Prosthodontics
What this domain tests
Material selection, design principles for removable and fixed prostheses, occlusion, and the diagnosis of prosthesis-related failure.
Core rules
- Removable partial denture components: rests and rest seats (direct the load along the long axis of the abutment), clasps, connectors, and the major connector.
- Clasp choice: circumferential (good retention, more coverage) versus bar/RPI (less coverage, better aesthetics, less torque). The RPI design uses a mesial rest, proximal plate, and I-bar.
- Major connectors: the maxillary plate/strap and mandibular lingual bar must avoid the gingival margin and the lingual frenum; the lingual bar needs at least 8 mm of vertical height.
- Fixed prosthodontics: a ferrule of at least 1.5–2 mm of sound axial dentine improves resistance; finish lines should be smooth and supragingival where possible.
- Occlusion: the aim is simultaneous, bilateral, even contact in centric relation with posterior disclusion in excursions (canine guidance or group function) and balanced occlusion for complete dentures.
- Denture stomatitis is usually candidal and linked to nocturnal wear and poor hygiene.
Worked example
A patient presents with a maxillary complete denture retained poorly in function. Reasoning: check border seal and extensions first, then the posterior palatal seal, then the occlusion and the denture-bearing tissue. Relining is not the first step - borders and extensions must be re-evaluated before any reline.
Traps
- Describing centric occlusion and centric relation as the same thing.
- Placing a rest seat on a non-vital, unsupported abutment without considering the crown-to-root ratio.
- Ignoring that a denture retaining "nothing at all" often has a deficient posterior palatal seal.