Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 13 6 2017 01 11 423 430 EN Javad Chalipa Assistant 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 Yasamin Farajzadeh Jalali Assistant Professor, Department of Orthodontics, School of Dentistry, Ilam University of Medical Science, Ilam, Iran Fatemeh Gorjizadeh Assistant Professor, Department of Orthodontics, School of Dentistry, Yasuj University of Medical Science, Yasuj, Iran Pedram Baghaeian Private Practice Tehran University of Medical Sciences, Tehran, Iran Mohammad Hashem Hoseini Assistant 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 Omid Mortezai Assistant Professor, Department of Orthodontics, Qazvin University of Medical Sciences, Qazvin, Iran 2015 12 27 2016 06 19 Objectives: The aim of this study was to evaluate the effect of conventional and high-power light emitting diode (LED) light curing units on shear bond strength (SBS) of metal and ceramic brackets to tooth surface. Materials and Methods: Forty sound bovine maxillary central incisors were used for the study. The teeth were divided into four groups (n=10). Teeth surfaces were etched with 37% phosphoric acid for 20 seconds. After applying a uniform layer of adhesive primer on the etched enamel, composite was placed on the base of brackets. The samples were light cured according to the manufacturer’s instructions and thermocycled. The SBS was measured. The failure mode was scored using the adhesive remnant index (ARI). Results: The mean SBS of samples in groups A (high-power LED, metal bracket), B (high-power LED, ceramic bracket), C (conventional LED, metal bracket) and D (conventional LED, ceramic bracket) was 23.1±3.69, 10.7±2.06, 24.92±6.37 and 10.74±3.18MPa, respectively. The interaction effect of type of LED unit (high-power/conventional) and bracket type on SBS was not statistically significant (P=0.483). In general, type of LED unit did not affect SBS. Type of bracket significantly affected SBS (P<0.001). The ARI score was not significantly influenced by the interaction between the type of LED unit and bracket. Conclusions: The obtained SBS is the same for both bracket types by use of high-power and conventional LED light curing units. Regardless of the type of LED unit, SBS of ceramic brackets was significantly lower than that of metal brackets.   https://fid.tums.ac.ir/index.php/fid/article/view/973 https://fid.tums.ac.ir/index.php/fid/article/download/973/920