Prosthodontics
What the exam tests
Whether you can design a removable or fixed prosthesis from named components, apply Kennedy and Applegate rules correctly, and control occlusion and vertical dimension.
Core rules
- Removable partial denture components: major connector, rests and rest seats (directing forces along the long axis), clasps (circumferential/Akers, bar/Roach), reciprocal arms, minor connectors, denture base. A rest seat is a preparation, not an impression finding.
- Kennedy classification uses the edentulous area, not the number of missing teeth; the most posterior edentulous span determines the class, and the number of additional spans gives the modification. Applegate's rules: classify after extractions that would change the class, and third molars are not considered when the second molar is present.
- Complete denture: record centric relation at an adequate occlusal vertical dimension, obtain a posterior palatal seal, and develop balanced occlusion in eccentric positions. The neutral zone positions teeth where the tongue and cheek will not dislodge the base.
- Fixed prosthodontics: all-ceramic needs 1.0-1.5 mm axial and occlusal reduction with a chamfer; metal-ceramic needs 0.3-0.5 mm metal plus 1.0-1.5 mm porcelain. Margin placement must be recordable and cleansable.
- Ante's law (combined abutment root surface area must exceed that of the replaced teeth) is a guideline, not a guarantee of success; splinting, span length and periodontal status decide.
Worked example
A patient is missing 36 and 37, plus 46 was lost earlier. Reasoning: the posterior edentulous span is in the mandibular right quadrant (46), so it is Kennedy Class II; the additional span on the left is a modification, giving Class II Modification 1. Design: a linguoplate or lingual bar major connector with rests on 35 and 44/45, and a stress-relieving clasping scheme.
Traps that cost marks
- Classifying by total missing teeth or by anterior appearance.
- Forgetting to prepare rest seats, then relying on clasping for support.
- Changing vertical dimension without a validated centric relation record.