Amalgam cavity design

Cavity Designs For Amalgam
Restorative

Contents
Introduction
Historical review
Definition of Cavity and Cavity preparation
Objectives of cavity preparations
Factors affecting tooth preparation
Nomenclature of tooth preparation
Cavity classification
Principles of tooth preparations for amalgam
Physical , Biological and Anatomical considerations
of cavity preparation
Armamentarium
Class l, ll , lll , lV, V Cavity Designs
Tooth preparation for pin amalgam and bonded
amalgam
Recent concept of cavity design v/s old design
Conclusion
References

Historical 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 – Defect in enamel or in enamel and dentin
resulting from the pathological process of dental
careis
( Acc Charbeneau 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 preparation
Factors affecting tooth preparation
 General factors
 Diagnosis
 Dental anatomy
 Patient factors
 Conservation of tooth structure
 Restorative material factors

 Cavity Line angle Point angle
 Class l 8 4
 Class 2 11 6
 MOD 14 8
 Class lll 6 3
 Class lV 11 6
 Class V 8 4

Classification 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

Modification of blacks original classification
Class Vl - cavities on both mesial and distal
proximal surfaces of bicuspids and molars when
restored will share a common occlusal isthmus
( Acc charbeneau )
(Markely and bronner )
Class ll – Cavities on single proximal surfaces of
bicuspids and molars

According to number of surfaces
involved
 Simple
 Compound
 Complex
Simple
Compound

New cavity of classification
Site 1. Pits fissures and enamel on occlusal surface of
posterior teeth or other smooth surfaces such as Cingulum
pits on anterior
Site 2. Approximal enamel immediately below areas in
contact with adjacent teeth
Site 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

Site2 ,size 1
Site2 ,size 2
Site 2,size 2

Site 2,size 3 Site 3,size 0 or 1
Site ,size 4 Site 3,size 2

Principles of tooth preparation for
amalgam
• Initial stages
• Final stages
- Out line 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 considerations
Stress 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

Class l, design 1
 Caries penetration into dentin does
not exceed 0.5-1mm
 Width- I/4 intercuspal distance
 Low caries index

General shape
Molar outline Premolar outline

Pulpal floor of
Lower premolar

Class l, design 2
Indication ; caries cones in dentin extend 1mm or more
from the DEJ
Pulpal floors have different levels

Class l, design 3
Indication ; in occlusal one to two thirds of facial
and lingual surfaces of molars and on lingual surfaces
anterior teeth of
General shape

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 : Indications
 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)

Class l, design 6 :
Includes occlusal surfaces of molars or premolars
as well as portion of facial, proximal
or lingual surface in form of a table of an entire
cusp or section of cusp (marginal ridges )
Gingival margin should extend to allow
Occlusal clearance of 1.5-3 mm from
Opposing teeth

Class l, Design 7
 Involves occlusal , facial and lingual surfaces of
molars and premolars
 Pins and posts are indicated

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

Out 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

Design features for the protection of mechanical integrity of
restoration
Axial wall

Class ll, Design 1
Conventional design
Indications
Moderate to large size proximal
Lesion with occlusal surface cavity
promotes the cavity width of cavity to
exceed 1/4 0f intercuspal distance

Proximal box
Inverted truncated shape

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

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 shape
Internal anatomy

Gingival margin
Middle third Gingival third

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-lingual
Cross section
Occlusal-gingival
Cross section

Class ll, Design 5
Part of proximal surface ,with a limited access area on facial
or lingual surface
Indications :
•1)Preparation will have 4 surrounding walls
•small proximal lesions
•Marginal ridge intact
•Does not involve contact area
1)Do not have dovetail
2) Preparation will not
have surrounding walls
•medium proximal lesion
2) Have dovetail

Class ll, Design 6
The occlusal ,proximal and part of the facial or lingual
surfaces
Indications ; Cusp is missing
Badly broken down teeth

Class ll, Design 7
(Combinations of class ll with class V )
Shape A : junctions between the class ll and class V via, the
Proximal , crossing the axial angles
Shape B : via buccal / lingual groove
Shape A Shape B

Class ll, Design 8
Two or more surfaces of an endodontically treated tooth
does not require post retention

Class lll
Amalgam is usually not indicated for anterior teeth due to
its esthetic , but distal surface of the cuspid is a unique
location
General principles are similar to class ll
cavity
preparation but with emphasis laid on in 5
areas of preparation
1 esthetic concern
2 extension for access
3 stress consideration enamel rod direction
Incisal access

Designs of cavity preparation at the distal slope of
the cuspid
Indications;
1 The lesion does not involve or undermine the distal
slope of cupid
2 bulky walls will remain, incisally, after removal of
Undermine tissues
3 the labials axial angle is intact
4 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 lV
Indications :
•Incisal angle is undermined
•Labial and lingual walls intact
Labio lingual cross section

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

Class V design 1
•lesion are confined to
gingival third of the
facisal or lingual third
of the facial or lingual
surface
- axial angles intact
- no furcation
involvement

Class 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 shape
Mesiodistal cross section

Mesio distal
Occluso gingival

Class 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 4
Multiple lesions in gingival third with sound tooth
structure separating them
General shape

Class V Design 5
Internal
anatomy
Involves bifurcation or part of it

Tooth preparation for pin amalgam

Recent concept of cavity designs
v/s old design
 Black concept :
 Extension for prevention :
 Outline form – the cause of the problem
 The logical alternatives :
 Outdated class l cavity design ;
Dental update 1985 360-370

Narrow occlusal outline maintains the
occlusal tooth structure

Modern Class l Cavity design
Occlusal surface

Drawback’s of black’s cavity design
1. 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 :

Outdated class ll cavity design
occlusal shape
is a wide isthmus necessary ?
Retention grooves Gingival floors

Evolution of the
Minimal class ll
Amalgam cavity
Preparation

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!

References
 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

Amalgam cavity design

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