well as portion of facial,

proximalproximalor lingual surface in form of a table of an or lingual surface in form of a table of an

entireentirecusp or section of cusp (marginal ridges )cusp or section of cusp (marginal ridges )Gingival margin should extend to allow

Occlusal clearance of 1.5-3 mm fromOpposing teeth

Class l, Design 7Class l, Design 7

Involves occlusal , facial and lingual surfaces of molars and premolars

Pins and posts are indicated

Class l, design 8Class l, design 8 Endodontically treated tooth Pulp chamber is retention form

Out line formOut line form• Extent of caries • Extent for convenience• Location of gingiva• Convexity of proximal surface• Location and extent of contact areas

Resistance form

Occlusal loading and its effects

Small cusps

Tensile stress

Compressive stress

Large cusps

Tooth structure Facial and lingual parts of restoration

Groove of restoration

facial or lingual parts of restoration

Cusps Cusps Crossing ridgesCrossing ridges

Axial parts of restorationAxial parts of restoration

Axial wall

Design features for the protection of mechanical integrity of restoration

Reverse curveReverse curve

Class ll, Design 1Class ll, Design 1

Moderate to large size proximal Lesion with occlusal surface cavity promotes the cavity width of cavity to exceed 1/4 0f intercuspal distance

Conventional design

Indications

Proximal box

Inverted truncated shape

Tunnel preparationTunnel preparation

Class ll, Design 2 (moderate design )Class ll, Design 2 (moderate design )Indications•Moderate to small sized proximal lesions•In stress concentration area•Width not exceeding 1/4 of intercuspal distance

General shape width

Bucco lingually

Mesiodistaly

Class ll, Design 3 (conservative design )Class ll, Design 3 (conservative design )• Involves primarily proximal surface and very limited part of occlusal Surface, not extending beyond adjacent triangular fossa•Sound occlusal crossing ridges•Minimal loading areas

General shapeInternal anatomy

Gingival marginGingival margin

Middle third Gingival third

Class ll, Design 4 (Simple design )Class ll, Design 4 (Simple design )•Proximal surface only•Indications; Decay restricted to contacting or proximal surface without undermining marginal ridges Diastema or adjacent tooth is missing

Bucco-lingualCross section

Occlusal-gingival

Cross section

Class ll, Design 5Class ll, Design 5

Part of proximal surface ,with a limited access area on facial or lingual surfaceIndications :

1)Do not have dovetail2) Have dovetail

•1)Preparation will have 4 surrounding walls •small proximal lesions•Marginal ridge intact•Does not involve contact area

2) Preparation will nothave surrounding walls

•medium proximal lesion

Class ll, Design 6Class ll, Design 6The occlusal ,proximal and part of the facial or lingual surfaces

Indications ; Cusp is missing Badly broken down teeth

Cusp reductionsCusp reductions

Class ll, Design 7Class ll, Design 7

Shape A : junctions between the class ll and class V via, theProximal , crossing the axial anglesShape B : via buccal / lingual groove

Shape A Shape B

(Combinations of class ll with class V )

Class ll, Design 8Class ll, Design 8

Two or more surfaces of an endodontically treated tooth does not require post retention

Class lll Class lll Amalgam is usually not indicated for anterior teeth due to Amalgam is usually not indicated for anterior teeth due to

its esthetic , but distal surface of the cuspid is a unique its esthetic , but distal surface of the cuspid is a unique location location

General principles are similar to class ll cavity preparation but with emphasis laid on in 5 areas of preparation1 esthetic concern2 extension for access3 stress consideration enamel rod directionIncisal access

Designs of cavity preparation at the distal slope of Designs of cavity preparation at the distal slope of the cuspidthe cuspid

Indications; 1 The lesion does not involve or undermine the distal slope of cupid2 bulky walls will remain, incisally, after removal of Undermine tissues3 the labials axial angle is intact4 the restoration will be directly loaded by vertical forces

