CAVITY PREPARATION IN PRIMARY TEETH

DR SUNNY PUROHITPEDODONTIA

SDCH

Introduction

CLASSIFICATION

BLACK’S CLASSIFICATION

Class I lesionLesions that begin in the structural defects

of teeth such as pits, fissures and defective grooves.

Locations include• Occlusal surface of molars and premolars• Occlusal two-thirds of buccal and lingual

surfaces of molars• Lingual surface of anterior tooth

Class II LesionsThey are found on the proximal surfaces of

the bicuspids and molars. Areas for class II decay involve:

Two-surface restoration of a posterior tooth. Three-surface restoration of a posterior tooth. Four- or more surface restoration of a posterior

tooth.

Class III lesions

Lesions found on the proximal surfaces of anterior teeth that do not involve or neccesitate the removal of the incisal angle.

Class IV lesions

Lesions found on the proximal surfaces of anterior teeth that involves the incisal angle.

Fig. 48-9 Class IV restoration.

Class V lesion

Lesions that are found on the gingival third of the facial and lingual surfaces of the anterior and posterior teeth.

Class VI

Lesions involving cuspal tips and incisal edges of teeth.

OTHER MODIFICATIONSCHARBENEU’S CLASSIFICATION

• Class II: Cavities on single proximal surface of bicuspids and molars.

• Class VI: Cavities on both mesial and distal proximal surfaces of posterior teeth that will share a common occlusal isthumus.

• Lingual surfaces of upper anterior teeth• Any other usually located pit or fissure

involved with decay.

STURDEVANT ’S CLASSIFICATION

CAVITY FEATURESimple cavity A cavity involving only one

tooth surface

Compound cavity A cavity involving two surfaces of a tooth

Complex cavity A cavity involves more than two surfaces 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 surfaces of anterior teeth which may or may not involve a labial or a lingual extention.

Class IV:• Cavities of the proximal surface of an

anterior tooth which involve the restoration of an incisal angle.

Class V • Cavities present on the cervical third of

all teeth of all teeth including proximal surface where the marginal ridge is not included in the cavity preparation.

BAUME’S CLASSIFICATION

Pit and fissure cavities Smooth surface cavities

CLASSIFICATION BY MOUNT AND HUME[1998]

This new system defines the extent and complexity of a cavity and at the same time encourages a conservative approach to the preservation of natural tooth structure. This system is designed to utilize the healing capacity of enamel and dentin.

THE THREE SITES OF CARIOUS LESIONS

• SITE I:• Pits, fissures and enamel defects on

occlusal surfaces of posterior teeth or other smooth surfaces.

• Proximal enamel immediately below areas in contact with adjacent teeth.

• The cervical one-third of the crown or following gingival recession, the exposed root

THE FOUR SIZES OF CARIOUS LESION

Size 1–minimal involvement in dentin just beyond treatment by remineralization alone

Size 2-moderate involvement of dentin. Following cavity preparation, remaining enamel is sound well supported by dentin and not likely to fail under normal occlusal load. 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 or are likely to fail or left exposed to occlusal or incisal load. The cavity needs to be further enlarged so that the restoration can be designed to provide support and protection to the remaining tooth structure.

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

Principles of Cavity Preparation

Initial Tooth Preparation Final Tooth Preparation

Principles of Cavity Preparation

CONVENIENCE FORM

RETENTION FORM

RESISTANCE FORM

OUTLINE FORM

Principles of Cavity Preparation- cont’dFinal cavity preparation

CLEANING INSPECTING ,VARNISHING AND CONDITIONING

FINISHING THE EXTERNAL WALLS

SECONDARY RESISTANCE AND RETENTION FORM

PULP PROTECTION

REMOVAL OF ANY REMAINING INFECTED DENTIN

Kidd & Smith (1994) 1.Gain access to caris 2.Excavate all caries 3.Consider design of cavity in relation toA-Final choice of the material B-Retention of the materialC. Protection of remaining tooth structureD.Optimal strength of restoration E.Shape & Protection of Cavity Margins

F.Refine & debride the cavity G.Placement of restoration

BASIC PRINCIPLES IN THE PREPARATION OF CAVITIES IN PRIMARY TEETH.

The steps in the preparation of a cavity in a primary tooth are not difficult but do require precise operator control

Many authorities advocate the use of small, rounded-end carbide burs in the high-speed handpiece for establishing the cavity outline and performing the gross preparation.

they are designed to cut efficiently and yet allow conservative cavity preparations

with rounded line angles and point angles.

