Residents’ journal review

Abstract

As restorative composite materials improve, the need to bond to existing restorations for orthodontic treatment is likely to increase. The purpose of this study was to evaluate the in-vitro shear bond strength of orthodontic brackets bonded to aged restorative composite resin surfaces treated with various surface-roughening methods. Ninety composite resin discs (Filtek Supreme XT, 3M ESPE, St Paul, Minn) (6 × 2 mm) were compressed on a glass slide, light-cured, and treated for 300 hours with an accelerated aging procedure. Each disc was randomly assigned to a different prebonding-procedure group: (1) control with no surface treatment, (2) 38% phosphoric acid, (3) 9.6% hydrofluoric acid, (4) airborne aluminum trioxide particle abrasion, (5) sodium bicarbonate particle abrasion, or (6) roughing with a diamond bur. After the prebonding procedure, metal brackets were bonded with adhesive (Transbond XT, 3M Unitek, Monrovia, Calif). All samples were stored in water for 7 days at 37°C and then thermocycled 1000 times (5°C-55°C). Shear bond strength was recorded as the maximum load to debond the brackets. The results showed that treatment with phosphoric acid was not significantly different from no pretreatment. All other treatment methods had significantly better shear bond strengths than did the control, but no statistical differences were found among the 4 other methods. The authors concluded that surface roughening was an effective pretreatment in bonding to aged composite surfaces and that clinically adequate shear bond strengths were found by using either hydrofluoric acid, sodium bicarbonate, aluminum trioxide particle abrasion, or a diamond bur.