Comparative assessment of bonding time and 1-year bracket survival using flash-free and conventional adhesives for orthodontic bracket bonding: A split-mouth randomized controlled clinical trial.

Abstract

A new flash-free adhesive promises to eliminate the flash removal step in bonding and to reduce bonding time by as much as 40% per bracket, with a bond failure rate of less than 2%. The aim of this trial was to compare bonding time and bracket failure rate over a 1-year period between the flash-free adhesive and a conventional adhesive for orthodontic bracket bonding. Forty-five consecutive patients had their maxillary incisors, canines, and premolars bonded with ceramic brackets (Clarity Advanced; 3M Unitek, Monrovia, Calif) using a flash-free adhesive (APC Flash-Free Adhesive Appliance System; 3M Unitek) on 1 side and a conventional adhesive (APCII Adhesive Appliance System; 3M Unitek) on the other side. The side allocation was randomized. Bonding was timed to the nearest second. Bond failure was recorded at standardized intervals of 4weeks. The primary outcome was bonding time (average per tooth for each patient and per quadrant). Secondary outcomes were bracket failure rate within 1year, time to first-time failure of a bracket, and bond failure type (adhesive remnant index score). Bonding times and adhesive remnant index scores upon bond failure were compared using paired t tests, with P<0.05 considered statistically significant. The adhesives were considered equivalent if the confidence interval for the difference between bracket failure rates fell within a margin of equivalence of ±5%. The bonding times were significantly shorter with the flash-free adhesive than with the conventional adhesive, both per tooth (P<0.001) and per quadrant (P<0.001). Compared with the conventional adhesive, the average bonding times per tooth and per quadrant with the flash-free adhesive were 37.3% and 32.9% shorter, respectively. The bracket failure rates at 1year were 3.7% for the flash-free adhesive and 0.9% for the conventional adhesive. This was statistically equivalent. The average times to first-time failure of a bracket were 25weeks for the flash-free adhesive and 11weeks for the conventional adhesive. Although there were no significant differences in the adhesive remnant index scores upon failure (P>0.05), the flash-free adhesive tended to fail more often at the enamel-adhesive interface than did the conventional adhesive. The use of the flash-free adhesive may result in bonding time savings of approximately one third compared with the conventional adhesive. With regard to bracket survival, a statistically significant difference was not found between the 2 adhesives when ceramic brackets were bonded. This trial was registered on December 3, 2013 (ClinicalTrials.gov ID, NCT02030002). The protocol was not published before trial commencement.