An investigation of the variables which may affect the bond between plastic teeth and denture base resin

Objectives: The failure of the bond between acrylic resin denture base mate rial and resin teeth remains a significant problem. This study evaluated th e tensile bond strength of specimens produced by commonly employed tooth pr eparation and processing methods as used in dental laboratories. Methods: Twenty-two experimental groups, each consisting of 36 specimens, w ere investigated by subjecting the tooth-resin bond to tensile loading. The groups were allocated-to one of five experimental sets to investigate: (a) effect of resin dough time, (b) effect of tooth surface condition, (c) eff ect of processing variables, (d) effect of monomer cementing, and (e) effec t of acrylic resin cement. The results were analysed statistically using a one factor ANOVA and a Student t test. Results: A significantly stronger bond was obtained when the resin was pack ed late in the dough stage, and a superior bond, in all cases, when high-im pact resin was used. Tooth surface modification by grinding or grooving mad e no significant difference when compared with unmodified surfaces. Wax-con taminated surfaces produced highly significant weaker bonds. Time of introd uction and duration of water-bath processing had no significant effect on b ond strength. Monomer cementing of the tooth surface, especially with high- impact monomer, significantly improved the bond strength. The application o f resin cements was found to produce the most significant increase in dentu re tooth bond strength. Conclusions: The important steps in obtaining a consistently high value den ture tooth bond are thorough dewaxing of the tooth surface followed by the application of a suitable resin cement. (C) 1999 Elsevier Science Ltd. All rights reserved.