This study was performed to evaluate the clinical performance of resin-bonded fixed partial dentures (FPDs) for various service periods. FPDs were divided into two groups: A, seated from 1982 to 1988 and B, seated from 1989 to 1996. The failure rate for each group was compared periodically, and the factors affecting the service period were considered. Group A consisted of 504 FPDs seated in 335 patients, whereas group B consisted of 331 FPDs in 275 patients.
The follow-up rate was 51% for group A, and 61% for group B. The failure rates after the specific service period observed in group B were 5% for 0-2 years, 9% for 3-5 years, and 22% for 6-8 years. The total group B failure rate was 9%, which was only one-fourth that of group A.
Two major factors were considered for improvement in the retentive rate of FPDs. One was decrease in original retainer design without retentive form. Specifically, the so-called Maryland retainer considerably reduced to less than 33%, while retainers with sufficient retentive structure such as proximal or incisal groove increased. The other factor was development of a new metal conditioner for noble metal alloys used in the majority of FPDs in group B.
The remaining problem to be solved was undoubtedly improvement in the survival rate after a longer service period.
