Enamel Water-Removal and Bracket Strength of an Experimental Bioactive Adhesive

Objectives: To evaluate/compare bracket shear bond strength of an experimental, bioactive orthodontic adhesive, using different methods of surface enamel water removal
Methods: Crown portions of forty freshly extracted bovine incisors were embedded in epoxy and wet-ground to 800 grit. The experimental, bioactive, water-requiring product (Pulpdent) was tested using thirty enamel surfaces that were acid-etched for 10s, water and air-rinsed, and then subjected to different methods of removing excess surface water: (1) enamel air-dried, a moistened, hand-squeezed cotton roll was applied once over the dried enamel surface; (2) a dry cotton roll was wiped once over the rinsed, etched enamel surface; (3) 2 successive, 0.5-s long air blasts were made. Brackets (MBT 22, 3M Unitek) were pasted with the experimental adhesive paste, and placed on the facial surface of each specimen. As control (4), a conventional, acid-etch, primer/adhesive system was used: acid etching (20s), followed by water-rinsing and air-drying, application of unfilled resin (Transbond XT Primer, 3M Unitek), and placement of the same type bracket having pre-pasted adhesive (Transbond XT). All brackets received 10-s mesial and distal exposures (Elipar S10, 3M). Bonded teeth were thermocycled (5°-55°C, 500x) and dark-stored in 37°C water for 7d. Brackets were removed in shear (model 5844, Instron). Peak debond value was divided by bracket base area to provide results in MPa. N=10/group. Debond strengths were compared using a 1-Way ANOVA and Tukey’s post-hoc test at a pre-set alpha of 0.05.
Results: Table presents results. Use of treatment (3) provided bracket bond strength values not significantly different from that of the control, commercial product (4), and provided more consistent results than any other treatment.
Conclusions: Use of short air blasts suffices to supply sufficient residual surface moisture for the experimental, moisture-requiring bracket adhesive to provide adequate short-term bond strength.