In vivo and in vitro study, with or without thermocycling, of shear bond strength of brackets bonded with halogen light

Sérgio Milton Martins de Oliveira PENIDO, Cláudia Valéria de Sousa Resende PENIDO, Ary dos SANTOS-PINTO, Tatsuko SAKIMA, Carla Raquel FONTANA

Objective: The purpose of this research was to assess the strength of metallic brackets bonded to human teeth, with lightcuring resin with halogen light, by means of mechanical tests of shear bond strength. Methods: In vivo tests with a portable digital dynamometer and in vitro tests with Universal testing machine were performed, with and without thermocycling, complemented by Adhesive Remaining Index (ARI). Edgewise standard brackets (Abzil) were bonded using Transbond Plus Self Etching Primer (SEP) and Transbond XT resin. Three groups of ten teeth each have been formed. In GI the brackets were bonded to second premolars in the patients’ mouths. In GII and GIII the brackets were bonded to first premolars extracted for orthodontic reasons. The mechanical tests of GI were performed 24 hours after the polymerization, directly in the patients’ mouths with a portable digital dynamometer. In GII the specimens were stored in distilled water and taken to sterilizer at 37ºC for 24 hours and afterwards, submitted to thermocycling with 1000 cycles at 5 and 55º C. In GIII the specimens were stored in distilled water at room temperature for 24 hours, and then submitted to mechanical tests. Results: The average values of the shear strength in Megapascal were: GI=4.39; GII=7.11 and GIII=7.35. Pictures of the bonding areas in both in vivo and in vitro samples were taken after the tests and they were amplified 5 times to be better visualized. The images obtained were analyzed, classified according to IAR and it was verified, by means of dispersion graphs, the relation between the shear bond strength and this index. Conclusion: The average of the in vivo mechanical tests was statistically lower than the in vitro tests. There were no differences in the in vitro shear bond strength between the thermocycled and non-thermocycled groups. There was no relation between shearing stress and kind of failure.

Keywords: Shear bond strength. Light. Universal testing machine. Thermocycling. Portable digital debonding device.

Thursday, May 02, 2024 23:57