Diagnostic Casts in Fixed Prosthodontics PDF

What is the Diagnostic Diagnostic Casts ? Diagnostic Casts and Related Procedures...

What is the Diagnostic Diagnostic Casts ? Diagnostic Casts and Related Procedures A dental diagnostic cast, also known as a study model or diagnostic model, is a detailed, three dimensional replica of a patient's teeth and surrounding oral structures. It is typically Dr. Wayel Mohammed Huraib made from a dental impression using materials like dental stone Fixed Prosthodontics I or plaster. Prosthodontics Division Dentistry Program Diagnostic Casts in Fixed Prosthodontics Prosthodontics Evaluating Edentulous Spaces Diagnostic casts are crucial in fixed prosthodontic treatment 1 Occlusocervical 2 Spatial Relationships 3 Soft Tissue Contours planning. They allow for comprehensive examination of static Dimension and dynamic tooth relationships. Measure the Assess spatial Evaluate soft tissue These casts provide insights not easily observable intraorally. occlusocervical relationships with contours in edentulous dimension of edentulous adjacent and opposing areas. This affects They are essential for accurate diagnosis and treatment spaces. This is crucial teeth. Consider emergence profile planning. for prosthesis planning. implications for planning. prosthesis design. Diagnostic Procedures Assessing Abutment Teeth Alignment Tooth Preparation Simulation Evaluate the relative alignment of proposed abutment teeth. Consider impact on Practice tooth preparations on duplicate casts. Refine techniques before intraoral prosthesis design. procedure. Angulation Assess angulation of abutment teeth. This affects path of insertion and retention. Diagnostic Wax-up Tooth Position Perform diagnostic wax-up procedures. Visualize and evaluate proposed treatment outcomes. Analyze subtle changes in individual tooth position. Note any drifting or rotation. Structural Integrity Examine structural integrity of abutment teeth. Consider need for additional restorative work. Occlusal Analysis Conduct detailed occlusal analysis. Identify potential interferences and harmonize occlusion. Advantages of Diagnostic Casts Casts Impression Making for Aspect Intraoral Examination Diagnostic Casts Diagnostic Casts Visibility Limited by oral Unobstructed cavity 360° view Accurate dental impressions are crucial for creating diagnostic Patient Reflexes Present Absent casts. Even small flaws can lead to significant inaccuracies. Proper technique and material selection are essential for Time Constraints Often limited Unrestricted successful outcomes. analysis time Reproducibility Challenging Easily reproducible  Irreversible Hydrocolloid Composition 1 Main Components Sodium or potassium salts of alginic acid, water-soluble. Importance of Accuracy 2 Chemical Reaction Forms insoluble calcium alginate when reacting with Void Prevention Border Extension Material Selection calcium sulfate. Small voids can create Impressions should extend Irreversible hydrocolloid is nodules on occlusal several millimeters beyond suitable for planning but surfaces, leading to the cervical line of teeth. not for definitive casts. 3 Additional Ingredients inaccurate articulator Trisodium phosphate to control setting rate. mounting. Tray Considerations Impression Material Behavior Retention Use adhesive, perforations, or undercuts for material retention. Imbibition Syneresis Pouring Time Size Alginate absorbs liquid from Alginate gives off liquid to the Impressions must be poured Larger trays allow for more material, the atmosphere, causing atmosphere, also causing immediately to prevent improving accuracy. distortion. distortion. distortion. Support Ensure full tray support to prevent impression distortion. Diagnostic Impression Technique Impression Taking Process Preparation 1 Tray Selection 1 Choose the largest tray that fits comfortably in the patient's mouth. Clean teeth and rinse mouth thoroughly. Material Preparation Material Application 2 2 Mix irreversible hydrocolloid to a homogenous consistency. Load tray and wipe material into occlusal crevices. 3 Impression Taking Tray Seating 3 Load tray, wipe material into crevices, and seat in patient's mouth. Insert tray and remind patient to relax cheek muscles. 