Recent knowledge gained from long-term observations in the field of prosthodontics.

Both cross-sectional and longitudinal studies have contributed data which provide a scientific basis to the prediction of outcome in prosthodontic treatment. 'Standard' cases have a more favourable and more predictable prognosis than those in which tooth loss is scattered about the mouth. However, the variability of patients' problems and the wide range of their abilities to adapt to denture wearing and the regular maintenance of their oral tissues significantly influence outcome. Long term success with partial prostheses lies in the time scale of 5-10 years. A prerequisite for this is a standard of oral hygiene better than practised before the loss of the dentition. Adverse factors are inadequate diagnosis and treatment planning, undetected errors in denture construction, failure of materials, thermal and abrasive effects of foods, behavioural changes in the patient and ageing. In planning the restoration of abutment teeth by inlays or crowns their suitability for attachments must be considered. As yet, there are no clear guidelines to determine when fixed or removable prostheses should be used. The design of partial dentures should be as simple as possible; they should be stable, easy to clean and, if required, easily modified. Success is most likely to attend the efforts of those dentists who use techniques with which they and their technicians are thoroughly familiar.