The purpose of this study was to compare the microshear bond strength (uSBS) to enamel prepared with different burs and to determine what type of bur were chosen when a self-etching primer adhesive was used.

Enamel of forty-two human molars were used. They were divided into one of six groups (n = 7), Group 1, coarse (125 - 150 µm) diamond bur; Group 2, standard (106 - 125 µm) diamond bur; Group 3, fine (53 - 63 µm) diamond bur; Group 4, extrafine (20 - 30 µm) diamond bur; Group 5, plain-cut carbide bur (no. 245); Group 6, cross-cut carbide bur (no. 557). Clearfil SE Bond and Clearfil AP-X (Kuraray Medical Inc.) was bonded to enamel surface. The bonded specimens were subjected to uSBS testing.

The uSBS of Group 4 was the highest among groups and it was significantly higher than that of Groups 1, 2, 3, and 6 (p < 0.05), but it was not significantly different from that of Group 5.

Different burs used on enamel surface affected the microshear bond strengths of a self-etching primer adhesive to the enamel surface. In the case of Clearfil SE Bond, extrafine diamond and plain-cut carbide bur are recommended for bonding to enamel.

The purpose of this study was to compare the microshear bond strength (µSBS) and bonding interfaces of two-step total-etching and self-etching adhesive systems to three etch types of dentin either the acid etched, laser etched or laser and acid etched.

The occlusal dentinal surfaces of thirty human molars were used. They were divided into six groups: group 1, 37% H₃PO₄ + Single Bond 2 (3M ESPE); group 2, Er:YAG laser (KEY Laser 3, KaVo) + Single Bond 2; group 3, Er:YAG laser + 37% H₃PO₄ + Single Bond 2; group 4, Clearfil SE Primer + Bond (Kuraray); group 5, Er:YAG laser + Clearfil SE Bond; group 6, Er:YAG laser + Clearfil SE Primer + Bond. The samples were subjected to µSBS testing 24 hr after bonding. Also scanning microscopic evaluations were made on the resin-dentin interfaces of six specimens.

The µSBS of group 2 was significantly lower than that of groups 1 and 3 in Single Bond 2 (p < 0.05). There were significant differences among the uSBS of groups 4, 5, and 6 in Clearfil SE Bond (p < 0.05). Very short and slender resin tags were observed in groups 2 and 5. Long and slender resin tags and lateral branches of tags were observed in groups 3 and 6.

Treatment of dentin surface using phosphoric acid or self-etching primer improved the adhesion of Er:YAG lased dentin.