The five-year and ten-year survival rates estimated by the life-table method are 80.8% (95% confidence interval 78.0-83.6%) and 80.4% (95% confidence interval 77.6-83.2%) respectively. The median survival cannot be estimated for this study as the survival probability remains above 80% even at the longest follow-up. Analysis of clinical variables influencing survival revealed that design of the restoration and experience of the operator providing the restoration were significant factors. Resin-retained bridges made with minimal tooth preparation are shown to be superior in terms of longevity than those for which other types of tooth preparation is made. Patient satisfaction with their treatment was high.

The reasons for failure of 142 bridges in 130 patients from general dental practice seen at the Bristol Dental Hospital from 1981 to 1986 were assessed. Most patients were either self-referred or sent by a dentist who had not made the bridge. The mean age of the bridges at failure was 6.2 years. The main single reasons for failure were secondary caries or apical pathology, but many bridges failed as a result of factors related to design and structure. Bridges of porcelain fused to gold or gold faced with acrylic lasted twice as long as those of porcelain fused to alloys. There was no correlation between the age of the patient at bridge placement and years of service. Eighteen per cent of the bridges were repaired, recemented or rescued by endodontics alone; 61% were replaced by a new bridge, and the remainder required a removable prosthesis.

A total of 142 failed bridges constructed in general dental practice were assessed for design factors that might relate to failure. The overall mean age of the bridges at failure was 6.2 years; anterior and complex bridgework had a mean age of about 5 years, compared with 7.5 years for posterior bridges. The lifespan of the bridgework was significantly correlated with the number of retainers but not with the number of units. Bridges with one or two retainers had an average lifespan of just over 7 years, whilst those with three or more retainers had been in service for, on average, only 4 years. The practical difficulties of constructing multi-abutment bridgework could account for this difference. One hundred and ninety-one of the 346 retainers were porcelain bonded to semi non-precious metal crowns, and had a mean lifespan of 3.7 years, whilst those that were gold based lasted at least twice as long. Post crowns as retainers survived on average for 6.2 years.

Eighty patients were selected, who were each deemed to require the replacement of a defective amalgam restoration. The patients had a mean age of 36.7 years and were dentally fit on average 40 months previously. The main reasons given for the replacement of the defective restorations were perceived radiographic secondary caries (31%), fracture of the restoration (20%), marginal defect (17%), and perceived secondary caries observed clinically (14%). Following the removal of the restorations, a highly significant relationship was found between the consistency and colour of the underlying dentine (P < 0.00001). Soft dentine was found underlying 36 (88%) of the 41 defective amalgam restorations which were diagnosed as having caries associated with them. However, hard dentine was found underlying only 19 (49%) of the 39 teeth where no caries had been diagnosed. The presence of soft dentine where not anticipated was mainly in association with fractured restorations (11 out of 16). Younger patients were more likely to have soft dentine underlying their defective amalgam restorations than older patients (P = 0.005). No relationship was found between the presence of corrosion products on the cavity walls associated with defects and the consistency of the underlying dentine.