The physical properties of two glass ionomer cements formulated for fissure sealing and two resin-based light cured fissure sealants before and after fluoride release and fluoride re-charge

A fluoride-releasing fissure sealant which is frequently used in pediatric dentistry is a material that is placed in the pits and fissures of teeth in order to prevent the development of dental caries by providing the maintenance of low level fluoride into saliva. The aim of this study was to investigate the compressive strength and surface roughness of two glass-ionomer cements (GICs) formulated for fissure sealing (Fuji VII-GC, Ketac Molar-3MESPE) and two resin-based light-cured fissure sealants (Clinpro-3MESPE, Embrace-PULPDENT) before and after fluoride release and fluoride re-charge.This study was carried out a hundred and four disc-shaped specimens. Of twenty-one specimens (4 mm diameter and 6 mm height) from each material were prepared for compressive strength experiment and five specimens (8 mm diameter and 2 mm height) from each material were prepared for surface roughness experiment. The prepared specimens were placed in plastic test tubes containing 3 ml of de-ionized water and put into an incubator at 370C. The twenty-one specimens were divided into three groups. First group was loaded in compression until failure and the initial compressive strength values were determined by using an Instron 3345 mechanical testing machine. Fluoride released from the remaining specimens were measured at 1st, 2nd, 3rd, 4th,7th,14th,21st and 28th days using a fluoride ion-selective electrode connected to an ion analyzer. All the materials released fluoride in these time intervals and the highest amount of fluoride was obtained during the first 24 hours. There was a statistically significant difference between the amounts of fluoride released from resin-based fissure sealants and non resin-based fissure sealants (p<0,0001). The highest amounts of fluoride released from ?Fuji VII? which is a non resin-based material and the lowest from ?Clinpro? which is a resin-based material in all measurement days. At 28th day, the second seven specimens from each group was loaded in compression and the compressive strength values after one monthly fluoride release were obtained. The remaining seven specimens from each group was exposed to 0,05% NaF (Sodium Fluoride) solution at 29th day. Exposing to the mouthwash was applied once a week at 29th and 35th days. At 42nd day, the same specimens were exposed to 1,23% APF (Asidulated Phosphate Fluoride) gel. After refluoridation by mouthwash and gel, fluoride amount was measured at 30th, 31st, 32nd, 35th, 42th, 43 th, 44th, 45 th, 49th,56th,63rd and 70th days, using the same method. At 70th day the last group was also loaded in compression and the compressive strength values after refluoridation were obtained.Surface roughness of five disc-shaped specimens from each material were quantitatively carried out by means of a surface roughness-measuring instrument (Mahr Perthometer M1) at 1st, 28th and 70th days. Surface roughness values of all materials were observed gradually increasing towards to 70th days. Furthermore, the highest surface roughness values were determined in ?Fuji VII? and the lowest in ?Clinpro?, in all measurement days. For all materials, there is a statistically significant difference between the initial and 70th days? surface roughness values (p<0,01, p<0,05).The statistical analysis were performed with GraphPad Prisma V3 program. The data were analysed by Friedman, Kruskal Wallis and Dunn?s multiple comparison tests. The comparisons were considered significant at p<0,05.As a conclusion, all fissure sealant materials released fluoride and non resin-based fissure sealants released relatively more fluoride than the resin-based fissure sealants. After exposure to mouthwashes, only non resin-based fissure sealants were re-charged, however after exposure to APF gel all fissure sealant materials were re-charged and continued releasing fluoride. It was shown that the surface roughness values of all materials after exposure to topical fluoride application were significantly increased and non resin-based fissure sealants were more effected than resin-based fissure sealants. Compressive strength values were gradually decreased, however the decline of its was more clear in non resin-based fissure sealants having lower initial compressive strength values.Key words: Fissure sealants, fluoride release, re-charge, surface rougness, compressive strength.