Submitted by:

Nency jain 2008-2009

Guided by:Dr. naveen mittal (h.o.d.)Dr. jaspal singh (m.d.s.)Dr. varun sardana (m.d.s.)Dr. anshul sharma (m.d.s.)Dr. kapildev gupta (m.d.s.)

MODIFICATIONS OF CAVITY PREPARATION IN primary teeth

Contents:

DEFINITIONMODIFIED GV BLACK CLASSIFICATION OF

CAVITY PREPARATIONOTHER MODIFICATIONSFINN’S MODIFICATION OF BLACKS CAVITY

PREPARATION FOR PRIMARY TEETHTYPES OF CAVITIESCLASS I CAVITY PREPARATIONCLASS II CAVITY REPARATIONCLASS III CAVITY PREPARATIONCLASS IV CAVITY PREPARATIONCLASS V CAVITY PREPARATIONCLASS VI CAVITY PREPARATION

* INTRODUCTION-

DEFINITION-CAVITY PREPARATION-

‘Cavity preparation is the mechanical alteration of a diseased or injured tooth to receive a restorative material, in order to return the tooth to proper anatomical form, function, and esthetics’.

STEP OF CAVITY PREPARATION- During cavity cutting , vital pulp should not be exposed, otherwise there will be very severe pain and filling of tooth will become complicated requiring direct pulp capping This will delay the final filling process by about six to eight weeks.

1. Obtaining outline form

2.Obtaining resistance and retention form

3.Obtaining convenience form

4.Removing remaining caries

5.Finishing of the cavity walls

6.Toilet of the cavity.

modified gv black CLASSIFICATION OF CAVITY PREPAR

modified g.v. black classification of cavity preparation

Class I cavity: Pit and fissure caries of the occlusal surface of the molar teeth and the buccal and lingual pits of all teeth.

Class II cavity: Proximal surface of molar and premolar teeth with access established from the occlusal surface.

Class III cavity: Proximal surface of anterior teeth, not involving incisal edge.

Class IV cavity: Cavities of the proximal surface of anterior teeth which involve the incisal angle.

Class V cavity: Cavities founds on the cervical third of all the teeth including the proximal surface, where the marginal ridge is not included in the cavity preparation.

Class VI cavity: Restoration on the incisal edge of anterior teeth or the occlusal cusp height of posterior teeth are class VI.

OTHER MODIFICATIONS-CHARBENEU’S MODIFICATION-

A-Class II: Cavities on single proximal surface of bicuspid and molar.

B-Class VI: cavities on both mesial and distal proximal surface of posterior teeth that will share a common occlusal isthmus.

C-Lingual surface of upper anterior teeth.

D-Any unusually located pit or fissure involved with decay . STURDEVANT’S CLASSIFICATION-

CAVITY FEATURES Simple cavity A cavity involving only one tooth surface Compound cavity A cavity involving two surface of a tooth Complex cavity A cavity that involves more than two surf- ce of a tooth

FINN’S MODIFICATION OF BLACK’S CAVITY PREPARATION FOR PRIMARY TEETH-

Class I: Cavities involving the pits and fissures of the molar teeth and the buccal and lingual pits of all teeth.

Class II: Cavities involving proximal surface of molar teeth with access established from the occlusal surface.

Class III: Cavities involving proximal surface of anterior which may or may not involve a labial or a lingual extension.

Class IV: Cavities of the proximal surface of an anterior tooth which involve the restoration of an incisal angle.

Class V: Cavities present on cervical third of all teeth, including proximal surface marginal ridge is not included in the cavity preparation.

BAUME’S CLASSIFICATION-

A-Pit and fissure cavities B- Smooth surface cavities

All the principles of cavity preparation of permanent teeth also hold good for he primary teeth. However, a few factors have to be taken into consideration while restoring the primary teeth.these include-

The smallar tooth dimension of the deciduous dentition.

The thin enamel covering the teeth.

Broad contact areas

Proximity of the pulp chamber to outer tooth surface

Narrow occlusal table

CLASSIFICATION OF CARIES ACCORDING TO SITE AND SIZE OF CARIOUS LESION-MOUNT G.J.(1997) CLASSIFIED DENTAL CARIES

BASED ON SITE AND SIZE-Site 1-Pits, fissures and enamel on occlusal surface of

posterior teeth smooth surfaces.Site 2-Includes lesions in the approximal enamel in

relation to contact areas of posterior and anterior teeth.Site 3-Includes lesion in the cervical one third of the

crown of all the teeth.Size 0-The earliest lesion that can be identified as the

initial stage of demineralization. This needs to be recorded but will be treated by eliminating the cause and should, therfore, not require further treatment.

Size 1(mild)-minimal surface cavitation with involvement of dentine just beyond treatment by remineralization alone. Some from of restoration is required to restore the surface and prevent further plaque accumulation.

Size 2 (Moderate)-Includes lesions which are moderate in size and are having adequate tooth structure to support the restoration. The lesion following cavity preparation should have sound enamel well supported by dentine and not likely to fail under normal occlusal load. The remaining tooth is sufficiently strong to support the restoration.

Size 3 (enlarge)- Includes lesions in whichthe tooth structure and the restoration is weakened to the extent that cusps or incisal edges are split,or are likely to fail if left exposed to occlusal load. The cavity needs to be further enlarged so that the restoration can be designed to provide support to the remaining tooth structure.

Size 4(Severe)-Includes extensive caries lesion characterized by bulk loss of tooth structure, e.g. loss of a complete cusp or incisal edge, has already occurred low.

