Resin sheer bond strength to porcelain and a base metal alloy using two polymerization schemes

Statement of problem. Fractures in ceramometal restorations can occur and n eed to be repaired because replacements are not an economic solution. Purpose. This study evaluated the shear bond strengths of 4 porcelain repai r systems (Metabond C&B [ME], Silistor [SI], Clearfil Lustre [CL], and Scot chbond Multipurpose Plus [SQ]) to a base metal alloy and porcelain in relat ion with the polymerization shrinkage of a visible light-cured composite su perstructure and compared with the ceramometal bond strength (Vita VMK 68). Material and methods. Thirty-two samples were prepared for each bonding sys tem: 16 for resin-metal bond strength test, and 16 for resin-porcelain bond strength test. For each group, bonding agent was applied to 8 substructure s and the resin superstructure was polymerized onto the bonding agent; and for the remaining 8 specimens, prepolymerized resin superstructures were bo nded with bonding agent. All specimens were subjected to 500 cycles between 5 degrees C and 55 degrees C with 20 seconds dwell time. Tests were perfor med in a mechanical testing machine with a 0.5 mm/min crosshead speed. Results. All materials showed an increase in shear bond strength when prepo lymerized resin superstructures were used. However, the effect of polymeriz ation shrinkage of resin superstructure was statistically sig nificant only for CL group (P<.05). The highest metal-resin bond was obtained from ME gr oup with prepolymerized resin superstructures (35.27 +/- 2.40 MPa), and the lowest value was obtained for the SI group in which resin superstructures were polymerized in situ (8.71 +/- 1.03 MPa). The highest porcelain-resin b ond was obtained from SC group with prepolymerized resin superstructures (2 0.71 +/- 1.13 MPa) and the lowest was obtained from SI group (9.99 +/- 1.52 MPa). Conclusion. Higher bond strength values were obtained with prepolymerized r esin superstructures compared to in situ polymerized superstructures. Metab ond C&B provided the best results for both prepolymerized and in situ polym erized resin superstructure preparation techniques at the failures where me tal was exposed. The best results in situations in which the fracture is li mited into porcelain were obtained with the use of Scotchbond Multipurpose Plus material. However, a variety of in vivo and in vitro tests are require d before a final judgment is made.