Correlation between shear bond strength and degree of conversion of four orthodontic adhesives.

Abstract

Background and objective: The study aims to assess the correlation between degree of monomer conversion (DC) and shear bond strength (SBS) of the different adhesives. The objective of the present study was to determine the efficiency of four orthodontic adhesives regarding shear bond strength (SBS), debonding characters and degree of conversion (DC) and to correlate SBS to the DC. Methods: Forty human upper first premolars, divided into four Groups (n = 10) were bonded with metal brackets using four different adhesives. Brackets were debonded in shear on an Instron universal testing machine with a crosshead speed of 1 mm per minute. The mode of bond failure was determined by the adhesive remnant index (ARI) index and the DC was determined by Fourier transform infrared spectroscopy (FTIR) analysis. Result: There was a statistically significant difference between the SBS of only Transbond XT and Orthobond plus color change adhesive while the two remaining adhesives showed no significant difference. All groups of adhesives showed a cohesive type of bond failure according to the ARI results. A statistically significant lower percentage of DC was noted for Orthobond plus (63 %) than Transbond XT (70.2 %) but it was within the accepted range reported in the literature (55-75%). Pearson’s correlation was significantly positive between SBS and DC for Smart Ortho, Heliosit Orthodontic and Orthobond Plus adhesives and insignificantly positive for Transbond XT. Conclusion: Within the limitations of this in vitro study it can be concluded that the Transbond plus color change has significantly higher fluoride release as well as recharge properties when compared to other ortho-adhesive materials. Keywords: Orthodontic Adhesive, Shear Bond Strength, Degree of conversion