Abstract
The purpose of this study was to investigate the influence of the thermal cycling test on the adhesion of the resin on young permanent enamel which was etched with different etching times.
Labial surfaces of 50 extracted and frozen bovine mandibular young permanent 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 Scotch Bond and Silux (3M Co.). After thermal cycling tests consisting of water baths with 10,000 temparature cycles between 60°C and 4°C, shear bond strengths on the ground enamel were measured. After the shear bond strength tests, 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 which were not thermal-cycled. The following conclusions were obtained.
1) The etching time which showed the highest bond strength was 60 seconds (33.40±5.75MPa).
2) The longer the etching times, the higher the bond strengths were.
3) In the etched groups, the bond strength with 10 seconds of etching time was significantly lower than those with 20,30 and 60 seconds of etching times and the bond strength with 60 seconds of etching time was significantly higher than that with 20 seconds of etching time.
4) In all the etching time groups, the bond strengths of the thermal-cycled groups were significantly lower than those of the non thermal-cycled groups.
5) The optimum etching time for Scotch Bond and Silux on the ground young permanent enamel was 60 seconds.
