ANALYSIS OF DEBOND RATES OF RESIN-BONDED PROSTHESES

Debonding rates of 164 resin-bonded prostheses (RBP) placed from 1974 to 1985 were examined at recall. The yearly debond rates were calculat ed, the cumulative probability of failure was determined for the debon ded RBPs, and Weibull distribution parameters were determined. For per forated prostheses, there was a high initial debond rate, followed by slowly decreasing rates for about 5 years. Increasing rates after 5 ye ars indicated the beginning of wearout. The Weibull parameters for the wearout period of the perforated prostheses were: characteristic life = 128 (SE = 2) months, modulus = 1.27 (0.06), and threshold parameter = 0. Data were available for etched frameworks for 6 years and showed decreasing debond rates during this time. The characteristic life of the etched bridges was 318 (84) months. The cumulative failure data we re also modeled with a cubic polynomial distribution that resulted in a U-shaped hazard function.