Presentation on theme: "Fundamentals in Tooth Preparation"— Presentation transcript:
1Fundamentals in Tooth Preparation Dr. Ramesh BhartiAssistant ProfessorConservative Dentistry &EndodonticsKing George’s Medical UniversityLucknow
2Definition of Operative Dentistry Operative dentistry is the ART and SCIENCE of the diagnosis, treatment, prognosis of defects of teeth which do not require full coverage restorations for correction, such treatments should results in the restoration of proper tooth form, function, and esthetics while maintaining the physiologic integrity of the teeth in harmonious relationship with adjacent hard and soft tissue, all of which enhance the general health and welfare of the patient.
3Objectives of Cavity Preparation Remove all defects and give the necessary protection to pulp.Locate the margins as conservatively as possible.Form the cavity so that both the restoration and tooth can withstand the load of mastication.Allow for the esthetic and functional placement of a restorative material.
4Need of Restoration Caries Malformed, discolored or fractured teeth Restoration replacement
5Factors affecting tooth preparation 1. General FactorsPulpal & periodontal statusOcclusal relationship2.Dental anatomyDirection of enamel rodsThichness of enamel /dentinSize and positionof pulpRelationship of tooth to its supporting tissues
63.Patient factors 4.Affected & infected Dentine AgeEsthetic considerationEconomic statusPatients with high risk caries4.Affected & infected Dentine5. Restorative material factors
7Approach of Operative. cont….. Cavity preparationMatrix applicationPreparation of materialsInsertion and carving of materialsFinishing and Polishing
8Cavity PreparationThe mechanical alteration of a defective, injured, or diseased tooth in order to best receive a restorative material which will re- establish a healthy state for the tooth including esthetic corrections where indicated, along with normal form and function.
13Stages and Steps in Cavity preparation Initial cavity preparation stageFinal cavity preparation stage
14Initial cavity preparation stage Step 1 Outline form and initial depthStep 2 Primary resistance formStep 3 Primary retention formStep 4 Convenience form
15Final cavity preparation stage Step 5 Removal of any remaining infecteddentin if indicatedStep 6 Pulp protectionStep 7 Secondary resistance & retention formStep 8 Procedure for finishing external wallsStep 9 Final procedures
16Outline Form and Initial Depth Definition:placing the cavity margins in the positions they will occupy in the final preparation.preparing an initial depth of 0.2~0.8 mm pulpally of the dentinoenamel junction position or normal root surface position.
23Outline Form and Initial Depth Principles:all friable and/or weakened enamel should be removedall faults should be includedall margins should be placed in a position to afford good finishing ofthe margins of the restoration.Margins of the preparation will be located on finishable, self –cleansing area.
24Outline Form and Initial Depth Features:preserving cuspal strengthpreserving marginal ridge strengthminimizing facio-lingual extensionusing enameloplastyconnecting two close faults or cavitiesrestricting the depth of the preparation into dentin.
25Auxillary Factors Conservation Adjacent enamel cracks or decalcification could be involved in the preparation.Type of restorative material.Extension for access.anatomy and alignment.If possible, no margins will be in occlusion with opposing teeth.Esthetics
29Outline Form and Initial Depth for pit and fissure cavities Controlled by three factors1- Extension to which enamel has been involved by caries.2- Extension to achieve sound and smooth margins.3- Limited bur depth while extending the preparaton
30RulesCapping of cusp should be done when cavity extension is two-third from central fissure to cuspal eminence.Include all fissures that cannot be eliminated by enameloplasty.Restrict the depth.Join two lesions if they are less than 0.5 mm apart.
31Outline Form and Initial Depth for smooth surface cavities Extension of cavity.Sufficient access.Depth.Sufficient clearance with adjacent tooth.
32Initial cavity preparation stage Step 1 Outline form and initial depthStep 2 Primary resistance formStep 3 Primary retention formStep 4 Convenience form
33Primary Resistance Form Definition:The shape and placement of the cavity walls that best enable both the restoration and the tooth to withstand, without fracture, masticatory forces delivered principally in the long axis of the the tooth.
34Primary Resistance Form Principles:To utilize the box shape with a relatively flat floor to resist occlusal loading by virtue of being at right angles to mastication force.To restrict the extension of the external walls (keep as small as possible) to allow strong cusp and ridge areas to remain with sufficient dentin support.
