The shear bond strength of bonded orthodontic attachments, coated with a silicon oxide layer to enhance adhesion, was tested and compared to that of untreated attachments. Twenty buttons for direct bonding (test group) were "silicoated" and bonded to surgically removed, unerupted human third molars, using "Right-On" adhesive. The control group consisted of 20 similar teeth to which untreated buttons were bonded. Half of the specimens in each group were then thermocycled to stress the bonds. Shear strength was tested with the use of the Instron Universal testing machine. The mean shear bond strength of the silicoated attachments was found to be higher than that of the untreated attachments. This was a highly significant finding (p less than 0.005). The bond strength after thermocycling decreased in both the test and control groups, although this decrease was only significant at the level p less than 0.01. The results obtained from this study indicate that silicoating of orthodontic attachments prior to bonding significantly increases their shear bond strength to dental enamel.