[Resin adhesion on the primary ground enamel. (2) Influence of the etched enamel]

The purpose of this study was to investigate the influence of the etching times on the adhesion of the resin on the primary ground enamel. Fifty extracted and frozen bovine mandibular primary incisors were used. The etchant used in this study was 37% 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 after etching. The bonding agent and composite resin used in this study were Dual Cured Scotch Bond and Silux (3M Co.). Shear bond strengths 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 results of this study were compared with the previous results using Photo Bond and Photo Clearifil A (Kurarey Co.). 1) The etching time which showed the highest bond strength was 20 seconds (76.77 +/- 12.99 Mpa). 2) When the enamel was etched with all of the etching times, the bond strength were significantly higher than that of the enamel without etching (p less than 0.01). 3) In the etched groups, there was no significant difference among the bond strengths with all of the etching times categories. 4) In the etched groups, the longer the etching times, the lower the standard deviations were. 5) On the enamel specimens after the shear bond strength test, the frequency of the resin tags fractured inside of the enamel prisms was higher in the group which showed a lower bond strength. 6) For the same etching times, significant difference between the bond strengths of Silux and those of Photo Clearfil A was obtained only with the 20 seconds of etching time (p less than 0.01) and the bond strength of Silux was higher.