en عمومى General پژوهشي Research <span style="font-size:12pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""><b>Background: </b>Although the prevalence of dental caries has decreased in recent decades, caries is still a major problem. The idea of preventing caries on masticatory surface of teeth has led scientists to use substances as fissure sealants to prevent pit caries and dental fissures. No study has been performed on potential changes in properties of expired fissure sealants. Therefore, considering the current conditions of society and potential coercion to use some expired substances, particularly in some deprived areas, we decided to evaluate the microleakage of these substances.</span></span></span><br> <span style="font-size:12pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""><b>Method:</b> In the present study, healthy human premolars extracted for orthodontics were used. First, enameloplasty was performed for premolar fissures by round bur; acid etching and fissure sealant were used to provide similar conditions in different groups and to remove the bonding effect. Then the samples were subjected to thermocycles; dye penetration was used to check the amount of microleakage.</span></span></span><br> <span style="font-size:12pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""><b>Results:</b> The results showed that, on average, the amount of microleakage increases after expiration date; in this way, the amount of microleakage 1 year after expiration date is about 13% higher than the non-expired group and the amount of microleakage 6 months after expiration date is about 7% higher than the non-expired group; however, this difference is not statistically significant.</span></span></span><br> <span style="font-size:12pt"><span style="line-height:115%"><span new="" roman="" style="font-family:" times=""><b>Conclusion:</b> Based on this study and previous studies, it seems that properties of dental substances will be less affected after about 1 year from the expiration date if they are stored properly and there is no prohibition to use them.</span></span></span><br> &nbsp; Dental caries, Fissure sealant, Microleakage, Dye penetration. 46 55 http://intjmi.com/browse.php?a_code=A-10-1-543&slc_lang=en&sid=1 Razieh Meshki 10031947532846006214 10031947532846006214 No Assistant Professor, Department of Pediatric Dentistry, School of Dentistry, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran Maryam Roayaei Ardekani 10031947532846006215 10031947532846006215 No Assistant professor of Pedodontics department, School of Dentistry, Jundishapur University of Medical Sciences, Ahvaz, Iran Negar Meshki 10031947532846006216 10031947532846006216 No Undergraduate student of dentistry, school of Dentistry, Ahvaz Jundishapur University of medical sciences, Ahvaz, Iran. Nazgol Ghahramani 10031947532846006217 10031947532846006217 Yes Pediatric Dental Resident, Department of Pediatric Dentistry, School of Dentistry, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran