Shear bond stability of current adhesive systems to enamel.

This study evaluated the micro-shear bond strength of two commercially available resin bonding systems (Single Bond, 3M, USA and SE Bond, Kuraray, Japan) to human enamel. One hundred and twenty enamel sections were prepared from extracted non-carious human molars by cutting with a slowly rotating blade. The enamel surfaces were polished with #280-grift SiC paper under running water. These surfaces were randomly divided into two groups and treated with either Single Bond or Clearfil SE Bond according to manufacturers' instructions. After the bonding procedures, a micro tygon tubing with an internal diameter approximately 0.7 mm and 0.5 mm in height was placed on the enamel surface and Clearfil AP-X resin filled the tube. After the resin was photo-irradiated, the tygon tube was removed. The specimens were further divided into 12 groups according to storage time. All specimens were stored in isotonic sodium chloride solution at 37 degrees C. The bond strength was then measured by means of microshear bond testing at one day, one week, one month, three months, six months and one year. After testing, the fractured surfaces and interfaces were observed using scanning electron microscopy (SEM). The data was analyzed by two-way ANOVA and Fisher's PLSD tests at 95% level of confidence. The result was that both factors (storage time and material) affected bond strength and there was a statistically significant interaction between them. In general, bond strength decreased with time for both materials. The highest bond strengths were achieved at one day with SE Bond and Single Bond. For Single Bond, from one month to one year, the bond strength dramatically decreased. For SE Bond, the decrease in bond strength was gradual. After one-year storage, the bond strength drastically decreased and this value was not significantly different from the results of the one-year storage of Single Bond.