DEPARTMENT OF CONSERVATIVE & OPERATIVE DENTISTRYDEPARTMENT OF CONSERVATIVE & OPERATIVE DENTISTRY

Presented by:Presented by:Anjali AroraAnjali AroraRoll no.06Roll no.06BDS final year (Batch2005-06)BDS final year (Batch2005-06)

SOME IMPORTANT TERMS :SOME IMPORTANT TERMS :

CAVITY:CAVITY: refers to a defect in the tooth enamel or in refers to a defect in the tooth enamel or in both enamel & dentin due to carious process.both enamel & dentin due to carious process.

Cavity preparation:Cavity preparation: It isIt is the mechanical alteration the mechanical alteration of a defective, injured, or diseased tooth to receive a of a defective, injured, or diseased tooth to receive a restorative material that reestablishes a healthy state restorative material that reestablishes a healthy state for the tooth including esthetic corrections where for the tooth including esthetic corrections where indicated along with normal form and function.indicated along with normal form and function.

Class I cariesClass I caries

Class VI cariesClass VI caries Class V cariesClass V caries

Class II cariesClass II caries Class III cariesClass III caries

Class IV cariesClass IV caries

Classification of cavityClassification of cavity

Walls of cavity preparation

Internal walls :Internal walls : surface of prepared cavity that is inside the tooth & does not extend onto the external tooth surface. Its 2 types are:

(1)(1) Axial wallAxial wall – – internal wall parallel to long axis of tooth.

(2)(2) Pulpal wallPulpal wall :: internal wall perpendicular to the long axis of tooth & is occlusal to dental pulp.External wallExternal wall : : prepared surface that extends to the external tooth surface. Eg. Eg. Facial, mesial, Facial, mesial, distal, lingual & gingival walls. distal, lingual & gingival walls.

Floor or seatFloor or seat : : refers to prepared wall that is refers to prepared wall that is relatively flat & perpendicular to the occlusal forces relatively flat & perpendicular to the occlusal forces which are directed along the long axis of tooth.which are directed along the long axis of tooth.

Enamel wallEnamel wall : : that portion of the prepared external that portion of the prepared external wall which is composed of enamel.wall which is composed of enamel.

Dentinal wallDentinal wall : : that portion of prepared external wall that portion of prepared external wall which is composed of dentin. This wall usually which is composed of dentin. This wall usually incorporates mechanical retentive featuresincorporates mechanical retentive features..

AnglesAngles in cavity preparationin cavity preparation

Line angleLine angle : : junction of junction of two walls in a cavity two walls in a cavity preparation along a preparation along a definite line.definite line.

Point anglePoint angle : : junction of junction of three walls in a cavity three walls in a cavity preparation at a point.preparation at a point.

Cavosurface angleCavosurface angle : : angle angle of the tooth structure of the tooth structure formed by the junction of formed by the junction of a prepared wall & the a prepared wall & the external tooth surface.external tooth surface.

What determines cavity What determines cavity design ?design ?

The structure & properties of the dental The structure & properties of the dental tissues.tissues.

The disease process itself.The disease process itself.

The properties of restorative material.The properties of restorative material.

Occlusal relationships & esthetic needs of the Occlusal relationships & esthetic needs of the patient.patient.

The economic status, age & health of the The economic status, age & health of the patient.patient.

Initial cavity preparation stageInitial cavity preparation stage

STEP 1: STEP 1: Outline form & initial depth.Outline form & initial depth. STEP 2: STEP 2: Primary resistance form. Primary resistance form. STEP 3: STEP 3: Primary retention form.Primary retention form. STEP 4:STEP 4: Convenience form. Convenience form.

Final cavity preparation stageFinal cavity preparation stage

STEP 5: STEP 5: Removing any enamel pit or fissure, infected dentinRemoving any enamel pit or fissure, infected dentin or old restorative material.or old restorative material. STEP 6: STEP 6: Pulp protection.Pulp protection. STEP 7: STEP 7: Secondary resistance.Secondary resistance. STEP 8: STEP 8: Finishing the external walls & marginsFinishing the external walls & margins STEP 9: STEP 9: Final procedures – cleaning, inspecting, varnishing Final procedures – cleaning, inspecting, varnishing

&&conditioning conditioning

placing the preparation margins in the position they will occupy in the final, preparation, except for finishing the enamel walls and margins.

preparing an initial depth of 0.2-0.5mm pulpally beyond the DEJ.

