fa Effect of bracket bonding with Er: YAG laser on nanomechanical properties of enamel ارتودنسی Orthodontics پژوهشي Research <b> Background</b>: The aim of this study was to compare the effects of conventional acid etching and laser etching on the nano-mechanical properties of the dental enamel using nano-indentation test. <div>  <b>Materials and Methods:</b> In this experimental in vitro study, buccal surfaces of 10 premolars were divided into three regions. One of the regions was etched with 37% phosphoric acid and another etched with Er:YAG laser, the third region was not etched. The brackets were bonded to both of etched regions. After thermocycling for 500 cycles, the brackets were removed and the teeth were decoronated from the bracket bonding area. Seven nano-indentations were applied at 1-31 μm depth from the enamel surface in each region. Mean values of the hardness and elastic modulus were analyzed with repeated measures analysis of variance and Tukey HSD tests, using the SPSS software (SPSS Inc., version16.0, Chicago, Il, USA). P < 0.05 was considered as signifi cant.</div><div><b> Results:</b> The hardness up to 21 μm in depth and elastic modulus up to 6 μm in depth from the enamel surface for laser-etched enamel had signifi cantly higher values than control enamel and the hardness up to 11 μm in depth and elastic modulus up to 6 μm in depth for acid-etched enamel had signifi cantly lower values than the control enamel. </div><div>  <b>Conclusion: </b>The mechanical properties of the enamel were decreased after bracket bonding with conventional acid etching and increased after bonding with Er:YAG laser.</div><hr><p class="MsoNormal" style="text-align: left direction: ltr unicode-bidi: embed"><b>Source: </b>Dental Research Journal </p> <p class="MsoNormal" style="text-align: left direction: ltr unicode-bidi: embed"><a href="http://drj.mui.ac.ir/index.php/drj/article/view/1541" target="_blank"><font color="#0000ff">Full Text</font></a></p> Elastic modulus, enamel, Er:YAG laser, hardness, nano-indentation test,orthodontic bracket 0 0 http://idai.ir/browse.php?a_code=A-10-32-3425&slc_lang=fa&sid=1 Shiva Alavi 100319475328460015706 100319475328460015706 No Dental Materials Research Center and Department of Orthodontics Reza Birang 100319475328460015707 100319475328460015707 No Torabinejad Dental Research Center and Department of Periodontics, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Fatemeh Hajizadeh hajizadeh_fatemeh @yahoo.com 100319475328460015708 100319475328460015708 Yes Department of Orthodontics, School of Dentistry, Ahvaz Jundishapur University of Medical Sciences, Ahvaz Hamed Banimostafaee 100319475328460015709 100319475328460015709 No Department of Orthodontics, School of Dentistry, Arak University of Medical Sciences, Arak, Iran