Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 14 5 2017 12 02 259 266 EN Hassanali Ghaffari Assistant Professor, Department of Orthodontics, School of Dentistry, Shahed University of Medical Sciences, Tehran, Iran Amir hossein Mirhashemi Associate Professor, Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran; Department of Orthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran Tahereh Baherimoghadam Assistant Professor, Department of Orthodontics, School of Dentistry, Yasuj University of Medical Sciences, Yasuj, Iran Amir Azmi Dentist, Private Practice, Shiraz, Iran Reza Rasooli Assistant Professor, Department of Orthodontics, School of Dentistry, Shahed University of Medical Sciences, Tehran, Iran 2017 01 16 2017 08 22 Objectives: This study sought to compare enamel cracks after orthodontic bracket debonding in the surfaces prepared with erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser and the conventional acid-etching technique. Materials and Methods: This in-vitro experimental study was conducted on 60 sound human premolars extracted for orthodontic purposes. The teeth were randomly divided into two groups (n=30). The teeth in group A were etched with 37% phosphoric acid gel, while the teeth in group B were subjected to Er,Cr:YSGG laser irradiation (gold handpiece, MZ8 tip, 50Hz, 4.5W, 60µs, 80% water and 60% air). Orthodontic brackets were bonded to the enamel surfaces and were then debonded in both groups. The samples were inspected under a stereomicroscope at ×38 magnification to assess the number and length of enamel cracks before bonding and after debonding. Independent-samples t-test was used to compare the frequency of enamel cracks in the two groups. Levene’s test was applied to assess the equality of variances. Results: No significant difference was noted in the frequency or length of enamel cracks between the two groups after debonding (P>0.05). Conclusions: Despite the same results of the frequency and length of enamel cracks in the two groups and by considering the side effects of acid-etching (demineralization and formation of white spot lesions), Er,Cr:YSGG laser may be used as an alternative to acid-etching for enamel surface preparation prior to bracket bonding.   https://fid.tums.ac.ir/index.php/fid/article/view/1699 https://fid.tums.ac.ir/index.php/fid/article/download/1699/970