Principles of Cavity Preparation - Lecture Notes PDF

Principles of Cavity Preparation Lecture 1: General principles. ILOs: By the end of this lecture the students should be able to: Define “Cavity preparation” List Objectives of cavity preparation Recognize and Different principles of cavity preparation dif...

Principles of Cavity Preparation Lecture 1: General principles. ILOs: By the end of this lecture the students should be able to: Define “Cavity preparation” List Objectives of cavity preparation Recognize and Different principles of cavity preparation differentiate Main parameters involved in the achievement of Discuss biological and mechanical principles How to avoid pulp injury and prevent caries Discuss recurrence through correct cavity preparation How to avoid tooth and/or restoration fracture Discuss and prevent restoration displacement through correct cavity preparation Cavity Preparation: Tooth preparation is the mechanical alteration of a defective, injured, or diseased tooth to receive a restorative material that reestablishes a healthy state for the tooth, including esthetic corrections where indicated and normal form and function.  Remove all defects Protection of the As conservatively pulp as possible Prevent further fracture of tooth and/or restoration Prevent displacement esthetic and functional of restoration placement of restoration Principles of cavity preparation: BIOLOGICAL MECHANICAL ESTHETIC PRINCIPLES PRINCIPLES PRINCIPLES Principles of cavity preparation: BIOLOGICAL MECHANICAL PRINCIPLES PRINCIPLES ESTHETIC PRINCIPLES  Biological principles Health and integrity of remaining tooth tissues Protection of the pulp Prevention of caries recurrence Protection of adjacent structures  I. Protection of the pulp Dentin bridge Pulpodentinal organ Protection of the pulp Mechanical irritation Thermal irritation Chemical irritation Bacterial irritation Mechanical irritation depth width pressure Sharp pointed tools Cutting across recessional lines of pulp Thermal irritation:  TTZ (thermal tolerance zone) of dentin which ranges between 85-132 F Minimizing the frictional heat Coolants 1. copious in amount, for an adequate rate of cooling 2. Multi directed 3. 37 C.  Thermal irritation: Air-water spray jet is considered to be the most appropriate air-drying stream can desiccate the water only disturbs the visibility during work. dentin Chemical irritation:  Bacterial irritation: Sterilization of instruments The use of rubber dam to isolate the field Curtesy: Misr International University  II. Prevention of caries recurrence: Recurrent caries Curtesy: Misr International University Remove all carious enamel and dentin Inclusion of all liable areas (pits &fissures) Prevention of caries recurrence: 3. Removal of all undermined enamel Prevention of caries recurrence: 4-Correct CSA compatible with restorative material 5-Extension for prevention Quiz What are the Possible causes? III. Protection of adjacent structures: Removal of all defective tooth structure that may encourage plaque accumulation Avoid unnecessary subgingival extension of the cavity margins Proper finishing and smoothening of the cavity margins especially the gingival margins Protection of the adjacent teeth during proximal tooth preparation, this may be done by the insertion of a steel band. to avoid slippage and injury proper use of guard and support during tooth cutting. Aseptic procedures 1. Use of sterile instruments 2. Isolation of operative field 3. Use of personal protective barriers Curtesy: Misr International University  Mechanical principles Structural integrity of both tooth and restoration demanding: Provision of correct resistance Provision of adequate retention Mechanical Principles: 1. Correct Cavity design Decrease the magnitude of the destructive stresses by: Inclination of walls Locating the margins Flat, smooth walls and floors Line and point angles Inclination of walls Carlos Rocha Gomes Torres, Falk Schwendicke. Modern operative dentistry. General Principles of Tooth Preparation and Carious Tissue Removal. Chapter 6. pg: 183-220  Flat, smooth walls and floors Heymann, H., Swift, E. J., Ritter, A. V., & Sturdevant, C. M. (2013). Sturdevant's art and science of operative dentistry. St. Louis, Mo: Elsevier/Mosby. 