SHEAR BOND STRENGTH OF RESIN-BONDED CERAMIC AFTER DIFFERENT TRY-IN PROCEDURES

Final cementation of porcelain laminate veneers may require a previous colour match try-in. The purpose of this in vitro study was to evalua te the effect on shear bond strength of resin bonded to porcelain afte r the application of different try-in procedures. Forty porcelain spec imens were fabricated, flattened with 600 grit SiC, etched with hydrof luoric acid and silane treated. After 24 h the specimens were divided into four groups at random and prior to bonding of a dual cure resin c omposite button were treated as follows: Group 1, no treatment (contro l), Group 2, non-activated resin applied for 5 min. cleaned in acetone for 3 min; Group 3. as for Group 2, with silane reapplied: Group 4, a s for group 3, but re-etched for 30 s before reapplication of silane. After bonding the specimens were stored in water at room temperature f or 7 days. Shear bond strength data were as follows: Group 1, 18.6 +/- 1.6, Group 2, 15.9 +/- 1.7; Group 3, 16.7 +/- 2.6; Group 4, 15.3 +/- 3.0 MPa. Fractured surfaces examined, under light microscopy and scann ing electron microscopy (SEM), showed cohesive failure within the porc elain in all cases. The reduction in mean bond strength after applicat ion of a try-in resin was significant in Groups 2 and 4 compared with the control (ANOVA P < 0.05). No other significant differences were me asured. In conclusion a single reapplication of silane maintained the bond strength of resin to porcelain when final cementation was precede d by a try-in procedure and cleaning (Della Bona et al. J Dent Res 199 3, 72: 733 (abstr no 371)).