Assessment of Enamel Surface Microhardness with Different Fluorinated Compounds under pH Cycling Conditions: An In-Vitro Study

Abstract

Introduction: Various studies have reported the effect of fluoride on the surface of dental enamel in preventing the development of carious lesions. Research conducted on the effect of fluoride on demineralization and remineralization has reported on the in vitro pH cycling model, in which samples of enamel or dentin were subjected to pH changes, such as those occurring in the oral cavity, to reduce the advancement of the cavitated lesions. Aim: To evaluate the remineralization of dental enamel after the application of three fluorinated compounds commonly used in paediatric dentistry sodium fluoride, acidulated phosphate fluoride, and silver diamine fluoride and the effect on enamel microhardness under pH cycling conditions. Materials and Methods: Sixty impacted 3rd molars, with intact anatomical crowns recently extracted and without repaired structural defects, were sectioned longitudinally in a mesiodistal direction using a diamond disc, obtaining two working surfaces (buccal and lingual). The 120 working surfaces obtained were immersed for 96 hours in a demineralization solution at 37°C in order to demineralize the enamel surface. All of the demineralized molars were then randomly divided into four groups (n=30 each) and their surfaces were treated with Silver diamine fluoride (SDF), Difluoride silane (DSF), and Acidulated phosphate fluoride (APF), and with no treatment undertaken in the Control group (CG). The samples were immersed in alternating solutions for demineralization and remineralization at pH 4.4 and pH 7.0, respectively. The Vickers hardness number (VHN) was determined after 5, 10, and 15 days using a microdurometer with a load of 25 gf for 20s. Data were analysed using the ANOVA statistical test. Results: The microhardness values obtained from the three remineralization groups (SDF, DSF and APF) were obtained, with the mean microhardness after 10 days of treatment higher in the occlusal and cervical areas and statistically significant differences were found (SDF p=0.016, DSF p=0.043 and APF p=0.035). By Day 15, an increase in mean microhardness was found in the SDF and DSF groups at different depths recorded, and statistically significant differences were found. Conclusion: We found a significant difference among the effects of the three fluorinated compounds (SDF, DSF and APF) on the enamel surface. This finding is clinically significant as the use of remineralizing agents such as SDF, DSF and APF increases the microhardness of the enamel surface, suggesting that fluorinated compounds are effective in the reduction and remineralization of incipient carious lesions in dental enamel.

Keywords

• dental enamel
• demineralization
• remineralization
• vickers hardness