Six principle of cavity preparation: 6

1. Outline form

2. Resistance and retention form

3. Convenience form

4. Removal of remaining caries dentine

5. Finishing of the enamel walls and margin

6. Toilet of cavity

Steps of cavity preparation:

There are two steps:

1. Initial

2. Final

Black suggested following precautions:2

Provision of definitive mechanical retention in the cavity

Extension into nearby deeps pits and fissure for prevention of recurrent caries

Removal of infected and affected enamel and dentine from all surfaces

Removal of even healthy tissue/structure to gain access good visibility

Cavosurface margin should be self cleansing area.

Classification of cavities:1

Class I

Class II

Class III

Class IV

Class V

Class VI

Another classification was improved by CHANDRA, by division and subdivision.

Abbreviation1

MOD, meso-ocluso distal

MB, mesio-buccal

DO, disto occlusal

Terminology:

Simple, compound, complex

1. Simple: termed simple if only one tooth surface is involved.

2. Compound: Two surfaces are involved.

3. Complex: preparation involving three or more surface.

Tooth preparation walls:

Internal wall: prepared surface that does not extend to the external tooth surface

Axial wall: internal wall parallel with the long axis of the tooth

Pulpal wall: internal wall that is perpendicular to the long axis of the tooth

External wall: prepared surface that extend to external tooth surface

Floor: prepared wall that is reasonably flat and perpendicular to the occlusal forces that are directed occlusogingivally.

Line angles, point angles:

Line angle: the junction of two different orientations along the line.

Point angle: the junction of three planel surface of different orientation.

Secondary retention device:

Slots, Locks, Grooves, Skirts, Pins.

Difference between proposed classification and equivalent classification4

Proposed classification Equivalent Black classification

Site 1- Pits and fissures and smooth surface

Class 1- Pits and fissures

Size 0- fissure seal Not classified

Size 1- minimal surgery Not classified

Size 2- equivalent to black class 1 Class 1

Size 3- requires protection of remaining tooth structure

Class 1

Size 3- lost cusp or similar Class 1

Site 2- contact area, all teeth Class 2 contact area, posterior teeth

Size 0- surface demineralization Not classified

Size 1- beyond remineralization Not classified

Size 2- moderate involvement Class 2

Size 3- requires protection of remaining tooth structure

Class 2

Size 4- bulk loss of tooth structure Class 2Class 3- contact area, anterior teeth

Not classifiedNot classifiedClass 3Class 3Class 3Class 4- Incisal edge lost, anterior toothNot classifiedNot classifiedClass 4

Class 4Class 4

Site 3- cervical third Class 5- cervical thirdSize 0- surface demineralization Not classifiedSize 1- minimal intervention Not classifiedSize 2- more extensive Class 5Size 3- a proximal root surface Class 2Size 4- two or more surfaces Class 5

Class I:

Pit and fissure caries, or caries occur on the occlusal surface of posterior teeth .or facial and lingual pits in posterior teeth.5

Preparation:

Conservative tooth preparation is recommended to protect the pulp preserve the strength of the tooth.

Line angles, fp,df,dp,dl ,lp

ml,mp,mf ,Point angles, dfp,dlp,mlp,mfp

Class1 tooth preparation on max: molar

Illulustring tooth prep: walls f, d, m, l, p

Initial cavity preparation steps: 2

Outline form and initial depth

Primary resistance form

Primary retention form

Convenience form

Secondary retention form

1. Outline form and initial depth

Class I cavity preparation is Started by entering the deepest or most carious pits using a round carbide bur at high speed with air water spray. The long axis of bur is held perpendicular to the plane visualized for pulpal floor; include all susceptible fissures in the outline form. This phenomenon of Extension for Prevention’ was first suggested by Marshall Ebb and was later adopted by Black. Extended the cavity margins to the place they will occupy in the final cavity preparation.1,6

Factors guide:

Extension of caries lesion, esthetic consideration, relationship of approximating and opposing teeth restorative material to be used. Initial depth is 0.2 to 0.8mm.

Primary resistance form:

Outline Form

Make a box shape cavity, establish extension of the external walls of the cavity preparation should be kept as small as possible; floor should be flat to resist the Occulsal stresses. Which help the tooth to resist Occulsal masticatory forces without any displacement, cusp and ridges with dentine support should not be undermined. The extensions of the external