The Black’s principles with some modification are basic principles in the preparation of the cavities in the primary teeth. There are two operative steps with the use of the high-speed handpiece:

Opening and conformation of the cavity with the use of the high-speed handpiece.

Eliminating the caries of the buccal, lingual, mesial and distal walls with the use of the high-speed handpiece. Eliminate the caries of the pulpal wall with the use of the lower-speed handpiece.

CLASS I CAVITIES

Incipient carious lesion in child under 2 years old should be eliminated. Small cavity preparation may be made with a No.329 or No. 330 pear-shaped bur. We should open the decayed area and extend the cavosurface margin only to the extent of the carious lesion. The preparation can be completed in a few seconds.

The outline form should include all pits, fissures and grooves into which a sharp explorer can penetrate.

The pulpal floor should be flat or slightly concave throughout to allow for greater depth of the filling material, for better distribution of stress in the restoration and to avoid endangering the high pulpal horns.

The depth of pulpal floor should be established just beneath the dentinoenamel junction (0.5 mm) to avoid pulp exposure.

All the internal line angles should be rounded.

The side walls should slightly converge towards occlusal so that the preparation will follow the outer form of the crown.

Beside the regular class I cavity preparations done in primary molars, occlusal spot preparations have been recommended.

In such preparations only the carious pits or groove is prepared and the tooth is restored in the usual manner. These preparations are applicable in any of the primary molars with exception of the lower second primary molars in which extension for prevention including all deep pits and fissures is recommended above all, if the child has high caries index

cavity should be covered with calcium hydroxide . A base of polycarboxlate, glass ionomer or rapid-setting zinc-oxide-eugenol cement may then be placed over the calcium hydroxide material to provide adequate thermal pulp protection.

Do not cross the oblique ridge in the upper second primary or first permanent molars and the transverse ridge of the lower first primary molar unless they are undermined with caries. These heavy ridges add support to the tooth.

 

CLASS II CAVITIES.

These preparations include an occlusal, an isthmus and proximal portion. The outline form of the occlusal step

should be dovetail-shaped including all carious pits, fissures, and developmental grooves.

The side walls of the occlusal step should converge from the pulpal wall to the occlusal surface.

The pulpal floor should be established just beneath the dentinoenamel junction.

The axio-pulpal line angle should be beveled to reduce the concentration of stresses and provide grater bulk of material in the isthmus area, which is liable to fracture

The greater constriction of primary teeth increases the danger of damaging the interproximal soft tissues during cavity preparation.

Extreme care must be taken when breaking through the marginal ridge to prevent damage to the adjacent proximal surface, especially when the bur is revolving at high speed.

The bur is used in a pendulum-swinging fashion to undermine the marginal ridge and at the same time to establish the gingival depth.

The gingival seat should be of sufficient depth to break contact with the adjacent tooth.

A liner or intermediate base should be placed before the insertion of the silver amalgam.

The amalgam restoration in the Class II cavity needs the use of a matrix retainer. The matrix should be rigid enough to allow adequate packing pressure, ensuring a well-condensed restoration free from an excess of residual mercury.

If the primary molars have an extensive carious lesions, especially first primary molars, should be used a stainless steel crowns, above all, in the first primary molar of a 3 years old child

Indications for use Stainless Steel Crown Restoration of primary molars requiring

large multisurface restoration.

Restorations in disabled persons or others in whom oral hygienic is extremely poor and failure of other materials is likely.

Restorations of teeth in children with rampant caries.

Restoration of teeth after pulp therapy

Restoration of teeth with developmental defects

Restoration of fructured primary molar

As abutment for space maintainer

CLASS III CAVITIES Carious lesions on the proximal surfaces

of anterior primary teeth sometimes occur in children whose teeth are in contact and in those children who have evidence of arch inadequacy or crowding.

If caries is not extensive, disking by sand paper disc is performed to remove the decay, and then fluoride is applied topically

If the carious lesion not involves the incisal angle, a small conventional Class III cavity may be prepared and the tooth may be restored with glass ionomer or composite resin.

The same basic principles for permanent anterior teeth should be considered in a primary teeth, modified, of course, by the size of the pulp and the relative thinness of the enamel. If it is necessary we modify the Class III cavities with the use of dovetail on the lingual or occasionally on the labial surface of the tooth.

Because of the narrow labiolingual width of the primary incisor teeth, the Class III preparation is very difficult to perform and often needs a labial or lingual dovetail to gain access and aid in retention of the restoration.

CLASS IV CAVITIES In these cavities caries involves the

incisal proximal angle of the anterior teeth. The principles in the cavity preparation are the same of the cavity preparation in permanent teeth

In regular class IV cavity preparations, composite resin material can be used for restoration.

