Principles of Cavity Preparation 1 Handout PDF

PRINCIPLES OF CAVITY PREPARATION DR. AMR RAMADAN LECTURER CONSERVATIVE DEPARTMENT AHRAM CANDIAN UNIVERSITY  PRINCIPLES) OF CAVITY PREPARATION A. BIOLOGICAL FUNDAMENTALS 1. Protection of dentin and pulp 2. Control of caries 3. Protection of investigating tissues and adjac...

PRINCIPLES OF CAVITY PREPARATION DR. AMR RAMADAN LECTURER CONSERVATIVE DEPARTMENT AHRAM CANDIAN UNIVERSITY  PRINCIPLES) OF CAVITY PREPARATION A. BIOLOGICAL FUNDAMENTALS 1. Protection of dentin and pulp 2. Control of caries 3. Protection of investigating tissues and adjacent tooth 1. PROTECTION OF DENTIN AND PULP 1. MECHANICAL 2. THERMAL 3. CHEMICAL 4. BACTERIAL IRRITATION IRRITATION IRRITATION IRRITATION 1. MECHANICAL IRRITATION 1. Excessive cutting of enamel (width) Increase Expose large Weakening width in area of of remaining enamel dentine tooth 2.Over cutting of dentine depth and unnecessary deepening of the cavity Decrease Deeper the remaining Increase cavity protective irritation dentin 3. The application of excessive pressure on the dentine forming the base of a deep cavity. 4.Cutting across the recessional lines of the pulp. The excavation of soft dentine must be carried out: Parallel to the pulp Scooping action Layer by layer 1. PROTECTION OF DENTIN AND PULP 1. MECHANICAL 2. THERMAL 3. CHEMICAL 4. BACTERIAL IRRITATION IRRITATION IRRITATION IRRITATION 2. THERMAL IRRITATION Unavoidable degree of fictional heat resulting during cavity preparation The goal is to keep this heat within the Thermal tolerance zone of dentin 29-56˚C=85-132˚F 2. THERMAL IRRITATION 1.Minimizing Frictional Heat Control 2.Coolant (air –water) 2. THERMAL IRRITATION 1. pressure 2. Cutting area 3. Time of cutting 1.Minimizing Frictional Heat Tool with high cutting efficiency: 1. Sharp 2. size 3. function 2. THERMAL IRRITATION 2.Coolant (air-water) 2. THERMAL IRRITATION 1. PROTECTION OF DENTIN AND PULP 1. MECHANICAL 2. THERMAL 3. CHEMICAL 4. BACTERIAL IRRITATION IRRITATION IRRITATION IRRITATION  3. CHEMICAL IRRITATION Chemicals during toilet of the cavity (alcohol – Phenol) Acid conditioners used with bond restorations 1. PROTECTION OF DENTIN AND PULP 1. MECHANICAL 2. THERMAL 3. CHEMICAL 4. BACTERIAL IRRITATION IRRITATION IRRITATION IRRITATION 4.BACTERIAL IRRITATION To avoid cross infection during cavity preparation sterilization of instruments, burs and armamentarium is essential. In case of very deep cavities with very thin remaining dentin bridge barrier ---- use rubber dam A. BIOLOGICAL FUNDAMENTALS 1. Protection of dentin and pulp 2. Control of caries 3. Protection of investigating tissues and adjacent tooth  2. CONTROL OF CARIES 1. Removal of all primary caries E&D 2. Extension for prevention 3. Removal of all undermined enamel and short lose or friable enamel rods 4. Correct CSA  ALL KNOWN PREVENTIVE MEASURES Oral hygiene Topical fluorides application Antibacterial agents Remineralizaing agents A. BIOLOGICAL FUNDAMENTALS 1. Protection of dentin and pulp 2. Control of caries 3. Protection of investigating tissues and adjacent tooth 3. PROTECTION OF INVESTIGATING TISSUES AND ADJACENT TOOTH This is achieved by 1. 1.Rounding and smoothing ragged cavity margins especially those adjacent to the gingiva 2. 2.Excision of the infectious lesions and elimination of defects which in encourage plaque retention 3. 3.Avoid unnecessary subgingival extensions whenever possible 4. 4.Protect adjacent tooth surface 5. 5.Proper guide and support for hand and rotary instruments B. MECHANICAL FUNDAMENTALS These principles are primarily concerned with 1. Resistance 2. Retention This can be achieved through a correct mechanical cavity design and maximum conservative conservation of tooth structure  C. ESTHETIC FUNDAMENTALS 2. Conservative cavity 1. cavity outline: design (limiting area of A. symmetrical display) B. Refined margins C. Smooth sweeping curves 3. Eliminating D. Margins must be either discolored E&D (use concealed or placed parallel to opaquers) dentin when respective tooth contours using aesthetic tooth E. Margins free of opaque , coloured discolored , pitted enamel CONSERVATIVE APPROACH IN CONSERVATIVE DENTISTRY The concept of conservation in dentistry refers to all procedures carried out to preserve the integrity of teeth and the masticatory system These procedures involves all measures of : Prevention Diagnosis To preserve the teeth integrity and functions Treatment Follow up methods G.V. Black in1891 believed that there are areas in the tooth structure that are less susceptible to caries these areas include: The outer two-thirds of cusps slopes tooth Axial line angles Above the buccal and lingual height of contour The embrasures.  