Prosthodontics
What the exam tests
Prosthodontics tests whether you can choose a defensible prosthesis, design it biologically and mechanically, and sequence occlusion, impressions, and cementation. Cases often combine failing crowns, shortened dental arches, and implant options.
Core rules
- Plan from prognosis: caries risk, periodontal support, endodontic status, occlusal load, and patient preference. A prosthesis cannot rescue a tooth with a poor foundation.
- For crowns, retention and resistance depend on preparation taper, height, surface area, and ferrule. Aim for a ferrule of about 1.5–2 mm of sound axial dentine; insufficient ferrule needs crown lengthening, orthodontic extrusion, or a different design.
- Margins must be supragingival where possible, accessible, and adapted. Material choice follows thickness and cementation: lithium disilicate needs adhesive bonding; zirconia needs adequate connector dimensions.
- For removable partial dentures, classify by Kennedy, survey the cast, place rests, design clasps and major connectors to protect abutments, and use altered-cast procedures where indicated.
- Complete dentures require verified occlusion, appropriate vertical dimension, and balanced occlusion.
- Implant prostheses need passive fit, cleansable contours, and a verified interocclusal record.
Worked example
A 46 molar has 3 mm of sound axial wall above the margin but only 1 mm ferrule; the patient wants a crown. The ferrule is inadequate for predictable resistance. Options are crown lengthening if biologic width and aesthetics allow, orthodontic extrusion, or an alternative such as an onlay or extraction with implant planning. Choosing a crown immediately risks fracture and decementation.
Traps
- Ignoring ferrule and taper.
- Taking an interocclusal record without verifying occlusion.
- Overcontouring implant crowns, making hygiene impossible.
- Designing an RPD without surveying the cast.