Prosthodontics and Implantology: Fixed, Removable, Complete Dentures, Implants
This domain tests complete dentures, removable partial dentures, fixed prostheses and implants - design logic, occlusion and biomechanics rather than memorised recipes.
Complete dentures
- Balanced occlusion in eccentric positions protects stability; freeway space is 2–3 mm; the neutral zone positions teeth where the tongue and cheeks exert balanced forces.
- The mandibular residual ridge resorbs faster than the maxillary; the posterior palatal seal improves retention.
- A large centre-of-resistance-to-occlusal-force discrepancy means anterior teeth should be set close to the ridge.
Removable partial dentures
Rests direct occlusal force along the long axis of abutments; clasps provide retention and bracing; major connectors (palatal plate, lingual bar) distribute load; indirect retainers resist rotation about the fulcrum line. The RPI design (mesial rest, proximal plate, I-bar) reduces torque on abutments.
Fixed prostheses and implants
Ante's law: combined root surface area of abutments must equal or exceed that of the pontic. A ferrule of 1.5–2 mm improves fracture resistance; ideal crown-root ratio is about 2:1. Osseointegration success (Albrektsson) means less than 0.2 mm bone loss per year after the first year, no mobility, pain or radiolucency. Peri-implant mucositis is reversible inflammation without bone loss; peri-implantitis adds progressive bone loss.
Worked example
A three-unit fixed prosthesis replaces a maxillary second premolar, with the first premolar and first molar as abutments. The two abutment root areas far exceed the premolar pontic, so Ante's law is satisfied. If the molar has 50% bone loss, its remaining root area drops sharply and an implant-supported single crown becomes the better plan.
Traps
Confusing mucositis with peri-implantitis; designing a distal-extension base without indirect retention; treating centric relation and maximum intercuspation as identical; ignoring ferrule and taper.