Shear bond strengths of a glass ionomer for direct bonding in orthodontics.

This study was undertaken to compare the shear bond strengths of mesh-backed orthodontic buttons bonded to human enamel using a glass ionomer marketed for direct bonding in orthodontics, both in conjunction with, as well as without, enamel etching and to compare the results with a no-mix composite bonding resin. Freshly extracted noncarious human premolar crowns were used, to which mesh-backed metal orthodontic buttons were bonded to the lingual surfaces with one of three methods: group 1, glass ionomer without enamel etching; group 2, glass ionomer with enamel etching; and group 3, with a no-mix orthodontic bonding resin with enamel etching. After being stored in water for 48 hours at 37 degrees C, the samples were tested to failure in an Instron with the Bencor testing system. The data were statistically analyzed with the Mann-Whitney U test. The debonded specimens were visually inspected in respect of failure mode. The no-mix bonding resin had a significantly higher shear bond strength than the glass ionomer cement. Enamel etching with 37% orthophosphoric acid increased the mean shear bond strength of the glass ionomer, however, not significantly. Less cement remained on enamel after debonding when the glass ionomer was used when compared with residual resin when the no-mix bonding resin was used. Clinical research by several investigators is advised to determine the bond failure rate of glass ionomers when used in conjunction with orthodontic bracket bonding.