6th edition Line and point angles Mechanical Principles: 2.The cavity design should decrease the damaging effect of tensile stresses created within the tooth as a result of defect by: a. Conservation b. Removal of weakened tooth structure and undermined enamel 3.Provision of bulk in the brittle restorations for stress distribution so that the destructive forces could not damage the brittle restoration. 4.Provision of adequate retention to prevent displacement of restoration under functional forces. Principles of Cavity Preparation Lecture 2: Cavity preparation “ The outline form” ILOs: By the end of this lecture the students should be able to: List List the steps of cavity preparation Define Define the term outline form Identify the significance of correct Identify outline form Steps of Cavity Preparation According to G.V Black, cavity preparation is outlined in six steps of procedures based on biological, physical and mechanical fundamental principles. This enables systematization and standardization of these procedures so that each step will be completed perfectly and consistently  2. 1. 3. Convenience Resistance and Form Outline form Retention Steps of cavity preparation: 5. 4. 6. Finishing of enamel Removal of Carious Toilet of the Cavity walls and margins dentin There are occasions, however, where it may be found necessary to overlap some of these steps, as in case of deep carious lesions, where step 4 must precede step 2. The Outline Form: The external shape or form of boundaries of the completed cavity. The internal outline form of the cavity describes the form and dimensions of its interior. Curtesy: MIU Photography Centre Significance of a correct outline form is: 1. Removal of the actual defects 2. Prevention of caries recurrence about the margins of restorations.  Cardinal Principles 1. Carious enamel, as well as all pits and fissures, and angular grooves which are continuous with or very close to the initial carious lesion should be included in the cavity outlined.. 2. Cavities, which approach closely to each other, should be united into a single cavity to avoid leaving of intervening thin ridges of tooth structure, which will be subject to fracture during mastication. Marcel Alves Avelino de Paiva, Dayane Franco Barros Mangueira Leite, Isabela Albuquerque Passos Farias, Antônio de Pádua Cavalcante Costa and Fábio Correia Sampaio. Dental Anatomical Features and Caries: A Relationship to be Investigated. December 20th, 2017. Carlos Rocha Gomes Torres, Falk Schwendicke. Modern operative dentistry. General Principles of Tooth Preparation and Cardinal Principles 3. All enamel undermined by caries or unsupported by sound dentin, must be Carious Tissue Removal. Chapter 6. pg: 183-220 eliminated. If such enamel is left at a cavity margin, it will break easily under mastication forces leaving a marginal “ditch”  Cardinal Principles 4. Margins of cavities should always be placed in sound enamel at areas, which are, considered to be less susceptible to caries and less stress bearing. 5. A further extension of cavity margins beyond the limits just mentioned and into areas, which are considered to be more immune to caries, is sometimes demanded to prevent an anticipated caries recurrence. This is known as “extension for prevention” or “cutting for immunity”. “Prevention of extension”!!! Conservation of tooth structure For class I or pit and fissure cavities Controlled by: 1. extent of caries in enamel, and 2. limits of lateral spread of caries in dentin. 3. All pits and fissures that cannot be eliminated by enameloplasty 4. Capping of weakened cusps is to be considered if the extension from the primary groove includes ½ or more of the cusp incline. While it is mandatory if the extension is 2/3 of the cusp incline; to avoid lying the cavity margin in an area of maximum stresses  Enameloplasty It is reshaping of enamel fissures to be non retentive. It is made in pits or fissures that do not penetrate more than 1/3 of enamel especially at end of fissure. Tom Gallop. How the Patient Reimbursement Shift Is Affecting Dental Instrument Selection. Compendium. May 2014. Volume 35, Issue 5 Cusp Capping: It is reducing the weakened cusp and covering the reduced tooth structure with a strong restoration Lee W. Boushell and Aldridge D. Wilder, Jr. Complex