Fixed and Removable Prosthodontics
Fixed and Removable Prosthodontics tests whether you can plan a prosthesis that fits the remaining dentition, restores occlusion and is maintainable. Cases cover crown and bridge design, removable partial denture design, complete dentures and occlusal records.
Core rules
- Crown preparation: 1.5-2 mm occlusal reduction, 1-1.5 mm axial reduction, a defined chamfer or shoulder margin, a single path of insertion, and removal of undercuts.
- Endodontically treated teeth need a ferrule of at least 2 mm of sound dentine where possible, and cuspal coverage where the tooth is at risk of fracture.
- Provisional restorations must have sealed margins, correct occlusion and adequate aesthetics; they are not temporary.
- For removable partial dentures, classify by Kennedy, place rests on rest seats to direct load along the tooth axis, use a rigid major connector, and design clasps for retention rather than direct pressure on gingivae.
- Complete dentures: record accurate impressions with border moulding, determine vertical dimension and centric relation, and extend the base to the vibrating line.
Worked example
A patient is missing 46 and 47, with 45 tipped mesially and 48 unopposed and extruded. Options are a cantilever or fixed-fixed bridge from 45, an implant-supported crown, or a removable partial denture. If a bridge is chosen, the 48 must be assessed for occlusal interference and the 45 preparation must align with a shared path of insertion. The plan should state the periodontal prognosis of the abutments, because a bridge splints failure.
Traps
- Under-reduced preparations leading to thin metal or ceramic and fracture.
- Ignoring the opposing arch and the existing occlusal plane.
- Designing a denture base that overextends into movable tissue.