EFFECT OF SURFACE TREATMENTS ON THE REPAIR STRENGTH OF A LIGHT-ACTIVATED DENTURE REPAIR RESIN USING CENSORED-DATA

Objectives. The aim of this study was to evaluate the effect of three different chemical surface modifications on the bond strength of light -activated denture repair resin (Triad, Dentsply International) to a h eat-cured resin (Lucitone, Dentsply international). Methods. Transvers e flexure test specimens were made, with surface treatment of 1) Triad bonding agent, 2) unreacted Lucitone monomer, and 3) a 1:1 mixture of methylene chloride and monomer, using two different application times (2 and 4 min). For all except one group, 18 specimens were made. The controls were solid single composition bars, 18 for each material. The elastic modulus in transverse flexure was measured for each material. The statistical analysis employed the Weibull distribution. Fracture strength values were obtained in a three-point flexure test. Results. It was noted that many fractures occurred away from the interface and the center member of the test fixture. For those fractures, the observ ed fracture strength is a censored value of the fracture strength. Alg orithms for the statistical treatment of censored data were used to ge t the maximum likelihood estimates of the fracture strength. A mechani cal model showed that under three-point bending of a beam of two joine d materials, fractures will occur in the part with the higher elastic modulus. This finding is indeed observed in the data. The 4 min monome r treatment showed the highest estimate of the bond strength (187.8 MP a). Significance. Censored data can be used to obtain fracture strengt h estimates, and the censoring indicates that the bond strength may ex ceed the strength of the bulk material.