Introduction
When some teeth are lost (partial edentulism), three kinds of prosthesis can replace them: a tooth-supported fixed bridge, a removable partial denture or an implant-supported restoration. Sometimes two are combined in the same arch. The choice depends on biomechanics, the periodontium, esthetics, cost and the patient's wishes.
The fixed bridge
A fixed partial denture (FPD), commonly called a bridge, is permanently cemented to remaining teeth (or implants) and replaces one or more missing teeth. Only the dentist can remove it. Its great advantage is that it passes chewing forces the physiological way: tooth, periodontium, bone. That makes it the preferred prosthesis whenever the abutments allow.
Components
A simple three-unit bridge has two retainers and one pontic. The health of the abutments and their reserve capacity decide how well, and how long, the bridge will work.
Types of retainer
Evaluating the abutments
- Periodontium: healthy and free of inflammation before any bridge is planned.
- Crown-to-root ratio: at least 1:1, better 2:3.
- Root shape: long, broad or widely separated roots support better than short, conical or fused ones.
- Periodontal ligament area: Ante's law: the root area of the abutments should be at least equal to that of the teeth being replaced. In Bulgarian practice, Balabanov's equilibrium rule (topic 22) is used for the same purpose.
- Position and alignment: abutments must allow one common path of insertion.