RESUMEN
Adhesion to dentin is the major problem in using tooth color composite resins. The way proposed is the use of hydrophile resins, of which, HEMA is the most important one. Because of the importance of the subject, this study was conducted to evaluate the effect of HEMA on shear bond strength of enamel bonding agent to dentin after 1 year water storage. This invitro study carried out experimentally on 36 extracted premolar teeth. The teeth randomly assigned to 4 groups, each group containing 6 samples. In group 1, the solution of%35 HEMA and Acetone and in group 2, the solution of%35 HEMA and Water was used. Multipurpose Scotchbond primer was used in group 4. In group 1 and 2, enamel bonding and in group 4 the adhesive was used. In group 3, teeth were dried and enamel bonded after etching. Composite cylinders were bonded on the areas with the same dimensions. The prepared samples were thermocycled 1000 times at 55°C and 5°C after keeping in distilled water for 1 year. Shear bond strength of the samples were tested by Instron machine. Results showed that the [HEMA and Acetone] group had the highest strength [25.12 +/- 3.52], and then, [Scotchbond] group [23.55 +/- 1.6]. [HEMA and Water] group [14.3H5.6] and [enamel bonding] group [4.25 +/- 2.61] had the next ranks respectively. Analysis of variance test showed that the overall difference between them was statistically significant [P<0.0001]. Difference in strength of HEMA and Scotchbond was not significant but was significantly different from other groups. Shear bond strength of [HEMA and Acetone] and [HEMA and Scotchbond] became acceptable after thermocycling and storage in distilled water for one year but not in enamel bonding group