Amalgam Restorations, Pocket Dentistry. Chapter 16 Textbook of operative dentistry. Chapter-08 Nomenclature, Classification and Fundamentals in Cavity (Tooth) Preparation Bansal Amol, Tyas Martin J. Textbook of operative dentistry. Chapter 2 The outline form should be sufficiently extended to allow for proper access to tooth preparation, restoration placement and finishing procedures Carlos Rocha Gomes Torres, Falk Schwendicke. Modern operative dentistry. General Principles of Tooth Preparation and Carious Tissue Removal. Chapter 6. pg: 183-220 When two preparations have less than 0.5 mm of sound tooth structure between them, they should be joined to avoid fracture of the weak intervening tooth structure  For proximal portions of classical class II, III, and IV Clearance cavities Free margins of the cavity from contact with adjacent tooth or restoration Accessibility for finishing and brushing Clearance A Restorative Approach for Class II Resin Composite Restorations: A Two-Year Follow-up. Operative Dentistry, 2015, 40-1, 19-24 The proximal outline is affected by: 1. The size and site of the contact area. 2. The width of the embrasures. 3. The position of the axial line angles of the tooth surfaces. 4. The position and health of the free gingival margin.  Class II Cavity Preparation: The junction between occlusal and proximal portions of classical class II (isthmus) is either: 1. Straight line 2. Uniform curve 3. Reverse curve A Restorative Approach for Class II Resin Composite Restorations: A Two-Year Follow- up. Operative Dentistry, 2015, 40-1, 19-24 For Class II Cavity : – Locating the buccal wall of proximal cavity free of contact. – Keeping the junction between the occlusal outline and the proximal surface at 90 degree to avoid either undermining or beveling of the CSA. This provides the necessary bulk for the restoration at the proximal buccal wall. – Avoid the unnecessary weakening of the distal cusp in first molar. Class III Preparation For class V cavities The outline form of class V cavity preparation is governed primarily by the extent of the lesion. The extension mesially, distally, gingivally, and occlusally (incisally) is limited by reaching sound tooth structure. Curtesy: Misr international university Class V The outline form of class V cavity preparation is governed primarily by the extent of the lesion. The extension mesially, distally, gingivally, and occlusally (incisally) is limited by reaching sound tooth structure. Some modifications could be applied to the classical outlines of different cavity designs for sake of: Conservation, Esthetics Convenient approach Oral hygiene and Occlusion of the particular patient. (Refer to notes)  Principles of Cavity Preparation Lecture 3: Cavity preparation “Resistance and Retention”  2. 1. 3. Convenience Resistance and Form Outline form Retention Steps of cavity preparation: 5. 4. 6. Finishing of enamel Removal of Carious Toilet of the Cavity walls and margins dentin ILOs: By the end of this lecture the students should be able to: Define Resistance form and retention form How to provide both resistance and Explain retention in the prepared cavity Examples for the correlation between Identify resistance and retention  Resistance Retention Form Form There are two distinct but yet inseparable steps The Resistance form refers to: The design features in the cavity, which provide for structural integrity of both the tooth and restoration of which will allow both to resist the functional stresses of mastication without fracture.  Factors Influencing Stress Response of Tooth and Restoration Occlusal loading: magnitude, direction, character Strength characteristics of the loaded structure: brittle vs ductile materials Design: walls direction, amount of retention Heymann, H., Swift, E. J., Ritter, A. V., & Sturdevant, C. M. (2013). Sturdevant's art and science of operative dentistry. St. Louis, Mo: Elsevier/Mosby. 