Internal anatomy ;

Axial convex Depth - .5 from DEJ

Retention points : Depth 1 to 2 mm in dentin

Class lVClass lV

Indications :•Incisal angle is undermined •Labial and lingual walls intact

Labio lingual cross section

ModificationsModifications

Class V cavityClass V cavity Involvement :smooth surfaces apical to height of contour Involvement :smooth surfaces apical to height of contour on facial and lingual surfaces of all teeth eg ; erosion, on facial and lingual surfaces of all teeth eg ; erosion,

abrasion , hypoplasia, aplasiaabrasion , hypoplasia, aplasia

Resistance and retention To minimize the effects of displacing

forces forces grooves occlusal and gingival walls are essential

- cementum completely removed- Gingival margins follow the curvature of

the furcation

•lesion are confined to lesion are confined to gingival third of the gingival third of the facisal or lingual third facisal or lingual third of the facial or lingual of the facial or lingual surfacesurface - axial angles intact - axial angles intact- no furcation - no furcation involvementinvolvement

Class V design 1

Class V ,design 2Class V ,design 2 Lesions on facial or lingual gingival third have

involved axial angle Lesion on facial or lingual gingival third are

apical to contact area

General shapeMesiodistal cross section

Mesio distal

Occluso gingival

Class V Design 3Class V Design 3 Indications;Lesion on gingival third facially or linguallly is continuous with isolated decalcifications or lesions occlusal to height of contour

Bilateral extension

Class V Design 4Class V Design 4

Multiple lesions in gingival third with sound tooth structure separating them

General shape

Class V Design 5Class V Design 5

Internal anatomy

Involves bifurcation or part of it

Class VIClass VI

Retention coves

Retention locks

Tooth preparation for pin Tooth preparation for pin amalgamamalgam

Pin location

Recent concept of cavity designs Recent concept of cavity designs v/s old design v/s old design

Black concept :Extension for prevention :Outline form – the cause of the problemThe logical alternatives :Outdated class l cavity design ;

Dental update 1985 360-370

Traditional occlusalTraditional occlusal

Narrow occlusal outline maintains the Narrow occlusal outline maintains the occlusal tooth structureocclusal tooth structure

Modern Class l Cavity design Modern Class l Cavity design

Occlusal surface

Cavosurface angleCavosurface angle

Drawback’s of black’s cavity designDrawback’s of black’s cavity design1. It is basically for gold inlays cavity preparation

2. Incorporation of wide occlusal dovetail

3. 1/3 rd intercuspal distance

4. Wide parallel proximal box extending gingival sulcus

5. Damage to adjacent tooth

6. Flat floors

•Conservative design (small is beautiful )•Tooth fracture :

Enamel –amalgam junctionEnamel –amalgam junction

Outdated class ll cavity designOutdated class ll cavity designocclusal shapeocclusal shapeis a wide isthmus necessary ?is a wide isthmus necessary ?

Retention grooves Gingival floors

Evolution of theMinimal class ll Amalgam cavityPreparation

Modern Class ll cavityModern Class ll cavity

operative dentistry vol 29,525-529

O

Conclusion

Although composite resins and crown and bridge restorative dental techniques receive much attention, amalgam will continue to be the most extensively used restorative material for many years to come .If it is used with care in minimal cavities, the restoration, the tooth and the occlusion will all last longer!

ReferencesReferences Marzouk –operative dentistry Sturdevant- opertive dentistry 4 th edition Charbeneau – principles and practise of operative dentistry Black’s operative dentistry Conservative amalgam restoration jol .of prosth. Dent.

1973 New approaches to cavity design british dental journal

1984 Axial wall revisited j. of operative dent. 1990,42-48 Evaluation of cavity preparation dent update 1985, 357-380 Modern class ll cavity –new zealand dent j 1972,132-137 Coservative class ii cavities j of dental reasearch 1984, 306