Objectives : The Rocatec system conditions the bonding surface by fusing a unique silica layer onto the surface. The purpose of this study is to determine the effect of Rocatec treatment on the bond strength of stainless steel brackets.
Materials and methods : The mesh bases of Victory Series upper central brackets (3M Unitek, REF 017-401) were sandblasted with Rocatec Plus material (3M ESPE) using Rocatec Junior Blasting Module (3M ESPE). The Rocatec Plus material is silica-coated alumina with a 110 μm average particle size. The sandblasting pressure was set at 2.8 bar and the distance was set at 10 mm as recommended by the manufacturer. The sandblasting direction was perpendicular to the bracket base. The sandblasting time was approximately 2 s. Rocatec sandblasted brackets were tapped and air blown to remove loose sand. A silane solution, 3M ESPE SIL, was applied to bracket bases by brushing and allowed to dry at room temperature for at least 5 min. Untreated brackets (no Rocatec sandblasting, no silane treatment) were included as a control. Transbond XT Adhesive (3M Unitek) was pasted onto the brackets, and the adhesive coated brackets were seated firmly against bovine teeth, which had been pumiced, rinsed and etched/primed with Transbond Plus Self-Etching Primer (3M Unitek) according to manufacturer’s instructions. Excess adhesive expressed around the periphery of the bracket base was removed. An Ortholux LED Curing Light (3M Unitek) was used to cure the adhesive with a 5-s curing time interval on the mesial and distal sides of each bracket The bonded teeth were stored overnight in 37 °C water. Bond strength was tested in a shear-peel mode or tensile mode at a crosshead speed of 0.20 in./min using a MTS QTest/5 Universal Test Machine (MTS Systems Corporation) until failure was observed. The maximum force (in lb) was recorded. Bond strength was converted to MPa by dividing the force by the bracket base area.
| Brackets | Shear peel bond strength | Tensile bond strength | ||
|---|---|---|---|---|
| lb/bracket | MPa | lb/bracket | MPa | |
| Untreated | 40.7 | 17.1 | 13.5 | 5.7 |
| Rocatec treated | 57.2 | 24.0 | 16.7 | 7.0 |
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