Iranian Dental Association Journal of Iranian Dental Association 3060-8201 21 4 2010 03 01 Effect of fluoride therapy before or after bleaching on enamel micro-hardness 307 313 EN Parvin Mirzakoucheki-Boroujeni Mohammad reza Malekipoor Solmaz Homayouni Journal Article 2010 03 30 2013 02 25  Effect of fluoride therapy before or after bleaching on enamel micro-hardness    <u> Dr. Mirzakoucheki-Boroujeni P </u><u>.,</u> 1 Dr. M alekipoor M ., 1 Dr. H omayouni S . 2  1 Assistant Professor, Department of Operative Dentistry, School of Dentistry, Islamic Azad University, Khorasgan, Isfahan, Iran. 2 Dentist.   <i> (Received 21 Feb, 2009 Accepted 6 Feb, 2010) </i>   <i> Abstract </i>   <i> Background and Aim </i>: Bleaching teeth can lead to decreased calcium, phosphate and fluoride content of enamel which may cause decreased enamel micro-hardness. Reportedly, the topical use of fluoride can help regaining those minerals. The aim of this study was to evaluate the effect of fluoride therapy on enamel micro-hardness when used before or after bleaching.  <i> Materials </i><i>and </i><i>Methods </i>: Total of 60 premolar teeth were divided into 5 groups. The occlusal surface in all teeth were flattened and covered with nail varnish. Initially, all specimens were inserted in artificial saliva for 7 days. Group 1 used as negative control. Samples in group 2 were bleached 2 times with 30 minutes interval for 5 days, using %45 carbamid peroxide. Group 3 samples were exposed to fluoride varnish for 5 minutes. Group 4 exposed to fluoride varnish for 5 minutes, bleached 2 times for 30 minutes in 5 day intervals. Group 5 samples were treated same as group 4, however, followed by fluoride varnish for 5 minutes. Micro hardness for each group measured in 3 points after cleaning the occlusal section. The LSD and ANOVA tests were used for data analysis.  <i> Results </i>: This study showed, reduction in enamel surface hardness can be compensated by fluoride application. Group 2 (bleached only) showed the minimum micro hardness (294.38), and group 3 (exposed to fluoride only) showed the maximum micro hardness (455.36).  <i> Conclusion </i>: <i>Fluoride therapy can affect enamel micro-hardness before and after bleaching. The application of fluoride varnish is recommended after exposing teeth to bleaching agents. </i> <i> Key words </i>: Tooth Bleaching – Fluorides - Dental Enamel.  <i> </i> <i> Corresponding Author </i>: <i><i>Dr. </i><i><i>Mirzakoucheki-Boroujeni P </i><i>., <i>Assistant Professor, Department of Operative Dentistry, School of Dentistry, Islamic Azad University, Khorasgan, Isfahan, Iran. </i><i /></i></i></i> <i> </i> <i> e.mail: </i><i><i>cosmeticmir@yahoo. com </i><i /></i> <i> </i>Â