4 Removal and Disinfection 4 Removal Remove quickly after gelation, rinse, and disinfect the impression. Remove quickly 2-3 minutes after gelation. Faunally Evaluate your Disinfection and Pouring Alginate impression Smooth Surface ? Disinfection Spray with glutaraldehyde and place in sealed bag for 10 minutes. Rounded periphery ? No oral cavity debris Timing Pour within 15 minutes of removal for accuracy. Stone Selection Use vacuum-mixed ADA type IV or V stone.  Diagnostic Cast Quality Evaluation Accuracy Check Examine for voids, nodules, and proper articulation. Cast Storage and Separation Surface Detail Ensure adequate reproduction of dental structures. Storage Position Tray side down Environment Covered with wet paper in humidor Repeat if Necessary Discard questionable impressions and casts, then repeat Duration 1 hour the process. Separation Time 1 hour after pouring Transferring Casts to Articulators Articulators Analyzing Occlusal Relationships 1 Facebow Transfer Centric Relation Maximum Intercuspation Use a facebow to transfer the maxillary cast. This The position of the mandible in relation to The occlusal relationship where the cusps ensures accurate spatial orientation. the maxilla where the condyles are in of the upper and lower teeth interdigitate their most upward, backward, and maximally when the jaws are closed in Centric Relation Record unstrained position within the glenoid their habitual position. 2 Utilize a centric relation interocclusal record fossae for mandibular cast articulation. Condylar Element Setting 3 Set condylar elements using protrusive and excursive interocclusal records. Occlusal Plane Analysis Analyzing Occlusal Relationships Anterior Guidance Evaluate anterior guidance and its influence on posterior disclusion. Centric Relation Maximum Intercuspation Mandibular Movements Group function Assess the centric relation Examine the maximum Analyze occlusal contacts Its an occlusal arrangement where multiple position. Evaluate any intercuspation position. Note throughout the range of posterior teeth on the working side (the side discrepancies between CR any slides from CR to MI. mandibular movements. towards which the jaw moves during lateral and MI. excursion) come into contact simultaneously during lateral jaw movements. Types of Articulators Articulator Selection Selection for Dental Prostheses Small Nonadjustable Semiadjustable Fully Adjustable Limited capacity to Practical for routine Wide range of positions. Can reproduce mandibular fixed prostheses. follow patient's border Articulators are mechanical devices that simulate mandibular movement. Can lead to Provides necessary movements accurately. movement. They are crucial for analyzing functional occlusal discrepancies. diagnostic information relationships in dental prosthetics. Proper articulator selection with minimal can significantly impact treatment outcomes and efficiency. adjustments.  Small Nonadjustable Semiadjustable Articulators Articulators Practical Approach Suitable for most routine fixed prostheses. 1 Limited Accuracy Minimal Adjustments Cannot reproduce full range of mandibular movement. Reduces need for clinical adjustments during treatment. 2 Occlusal Discrepancies Anatomical Accuracy May lead to restorations with occlusal interferences. Size similar to anatomic structures they represent. 3 Hinge Closure Issues Distance between hinge and tooth is less than in Time-Efficient patients. Does not require excessive time or expertise to use. Arcon vs Nonarcon Designs Semiadjustable Articulator Adjustments Arcon Design 1 Condylar spheres on lower component. Anatomically "correct" design. Condylar Inclination 2 Nonarcon Design Adjusts to mimic patient's condylar path. Popular in complete denture prosthodontics. Rigidly attached upper and lower members. Progressive Side Shift Simulates lateral movement of the mandible. Movement Simulation 3 Arcon easier to understand. Nonarcon movements are Immediate Side Shift "backwards". Replicates initial lateral movement of the condyle. Interocclusal Records To transform the relation between the upper & lower dental arch from the patient mouth to the articulator. Material Thickness Purpose Wax Several mm Adjust mechanical Fully Adjustable Articulators fossae Mimic patient Other suitable Varies mandibular materials High Accuracy Complex Use Pantographic Tracings movements Can follow patient's border Requires high skill level and Used instead of wax records movements precisely. understanding. for adjustment. Advantages of Fully Adjustable Choosing the Right Articulator Adjustable Articulators Treatment Complexity Consider the type and complexity of treatment needs. 