V17N04 | 2012 | Original Article | Pages 187 to 191
Silvia Amélia Scudeler Vedovello, Marcelo Grigoletto, Mário Vedovello Filho, Heloísa Cristina Valdrighi, Mayury Kuramae
Composite resins, Orthodontic brackets, Hardness, Shear strength,
Objective: The aim of this study was to evaluate the Knoop hardness of enamel, shear bond strength and failure pattern (adhesive, bracket/resin interface and mixed) after bonding and debonding brackets, using resin composite with fluoride (Ortho Lite Cure, Ortho Source®) and without fluoride (Orthobond, Morelli®). Methods: Fragments (6 mm x 6 mm) of 40 bovine incisor crowns were embedded in acrylic self-polymerizing resin. The Knoop hardness measurements were performed before and after bonding metal brackets. The specimens were divided into 2 groups, according to composite resin: with fluoride (Ortho Lite Cure, Ortho Source®) and without fluoride (Orthobond, Morelli®). After bonding, the specimens were submitted to demineralization and remineralization cycling for 14 days. Shear bond strength testing was performed in a universal test machine (EMIC), at 5 mm/min crosshead speed. Results: There was no significant difference in shear bond strength between groups 1 and 2. After demineralization and remineralization procedures, the specimens bonded with Ortho Lite Cure showed higher Knoop hardness than Orthobond. For both groups there was predominance of failure at bracket/resin interface. Conclusion: specimens bonded with fluoride resin composite showed higher microhardness after de-re cycling than those bonded with resin composite without fluoride, although no difference in shear bond strength was found.