Objectives: The clinical step of dentin bonding has been simplified with the development of all-in-one adhesives. Some of these adhesives are instructed as double application in bonding procedure and reported to show high bond strength to dentin. This study aims to evaluate the effect of double application of all-in-one adhesives to human dentin using micro-shear bond test (Shimada et. al. JDR abstract, 2000). Methods: The occlusal surfaces of extracted human third molars were ground perpendicular to the long axis of the tooth to expose a flat dentin surface. Three commercially available systems and one experimental bonding system were used in this study; newly developed OBF-2 (OB2, Tokuyama), Adper Prompt L-Pop (PL, 3M ESPE), REACTMER BOND (RB, Shofu), and XENO III (Xeno, Dentsply-Sankin). These adhesives were applied on the dentin surfaces according to the following each method; manufactures' instruction (single application) or experimental method (double application). Resin composite (Clearfil AP-X, Kuraray) was then mounted and light-cured for 40s. After 24 h immersion in water, a micro-shear bond test with a wire loop was carried out at a crosshead speed of 1.0 mm/min to assess the micro-shear bond strength. Results were analyzed by one-way ANOVA and Tukey's HSD test (p<0.05). Results: Micro-shear bond strengths (mean±S.D. in MPa) of tested adhesives were:
|
Adhesive |
OB 2 |
PL |
RB |
Xeno |
|
Single-application |
34.6±4.9 |
22.7±8.7 |
28.3±6.7 |
30.3±7.1 |
|
Double-application |
32.5±6.4 |
29.5±9.2 |
27.2±6.1 |
29.6±6.4 |
The bonding strengths of OB2 (single-application and double-application) were significantly higher than single-application of PL. Conclusions: Micro-shear bond strengths of all-in-one adhesive used in this study showed no significant difference between the single-application method and double-application method. (Supported by grant-in-aid for Scientific Research, #15390573 from The Ministry of Education, Culture, Sports, Science and Technology, Japan.)