6th edition  Design features: Walls direction which must be parallel and perpendicular to the direction of expected forces to get these forces balanced out and thus prevent splitting tendencies Walls smoothness and flatness Lines and point angles must be rounded Bulk Cavity width The amount of retention in the cavity which makes for stability of the structure and prevents its displacement or fracture  Design Features Walls direction which must be parallel and perpendicular to the direction of expected forces to get these forces balanced out and thus prevent splitting tendencies  Design Features Walls smoothness and flatness Lines and point angles must be rounded Carlos Rocha Gomes Torres, Falk Schwendicke. Modern operative dentistry. General Principles of Tooth Preparation and Carious Tissue Removal. Chapter 6. pg: 183-220  Bulk Design Features Cavity width  Design Features The amount of retention in the cavity which makes for stability of the structure and prevents its displacement or fracture The CSA in accordance to the physical properties of the restorative materials Pocket Dentistry, Fastest Clinical Dentistry Insight Engine,https://pocketdentistry.com/19-cutting-instruments/  Box (mortise) or modified box form: 1. Seat of the restoration (pulpal and gingival wall) is placed at a distinct right angle to the direction of functional stresses a) neutralization of these stresses b) prevent them getting resolved into components of destructive tensile stresses which tend to fracture the tooth and or the restoration Carlos Rocha Gomes Torres, Falk Schwendicke. Modern operative dentistry. General Principles of Tooth Preparation and Carious Tissue Removal. Chapter 6. pg: 183-220 Pocket Dentistry, Fastest Clinical Dentistry Insight Engine. https://pocketdentistry.com/19-cutting-instruments/ Box (mortise) or modified box form: 2. Tendency to splitting of the buccal and lingual cusps of biscupids and molars by forces transmitted through the restoration is greatly diminished; the restoration otherwise may act as a wedge inside the tooth.  Box (mortise) or modified box form: 3. It augments retention 4. It improves access to and easy visualization of the interior of the cavity, for easier, and better instrumentation and filling. 5. Restorative materials tend to adapt better against plane surfaces. 6. It allows to create retentive features in dentine.  The retention form: Describes the design features in the cavity, which enables it to hold in or retain the restoration securely in function. It helps maintenance of stability and adaptation of the restoration against mastication forces that tend to displace it out of the cavity  Types of retention: Retention is generally classified according to the possible direction of displacement into: axial ▪ Axial lateral ▪ Lateral Nisha Garg; Amit Garg; Ibrahim Abu Tahun.Textbook of operative dentistry. Jaypee Brothers,Medical Publishers Pvt. Limited, 2019 a) Axial retention: This prevents displacement axial of restoration in a direction parallel to the long axis of the tooth i.e. in occlusal or apical (pulpal or gingival) directions. 1. Undercuts 2. Frictional parallelism 3. Dentine ledges Undercuts  Carlos Rocha Gomes Torres, Falk Schwendicke. Modern operative dentistry. General Principles of Tooth Preparation and Carious Tissue Removal. Chapter 6. pg: 183-220 Frictional Parallelism Pocket Dentistry, Fastest Clinical Dentistry Insight Engine. https://pocketdentistry.com/19-cutting-instruments/  Dentin ledge Marcel Alves Avelino de Paiva, Dayane Franco Barros Mangueira Leite, Isabela Albuquerque Passos Farias, Antônio de Pádua Cavalcante Costa and Fábio Correia Sampaio. Dental Anatomical Features and Caries: A Relationship to be Investigated. December 20 th, 2017. Dentin ledge Dentin Ledge HILTON, T. J., FERRACANE, J. L., & BROOME, J. C. (2013). Summitt's fundamentals of operative dentistry: a contemporary approach. https://search.ebscohost.com/login.aspx?direct=true&scope=site&db=nlebk&db=nlabk&AN=784581. b) Lateral retention: The features provided to prevent displacement in any lateral other direction than the axial is considered lateral, e.g proximal, buccal or lingual directions. 1. Frictional opposing wall parallelism, 2. Dove-tail locks in compound cavities 3. Proximal axial grooves. In compound class Il cavities 4. Buccal or lingual extensions in molars and extensions onto the other side in premolars. 5. Skirting 6. Reverse bevel 7. Gripping action of dentine 8. Pin holes and pins. Carlos Rocha Gomes Torres, Falk Schwendicke. Modern operative dentistry. General Principles of Tooth Preparation and Carious Tissue Removal. Chapter 6. pg: 183-220 Parallelism  Dove tail locks Satish Chandra, Shaleen Chandra, Girish Chandra. Textboom of Operative dentistry. Chapter 39 Various Designs and Shapes of Margins of Tooth Preparations and Restorations.  