Crown Preparation PDF

Complete Cast Crown, Porcelain Fuse To Metal and All Ceramic Preparation Dr. Wayel Mohammed Huraib Fixed Prosthodontics I Prosthodontics Division Dentistry Program preencoded.png I-Complete Cast Crown Crown Preparation The complete cast crown is a durable restoration f...

Complete Cast Crown, Porcelain Fuse To Metal and All Ceramic Preparation Dr. Wayel Mohammed Huraib Fixed Prosthodontics I Prosthodontics Division Dentistry Program preencoded.png I-Complete Cast Crown Crown Preparation The complete cast crown is a durable restoration for badly damaged posterior teeth. It covers all axial walls and the occlusal surface. This restoration offers excellent longevity and can be used for single teeth or as retainers for fixed dental prostheses. preencoded.png Preparation Process 1 Tooth Structure Removal Adequate tooth structure must be removed to allow restoration to original contours. 2 Preservation Tooth structure should be preserved when possible. 3 Strength Consideration Reduction should produce a crown of acceptable strength. preencoded.png Advantages: Retention and Resistance Greater Retention Improved Resistance Strength Complete cast crowns have They offer better resistance The cylinder-like configuration superior retention compared to form than partial-coverage provides superior strength. conservative restorations. restorations. preencoded.png Advantages: Contour Modification 1 Axial Tooth Contour 2 Malaligned Teeth 3 Furcation Access Complete cast crowns Especially beneficial for Improved access to allow modification of axial malaligned teeth, within furcations through tooth contour. periodontal limits. recontouring of buccal and lingual walls. preencoded.png Advantages: Special Requirements Partial Removable Dental Prostheses Allows creation of properly shaped survey lines, guide planes, and occlusal rests. Occlusion Modification Permits easy modification of occlusion, important for supraerupted teeth. Occlusal Plane Helpful when reestablishing the occlusal plane is necessary. preencoded.png Disadvantages Extensive Tooth Structure Removal Can have adverse effects on pulp and periodontium. Gingival Inflammation Proximity to gingiva may cause inflammation of gingival tissues. Vitality Testing Electric vitality testing is no longer feasible after cementation. preencoded.png Esthetic Considerations Patient Objection Patients may object to the display of metal. Smile Line Normal smile line may restrict use to specific teeth. Placement May be limited to maxillary molars and mandibular molars and premolars. preencoded.png Indications Extensive coronal Maximum retention needed destruction Short clinical crowns High displacement forces anticipated Correction of axial contours Support for partial removable dental prosthesis preencoded.png Contraindications 1 Conservative Options Contraindicated if treatment objectives can be met with a more conservative restoration. 2 Intact Walls Not recommended if intact buccal or lingual wall exists. 3 Esthetic Needs Contraindicated for anterior teeth with high esthetic needs. preencoded.png Special Considerations Endodontically Treated Teeth Additional Retentive Features Complete cast crown is indicated on endodontically Grooves can be included for additional retention in treated teeth for superior strength. specific cases. preencoded.png Cast Crown Preparation: Key Principles h preencoded.png Occlusal Reduction Guidelines Guidelines 1 Non-functional Cusps Minimum 1 mm clearance required. 2 Functional Cusps Minimum 1.5 mm clearance needed. 3 Anatomic Contours Follow natural tooth shape for conservative preparation. preencoded.png Axial Reduction and Margin Design Axial Reduction Margin Configuration Smoothness Parallel to tooth's long axis. 6° Chamfer design. Ideally Ensure distinct, smooth margins taper recommended. supragingival. 0.5 mm metal for optimal fit. thickness. preencoded.png Functional Cusp Bevel 1 Placement Directly beneath crown cusps for optimal contour. 2 Angle Flatter than external surface, typically 45 degrees. 3 Purpose Ensures durability and conserves tooth structure. preencoded.png Nonfunctional Cusp Considerations Clearance Additional Bevel Mandibular Molars Minimum 0.6 mm at Often needed for maxillary May not require additional occlusoaxial line angles. molars. reduction due to inclination. preencoded.png Key Takeaways for Crown Preparation Precise Measurements Follow recommended clearances for each area. Anatomic Contours Maintain natural tooth shape during reduction. Margin Quality Ensure smooth, distinct chamfer margins. Proper Bevels Angle functional and nonfunctional cusps correctly. preencoded.png Step By Step Procedure For Preparing a tooth preencoded.png Guiding Grooves for Occlusal Reduction 1 Central Groove Place 1mm deep holes in fossae, connect along central groove 2 Developmental Grooves Place guiding grooves in buccal and lingual developmental grooves 3 Functional Cusp Bevel Place 1.5mm deep groove for centric stop, diminishing cervically preencoded.png Occlusal Reduction Technique Place Guiding Grooves Ensure accurate position, depth, and angulation of grooves Remove Tooth Structure Use carbide or diamond to remove structure between grooves Check Clearance Verify 1.5mm clearance on functional cusps, 1.0mm on nonfunctional preencoded.png Alignment Grooves for Axial Reduction 1 Placement Three grooves on buccal and lingual walls 2 Instrument Angle Diamond bure parallel to restoration path of placement 3 Depth Control Tip buried to midpoint to avoid unsupported enamel 4 Path of Placement Grooves determine restoration's path of placement preencoded.png Axial Reduction Technique 1 Remove Islands Remove tooth structure between alignment grooves 2 Interproximal Care Prevent damage to adjacent teeth during reduction 3 Chamfer Placement Place 0.5mm wide cervical chamfer during axial reduction preencoded.png Finishing the Preparation Smooth Transitions Margin Refinement Create smooth transitions from occlusal to axial Use fine-grit diamond for smooth chamfer