STEP 1: OUTLINE FORM AND INITIAL DEPTH

Establishing the outline form means:

DEFINITION:DEFINITION:

FACTORS:FACTORS:

Certain factors affect the decision regarding the extent of Certain factors affect the decision regarding the extent of the outline form. They are:the outline form. They are:

1)Extent of the carious lesion, defect or faulty old restoration.

2) Esthetic requirements which may affect the choice of the restorative material and modify the cavity design.

3) Occlusal relationships which may require alterations in the outline form.

4) Contour of the adjacent tooth which may dictate certain modifications to secure proper form and strength.

5) Cavosurface marginal configuration will vary

depending on the restorative material employed.

FEATURES:1) Preserve cuspal strength.

2) Preserve marginal ridge strength.

3) Minimize faciolingual extensions.

4) Use enameloplasty wherever possible.

6) Restrict the depth of the preparation into dentin to a maximum of 0.2-0.5mm.

This is that shape and placement of the cavity walls This is that shape and placement of the cavity walls that best enables both the restoration and the tooth to that best enables both the restoration and the tooth to withstand, without fracture, the masticatory forces withstand, without fracture, the masticatory forces delivered principally along the long axis of the tooth. delivered principally along the long axis of the tooth.

DEFINITION-

STEP 2: PRIMARY RESISTANCE FORM STEP 2: PRIMARY RESISTANCE FORM

FEATURES-The following features enhance primary resistance form:

Relatively flat floors.

Box shape.

Including all weakened tooth structure.

Preservations of cusps and marginal ridges.

Rounded internal line angles.

Adequate thickness of the restorative material.

Reduction of cusps for capping when indicated.

FACTORS-Certain factors affect the resistance form of Certain factors affect the resistance form of the preparation:the preparation:

Amount of remaining occlusal contact.

Amount of remaining tooth structure.

Type of restorative material.

Whether or not the restoration can be bonded to the tooth.

STEP 3: PRIMARY RETENTION FORM

DEFINITION- This is that shape or form of the tooth preparation that resists displacement or removal of the restoration tipping or lifting forces. Often features that enhance retention form also enhance resistance form.

For Amalgam : occlusal dovetail – prevent tipping of restoration & occlusal convergence of walls.

For Composite : acid etching & bonding ( micromechanical retention) - enamel bevel

For cast metal : close parallelism of opposing walls with slight divergence occlusally

For direct filling gold : elastic compression of dentin during condensation

PRINCIPLES-The principles of primary retention form vary according to the restorative material:

Occlusal dovetail prevents tipping of the restoration by occlusal forces.

Occlusal convergence of the preparation walls.

RETENTION FORMRETENTION FORM

STEP 4: CONVENIENCE FORM

DEFINITION:

This is that shape or form of the cavity that provides for • adequate observation• accessibility • ease of operation in preparing • restoring the tooth.

FEATURES:

•Providing adequate width and lateral extensions•Refining line and point angles•Providing proximal clearance from the adjacent tooth•Occlusal divergence for cast gold inlays

1.Infected dentin more superficial layer

soft and Leathery in consistency

light brown in color.

high concentration of bacteria and the collagen is irreversibly denatured.

This layer is not remineralizable and must therefore be removed.

2.Affected dentin - deeper layer

hard in consistency dark brown in colour. It does not contain bacteria and is reversibly denatured.

This layer must therefore be preserved.

If infected dentin remains after establishing the pulpal and axial walls during initial tooth preparation, then it has to be eliminated during the final tooth preparation stage.

PRINCIPLES:PRINCIPLES:The deeper portions of carious dentin may generally exhibit two distinct areas:

STEP 5: REMOVAL OF ANY REMAINING ENAMEL PIT OR FISSURE, STEP 5: REMOVAL OF ANY REMAINING ENAMEL PIT OR FISSURE, INFECTED DENTIN OR DEFECTIVE OLD RESTORATIVE MATERIALINFECTED DENTIN OR DEFECTIVE OLD RESTORATIVE MATERIAL left left in the tooth after initial tooth preparationin the tooth after initial tooth preparation..

