Chemical composition of enamel surface as a predictor of in-vitro shear bond strength

Introduction Orthodontic bond failure varies between patients. It has been speculated that the chemical composition of the enamel surface might play a role in the variations in bond failure. Methods X-ray photoelectron spectroscopy was used in analyzing the surface chemical composition of 49 pairs of maxillary right and left first premolars from patients requiring extractions as part of the orthodontic treatment. After x-ray photoelectron spectroscopy analysis, 49 enamel samples were randomly selected for an in-vitro shear bonding study with a materials testing system, Synergie 400 machine (MTS Systems, Eden Prairie, Minn). Results The in-vitro shear bond strength was found to have a mean of 6.93 ± 2.71 MPa. Twelve elements were detected; the major ones were calcium, phosphorus, oxygen, nitrogen, and carbon. Regression analysis with the 12 elements explained 33.3% of the variations in bond strength. However, the contribution was not significant ( P = 0.170). Conclusions The chemical composition of the buccal surface of maxillary first premolars was not significant in predicting in-vitro mean shear bond strength. Other factors are likely to be important contributors to the large variations frequently seen in bond strength studies.