TYPES OF CAVITIES-

RECENT CONCEPT OF CAVITY PREPARATION-Black’s concept of cavity preparation was based on

‘Extension for prevention’.The present day dentistry is based on the principle

of ‘Constriction with conviction’.The following principles should be considered while

preparing a cavity according to the recent concept-Cavity designs should be dictated under the site

and extent of the lesion and not by any preconceived notion of mechanical interlocking patterns.

Should not be expectation of extending cavity out to the ‘caries free’ area.

The first choice of a restorative material should be one that display some degree of biological activity and will therefore assist in the process of remineralization and healing of remaining tooth structure.

Only one part of the tooth crown that is irretrievably degenerated and broken down should be removed and the reminder even though demineralization and softened, should be retained and remineralized.

The first function of the restoration will be to eliminate any surface cavitation that has resulted from caries because, in the continuing presence of defects on the surface, it will not be possible to completely control plaque accumulation.

Modified CLASS I CAVITY PREPARATION-Due to the narrow occlusal table isthmus should not be more than

1/3rd the intercuspal distance in the case of a small carious lesion.

The depth should not be more than 0.5 mm. into dentin.

The pulpal floor should be flat.any remaining carious should be removed using round bur in slow speed.

Use of preventive resin restoration is advocated rather than the conventional cavity preparation which includes all pits and fissures.

CLASS I CAVITY PREPARATION

MODIFIED CLASS II CAVITY PREPARATION-Due to the presence of broad contact areas, the gingival

floor of the proximal box should be wide so as to place the margins in self-cleansing areas.

The wall of the proximal box should meet the occlusal walls in a straight to avoid any stress points.

The walls of proximal box should not be flared as it would lead to unsupported enamel.

The isthmus should not exceed 1/3rd the inercuspal width in primary molars.

The axiopulpal line angle must be either rounded, tunneled or grooved for sufficient bulk of the restoration.

The strength of amalgam at the isthmus area can be increased by an adequate depth of the preparation.

Retention can be improved by a ‘U- shaped retention groove along the amelodentinal junction of the proximal box.

When the cavity margins exceed that of an ideal preparation particularly in the case of a mandibular first primary molar, it is recommended that ad overlay of the distobuccal cusp be prepared.

The weakened cusp is reduced to the level of the pulpal floor of the occlusal preparation. Mesiodistally the cusp should not be reduced more than 1/3 rd the crown’s mesiodistal length.

Since the enamel rods, at the cervical area of the tooth, are oriented occlusally the gingival seat should not be beveled, rather should follow the enamel rod inclination.

If the depth of the lesion is farther gingivally, the axial wall should follow the contour of the external surface. This will prevent pulp exposure from occuring.

Care should be taken to avoid the mesiobuccal pulp horn from exposure in the case of small first molars. Since the contact is a point contact , the proximal box extension and the gingival flare can be minimized.

The proximal box should allow the passage of an explorer tip between its margins and adjacent tooth in all three directions, buccally, gingivally and lingually.

CLASS II CAVITY PREPARATION-Cavity preparation and modification from the cavity in permanent

teeth include the following-

PROXIMAL BOX- Deciduous teeth have more constriction cervically.

The danger of pulp exposure is increased very much if gingival wall is made more cervically and axial wall is formed more toward the pulp. in deep proximal caries when it extend below the contact point, proximal box is rounded uptil the wall remains approximately perpendicular to the axis of the tooth.

GINGIVAL WALL- It seat should contain both enamel and dentin width of gingival wall, or gingival seat should about 1mm in width.

AXIAL WALL-Axial wall should be contoured according to the contour of the tooth to avoid pulp exposure.

LINE ANGLE-All the line angle should be slightly rounded.

RETENTION- Sometime retention grooves are made at the buccoaxial and linguoaxial line angle to enhance retention.

PULPAL WALL- It should be about 0.5mm in dentin and made concave to avoid injury to pulp horn and exposing the pulp.

During finishing of pulpal floor, care should be taken in the mesiobuccal area not to expose the pulp horn.

AXIOPULPAL LINE ANGLE-It should be roundepd with bur or sharp hand instrument like enamel hatchets to prevent fracture of the restoration at this line angle.

OCCLUSAL DOVETAIL-It should be made including all carious areas and shapes should be such that it locks the occlusal portion of filling.

PULP-OCCLUSAL WALL- Buccal and lingual walls should be parallel to each other or slightly converging toward the occlusal surface.

CLASS II CAVITY PREPARATION

PREPARATION OF CLASS I &CLASS II CORRECT &INCORRECT

CLASS III CAVITY PREPARATION-When the contact is open the outline is triangular with

base towards the gingival aspect of the cavity.

Gingival cavity wall is inclined occlusally to parallel the enamel rod direction.

Retention pits can be placed at the axiobuccogingival and axiolinguogingival point angles.

A dovetail may be placed in the middle one third of the lingual surface of the tooth.this help in gaining access to the carious lesion and in facilitating retention of the restoration.

CLASS III CAVITY PREPARATION-

CLASS IV CAVITY PREPARATION-In anterior teeth, if

incisal angle is involved along with proximal caries, then it comes under class IV cavity.

CLASS V CAVITY PREPARATION

A cavity which is present at the gingival third or cervical third of any tooth comes under class V cavity. It is in kidney shape.

CLASS VI CAVITY PREPARATION-In GV Black classification,

description of class VI cavity is not given. It was added later on. It includes cavities, both on mesial and distal surface of molar that when restored, share a common occlusal isthmus, mesio- occlusal cavities and cavities on the incisal edges of anterior or cusp tip of molar teeth.

REFERENCE-SHOBHA TONDON

2nd EDITIONSATISH CHANDRASHALEEN

CHANDRA RK BALI