Proximal axial grooves: Satish Chandra, Shaleen Chandra, Girish Chandra. Textboom of Operative dentistry. Chapter 39 Various Designs and Shapes of Margins of Tooth Preparations and Restorations.  Skirting Heymann, H., Swift, E. J., Ritter, A. V., & Sturdevant, C. M. (2013). Sturdevant's art and science of operative dentistry. St. Louis, Mo: Elsevier/Mosby. 6th edition  Reverse Bevels Gingival Lock Satish Chandra, Shaleen Chandra, Girish Chandra. Textboom of Operative dentistry. Chapter 39 Various Designs and Shapes of Margins of Tooth Preparations and Restorations. Carlos Rocha Gomes Torres, Falk Schwendicke. Modern operative dentistry. General Principles of Tooth Preparation and Carious Tissue Removal. Chapter 6. pg: 183-220 Pin holes and pins  Other retentive features ▪ Acid–etching of enamel ▪ Dentinal bonding ▪ Intra-radicular, i.e, through posts inserted in the root canals of pulpless teeth. Marcel Alves Avelino de Paiva, Dayane Franco Barros Mangueira Leite, Isabela Albuquerque Passos Farias, Antônio de Pádua Cavalcante Costa and Fábio Correia Sampaio. Dental Anatomical Features and Caries: A Relationship to be Investigated. December 20th, 2017.  Factors controlling the selection of retention features: 1. Size of cavity and amount of remaining tooth structure 2. Number of missing walls (C factor) 3. Site of cavity and occlusal stress 4. Type of restoration (direct vs indirect, amalgam vs composite) 5. Pulp vitality (type of pin, posts) 6. Esthetic requirements (skirting) Size of cavity and amount of remaining tooth structure Size Number of missing walls (C factor) C factor number of missing walls  Site of cavity and occlusal stress Site of cavity and occlusal stress Site of cavity and occlusal stress  Type of restoration (direct vs indirect, amalgam vs composite) Pulp vitality (type of pin, posts) Esthetic requirements (skirting) Retention here serves two-fold purposes; 1. stability of the restoration within the cavity (retention) 2. at the same time prevents its fracture (resistance) Retention & resistance are interrelated This may partly be provided automatically during making the resistance form. 1. A box form preparation is a form of resistance, will at the same time provide for retention by friction or gripping action of dentin. 2. Inverted truncated cone prevents wedging action inside the tooth (resistance) meanwhile it provides retention by undercuts. 3. Bulk: a. Prevents fracture of brittle materials b. Increases retention by friction and undercut  Retention & resistance are interrelated 4. Every portion of the compound cavity must be provided with its own retention features and should never depend on other portions of the same cavity for retention. Otherwise, tensile stresses will set up and cause isthmus fracture of the restoration. 5. Instability of restoration leads to premature contact disturbing the relation between the load and loaded surface Retention & resistance are interrelated Pins for retention and reinforcing amalgam: If improperly designed would cause fracture of tooth/ restoration Marcel Alves Avelino de Paiva, Dayane Franco Barros Mangueira Leite, Isabela Albuquerque Passos Farias, Antônio de Pádua Cavalcante Costa and Fábio Correia Sampaio. Dental Anatomical Features and Caries: A Relationship to be Investigated. December 20 th, 2017. Retention & resistance are interrelated Dentin ledge a. Prevents pulpward movement of restoration b. Prevents fracture of thin dentin bridge Principles of Cavity Preparation Lecture 4: Convenience form  2. 1. 3. Convenience Resistance and Form Outline form Retention Steps of cavity preparation: 5. 4. 