1 Precise Replication Accuracy Requirements Can track irregular pathways of movement throughout entire trajectories. Assess the demands for procedural accuracy. Complex Prostheses Time Efficiency 2 Evaluate the potential for time savings in subsequent treatment stages. Enables fabrication of intricate dental work. Minimal Adjustments Skill Level 3 Consider the expertise of the dentist and technician. Reduces chairside time for complex cases.  Principles Of Tooth Preparation Principles Principles Of Tooth Of Teeth do not possess the regenerative ability found in most other tissues. Preparation Therefore, once enamel or dentin is lost as Tooth Preparation a result of caries, trauma, or wear, restorative materials must be used to reestablish form and function. Dr.Wayel Mohammed Huraib Dr.Wayel Mohammed Consultant Huraib in Prosthodontics Fixed Prosthodontics-D3 15/09/2021 Principles Of Tooth Preparation Principles Of Tooth Preparation 1 Biological Considerations Principles Of Tooth Preparation Principles Of Tooth Preparation I I Biological Biological Considerations Considerations I- Surgical precision crucial : II- Consequences of poor preparation: Surgical procedures on living tissues require Inadequate marginal fit or deficient crown careful execution to prevent unnecessary contour resulting from poor preparation can damage. complicate plaque control around fixed restorations. Principles Of Tooth Preparation I I Prevention of Damage During Tooth Preparation Biological Biological Considerations Considerations 1- Adjacent teeth III- Risks to adjacent structures: Iatrogenic Damage to Adjacent Teeth: Teeth, soft tissues, and the pulp of the Common error in dentistry involves iatrogenic prepared tooth are susceptible to damage damage to adjacent teeth during procedures. during tooth preparation. Reshaping and polishing a damaged proximal contact area may not prevent increased susceptibility to dental caries compared to the original undamaged tooth surface.  Principles Of Tooth Preparation I Prevention of Damage During Tooth Preparation I Biological Biological Considerations Considerations 1- Adjacent teeth 2- Soft tissues. To protect the Adjacent tooth: To prevent a damage to the - Use a Metal matrix band soft tissues - retraction with - Use a thin tapered diamond an aspirator tip, mouth mirror. Principles Of Tooth Preparation Principles Of Tooth Preparation I I Biological Biological Considerations Considerations 3- Pulp. 3- Pulp. Extreme temperatures, Pulp size which can be Chemical irritation, evaluated on a radiograph or microorganisms can cause and decreases with age. an irreversible pulpitis Principles Of Tooth Preparation Principles Of Tooth Preparation I I Biological Biological Considerations Considerations 3- Pulp. 3- Pulp. ! Temperature Temperature Excessive pressure, higher Even with the lightest touch, rotational speeds, and the the tooth overheats unless a type, shape, and condition of water spray is used. the cutting instrument increase generated heat. Principles Of Tooth Preparation Principles Of Tooth Preparation I I Biological Biological Considerations Considerations 3- Pulp. 3- Pulp. ! Chemical Action Bacterial Action All carious dentin should be Bases, Restorative Resins, removed before placement of Solvents, and Luting Agents a restoration that will serve as can cause palpal damage, a foundation for a fixed particularly when they are prosthesis. applied to freshly cut dentin.  Principles Of Tooth Preparation Principles Of Tooth Preparation I I Biological Biological Considerations Considerations Tooth structure is conserved Tooth structure is conserved through adherence to the through adherence to the following guidelines: following guidelines: 1- Use of partial coverage 2- Preparation of teeth with rather than complete the minimum practical coverage restorations. convergence angle (taper) between axial walls Principles Of Tooth Preparation Principles Of Tooth Preparation I I Biological Biological Considerations Considerations Tooth structure is conserved Tooth structure is conserved through adherence to the through adherence to the following guidelines: following guidelines: 3- Preparation of the occlusal 4- Preparation of the axial surface so that reduction surfaces so that a maximal follows the anatomic planes thickness of residual tooth to give uniform thickness in structure surrounding pulpal the restoration. tissues is retained. Principles Of Tooth Preparation Principles Of Tooth Preparation I I