Comparing the retention of two different designs of resin bonded restorations

Prosthesis design has an important effect on its retention, especially in Resin Bonded Restorations (RBRs) in which preparation is conservative since there are different design possibilities to fabricate RBRs. The aim of this study was to compare the retention of RBRs with two different designs. In this experimental study, twenty-two RBRs were fabricated from twenty-two premolar and second molar teeth which had the same size and no carries. In the first group, conventional preparation which included lingual preparation, guiding planes, occlusal rests and two grooves in interproximal areas, was perfomed. In the second group, preparation included only class II inlay cavity preparation on the edentulous side. After frame work fabrication, the samples were cemented with resin cement (Panavia F), and subjected to tensile force. The force required to separate each sample was recorded and the results in the two groups were compared by t test. Average retention in the group with conventional design was 39.523 ± 8.62 kgf and 25.715 ± 4.10 kgf in the group with modified design. The difference was shown significant by the statistical t test (P<0.001). Results indicate that the design with conventional preparation had a higher retention than the modified design that has only Class II intercoronal retainers..