Nasrin Farhadian - Associated Professor, Hamadan Dental Faculty, Department of Orthodontics Hamadan Dental Faculty, Department of Orthodontics
Amirfarhang Miresmaeili - Associated Professor, Hamadan Dental Faculty, Department of Orthodontics Hamadan Dental Faculty, Department of Orthodontics
Loghman Rezaei Soufi - Assistant Professor, Hamadan Dental Faculty, Department of Restorative Dentistry
Fahimeh Baghaei - Assistant Professor, Hamadan Dental Faculty, Department of Restorative Dentistry
Ehsan Shahvali - Postgraduate Student, Hamadan Dental Faculty, Department of Orthodontic

Aim: of this in vitro study was to evaluate the effects of Co۲ laser irradiation on demineralization adjacent to orthodontic brackets and their shear bond strength in human premolar teeth. Enamel demineralization adjacent to orthodontic brackets is a major problem that requires new professional method independent to patient cooperation. Materials and methods: Sixty human premolars were randomly divided to two groups (n=۳۰). Group۱, enamel surface irradiated with Co۲ laser. Group۲ without any enamel surface treatment. In both groups, a bracket at buccal surface was bonded with Transbond XT and cured with conventional light cure. Demineralization in all sample induced with artificial caries solutions. A universal testing machine was used to determine shear bond strengths. The teeth were sectioned bucco-lingually and were evaluated under polarized light microscope. Average lesion depths were calculated from three depth measurements. The Two independent sample T- tests were used to compare the study type group in detail. Results: The mean of shear bond strengths in the group۱ and ۲ were ۱۳.۹۰±۵.۰۱and ۱۵.۸۴ ±۳.۶۸ Mpa respectively, but not statistically significant (P=۰.۱۰۲).The mean lesion depth in group۱and ۲ was ۷۲.۲۹±۵۸.۰۹ µm ۱۲۰.۰۱±۷۶.۴۹µm respectively, which was significant (P=۰.۰۱۸). Conclusion: Co۲ laser irradiation can reduce enamel demineralization while not affecting the shear bond strengths significantly.

Co۲ Laser, Shear Bond Strength, Enamel Demineralization