Biological Biological Considerations Considerations Tooth structure is conserved Tooth structure is conserved through adherence to the through adherence to the following guidelines: following guidelines: 5- Selection of a margin 4- If necessary, teeth should geometry that is be orthodontically conservative and yet repositioned. compatible with the other principles of tooth preparation Principles Of Tooth Preparation Principles Of Tooth Preparation I I Biological Biological Considerations Considerations Margin Placement Tooth structure is conserved I Supra-gingival Margin through adherence to the following guidelines: 6- Avoidance of unnecessary apical extension of the preparation. II Subgingival Margin  Principles Of Tooth Preparation Principles Of Tooth Preparation I I Biological Biological Considerations Considerations Margin Placement Margin Placement I-Supragingival Margin. I-Supragingival Margin. They can be easily finished They are more easily kept without associated soft- plaque free. tissue trauma. Principles Of Tooth Preparation Principles Of Tooth Preparation I I Biological Biological Considerations Considerations Margin Placement Margin Placement I-Supragingival Margin. I-Supragingival Margin. Impressions are more Restorations can be easily easily made, with less evaluated at the time of potential for soft tissue placement or at recall damage. appointments Principles Of Tooth Preparation Principles Of Tooth Preparation I I Biological Biological Considerations Considerations Margin Placement Margin Placement II-Subgingival Margin. II-Subgingival Margin. Dental caries, cervical The proximal contact area erosion, or restorations extends to the gingival extend subgingivally. crest. Principles Of Tooth Preparation Principles Of Tooth Preparation I I Biological Biological Considerations Considerations Margin Placement Margin Placement II-Subgingival Margin. II-Subgingival Margin. Additional retention and/or The margin of a resistance is needed metalceramic crown is to be hidden behind the labiogingival crest.  Principles Of Tooth Preparation Principles Of Tooth Preparation I Biological Considerations Margin Placement II Mechanical II-Subgingival Margin. Considerations Root sensitivity cannot be controlled by more conservative procedures, such as the application of dentin bonding agents. Principles Of Tooth Preparation Principles Of Tooth Preparation II II Mechanical Mechanical Considerations Considerations The success of fixed prosthodontics relies on adherence to mechanical principles. Mechanical considerations can be divided into three categories: These principles ensure the restoration's stability and durability. 1. Providing retention form. 2. Providing resistance form. 3. Preventing deformation of the restoration. Principles Of Tooth Preparation Principles Of Tooth Preparation II II Mechanical Mechanical Considerations Considerations Retention Form Retention Form The quality of a preparation that prevents the Factors affecting retention form : restoration from becoming dislodged by such forces parallel to the path of placement. 1. Magnitude of the dislodging forces. 2. Geometry of the tooth preparation. 3. Roughness of the restoration fitting surface. 4. Materials being cemented. 5. Film thickness of the luting agent. Principles Of Tooth Preparation Principles Of Tooth Preparation II II Mechanical Mechanical Considerations Considerations Retention Form Retention Form 1-Magnitude of the dislodging forces 2-Geometry of the tooth preparation Forces that tend to remove a cemented restoration Most fixed dental prostheses depend on the along its path of placement are small in comparison geometric form of the preparation rather than on with those that tend to seat or tilt it. A fixed dental adhesion for retention because most of the traditional prosthesis can be subjected to such forces by cements (e.g., zinc phosphate) are nonadhesive. pulling with floss under the connectors or when exceptionally sticky food is eaten. They do not have a specific adhesion to metal, but they increase the friction between sliding metal parts.  