6. Finishing of enamel Removal of Carious Toilet of the Cavity walls and margins dentin Convenience form: The convenience form describes those features in the prepared cavity which improve the accessibility & visibility of the preparation. Obtaining the convenience form: Slightly more extension of a cavity margin Accentuation of line or point angles, Sweeping curves Elimination of undermined enamel for removal of decay Obtaining the convenience form: Instruments: rotary, hand Visibility: fiber optic light, caries detection dies New instruments Peter Walford Dentistry Dental Treatment, Science, and Nisha Garg; Amit Garg; Ibrahim Abu Tahun.Textbook of operative dentistry. Jaypee Education. https://www.peterwalforddentistry.com/caries- Brothers,Medical Publishers Pvt. Limited, 2019 detector-to-reveal-caries/ REMOVING THE REMAINING CARIOUS DENTIN: In the average case, most of carious dentin is removed during the previous procedures. The cavity must then be thoroughly inspected with sharp explorers, aided by good illumination and dryness of the operative field. REMOVING THE REMAINING CARIOUS DENTIN: This inspection may then reveal the cavity floor to be composed of: 1. Hard sound viable dentin free from lateral spread or discolorations along the D.E.J, no more deepening should be made. Springer Nature Switzerland AG 2019 47 M. S. Kher, A. Rao, Contemporary Treatment Techniques in Pediatric Dentistry, https://doi.org/10.1007/978-3-030-11860-0_2 The cavity must be extended deeper to the D.E.J. for the following reasons: 1. To get sure that there is no more lateral spread of caries along the D.E.J. which will otherwise undermine the overlying enamel. 2. To avoid cutting at and then placing a restoration against a most sensitive area of dentin at the D.E.J. where the dentinal tubules branch and anastomose. 3. To place retentive means in dentine. 4. To give sufficient bulk for the restoration. 5. To ensure sufficient protective dentin bridge. REMOVING THE REMAINING CARIOUS DENTIN: 2. Hard but discolored dentin. Stained dentin is not always a carious dentin indicated for removal. If such a dentin is hard, then the depth of the cavity should determine whether this dentin is to be removed. If this cavity seat lies at a correct depth, then there is no harm in leaving this dentin, except in case of anterior teeth where it must be carefully removed for esthetic reasons. Nicola Innes & Falk Schwendicke. Treatment options for carious tissue removal. Clinical Dentistry Reviewed (2019) 3:3 https://doi.org/10.1007/s41894-019-0042-z REMOVING THE REMAINING CARIOUS DENTIN: 3. Soft dentin. Which is painful, denoting presence of viable protoplasmic processes, and which may be discolored (chronic caries) or not (acute caries). This layer constitutes the floor of deep and moderately deep cavities. Removal of this carious dentin, if advisable, must be done with extreme care, since, it is too close to the pulp which may easily get exposed. Nicola Innes & Falk Schwendicke. Treatment options for carious tissue removal. Clinical Dentistry Reviewed (2019) 3:3 https://doi.org/10.1007/s41894-019-0042-z  Selective caries removal Partial caries removal Stepwise excavation a) Deep carious lesion showing caries-infected zone (A) and caries-affected zone (B). b) Selective caries removal clearing the periphery of the cavity but leaving affected dentine over the pulp, with c) conventional complete caries removal risking pulp exposure Methods of caries removal Physical methods: ▪ Mechanical: manual excavation, round bur, air abrasion. ▪ Thermal: Laser. Chemical methods: ▪ Carisolv and Caridex. Mechanical Different types of burs. Excavators. Air Abrasion Thermal (LASER) Parker S. Laser-tissue interaction. British Dental Journal 2007;202(2):73-81.  Chemical Marcel Alves Avelino de Paiva, Dayane Franco Barros Mangueira Leite, Isabela Albuquerque Passos Farias, Antônio de Pádua Cavalcante Costa and Fábio Correia Sampaio. Dental Anatomical Features and Caries: A Relationship to be Investigated. December 20th, 2017. The caries excavation techniques for removing deep carious dentin lesions. (A-1) rotary excavation, (B-1) Brix 3000 application, (C-1) Ultrasonic Caries Removal Tip SB1, (D-1) Waterlase iPlus Er,Cr:YSGG Laser. (A-2,B-2,C-2,D-2) The residual dentin after each technique, respectively. a, b, c) Definitive clearing of the amelodentinal junction to sound high-quality enamel and dentine margins. The pulpal wall remains unprepared at this stage. Self study topic: intermediary bases and liners, to be included in spring 25 midterm exam for 5 marks Principles of Cavity Preparation Lecture 5: Finishing of the cavity Toilet of the cavity  2. 1. 3. Convenience Resistance and Form Outline form Retention Steps of cavity preparation: 5. 4. 