Prosthodontics and Restorative Dentistry
Scope
Tests the design of removable and fixed prostheses, occlusal principles, and the material and biological choices that determine fit, retention and longevity.
Removable partial dentures
- Components: major connector, rests, minor connectors, clasp assemblies and denture bases.
- A clasp assembly is a rest, proximal plate, reciprocal arm and retentive arm.
- Surveying defines the path of insertion and the height of contour. Cast cobalt-chromium retentive tips engage about 0.25 mm of undercut; wrought wire about 0.5 mm.
- Rests seat perpendicular to the path of insertion; a rest on a slope will drift the prosthesis.
Fixed prosthodontics
- A ferrule of 1.5–2 mm of sound tooth structure improves resistance to fracture.
- Place margins supragingivally where possible for cleansability and impression accuracy.
- Mutually protected occlusion is the standard for natural dentition and most fixed work; group function is acceptable where canine guidance cannot be achieved.
Complete dentures
- Mandibular support comes from the buccal shelf and retromolar pad; maxillary support from the hard palate.
- The posterior palatal seal lies at the junction of hard and soft palate; balanced occlusion improves stability.
Worked example
A Kennedy Class II modification 1 mandible has a mobile premolar adjacent to the edentulous space. Reasoning: the tooth needs a rest seat and a clasp whose reciprocal arm opposes the retentive arm; an RPI design (rest, proximal plate, I-bar) on a distal-extension premolar reduces torque compared with a circumferential clasp.
Traps
- Placing a retentive arm above the height of contour, so there is no retention, or a reciprocal arm inside the undercut.
- Ignoring the path of insertion when surveying and designing.