The Effect of One versus Two Applications of Self- etch Primers on Micro-Shear Bond Strength to the Enamel and Dentin

Statement of problem: 

Self etch acidic primers may be unable to etch the enamel and penetrate the thick dentinal smear layer and as a result produce inadequate bond strength.

The present study aimed to evaluate the effect of the second layer application of two self-etch primers on etching pattern and micro-shear bond strength to the enamel and dentin.

In an experimental study, 104 human premolar teeth were divided into two groups. The buccal surfaces of the teeth were prepared for enamel and dentinal evaluation. Self-etch primer of clearfil SE Bond and clearfil S3 Bond were applied in one or two layers on the prepared enamel and dentin surfaces. One specimen of each prepared group was selected for SEM group evaluation. The composite resin cylinders were bonded to the rest of the specimens for micro-shear bond strength measurement. The data were analyzed using two- way ANOVA and HSD -Turkey's tests. 

Application of the second layer had no significant effect on micro-shear bond strength to the enamel and dentin (p>0.05). The dentinal micro- shear bond strength values of the specimens treated by Clearfil SE Bond, were significantly higher compared to Clearfil S3 Bond (p< 0.05) but no significant effect was found on enamel bond strength (p> 0.05).

Application of one layer of self- etch primer produced sufficient bond strength and there is no need to apply the second layer.