CLASS V CAVITIES The Class V cavities are realized more

frequently in buccal surface of the primary canines.

The principles in the cavity preparation are the same of the cavity preparation in permanent teeth, although the depth is not carried more than 1.5 mm.

Walls of preparation converge toward buccal surface of tooth for retention of restoration.

When a necessary, retentive groove can be placed along the gingivoaxial and occlusoaxial line angles. Use round bur at slow speed.

Glass ionomer cement could be used effectively for restoring these cavities.

Patient Preparation for Restorative Procedures

• Inform the patient of the procedure to be performed and what to expect during the treatment.

• Position the patient correctly for the dentist and the type of procedure.

• Explain each step as the procedure progresses.

DIFFERENCES IN CAVITY PREPARATION FOR PRIMARY AND PERMANENT TEETH

PRIMARY TEETH PERMANENT TEETH

DEPTH OF THE CAVITY Less More

OCCLUSAL TABLE Occlusal table is narrow as the buccolingual width of the tooth is less

Occlusal table is wider than the primary teeth

CONTACT POINT /POINT Because of the presence of contact area, buccal and lingual margins of the interproximal box must extend far enough towards the embrasure at the gingival margin to make them accessible for cleaning.

Because of the presence of contact area, buccal and lingual margins of the interproximal box don’t have to extend too far into the embrasure.

MARKED CERVICAL CONSTRICTION

Because of the marked cervical constriction the floor of the cavity can become too narrow if placed more gingivally

The cervical constriction is not that marked therefore sufficient width of the floor of interproximal box can be maintained.

ISTHUMUS OF THE CAVITY

Isthumus is narrow because the buccolingual width of the tooth is less.cavities with wide isthumus can lead to fracture of the tooth.

Isthumus is wider compared to primary teeth.

BEVEL IN CAVOSURFACE MARGIN OF GINGIVAL SEAT

Bevel is not given in the cavosurface margin of gingival seat

Bevel is given in the gingival seat

OCCLUSAL ASPECT OF THE PROXIMAL BOX

Must be kept narrow to prevent weakening of the cusp

Its not that narrow

GINGIVAL SEAT PLACEMENT

They are placed clear of contact with the adjacent tooth, so that the margins of the restorations can be cleaned.

It is not that wide.

BUCCAL AND LINGUAL WALLS OF THE PROXIMAL BOX

Because of the wider contact area the buccal and the lingual walls of the interproximal diverge buccally and lingually to clear the contact area.

Because of the presence of contact point the buccal and the lingual walls of the interproximal need not be diverged towards the embrasure.

MOD CAVITY Should not be restored for amalgam alone.

It may be restored with amalgam.

AAPD Guideline on Restorative Dentistry 2014

Historically, the management of dental caries was based on the belief that caries was a progressive disease that eventually destroyed the tooth unless there was surgical and restorative intervention.

It is now recognized that restorative treatment of dental caries alone does not stop the disease process

and restorations have a finite lifespan, some carious lesions may not progress and, therefore, may not

need restoration. Consequently, management of dental caries includes

1)identification of an individual’s risk for caries progression, 2)understanding of the disease process for that individual, and 3)active surveillance to assess disease progression and manage with appropriate preventive services, supplemented by restorative therapy when indicated

When to Restore? Recommendations: 1. Management of dental

caries includes identification of an individual’s risk for caries progression, understanding of the disease process for that individual, and active surveillance to assess disease progression and manage with appropriate preventive services, supplemented by restorative therapy when indicated.

2. Decisions for when to restore carious lesions should in- clude at least clinical criteria of visual detection of enamel cavitation, visual identification of shadowing of the enamel, and/or radiographic recognition of enlargement of lesions over time.

Deep caries excavation and restoration

1.Complete Excavation

2.Incomplete Excavation A)One Step B)Two Step

3.No Excavation

Deep caries excavation and restoration

Recommendations 1. There is evidence from randomized controlled trails and

systematic reviews that incomplete caries excavation in primary and permanent teeth with normal pulps or reversible pulpitis, either partial (one-step) or stepwise (two-step) excavation, results in fewer pulp exposures and fewer signs and symptoms of pulpal disease than complete excavation.

2. The rate of restoration failure in permanent teeth is no higher after incomplete rather than complete caries excavation.

3. Partial excavation (one-step) followed by placement of final restoration leads to higher success in maintaining pulp vitality in permanent teeth than stepwise (two-step) excavation.

Why Vitality Important for Young Permanent Teeth?

Open Apex Incomplete Rhizogenesis