Ideal method of removing this material would be one in Ideal method of removing this material would be one in

achieved by-achieved by-

use of a round carbide bur, in -high speed hand piece -with air coolant

- slow speed

complete control of operator on the instrument

which minimal pressure which minimal pressure is exerted,is exerted,frictional heat is frictional heat is minimized,minimized, complete control of the complete control of the instrument is available.instrument is available.

Infected dentin can be removed by :- - spoon excavator -round steel burs at slow speed - slow speed round carbide bur with water coolant.

Old restorative material Old restorative material removal is indicated if :removal is indicated if :

- - it affects esthetics.it affects esthetics.

- compromise retention of new restoration. - compromise retention of new restoration.

- evidence of secondary caries.- evidence of secondary caries.

- marginal deterioration of old restoration.- marginal deterioration of old restoration.

Need for pulp protectionelectrical insulationchemical protection

Barrier to prevent microleakage

Pulp medication to allow pulp recovery in case of deep defects

Thermal and Mechanical protection

STEP 6 PULP PROTECTION

This is actually not a step in tooth preparation in the strictest sense it is a step in adapting the preparation for receiving the final

restoration it is considered under final preparation stage.

Need for pulp protection

Pulp ProtectionPulp Protection BasesTraditional liners

Bases are theBases are the cements cements used in used in thicker dimensions thicker dimensions beneath beneath permanent restorationspermanent restorations

Bases provide :Bases provide :for mechanical, chemical, and for mechanical, chemical, and

thermal protection of the pulp.thermal protection of the pulp.

ExamplesExamples zinc phosphate;zinc phosphate; zinc oxide-eugenol;zinc oxide-eugenol;calcium hydroxide; calcium hydroxide; polycarboxylate;,polycarboxylate;,some type of glass ionomer.some type of glass ionomer.

Liners provide:Liners provide: Barrier that protects the dentin Barrier that protects the dentin

from noxious agents from from noxious agents from either the restorative material or either the restorative material or oral fluidsoral fluids,,

initial electrical insulation,initial electrical insulation,

some thermal protection. some thermal protection.

Liners are volatile or aqueous suspensions or dispersions of zinc oxide or calcium hydroxide that can be applied to a tooth surface in a relatively thin films'

Dycal

The specific pulpal response desired dictates the choice of liner :The specific pulpal response desired dictates the choice of liner :

if removal of infected dentin does not extend deeperdoes not extend deeper than 1 to 2 mm than 1 to 2 mm from the initially prepared pulpal or axial wall, usually no liner is indicated. no liner is indicated.

If deep excavationsdeep excavations ,no pulpal exposuresno pulpal exposures zinc oxide eugenol linerzinc oxide eugenol liner (except for composite restorations)

if very deep excavations very deep excavations , pulpal exposures. Calcium HydroxideCalcium Hydroxide Stimulate reparative dentin

Liners and bases in exposure areas should be applied without pressure. without pressure. approx 1-mm thickness 1-mm thickness (Calcium Hydroxide ) overlaid with a base for amalgam or cast metal restorations. amalgam or cast metal restorations.

for composite restorative materialscomposite restorative materials,, a liner of calcium hydroxide is indicated only when pulpal exposure or the excavation is judged to be within 0.5 mm of the pulp

RetentionRetention groovegroove

Step- 7 SECONDARY RESISTANCE AND RETENTION FORM.

Beveled enamel margins

amalgapins. (Ref.F, Pg.89)

Slot

ETCHING AND SEALING

Featured as two forms :

Mechanical feature include:

- retention grooves & coves

- groove extensions

- skirts

- beveled enamel margins

- pins, slots, steps & amalgampins

Conditioning procedures :

- etching & bonding ( for GIC)

SECONDARY RESISTANCE AND RETENTION FORM.

