Fixed Prosthodontics: Treatment Planning

• Fixed prosthodontics involves the replacement or restoration of missing or damaged teeth with prostheses that are cemented or bonded to abutment teeth or dental implants and cannot be removed by the patient.

Treatment Planning

• Diagnosis involves a thorough evaluation of the patient's dental and medical history, clinical examination, radiographic assessment, and diagnostic casts.
• Treatment plan should consider the patient's needs, desires, and financial constraints, as well as the biological, mechanical, and esthetic principles of fixed prosthodontics.
• Prognosis depends on factors such as the periodontal health, endodontic status, caries risk, and occlusal scheme of the remaining teeth.

Tooth Preparation

• Principles include preservation of tooth structure, retention and resistance form, structural durability, marginal integrity, and preservation of the periodontium.
• Margin placement can be supragingival, equigingival, or subgingival, depending on esthetics, caries control, and periodontal health.
• Finish lines include chamfer, shoulder, and knife-edge designs, each with specific indications and advantages.

Impression Techniques

• Materials commonly used include elastomers (polyvinyl siloxane, polyether) and reversible hydrocolloids (agar).
• Techniques include single-step and two-step impressions, as well as open tray and closed tray implant impressions.
• Retraction methods include the use of retraction cord, chemical agents, and surgical procedures to expose the margins of the preparation.

Provisional Restorations

• Purposes include protecting the prepared tooth, maintaining periodontal health, providing esthetics, and evaluating the planned occlusion.
• Materials include acrylic resins (poly methyl methacrylate) and composite resins (bis-acrylic).
• Fabrication techniques include direct, indirect, and indirect-direct methods.

Cementation

• Cements can be classified as traditional cements (zinc phosphate, glass ionomer) or resin cements (adhesive).
• Factors influencing cement selection include the type of restoration, retention requirements, esthetic demands, and biocompatibility.
• Cementation procedures involve cleaning the internal surface of the restoration, isolating the prepared tooth, applying the cement, seating the restoration, and removing excess cement.

Occlusion

• Concepts include mutually protected occlusion, canine guidance, and group function.
• Articulators are used to simulate jaw movements and fabricate restorations that harmonize with the patient's occlusion.
• Occlusal adjustments may be necessary to eliminate interferences and ensure proper function.

Pontic Design

• Requirements include cleansability, access for hygiene, esthetics, and preservation of the edentulous ridge.
• Designs include saddle (ridge lap), modified ridge lap, ovate, and hygienic (sanitary) pontics.
• Selection depends on the location of the edentulous space and the esthetic demands of the patient.

Materials

• Metals and alloys include gold alloys, base metal alloys, and titanium alloys.
• Ceramics include porcelain, zirconia, and lithium disilicate.
• Polymers include acrylic resins and composite resins.

Failure

• Biological complications include dental caries, periodontal disease, pulpal pathology, and soft tissue irritation.
• Mechanical complications include fracture of the restoration, loss of retention, and wear of the opposing dentition.
• Esthetic complications include discoloration, marginal staining, and inadequate shade matching.

Maintenance

• Oral hygiene instructions should be provided to the patient, including brushing, flossing, and the use of interdental cleaning aids.
• Regular recall appointments are necessary to monitor the condition of the restoration and the health of the surrounding tissues.
• Professional cleaning and polishing should be performed to remove plaque and calculus.

Resin-Bonded Fixed Dental Prostheses (RBFDPs)

• Conservative alternative to traditional fixed prostheses, relying on adhesive bonding to abutment teeth.
• Typically used for single missing teeth in areas of low occlusal force.
• Framework materials include metal alloys, ceramics, and fiber-reinforced composites.
• Etching and silanization of the abutment teeth are crucial for achieving adequate bond strength.

Implant-Supported Fixed Prostheses

• Provide support and retention for fixed restorations via osseointegrated dental implants.
• Treatment planning involves assessing the patient's bone volume, implant position, and occlusal scheme.
• Restorations can be cemented or screw-retained to the implant abutments.
• Maintenance includes regular hygiene appointments and monitoring of the implant-tissue interface.

All-Ceramic Restorations

• Offer excellent esthetics due to their translucency and ability to mimic natural tooth structure.
• Materials include feldspathic porcelain, lithium disilicate, and zirconia.
• Can be used for single crowns, inlays, onlays, and veneers.
• Bonded all-ceramic restorations rely on adhesive luting to achieve optimal strength and retention.

Complications

• Framework fracture can occur due to excessive occlusal forces, inadequate framework design, or material fatigue.
• Veneer delamination is a common complication of porcelain-fused-to-metal (PFM) restorations, resulting in esthetic failure.
• Cement failure can lead to microleakage, secondary caries, and loss of retention.
• Biological complications, such as periodontal inflammation and peri-implantitis, can compromise the long-term success of fixed prostheses.

Digital Dentistry

• CAD/CAM technology is used increasingly in fixed prosthodontics for designing and manufacturing restorations.
• Intraoral scanners allow for digital impressions, eliminating the need for conventional impression materials.
• 3D printing can be used to fabricate provisional restorations, surgical guides, and definitive restorations.
• Digital workflows offer improved accuracy, efficiency, and predictability in fixed prosthodontic treatment.

Impression Materials

• Polyvinyl siloxane (PVS) is a commonly used elastomeric impression material known for its high accuracy and dimensional stability.
• Polyether is another elastomeric impression material with excellent detail reproduction and inherent hydrophilicity.
• Reversible hydrocolloid (agar) is an elastic impression material that requires specialized equipment for heating and cooling.
• Alginate is an irreversible hydrocolloid impression material commonly used for diagnostic casts and preliminary impressions.

Provisional Materials

• Poly methyl methacrylate (PMMA) is an acrylic resin commonly used for provisional restorations due to its low cost and ease of manipulation.
• Bis-acryl composite is a resin material with improved esthetics and strength compared to PMMA, used for provisional restorations.
• Pre-fabricated polycarbonate crowns are used for single-unit provisional restorations, offering convenience and adequate esthetics.
• Light-cured resin composites are used for chairside fabrication of provisional restorations, allowing for precise shade matching and adjustments.

Cements

• Zinc phosphate cement is a traditional luting agent with a long history of use, known for its high compressive strength but lacking adhesive properties.
• Glass ionomer cement is a biocompatible luting agent that releases fluoride and bonds chemically to tooth structure.
• Resin-modified glass ionomer (RMGI) cement combines the benefits of glass ionomer and resin, offering improved strength and adhesion.
• Resin cements provide the highest bond strength and esthetics, requiring the use of bonding agents for optimal adhesion to tooth structure and restoration.