Effect of surface treatments and bonding type on elemental composition and bond strength of dentin

The objective of this study was to explore the effect of different surface treatments and bonding types on elemental composition and bond strength of dentin. Under water cooling, 1.5 mm of tooth structure containing just dentin was cut from 39 extracted human molars. Dentin surfaces were untreated (control) or treated by erbium: yttrium aluminum garnet or femtosecond laser (n = 13, each). One sample from each group underwent scanning electron microscopy. Then, dentin surfaces were bonded by Clearfil SE Bond or Clearfil SE Protect (n = 6, each). Energy dispersive X-ray spectroscopy was performed both after surface treatment and bonding application. The dual-polymerized resin cement was applied to dentin surfaces with a special teflon mold (diameter:3 mm × height:3 mm). After polymerization of the resin cement, shear force was applied at the resin cement-dentin interface. Elemental composition value (weight%) of dentin after surface treatment was analyzed by one-way analysis of variance (ANOVA), and the difference value in pre and post-bonding elemental composition by two-way ANOVA. Paired t-tests were executed to compare the weight% values of each element before and after each bonding application. Bond strength was analyzed by two-way ANOVA. The post-hoc test was Tukey's honest significant difference test. Both laser treatments increased the mineral content of dentin, compared to the controls (P<0.05). Application of bonding agents decreased the mineral content of dentin compared to the surface treated dentin. Bond strength was unaffected by either surface treatment or bonding type (P>0.05). For resin cementation, either surface treatment is suitable. After laser treatment, Clearfil SE Bond is recommended over Clearfil SE Protect.