Objectives: A whitening restorative system (SI-R20209, Shofu) was newly developed for improving tooth discoloration showing a short-term duration. This study was to evaluate the microtensile bond strength (MTBS) of this system to normal and bleached tooth substrate and the fracture mode to estimate its utility.
Methods: Twenty seven human extracted teeth were ground flat to expose the enamel or dentin and finished by #1500 sandpaper as a specimen and assigned to five groups: Group 1, application of primer on enamel or dentin; Group 2, application of primer and activator on enamel or dentin; Group 3, application of primer on bleached enamel or dentin immersed in water (37˚C, 14d); Group 4, application of primer and activator on bleached enamel or dentin immersed in water (37˚C, 14d); Group 5, application of bonding agent of FL-Bond system on etched (37% H3PO4) enamel (as control). Each specimen (n=3 teeth/group) was filled with white based composite-resin to 5mm in thickness, light-cured, immersed in water (37˚C, 24h) and sectioned to 1mm x 1mm stick for measuring MTBS at a crosshead speed of 1.0 mm/min. The fractured surfaces were observed by SEM. The statistic analysis was performed by One-way ANOVA and Fisher's PLSD test.
Results: MTBS in MPa (s.d.)
|
Group 1 |
Group 2 |
Group 3 |
Group 4 |
Group 5 |
|
|
Enamel |
22.3(5.4)a |
25.3(5.3) a |
22.0(5.3) a |
25.3(8.3) a |
39.4(8.5) b |
|
Dentin |
19.1(9.1) a |
59.4(11.6) c |
34.8(14.7) b |
64.1(14.8) c |
- |
Different superscript indicated significant difference (p<0.05).
The fractured surfaces except for Group 5 showed mostly failure in adhesive and cohesive in composite-resin with less damage to tooth.
Conclusion: Except the use of activator on dentin, it is suggested that the system will be available as a temporary whitening remedy for discolored tooth.