Principles Of Tooth Preparation Principles Of Tooth Preparation II II Mechanical Mechanical Considerations Considerations Retention Form Retention Form 2-Geometry of the tooth preparation 2-Geometry of the tooth preparation Taper is defined as the convergence of two Surface area If the restoration has a limited path of opposing external walls of a tooth preparation as placement, its retention depends on the length of this path or, more precisely, on the surface area that is in viewed in a given plane. sliding contact. Therefore, crowns with tall axial walls are more retentive The recommended convergence between opposing than those with short axial walls, and molar crowns are walls is 6 degrees. more retentive than premolar crowns of similar taper. Principles Of Tooth Preparation Principles Of Tooth Preparation II II Mechanical Mechanical Considerations Considerations Retention Form Retention Form 2-Geometry of the tooth preparation 2-Geometry of the tooth preparation Surface area Retention form of an excessively Stress concentration Sharp occlusoaxial line tapered preparation can be increased by adding angles should be rounded to minimize these grooves stresses, which can precipitate retentive failure Principles Of Tooth Preparation Principles Of Tooth Preparation II II Mechanical Mechanical Considerations Considerations Retention Form Retention Form 2-Geometry of the tooth preparation 3-Roughness of the surfaces being cemented. Type of preparation Different types of preparation When the internal surface of a restoration is very have different retentive values. smooth, retentive failure occurs not through the cement but at the cement-restoration interface. The retention of a complete crown is more than double that of partial coverage restorations. Principles Of Tooth Preparation Principles Of Tooth Preparation II II Mechanical Mechanical Considerations Considerations Retention Form Retention Form 4-Materials being cemented 4-Materials being cemented The cement adhered better to amalgam than to Retention is affected by both the type of casting composite resin or cast gold. alloy and any core or buildup material that is present on the axial walls of the crown preparation. The base metal alloys are better retained than are less reactive metals with high gold content.  Principles Of Tooth Preparation Principles Of Tooth Preparation II II Mechanical Mechanical Considerations Considerations FACTORS INFLUENCING THE RETENTION OF A CEMENTED RESTORATION Resistance Form Restoration ability to oppose lateral dislodging forces. Principles Of Tooth Preparation Principles Of Tooth Preparation II II Mechanical Mechanical Considerations Considerations FACTORS INFLUENCING THE RESISTANCE OF A CEMENTED RESTORATION Resistance Form Factors affecting resistance form : 1.Magnitude and direction of the dislodging forces. 2.Geometry of the tooth preparation. 3.Physical properties of the luting agent. Principles Of Tooth Preparation Principles Of Tooth Preparation II II Mechanical Mechanical Considerations Considerations Preventing Deformation Preventing Deformation A restoration must have sufficient strength to Factors affecting deformation : prevent permanent deformation during function 1.Alloy selection. 2.Adequate tooth reduction. 3.Margin design. Principles Of Tooth Preparation Principles Of Tooth Preparation II II Mechanical Mechanical Considerations Considerations Preventing Deformation Preventing Deformation Adequate tooth reduction Margin Design A minimum alloy thickness of about 1.5 mm Tooth reduction should provide sufficient room over functional cusps. (buccal in the mandible, for bulk of metal at the margin to prevent lingual in the maxilla). The less stressed distortion. nonfunctional cusps can be protected with less metal 1 mm is adequate.  Principles Of Tooth Preparation Principles Of Tooth Preparation III Easthetic Considerations III Dental restorations should look’s as natural as possible. ESTHETIC CONSIDERATIONS Principles Of Tooth Preparation Principles Of Tooth Preparation III III Easthetic Easthetic Considerations Considerations All-Ceramic All-CeramicRestorations. Restorations. ESTHETIC CONSIDERATIONS Is the most pleasing esthetic restorations. 1.All-Ceramic Restorations. A minimal material thickness of approximately 1 to 1.2 2.Metal-Ceramic Restorations. mm is necessary to ensure optimal esthetics. 3.Partial-Coverage Restorations. Principles Of Tooth Preparation Principles Of Tooth Preparation III III Easthetic Easthetic Considerations Considerations Metal-Ceramic Restorations. Partial-Coverage Restorations. A metal-ceramic crown has two layers A metal-ceramic crown has two layers I- Metal acts as a frame. I- Metal acts as a frame. II- Ceramic, applied over the metal and is responsible for II- Ceramic, applied over the metal and is responsible for aesthetics. aesthetics.