6. Finishing of enamel Removal of Carious Toilet of the Cavity walls and margins dentin  Finishing of enamel walls and margins: The marginal seal of the finished restoration largely depends on the proper carrying out of this step. The enamel walls and margins must be finished smooth, free of short, loose or undermined enamel rods and be given an inclination which depends primarily on the physical properties of the restorative material to be used. Objectives: 1. To remove undermind enamel 2. Give CSA inclination suitable to the restorative material 3. Give the cavity wall the proper inclination 4. Render walls smooth for better adaptation 5. Making outline in Sweeping curves 6. Elimination of sharp line angles This is essential for the marginal seal of the finished restoration According to Noyes, the maintenance of a strong enamel wall at the cavo-surface angle demands that: 1. The enamel should rest upon sound dentin. 2. The enamel rods, which form the cavo-surface angle, must have their inner ends resting on sound dentin. According to Noyes, the maintenance of a strong enamel wall at the cavo-surface angle demands that: 3. The enamel rods, which form the cavo-surface angle, must be supported by a portion of enamel in which the inner ends of the rods rest on sound dentin and the outer ends are covered by the restorative material. This gives the strongest enamel wall possible. This is produced by beveling the cavo- surface angle.  Cavo-surface Angle (CSA): The CSA must be in accordance to the physical properties of the restorative material HILTON, T. J., FERRACANE, J. L., & BROOME, J. C. (2013). Summitt's fundamentals of operative dentistry: a contemporary approach. https://search.ebscohost.com/login.aspx?direct=true&scope=site&db=nlebk&db=nla Factor affecting the CSA 1. The physical properties of the restorative material 2. Stress acting on the cavity margin 3. Location of cavity margin and direction of the enamel rods 4. Condition of enamel (friability) 5. Pulp vitality 6. Esthetic demands (labial enamel) Nisha Garg; Amit Garg; Ibrahim Abu Tahun.Textbook of operative dentistry. Jaypee Brothers,Medical Publishers Pvt. Limited, 2019  Short Long Full counter Composite resin restorations: 1. For better etching as it exposes rod ends rather than sides 2. It refreshes enamel surfaces 3. It increases the surface area available for bonding 4. Improve esthetics by gradual degradation between optical properties of tooth and restoration (contraindications: stress bearing areas, gingival margin) Cast restoration 1. to protect enamel rods 2. to provide better burnishing for the edge of the cast restoration to the cavity margins for further protection of the cement line Gold foil restorations For protection of marginal enamel during malleting  Types of Cavo-surface bevels: 2. Long bevel ending at the D.E.J, it is distinct. 3. Full bevel ending at the cavity seat (if done, it is at the expense of retention). Whenever indicated, the bevel must be definite, distinct, even and straight along its full depth.  Types of Cavo-surface bevels: 4. Counter bevel extends 2-3 mm over the cusps to form an onlay preparation. It protects weak cusps from fracture due to cuspal flections and deflections Increases the fracture resistance of the remaining tooth structure Sometimes termed reverse enamel bevel as it is made against the direction of the enamel rods (cusp capping) Nisha Garg; Amit Garg; Ibrahim Abu Tahun.Textbook of operative dentistry. Jaypee Brothers,Medical Publishers Pvt. Limited, 2019 Toilet of the cavity. This is the final step in cavity preparation prior to the restoration. A sharp explorer is used to free all debris and dentin chips at the corners of the cavity while subjecting it to a blast of warm air. No medicaments should be used. The cavity should be perfectly clean and dry before insertion of the restorative material Objectives: 1. Elimination of bacteria, debris and saliva 2. Removal of remnants of dentin chips and temporary restoration 3. Improve adaptation thus hindering caries recurrence around the restoration 4. Prepare and condition the tissues to receive the entitled restoration Toilet of the cavity. ▪Technique: Flush cavity with water the dry gently air blows ▪Contraindications: 1. Cavity sterilizers 2. Cavity cleansers 3. Excessive dryness