margin surfaces Surface Finishing Additional Features Round line angles and place nonfunctional cusp bevel Add retentive features like grooves or boxes if needed preencoded.png Evaluation of Preparation Taper Assessment Undercut Check Clearance Verification Check for overtapering of Ensure no undercuts between Assess occlusal and proximal opposing axial walls opposing axial walls clearances for adequacy preencoded.png Common Errors and Corrections Corrections Error Correction Overtapering Upright walls or add retentive features Undercuts Eliminate with diamond instrument Inadequate clearance Adjust before making interim restoration preencoded.png Tools and Instruments Diamond Burs Carbide Burs Periodontal Probe Wax Caliper For initial reduction and For occlusal reduction For measuring For checking occlusal finishing and retentive features reduction depth clearance preencoded.png preencoded.png Final Steps Interim Restoration Impression Making Create temporary crown after preparation is Take final impression for fabrication of permanent complete crown preencoded.png II-Metal-Ceramic Crown preencoded.png The Metal Ceramic Crown Widely used fixed restoration combining metal and porcelain. Offers durability and esthetics in dental practices. preencoded.png Composition and Structure Metal Substructure Porcelain Veneer Thickness Requirements Complete coverage cast metal Fused layer mimics natural Considerable reduction needed crown as base. tooth appearance. to mask metal color. preencoded.png Fabrication Process 1 Waxing and Casting Special metal-ceramic alloy used for substructure. 2 Preparatory Finishing Framework prepared for porcelain application. 3 Porcelain Fusing Dental porcelain fused at 960° C. preencoded.png Indications 1 Complete Coverage Needs Suitable for teeth requiring full crown restoration. 2 Esthetic Demands Meets high cosmetic requirements, especially for anterior teeth. 3 Versatility Can serve as retainer for fixed dental prosthesis. 4 Structural Support Ideal for endodontically treated teeth with post-core. preencoded.png Contraindications Active Dental Issues Young Patients Conservative Options Available Not suitable for patients with High risk of pulp exposure in active caries. large chambers. Avoid when more conservative restorations are feasible. preencoded.png Advantages of Metal-Ceramic Crowns Strength Aesthetics Retention Cast metal substructure Natural appearance achieved Excellent retention due to full reinforces brittle ceramic. through characterization axial wall coverage. techniques. preencoded.png Preparation Considerations 1 Tooth Reduction Significant reduction required for material thickness. 2 Margin Placement Subgingival margins for aesthetics, potential periodontal concerns. 3 Difficulty Level Comparable to posterior complete cast crown preparation. preencoded.png Aesthetic Considerations and Challenges 1 Shade Selection Accurate color matching crucial for natural appearance. 2 Communication Clear instructions to ceramist essential for desired outcome. 3 Porcelain Layering Multiple steps required for optimal aesthetics. preencoded.png Limitations and Alternatives Brittle Fracture Cost Factors All-Ceramic Option Risk of porcelain chipping due to Higher laboratory expenses due Consider for superior aesthetics glasslike nature. to complex fabrication process. in low stress situations. preencoded.png preencoded.png III- All Ceramic Restorations Esthetically pleasing prosthodontic restorations with superior color and translucency. preencoded.png Types and Fabrication 1 Platinum Foil Matrix Original technique using foil to support porcelain during firing. 2 Hot-Pressing Modern fabrication process for ceramic restorations. 3 Slip-Casting Another popular method for creating all-ceramic restorations. preencoded.png All Ceramic Crowns 1 Thickness 1 to 1.5 mm circumferentially. 2 Incisal Thickness May require greater thickness for esthetic results 2 mm. 3 Preparation Design Minor differences exist among various fabrication techniques. preencoded.png Advantages of Ceramic Crowns Esthetics Conservation Customization Superior appearance and Allows more conservative facial Appearance can be modified excellent translucency. reduction than metal-ceramic with different luting agent crowns. colors. preencoded.png Disadvantages of Ceramic Crowns Strength Reduced strength due to absence of metal substructure. Tooth Reduction Significant reduction needed for shoulder type margin circumferentially. Brittleness Porcelain brittleness requires careful preparation design. Fitting Difficulties may occur in obtaining well fitting margins. preencoded.png Critical Preparation Design 90-Degree Angle Incisal Support High-Strength Core Cavosurface angle needed to Preparation should support Exception for systems with high- prevent unfavorable stress entire incisal edge of porcelain. strength core materials. distribution. preencoded.png Limitations in Fixed Dental Prostheses 1 Retainer Ineffectiveness 2 Connector Size 3 Periodontal Risk Large connectors (4x4 mm Large connectors may Not effective as retainers minimum) required for impinge on interdental for fixed dental strength. papilla. prostheses. preencoded.png Indications for Ceramic Crowns Esthetic Requirement High esthetic demand areas where conservative restoration is inadequate. Tooth Structure Relatively intact coronal structure to support restoration. Occlusal Load Favorable distribution of occlusal load required. preencoded.png Contraindications for Ceramic Crowns Crowns Conservative Options When more conservative restorations can be used. Molar Teeth Rarely recommended for molar teeth due to occlusal load. Unfavorable Load When occlusal loading is unfavorable. Inadequate Support If unable to provide adequate support or even shoulder. preencoded.png Considerations for Opposing Teeth Issue Observation Wear Natural teeth opposing porcelain may show wear Specific Concern Mandibular incisors can exhibit significant wear over time preencoded.png preencoded.png preencoded.png preencoded.png