Step 8 :Finishing the external walls of the Step 8 :Finishing the external walls of the preparation:preparation:

Objectives :Objectives :

- provides smooth marginal junction b/w the - provides smooth marginal junction b/w the restoration & toothrestoration & tooth

- provide close adaptation b/w the restoration & - provide close adaptation b/w the restoration & toothtooth

- provide maximum strength- provide maximum strength

Factors :Factors :

- - direction of enamel rodsdirection of enamel rods

- support of enamel rods both at DEJ & at - support of enamel rods both at DEJ & at preparation sidepreparation side

- choice of restorative material- choice of restorative material

- location of margin - location of margin

- degree of smoothness desired- degree of smoothness desired

Features :Features :

- Design of the cavosurfaceDesign of the cavosurface angle angle

For amalgamFor amalgam – – 90 degree cavosurface 90 degree cavosurface angle to compensate for the low edge angle to compensate for the low edge strength of materialstrength of material

Degree of smoothness or roughness of Degree of smoothness or roughness of the wall the wall

STEP 9: FINAL PROCEDURES: CLEANING, INSPECTING, AND SEALING

Final procedures in tooth preparation Final procedures in tooth preparation includeinclude

cleaning cleaning of the preparation inspectinginspecting the preparation applying a sealerapplying a sealer when indicated.

-removing all chips and loose debris accumulated,-drying the preparation

if debris clings to the wallsdebris clings to the walls -loosen this material with an explorer or small cotton pellet.It is important not to dehydrate important not to dehydrate the tooth by overuse of air or by the application of alcohol

final complete inspection of the preparationfinal complete inspection of the preparation done for :

-any remaining infected dentin, -unsound enamel margins, -Or any condition that renders the preparation unacceptable to receive the restorative material.

cleaning of the preparationcleaning of the preparation

visual inspection is done to confirm its appropriatenessvisual inspection is done to confirm its appropriateness..

Composite restorationsComposite restorations, require some treatment which includes

-etching enamel and dentinetching enamel and dentin and placing a dentin bonding agentplacing a dentin bonding agent

creates a strong mechanical bondstrong mechanical bond between the composite and the dentin.

applying a sealerapplying a sealer when indicated.

Class V restorationsClass V restorationsFoundations (including Foundations (including for badly broken-down for badly broken-down teethteeth

Moderate to large Class I and Class 11 restorationsModerate to large Class I and Class 11 restorations

amalgam amalgam foundations foundations placedplaced

INDICATION FOR AMALGAM RESTORATIONINDICATION FOR AMALGAM RESTORATION

Basic bur head shapes.

Bur no.245 is usedBur no.245 is used

Pear shapedPear shaped

Head length-3mmHead length-3mm

Diameter-0.8mmDiameter-0.8mm

PROCEDURE FOR MAKING CAVITY PREPRATION FOR AMALGAM RESORATIONPROCEDURE FOR MAKING CAVITY PREPRATION FOR AMALGAM RESORATION

Class 1 cavity preparation Class 1 cavity preparation design for other teeth design for other teeth

Step in placing a class Step in placing a class 1amalgam restoration1amalgam restoration

Step in Step in placing a placing a

class class 1amalgam 1amalgam restorationrestoration

Step in Step in placing a placing a

class class 1amalgam 1amalgam restorationrestoration

Classification of Restorative Materials

Lasting QualitiesLasting Qualities Working PropertiesWorking Properties Mode of UseMode of Use

Temporary

Zinc Oxide- eugenol

Zinc phosphate cement

Silicate cement

Self-curing acrylic resin

Gutta-percha

Permanent

Pure Gold

Cast Metal Alloy

Amalgam

Ceramics

Plastic restorative material

Amalgam

Cements

Resins

Pure Gold

Ceramics

Non-Plastic restorative material

Cast Gold Alloys

Castable dental ceramics

Autocopy milling ceramics-

Directly used restorative materials

Amalgam

Cements, Bases

Bonding agents

Pit and fissure sealants

Composites

Glass ionomer cements

Direct filling gold

Direct filling ceramics

Indirectly used using restorative materials

Cast metal restorative materials

Indirect dental ceramic materials

Metal ceramic material

Restorative Materials can be classified according to :

PREVENTION IS ALWAYS BETTER THEN CUREPREVENTION IS ALWAYS BETTER THEN CURE