en orthodontic orthodontic Original article Original article <div style="text-align: justify;"><span style="font-size:13pt"><span style="line-height:110%"><span new="" roman="" style="font-family:" times=""><b><span style="font-size:9.0pt"><span style="line-height:110%"><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:110%"><span style="font-family:" verdana=""><span style="color:#2e74b5">:</span></span></span></span></b> <span style="font-size:9.0pt"><span style="line-height:110%"><span style="font-family:" verdana="">This study compared the efficacy of an experimental resin containing polyhedral oligomeric silsesquioxane (POSS) nanoparticles with methacrylate groups (MA-POSS) versus the Icon resin regarding the masking, color stability, and microhardness of artificially induced white spot lesions (WSLs). </span></span></span>&nbsp;</span></span></span><br> <span style="font-size:13pt"><span style="line-height:110%"><span new="" roman="" style="font-family:" times=""><b><span style="font-size:9.0pt"><span style="line-height:110%"><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:110%"><span style="font-family:" verdana="">In this in vitro study, 60 bovine enamel specimens were assigned to two groups for assessment of color (group C) and surface microhardness (group H). white spot lesions were induced on the specimens using demineralizing and remineralizing solutions. Each group was divided into two subgroups for the application of experimental resin and Icon. the color and surface microhardness of specimens were measured, after the induction of WSLs, and after infiltration. Group C samples were immersed in coffee (1 hour/day for one week) and their color was measured again. ANCOVA was used to compare microhardness between the two resin groups. To compare the masking and staining of infiltrated lesions, &Delta;E, &Delta;L and L* values after infiltration and staining were compared with the values after the induction of WSLs using independent t-test and repeated measures ANCOVA (&alpha;=0.05).</span></span></span>&nbsp;</span></span></span><br> <span style="font-size:13pt"><span style="line-height:110%"><span new="" roman="" style="font-family:" times=""><b><span style="font-size:9.0pt"><span style="line-height:110%"><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:110%"><span style="font-family:" verdana=""><span style="color:#0e101a">Microhardness analysis by ANCOVA revealed no significant difference between the groups following resin infiltration (P=0.144). The performance of the two resins after infiltration (P=0.75 for &Delta;E, P=0.20 for &Delta;L, P=0.57 for L*) and after staining (P=0.31 for &Delta;E, P=0.07 for &Delta;L, P=0.32 for L*) was not significantly different.</span></span></span></span><span style="font-size:9.0pt"><span style="line-height:110%"><span style="font-family:"Verdana",sans-serif"></span></span></span></span></span></span><br> <span style="font-size:13pt"><span style="line-height:110%"><span new="" roman="" style="font-family:" times=""><b><span style="font-size:9.0pt"><span style="line-height:110%"><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:110%"><span style="font-family:" verdana=""><span style="color:#0e101a">The experimental resin was comparable to Icon with the main advantage of easier availability in Iran.</span></span></span></span></span></span></span></div> Resins, Synthetic, Dental Caries, Polyhedral Oligomeric Silsesquioxane Methacrylate, Tooth Discoloration 297 304 http://jrdms.dentaliau.ac.ir/browse.php?a_code=A-10-1393-1&slc_lang=en&sid=1 Soodeh Tahmasbi tahmasbisoodeh@gmail.com 100319475328460013407 100319475328460013407 No Department of Orthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Shiva Tavakol Davani sh.tavakoldavani@gmail.com 100319475328460013408 100319475328460013408 Yes Department of Orthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Mahshid Namdari mah.namdari@gmail.com 100319475328460013409 100319475328460013409 No Department of Community Oral Health, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Mohammad Atai m.atai@ippi.ac.ir 100319475328460013410 100319475328460013410 No DDepartment of Polymer Science, Iran Polymer and Petrochemical Institute (IPPI), Tehran, Iran