Shear bond strength of orthodontic brackets using different static loading application

Carla GIANINI, Paulo Afonso Silveira FRANCISCONI

Aim: The purpose of this study was to test differences on bond strength between auto-cured (Concise) and lightcured (Transbond XT) cements after static loading and shear test. Methods: Eighty bovine teeth and metallic orthodontic brackets (Morelli Ortodontia Braquete Edgewise/Rickets) were tested after static loads of 30, 70 and 120grs. Bovine enamel was conditioned with 37% phosphoric acid gel for one minute, rinsed and dried. Adhesives were applied and brackets were bonded according to manufacturer’s instructions. Cement thickness was standardized with the use of a heavier Gilmore needle. After 24 hours, half of the specimens were submitted to the static loads of 30, 70 and 120grs. Control group remained unloaded. Then, specimens were immersed in distilled water for 28 days at 37ºC. Afterwards, orthodontic brackets were attached to a loop wire and submitted to a shear force (Máquina de Ensaios Kratos Universal Kratos) under a crosshead speed of 0.5mm/min and load cell of 500Kgf. A two-way ANOVA test (α฀= 0.05) was used to detect significant interactions between cements and static loads. Conclusions: (1) The Concise cement showed more statistically significant bond strength values than the Transbond XT cement for all static loads; (2) No statistically significant differences were observed regarding static loads for all cements tested and (3) Higher static loads provided less enamel fracture in the Concise group after shear test, whereas in the Transbond XT the rate of enamel fracture remained unchanged regardless of previous load applied.

Keywords: Shear bond strength. Orthodontic bracket. Bonding. Load.

Saturday, November 23, 2024 09:55