COMPARISON OF CAVITY PREPARATION OF DIFFERENT RESTORATIVE

MATERIALS

Department of Pediatric & Preventive Dentistry

Presented By:

Rahul Mishra,

Junior Resident-I,

UPDC&RC, Lucknow.

PRINCIPLES AMALGAM CAST GOLD COMPOSITE GOLD FOIL

OUTLINE FORM

Pulpal wall depth=1.5-2.0 mm.

Box shaped cavity.

Extension for prevention.

Line & point angles rounded.

Mesiodistal divergence (2-5°) & Buccolingual convergence (2-5°).

Cavity margins 1/4th of the intercuspal distance.

Convergence of proximal walls occlusally in Class II cavity preparation.

Pulpal wall depth=1.5 mm.

Box shaped cavity.

Complete cavity walls parallel or diverge (2-5°).

Line & point angles rounded.

Cavity margins 1/3 rd of the intercuspal distance

Proximal walls diverge or parallel (Proximopulpal angle=100°-110°)in Class II cavity Preparation

Seldom a need for cavity extension for prevention.

In proximal lesions contact areas or parts of the contact area should be in tooth structure and not in restoration as far as possible because these materials can not maintain the integrity of the contact or mesiodistal dimension for a long time.

Definite lines with rounded junctions between these lines.

Box shaped cavity.

All walls converge occlusally.

Initial depth 0.5 mm below the DEJ. Convenience points on all four point angles- Buccomesiopulpal, Linguomesiopulpal, linguodistopulpal & Buccodistopulpal.

RESISTANCE FORM

Flat pulpal floor.

Pulp floor within dentin.

All line & point angles rounded.

Rounding of Axio-Pulpal Line Angle in Class II cavity Preparation.

Proximal Box Depth=0.8 mm.

Gingival floor apical to the carious lesion or the contact point whichever is apical with 0.5 mm

No undercuts so that inlay wax can be taken out properly.

All line & point angles rounded.

Plunger cusp should not fall on tooth restoration interface (true for all restorations).

i. Acid conditioning of surface enamel.

ii. Retentive cavity preparation with internal details.

iii. Physico-chemical adhesion to some components of the tooth structure.

iv. Pins and posts.

v. Combination of all of the above.

- Performing proper STEPPING & avoiding BRIDGING

clearance from adjacent tooth

PRINCIPLES AMALGAM CAST GOLD COMPOSITE GOLD FOIL

RETENTION FORM

Bulk of amalgam.

Dove tail formation.

Secondary retentive features (slots, coves, pins, grooves, etc.)

Frictional Wall retention aid by enamel & dentin, very less from the cement used during luting).

Nearly parallel/ divergent cavity walls.

Secondary retentive features: REVERSE BEVEL- Sliding Fit.

Micromechanical retention

Two types:(i) Within the bulk of

restoration: interatomic forces.

(WEDGING)(ii) To the tooth by

parallelism of walls (WELDING)

-- Secondary

retentive grooves placed on faciopulpal & linguopulpal line angles.

-- Cavosurface bevel

(0.2 mm width) of 30°-40°.

CONVENIENCE FORM

Straight line visible access to the carious lesion & restoration.

Carrying the margins of the preparation in the self cleansing area.

Proper visibility & accessibility.

Extension, taper & flare of the proximal wall to permit access for disking & bevel placement.

Includes some modifications in outline form, internal anatomy of cavity preparation, & instrumentation for convenience and preparation. Ex :i. Separation, using

different devices, helps to gain access proximally in anterior teeth.

ii. Make the wall of the access side shorter and divergent compared to the wall on the non-access side.

iii. Reduce or eliminate

Placement of convenience points at all four point angles within the cavity.

convexity of the axial wall.

PRINCIPLES AMALGAM CAST GOLD COMPOSITE GOLD FOIL

PULP PROTECTION

Placement of Proper sub base, base followed by varnish placement

Proper cementation of cast inlay to prevent any salivary seepage.

Placement of Ca(OH)2 in deep cavities.

Placement of ZOE contraindicated

Placement of Proper sub base, base followed by varnish placement.

FINISHING OF THE CAVITY

WALLS

All unsupported enamel removed.

Rounding of all line & point angles.

No undermining of enamel should be present.

All unsupported enamel removed.

Rounding of all line & point angles.

No undermining of enamel should be present.

Removal of Smear layer followed by proper conditioning of cavity walls.

Bevelling of Labial surface of anterior teeth so as to merge the color of composite & enamel. Also in Class V cavity but only on occlusal wall & not on gingival wall.

All unsupported enamel removed

SPECIAL CONSIDERATIONS FOR GLASS-IONOMER RESTORATIONS

Glass Ionomer Restorations are typically indicated in Restorations of low stress areas and in areas where esthetics though necessary are not of prime considerations, they are generally indicated in Cl-V, conservative Cl-III and conservative Cl-I & II Restorations.

Retentive grooves may be indicated although bevels are not generally used. Cavity preparations for slot restorations with GIC are similar to amalgam slot preparations.

A facial or lingual approach is used.

Pulpal depth is limited to 0.75 to 1mm at the gingival aspect increasing to 1 to 1.25mm at the occlusal wall.

The external walls should form 90o cavosurface angle.

Facial wall must be extended for convenience form.

Retention grooves 0.2mm inside DEJ or 0.3 to 0.5mm from cemental margin are placed into the occlusal and gingival walls, measuring 0.25mm in depth.