Phosphoric acid etching has been widely used to achieve a strong and
long lasting mechanical bonding between composite resin restoration
and tooth structure. The bond strength between the composite resin
restoration and the enamel of permanent teeth can be measured by the
shear bond strength of the composite resin restoration. The aim of this
study was to evaluate the bond strength between the enamel of
permanent teeth and the composite resin restoration by measuring the
shear bond strength after different durations of etching. In total 27
premolar teeth were divided into 3 groups where the enamel of the
buccal surface was etched with 37% phosphoric acid for 5″, 15″, and
25″ before placing the composite resin restoration. After keeping the
teeth inside an incubator for 24 hours, the shear bond strength was
measured using a universal testing machine Shimazu AG-5000 at a
crosshead speed of 0.5 mm/min. ANOVA was used for statistical
analysis of the results, with p<0.05 assumed to imply significance.
The mean shear bond strength after etching for 5″, 15″, and 25″ was
16.1 MPa, 17.3 MPa and 19.0 MPa, respectively. The results of ANOVA showed significant difference between the 3 groups. However, subsequent Tukey test showed significant difference between 5″ and 25″ of etching (p<0.05), but no significant difference between between the 5″ and 15″ groups nor between the 15″ and 25″ groups (p>0.05). Conclusion: Shear bond strength of the composite resin on the permanent teeth enamel increased with increasing etching time. Significant difference was showed between 5″ and 25″ of etching time.
