en orthodontic orthodontic Original article Original article <div style="text-align: justify;"><span style="font-size:13pt"><span style="line-height:105%"><span new="" roman="" style="font-family:" times=""><b><span style="font-size:9.0pt"><span style="line-height:105%"><span style="font-family:" verdana=""><span style="color:#2e74b5">Background and Aim</span></span></span></span></b><b><span style="font-size:9.0pt"><span style="line-height:105%"><span style="font-family:" verdana=""><span style="color:#2e74b5">:</span></span></span></span></b> <span style="font-size:9.0pt"><span style="line-height:105%"><span style="font-family:" verdana="">No consensus has been reached on a safe method for disinfection of orthodontic retainers without altering their physical properties. This study investigated the effects of 5.25% sodium hypochlorite (NaOCl) and 10% hydrochloric acid on hardness and surface roughness of thermoplastic orthodontic retainers.</span></span></span></span></span></span><br> <span style="font-size:13pt"><span style="line-height:105%"><span new="" roman="" style="font-family:" times=""><b><span style="font-size:9.0pt"><span style="line-height:105%"><span style="font-family:" verdana=""><span style="color:#2e74b5">Materials and Methods: </span></span></span></span></b><span style="font-size:9.0pt"><span style="line-height:105%"><span style="font-family:" verdana="">In this in vitro study, 40 samples measuring 10 x 8 x 2 mm were prepared using 1-mm-thick polyethylene terephthalate glycol (PETG) Essix sheets, and randomly divided into 4 groups (n=10). In group A, the samples were immersed in 5.25% NaOCl for 15 minutes followed by immersion in 10% hydrochloric acid for 15 minutes. This process was repeated twice in group B and thrice in group C. Group D served as the control group. Surface roughness was measured by a profilometer, and hardness was measured by a Vickers hardness tester. Data were analyzed by the Kruskal-Wallis, Mann-Whitney, and Bonferroni tests (alpha=0.05).</span></span></span>&nbsp;</span></span></span><br> <span style="font-size:13pt"><span style="line-height:105%"><span new="" roman="" style="font-family:" times=""><b><span style="font-size:9.0pt"><span style="line-height:105%"><span style="font-family:" verdana=""><span style="color:#2e74b5">Results: </span></span></span></span></b><span style="font-size:9.0pt"><span style="line-height:105%"><span style="font-family:" verdana=""><span style="color:#0e101a">Immersion frequency had no significant effect on surface roughness (P=0.096). A significant difference was found in hardness among the groups (P=0.008). The mean hardness of group B was significantly lower than that of group C (P=0.004). The three test groups had no significant difference with the control group in this regard (P>0.05).</span></span></span></span><span style="font-size:9.0pt"><span style="line-height:105%"><span style="font-family:"Verdana",sans-serif"></span></span></span></span></span></span><br> <span style="font-size:13pt"><span style="line-height:105%"><span new="" roman="" style="font-family:" times=""><b><span style="font-size:9.0pt"><span style="line-height:105%"><span style="font-family:" verdana=""><span style="color:#2e74b5">Conclusion:</span></span></span></span></b> <span style="font-size:9.0pt"><span style="line-height:105%"><span style="font-family:" verdana=""><span style="color:#0e101a">According to the results, 15 minutes of immersion in 5.25% NaOCl followed by 15 minutes of immersion in hydrochloric acid for 3 times had no significant clinical effect on the hardness and surface roughness of PETG sheets used for the fabrication of thermoplastic orthodontic retainers.</span></span></span></span></span></span></span><br> &nbsp;</div> Hydrochloric Acid, Sodium Hypochlorite, Orthodontic Retainers, Polyethylene Terephthalates 51 58 http://jrdms.dentaliau.ac.ir/browse.php?a_code=A-10-1774-1&slc_lang=en&sid=1 Ailin Ehteshami ailin.ehteshami2008@gmail.com 100319475328460013977 100319475328460013977 Yes Dental Research Center, Department of Orthodontics, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran Mohammad Rashno rashnomohamad76@gmail.com 100319475328460013978 100319475328460013978 No Graduate Student, Dental Students’ Research Committee, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran