It has been introduced some office bleaching agents which contains titanium dioxide (TiO2) as a photocatalist. TiO2 can be activated by visible blue-violet light and it can accelerate the radical reaction of hydrogen peroxide (H2O2) even if its concentration is lower than TiO2-uncontained agent. Since application of hydrogen peroxide to dentin has known to interrupt the polymerization of adhesive resin, it causes the reduction of resin bond strength. TiO2-contained bleaching agent may reduce the influence of the interruption of polymerization caused of the low concentration of H2O2. The aim of this study was to evaluate the influence of bleaching agent on microtensile bond strength (micro-TBS) to bovine dentin.
Method:
Extracted bovine teeth were randomly divided to three groups (n=9). The coronal labial pulp chamber dentin was applied with an office bleaching agents which contains TiO2 and a 3.5% H2O2 (Pyrenees, Mitsubishi Gas Chemicals) and activated with 405-nm diode laser for 15 min (Group 1); 30% H2O2 and irradiated with quartz-tungsten-halogen light-curing unit for 15 min (Group 2); and distilled water for 15 min (Group 3). Resin composite (Clearfil AP-X, Kuraray) was then bonded with Clearfil S3 Bond (Kuraray). After storage in water for 37 degrees centigrade for 24 h, each specimen was then sectioned to four slabs and trimmed to an hourglass-shape. Micro-TBS were determined at cross-head speed of 1.0 mm/min. Data were analyzed statistically using ANOVA and Tukey test (p<0.05).
Result:
Although mean micro-TBS of Group 1 (7.4 ± 9.4 MPa) was significantly lower than that of non-bleached control (Group 3; 24.0 ± 5.6 MPa), that of Group 1 was significantly lower than that of Group 2 (0 ± 0 MPa).
Conclusion:
It can be concluded that influence of an office bleaching agent which contains TiO2 and 3.5% H2O2 on resin bonding was lower than 30% H2O2.