Effects of argon laser on bond strength of orthodontic brackets

Objectives: Argon lasers, because of their significant time savings over conventional curing lights, have been investigated for use in bonding orthodontic brackets. They are also being investigated for their ability to confer demineralization resistance on enamel which is of great interest in orthodontics. The purpose of this study was to assess the effects of argon laser irradiation on shear bond strength at three time points i.e. before, during and after bracket placement.

Methods:Fifty intact human premolars were randomly divided in to 5groups. In group1 (control) and 2, the brackets were bonded with conventional light (600mW) and argon laser (200mW), respectively. In group 3 and 4, the enamel was prelased, and then brackets were bonded similar to group 1 and 2, respectively. Brackets in group 5 were bonded conventionally, after 2 days immersing in artificial caries solution, laser was applied. Then all of the samples immersed in Ten Cate solution for 10 days. Then shear bond strength was measured automatically using an Instron machine (0.5 mm/min). One-way ANOVA, Dunnett's t test and Tukey test were used for data analysis . Adhesive remnant index was evaluated for each tooth .

Results: The mean shear bond strength of group 2 and 5 were significantly lower than control group (P=0.02, P=0.01 respectively). There were no statistically significant differences between all laser treated groups (P > 0.05). The adhesive remnant index analysis revealed no statistically significant difference between all 5 groups (P > 0.05).

Conclusions: Lasing the enamel before bracket bonding, using either conventional light or argon laser curing, had no effect on bond strength. Laser application, during or after bracket bonding may lead to lower bond strength, comparing with control group.