Rebonding of a dislodge bracket is considered as an economic saving option which can be done with use of in-office methods or by commercial recycling. The aim of this study was to compare the shear rebond strength (SRS) of brackets recycled with different resin removal methods. Eighty premolars were divided into four experimental groups. The teeth were bonded with metal brackets. The brackets were debonded and adhesive remnants were removed from bracket bases by means of Er:YAG laser, sandblasting, direct flame, and CO2 laser, respectively. Following adhesive removal from enamel surfaces with carbide bur, recycled brackets were rebonded. Finally, all brackets were debonded with a Dartec testing machine and the SRS values were determined. The SRS values of groups 3 and 4 were significantly lower compare to other groups (P value < 0.001). SEM examination showed complete adhesive removal from bracket base cleaned with Er:YAG laser irradiation. Microroughening of the base of sandblasted bracket was observed in the SEM image. Resin removal with direct flame and CO2 laser irradiation was incomplete. Er:YAG laser recycling of brackets is an efficient in-office method of reconditioning which caused minimum damage to the bracket base.

Introduction: Plaque accumulation can cause white spot lesions. Adding nanoparticles to composites can be effective in reducing the number and function of microorganisms. Objective: The aim of this study was to evaluate the antibacterial effects of orthodontic composites containing different nanoparticles on Streptococcus mutans at different times. Methods: Hydroxyapatite, titanium oxides, zinc oxide, copper oxide and silver oxide nanoparticles were prepared at 0.5% and 1% weight concentrations. Accordingly, ten study groups and one control group were obtained. Then, 26 composite discs were prepared from each group. Strain of Streptococcus mutans was cultured, and colonies of Streptococcus mutans were counted. Further bacterial culture was swapped onto enriched Mueller-Hinton agar. The composites were placed on the culture medium, and after incubation the diameter of growth inhibition was measured. To investigate the long-term effect of nanoparticles, the colonies were counted at days 3, 15 and 30. Results: The results showed that 1% copper oxide and 1% silver oxide significantly reduced the number of bacteria (p< 0.05), but there was no significant difference between the other groups and control group (p> 0.05). At day three, there was a significant difference between control group and 0.5% silver oxide, 1% silver oxide and 1% copper oxide groups (p< 0.05). However, colonies had grown in all groups at day 30 but showed no significant difference with control group (p> 0.05). Conclusion: Addition of 1% copper oxide and 1% silver oxide has short-term antibacterial effects, so the clinical use of these nanoparticles cannot be justified.

Er:YAG laser can be a suitable method for bonding of orthodontic brackets to porcelain surfaces.

The aim of this study was to determine changes of tongue position and oropharyngeal space following treatment with functional appliance in patients with class II div I malocclusion. In this before-after clinical trial, 28 patients with class II div 1 malocclusion were investigated. The range of age of females was 10 -13 years and males 11 -14 years. These samples were treated for 11 months. McNamara analysis and some linear variables were used to determine positional changes of tongue and oropharyngeal space. In this study, tongue moved significantly (P.value &lt; 0.05) forwards in the horizontal dimension and non – significantly downwards in the vertical dimension. Treatment with functional appliance leads to significant alterations in tongue position and significantly increases the extent of oropharyngeal space.

Laser-assisted debonding of ceramic brackets could reduce the risk of enamel damage, without causing thermal damage to the pulp. However, some increases in the length and frequency of enamel cracks should be expected with all debonding methods.