Indirect bonding--a new transfer method

The aim of this in vitro study was to investigate both shear bond strength (SBS) by shear testing of indirectly bonded brackets, and the accuracy of a new transfer method, the Aptus bonding device (ABD). For comparison, the SBS of directly bonded brackets in two experimental arrangements was also measured. The precision of the positioning of the indirect bracket transfer was assessed by photographic superimposition and three-dimensional (3D) measurement of the bracket positions on the working and plaster models using a 3D laser scan. Statistical analysis was carried out by means of descriptive and explorative data using the SPSS program. To compare groups, a one-factor analysis of variance and post hoc tests (Tukey-HSD) were used. The level of significance was set at P < 0.05. SBS using indirect and direct bonding, with the same experimental arrangement and the same adhesives (Concise and Transbond), showed no significant differences. For direct bonding, using only one adhesive (Transbond), lower values were observed, but they were only statistically significant for the premolar teeth. The clinically required minimum bond strength of 6 MPa was achieved in all groups. Superimposition of the photographs of the indirectly bonded upper labial segment brackets showed no deviations. The results of the 3D measurement of the positions of the brackets on the working and plaster models only yielded small deviations (0.15 mm along the X-axis in the centre, 0.17 mm along the Y-axis, and 0.19 mm along the Z-axis). The ABD is a useful adjunct to bond placement and does not compromise bond strength.