He advocated that all cavity margins should be extended to these self-immune. This concept was known as extension for prevention or cutting for immunity 1. G.V. Black (1891): extension for prevention or cutting for immunity 2. Markley (1951): extension for convenience 3. Sealing for prevention (pit and fissure sealant) 4. Loeche (1982): extension of prevention  ADVANTAGES OF CONSERVATIVE DESIGN 1. Preservation of valuable intact health tooth structure 2. Decrease irritation to D-P complex and investigating structure 3. Decrease fracture liability of tooth and restoration 4. Decrease displayed areas of restorations 5. Easier, quicker and standardized procedures STEPS OF CAVITY PREPARATION (G.V. BLACK) 1.Obtaining the outline form 2. Obtaining the resistance and retention form 3. Obtaining the convenience form 4. Removal of remaining carious dentin 5. Finishing of cavity walls and margins 6.Performing the toilet of the cavity STEPS OF CAVITY PREPARATION (G.V. BLACK) 1.Obtaining the outline form 2. Obtaining the resistance and retention form 3. Obtaining the convenience form 4. Removal of remaining carious dentin 5. Finishing of cavity walls and margins 6.Performing the toilet of the cavity STEPS OF CAVITY PREPARATION (G.V. BLACK) 2. Obtaining the 3. Obtaining the 1.Obtaining the resistance and convenience outline form retention form form 4. removal of 5. finishing of 6.Performing remaining cavity walls and the toilet of the carious dentin margins cavity 1. OUTLINE FORM The shape of boundaries of the completed cavity External Marginal outline form boundaries Outline form Internal Shape of the internal form of outline form the preparation  GENERAL FACTORS AFFECTING THE OUTLINE Factors Affecting The Outline 1. Extension of the caries defect in enamel and its lateral spread in dentin at the dentino-enamel junction Access=starting point (near pathology) Factors Affecting The Outline 2. Defective , non reminiralizable and retentive enamel ( pits, fissures and grooves) which are deeper than one third the enamel thickness and are continuous with the cavity outline should be included in the outline. A. Liable to caries as they are retentive for food B. Adaptation. when the restoration tooth interface is located at this area, this will prevent securing of adequate adaptation of the restoration. Factors Affecting The Outline 3. To achieve conservative approach: i. Slanting bur technique ii. Pit and fissure sealing Pit and fissures if : non carious or caries doesn’t extend more than of the outer two third of enamel thickness:  SLANTING BUR TECHNIQUE Preventive measures for treatment of supplementary or defective fissures approximating the outline of the cavity  SLANTING BUR TECHNIQUE Technique: The fissure bur is placed on the wall of the preparation and slanted or tilted to 110˚ to include the fissure. The prepared area is usually included in the restoration. However, this technique achieves conservation of tooth structure at the expense of mechanical retention and resistance at this area.  PIT AND FISSURE SEALING Deep angular grooves liable to stagnation and difficult to clean as in recently erupted permanent molars Preventive resin restoration (PRR) 4. All enamel which is weak or undermined by caries must be eliminated. Enamel is brittle and depends on elasticity of D for support Break Brittle Marginal under enamel Ditch mastication 5. Adjacent cavities , closely approaching to each other , should not be joined into a single cavity Unless if the intervening enamel is: A. Carious B. Undermined C. Weak (0.5mm) D. Crossed by deep fissure ( more than 2/3 thickness of E)  This should be especially considered with Oblique and transverse ridges Reinforce the tooth against splitting by lateral forces of mastication (strongly cross tie the two halves of the crown) 6. Cusps and ridges that are severely weakened and subjected to occlusal forces must be reduced and restored with appropriate restoration (cusp capping) 7. The outline form must be in the form of harmonious sweeping curve. To avoid stress concentration and provide better esthetics  8. The pulp should be protected against inadvertent cutting of dentin, thermogenesis, pressure , desiccation. Ideal depth 0.2-0.8mm beyond DEJ. According to : Strength requirements Retention Removal of carious tissues 9.The cavo-surface angle should be given correct angulation according to : A. physical properties of material B. Located in areas less liable to caries recurrence C. Less stress bearing 10. Age Considerations : Old Patients Occlusal Attrition Shallow Grooves Broad Contacts THANK YOU