Int Orthod. 2013 Sep;11(3):290-302. doi: 10.1016/j.ortho.2013.05.004. Epub 2013 Jul 15.
OBJECTIVES: The aim of this study was to determine what effect various combinations of particular bracket bases and composites of different viscosity have on adhesion force.
MATERIALS AND METHODS: Eighty extracted premolars, upper and lower, were randomly assigned to four groups of 20 teeth and the combinations of either flowable or paste composite and brackets with either 80-gauge or 100-gauge foil mesh were applied to their labial surfaces accordingly: group A: flowable composite+80-mesh base; group B: flowable composite+100-mesh base; group C: paste composite+80-gauge base; group D: paste composite+100-gauge base. Each sample was subjected to shear bond stress to failure using a Zwick Roell Z050 testing machine at 50N/min load. The load required to detach each bracket was recorded in N and subsequently converted to MPa. After debonding, each tooth was analysed under optical microscope at 12× magnification and photographed prior to calculation of the Adhesive Remnant Index (ARI).
RESULTS: The paste composite showed greater adhesion strength than the flowable in all cases, but this was further increased when the 80-gauge, rather than the 100-gauge, mesh was used. No statistically significant difference in ARI values was found between the flowable groups (groups A and B), on the other hand, in the paste composite groups, a statistically significant difference was highlighted between the 80-gauge (group D) and 100-gauge (group C) mesh bracket bases.
CONCLUSIONS: Both the density of the composite and the gauge of a mesh bracket base are able to influence bond strength and the bond failure interface.