35Primary Resistance Form Principles:To have a slight rounding of internal line angles to reduce stress concentration in tooth structure;The presence of sharp internal line angles in GOLD FOIL resist the movement of the restorationSharp internal line and point angles in dentin serve as convenient “starting” points for compacting of direct gold.To provide enough thickness of restorative material to prevent its fracture under load.
36Primary Resistance Form Feature:Box shapeRelatively flat floorsInclusion of weakened tooth structurePreservation of cusps and marginal ridgesRounded internal line anglesAdequate thickness of restorative materialsReduction of cusps for capping if indicated
37Primary Resistance cont…. Designing the outline form so that minimal of restoration is exposed to occlusal stress.Seat on sound dentin.
38Vale Experiments 1 MR at 1/4th ICD -10% Loss of FR 1 MR at 1/2 of ICD -40% Loss of FR2 MR at ½ of ICD -45% Loss of FR
40Initial cavity preparation stage Step 1 Outline form and initial depthStep 2 Primary resistance formStep 3 Primary retention formStep 4 Convenience form
41Primary Retention Form Definition:The shape or form of the prepared cavity that resists displacement or removal of the restoration from tipping or lifting forces.
42Primary Retention Form Principles: depending on the materialsAmalgam restoration:developing external cavity walls that converge occlusally and dovetail design
43The devotail design provide retention form to the occlusal portion of the cavity.The occlusal convergence of the walls offersretention in the proximal portion of the cavityagainst displacement occlusally.
54Final cavity preparation stage Step 5 Removal of any remaining infecteddentin if indicatedStep 6 Pulp protectionStep 7 Secondary resistance & retention formStep 8 Procedure for finishing external wallsStep 9 Final procedures
55Removal of any remaining infected dentin if indicated Definition:The elimination of any infected carious tooth structure or faulty restorative material left in the tooth after initial cavity preparation.
56Removal of dentinal caries using round burs and spoon excavators A: use of a round carbide bur, with air coolant and slow speed.B: use of spoon excavators.Removal of dentinal caries using round burs and spoon excavators
57Pulp protectionUsing liners or bases to protect the pulp or to aid pulpal recovery or both.If the infected dentin more than 2 mm deeper from the initial pulpal or axial wall then a Liner is indicated.
62Final cavity preparation stage….. Step 5 Removal of any remaining infecteddentin if indicatedStep 6 Pulp protectionStep 7 Secondary resistance & retention formStep 8 Procedure for finishing external wallsStep 9 Final procedures
63Secondary resistance and retention forms Most compound and complex cavity preparations require additional resistance and retention form.The exception being those preparations that are very conservative.
64Secondary resistance and retention forms Mechanical formsCavity wall conditioning form
70Final cavity preparation stage…. Step 5 Removal of any remaining infecteddentin if indicatedStep 6 Pulp protectionStep 7 Secondary resistance & retention formStep 8 Finishing external wallsStep 9 Final procedures
71Finishing the external walls Definition:Finishing the preparation walls is the further development of a specific cavosurface design and degree of smoothness that produces the maximum effectiveness of the restorative material being used.
72Finishing the external walls Objectives:To create the best marginal seal possible between the restorative material and tooth structure;To afford a smooth marginal junction;To provide maximum strength of both the tooth and the restorative material at and near the margin.
73The strongest enamel margin is that margin which is composed of full-length enamel rods that are supported on the cavity side by shorter enamel rods, all of which extend to sound dentin.
74Finishing the external walls The design of the cavosurface angleThe degree of smoothness of the wall
75The design of the cavosurface angle depending on the material: Amalgam: 90°Composite: beveling 30°~ 40°
83Multiple Choice Questions Q.1. In cavity prepartion cavo-surface margin will be a junction between : a) Cavity wall/floor and adjacent tooth surface. b) Cavity wall and floor. c) Floor of the occlusal box and aproximal box d) Axial wall and occlusal floor.
84Q.2 Toilet of the cavity is: a) Removal of debris by washing with waterb) Removal of debris by cold airc) Removal of debris by hot aird) Washing the cavity with water.
85Q.3 Most common fracture seen in amalgam restoration at: a) Cavosurface margin.b) Contact areac) Isthmus aread) Proximal box
86Q 4 G. V Black concluded that following area of tooth surface are relatively non-selfcleansing: A) Pit and fissuresB) Tips and cuspsC) FossaD) Marginal ridge
87Q.5 Class III amalgam restorations areusualy prepared on: a) Distal surface of anterior teethb) Mesial surface of caninec) Distal surface of caninec) Mesial and distal surface of all teeth.