[Resin adhesion on the primary ground enamel. (Report 1). Influence of the etching times]

The purpose of this study was to investigate the influence of the etching times on the adhesion of the resion on the primary ground enamel. Fifty extracted and frozen bovine mandibular primary incisors were used. The etchant used in this study was 40% phospholic acid gel and the etching times were 0, 10, 20, 30 and 60 seconds. All of the specimens were washed with an air water spray for 30 seconds after etching. The bonding agent and composite resin used in this study were Photo Bond and Photo Clearfil A (Kuraray Co.). Shear bond strength on the ground enamel were measured. After the shear bond strength test, all the test surfaces of the enamel and resin specimens were observed using the SEM. The following conclusions were observed. 1) The etching time which showed the highest bond strength was 30 seconds (80.10 +/- 13.01 MPa). 2) When the enamel was etched with all of the etching times, the bond strengths were significantly higher than that of the enamel without etching. 3) The bond strength with 10 seconds of etching time was significantly higher than that with 20 seconds of etching time, and the bond strength with 30 seconds of etching time was significantly higher than that with 10 seconds of etching time, and the bond strength with 30 and 60 seconds of etching time was significantly higher than that with 20 seconds of etching time. 4) On the enamel specimens after the shear bond strength test, clear prism structures were observed in the group which showed a higher bond strength. 5) On the enamel specimens after the shear bond strength test, the frequency of the resin tags were fractured inside of the enamel prisms was lower in the group which showed a higher bond strengths. 6) Thirty seconds is a sufficient time for etching on the primary ground enamel using Photo Bond and Photo Clearfil A.