Shear bond strength of orthodontic metal brackets using Assure® Plus with and without Pro Seal®: An in vitro study

To evaluate the shear bond strength (SBS) of orthodontic brackets bonded with Assure Plus® alone and in combination with Pro Seal®, and to assess the adhesive remnant index (ARI) scores following bracket debonding.

This in vitro experimental study included forty-two extracted human premolar teeth, randomly assigned to two bonding groups: the control group (Assure Plus®) and the test group (Assure Plus® with Pro Seal®). After bonding, all specimens were stored at 37̊C for 24h before SBS testing. The Shapiro-Wilk test was used to assess normality, and group comparisons were performed using the Mann-Whitney U test (α=0.05).

The control group demonstrated a mean SBS of 11.20±2.51MPa and a mean peak load of 90.09±20.21N, while the test group (Assure Plus® with Pro Seal®) showed a mean SBS of 10.62±3.56MPa and a mean peak load of 85.47±32.61N. The Mann-Whitney U test revealed no statistically significant differences between the groups for either SBS (P=0.094) or peak load (P=0.134). Both groups exceeded the clinically acceptable SBS threshold of 6-8MPa. ARI scores were identical between groups, with 95% of samples scoring 2 and 5% scoring 1, indicating adhesive failures with more than 50% of the adhesive remaining on the tooth surface.

The combination of Pro Seal® and Assure Plus®, as recommended for bonding to atypical enamel surfaces, produced bond strengths comparable to Assure Plus® alone. These findings support its use as a clinically acceptable bonding protocol in orthodontic practice.