Aim: To evaluate the influence of the sealant on the shear bond strength of a composite resin orthodontic adhesive. Methods: Sixty freshly extracted human molars were collected and stored in a solution of 0.1% (weight/volume) thymol. The teeth were cleaned, polished, and etched with a 37% phosphoric acid gel. The teeth were randomly separated into 3 groups of 20 teeth each: in group 1 (control), the sealant was applied, and the brackets were bonded with the adhesive and light cured for 20 seconds; in group 2, the sealant was applied and light cured for 10 seconds, then the brackets were bonded with the adhesive and light cured for 20 seconds; in group 3, no sealant was applied and the brackets were bonded with the adhesive and light cured for 20 seconds. All teeth were stored at 37°C and 100% humidity for 24 hours before bonding. Results: The analysis of variance comparing the 3 experimental groups (F = 11.81) indicated significant differences between the 3 groups (P = 0.0001). In general, the shear bond strength was significantly greater in the group in which the sealant was not light cured (mean = 10.4 ± 2.8 MPa) when compared to the group that was light cured for 10 seconds (mean = 7.9 ± 5.7 MPa). In addition, the shear bond strength was significantly lower in the group in which the sealant was not applied (mean = 4.7 ± 3.4 MPa). Conclusion: The present findings indicated that the bond strength of the composite resin adhesive is significantly increased if the sealant is applied before bonding, but that light curing the sealant did not enhance bond strength. On the other hand, not applying the sealant significantly decreased shear bond strength. World J Orthod 2000;1:152-156.