Prosthodontics and Crown & Bridge: Design Decisions
Prosthodontics and Crown & Bridge
This domain tests complete denture sequence and occlusion, removable partial denture classification and design, fixed prosthodontic principles, and implant-supported prostheses.
Core rules
- Complete denture sequence: primary impression in stock tray, border moulding with modelling compound, wash impression, record bases with wax rims, jaw relation records, try-in, processing, insertion and review. Freeway space should be about 2–4 mm.
- Balanced occlusion in complete dentures requires simultaneous bilateral contact in centric and eccentric positions to stabilise the bases; lingualised occlusion concentrates forces and suits resorbed ridges.
- Combination syndrome follows an opposing complete maxillary denture: anterior maxillary resorption, tuberosity enlargement, anterior mandibular bone loss, papillary hyperplasia and extrusion of mandibular anterior teeth.
- RPD uses Kennedy classification (I–IV) refined by Applegate's rules, with rests, guiding planes, a major connector and reciprocating clasps; RPI design uses a mesial rest, proximal plate and I-bar to reduce torque.
- Fixed prosthodontics: Ante's law guides abutment selection, margins are chamfer or shoulder, connectors need adequate bulk, and Pontic design must allow cleansability.
Worked example
A patient is missing 36 and 46, with all other teeth present. Each edentulous span is bounded anteriorly and posteriorly by natural teeth, so each is a Kennedy Class III; with two separate edentulous areas the arch becomes Kennedy Class III, Modification 1. Applegate's rules require that the most posterior edentulous area determines the class, that modifications count additional edentulous areas, and that a third molar is not considered when it would otherwise change the classification - so the design is a bounded saddle with rest seats on the adjacent premolar and molar.
Traps
- Classifying by the anterior edentulous space instead of the most posterior one.
- Confusing physiological rest position with occlusal vertical dimension.
- Designing a fixed bridge across a span that violates Ante's law without considering implants.
- Ignoring cleansability under a pontic, which drives ridge loss.