Effect of orthodontic adhesive thickness on force required by debonding pliers.

This in vitro study evaluated the relationship between removal force and the thickness of three orthodontic adhesives, namely, light- and chemical-cured resin cements and a resin-modified glass ionomer cement. The thickness of each adhesive was 50, 100, 150, or 200 µm, and all adhesives were bonded on bovine incisors. Removal force was measured before (TC-0) and after 1,000 thermal cycles (TC-1000), and values were compared. At TC-0, the removal strengths for adhesive thicknesses of 50 and 100 µm were significantly lower than those for thicknesses of 150 and 200 µm (P < 0.05). At TC-1000, removal strengths for adhesive thicknesses of 50 and 100 µm were also significantly lower than those for 150 and 200 µm. Superbond Orthomite specimens showed a significant difference in removal strength between TC-0 and TC-1000 (P < 0.05) at all thicknesses. There was no significant difference in the distribution of adhesive remnant index scores at any thickness. These findings indicate that decreasing the thickness of applied orthodontic adhesive reduces the removal strength required.

The use of easily debondable orthodontic adhesives with ceramic brackets.

We experimentally produced an easily debondable orthodontic adhesive (EDA) containing heat-expandable microcapsules. The purpose of this in vitro study was to evaluate the best debondable condition when EDA was used for ceramic brackets. Shear bond strengths were measured before and after heating and were compared statistically. Temperatures of the bracket base and pulp wall were also examined during heating. Bond strengths of EDA containing 30 wt% and 40 wt% heat-expandable microcapsules were 13.4 and 12.9 MPa, respectively and decreased significantly to 3.8 and 3.7 MPa, respectively, after heating. The temperature of the pulp wall increased 1.8-3.6°C after heating, less than that required to induce pulp damage. Based on the results, we conclude that heating for 8 s during debonding of ceramic brackets bonded using EDA containing 40 wt% heat-expandable microcapsules is the most effective and safest method for the enamel and pulp.