Diode-pumped solid-state laser for bonding orthodontic brackets: effect of light intensity and light-curing time

This study evaluated the shear bond strength (SBS) of orthodontic brackets bonded to teeth using a diode-pumped solid state (DPSS) laser of 473 nm with various light intensity and light-curing settings. For the study, a total of 150 extracted human teeth were divided into ten groups. In the control group, the brackets were bonded to the teeth using a quartz-tungsten-halogen (QTH) light with an intensity of 900 mW/cm2. In the experimental groups, the brackets were bonded using a DPSS laser with three different light intensities and light-curing times. The same bracket type and adhesive were used in all groups throughout the study. Statistical analysis was performed to compare the SBS, and adhesive remnant index (ARI) among the groups. As results, brackets bonded using the DPSS laser with an intensity of 700 mW/cm2 for 40 s (totally) showed a slightly higher SBS (12.2 ± 1.8 MPa) than that of those bonded using a QTH light (control; 11.6 ± 1.6 MPa). The SBS values linearly increased with increasing energy density (light intensity × light-curing time) of the DPSS laser (R = 0.95, p < 0.001). However, the SBS values among the test groups were similar regardless of the difference in light-curing conditions. A comparison of the ARI scores among the groups suggested a similar bracket failure mode.