To investigate the effect of the usage of two different nano-filled and resin based surface coatings on the fluoride release, surface roughness and surface hardness of the three different resin modified and conventional glass ionomer and a flowable composite resin materials

Fluoride-releasing dental materials which is frequently used in pediatric dentistry in order to prevent the development of dental caries by providing the maintenance of low level fluoride into saliva. It is an important fact to make effective finishing and polishing procedures of the dental restorations in order to have proper dental surfaces. For this purpose there are lots of finishing and polishing materials and techniques. ?resin based surface coatings (glaze materials)? are noteworthy applications in order to decrease surface roughness of the restorations and protect them from the changes in the oral environment.The aim of this study was to investigate the fluoride release, surface roughness and surface hardness of the three different glass ionomer cements (EQUIA/GC, Ketac N100 /3M, Ionolux/VOCO) and a flowable composite resin (Vertise Flow/KERR) with the usage of two different nano-filled and resin based surface coatings (G-Coat Plus/GC ve Easy Glaze/VOCO).This study was carried out a two hundred and eighty-four disc-shaped specimens. Of each material with 10 mm diameter and 2 mm height twenty-one specimens were prepared for fluoride release experiment, twenty specimens were prepared for surface roughness experiment and thirty specimens were prepared for surface hardness experiment.The twenty-one specimens which were prepared for fluoride release experiment were divided into three groups. First group (n=7) were coated with G-COAT PLUS and the second group of specimens were coated with Easy Glaze (n=7). The remaining group (n=7) were left uncoated. The specimens were placed in plastic test tubes containing 3 ml of de-ionized water and put into an incubator at 370C. Fluoride released from the 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. Orion 720A+ and Orion Fluorid electrode were used for the fluoride release measurements. The highest amount of fluoride release was obtained from the EQUIA material for the first day. At second day and the days after the highest amount of fluoride release was obtained from the Ketac N100 material. For all the measurement days the lowest amount of fluoride release was obtained from the Vertise Flow material. The coated specimens released lower fluoride than the uncoated specimens and the difference was statistically significant (p<0,01).The twenty specimens were prepared from each material and divided into two groups. The beginning surface roughness measurements of the twenty specimens were taken and then all the specimens were polished in the presence of water with 1200 grit silicone carbide paper. After this polishing the second surface roughness measurements were taken. Then G-COAT PLUS was applied to the first group of specimens and Easy Glaze was applied to the second group of specimens after that the last (after glaze) surface roughness measurements were taken. Surface roughness measurements were carried out by using ?Mahr Perthometer M1? surface roughness-measuring instrument. EQUIA had the highest surface roughness values at the first surface roughness measurements. In contrast Vertise Flow had the lowest surface roughness values. The first surface roughness measurements are lower than the measurements which were taken after polishing for all groups and the comparison between these measurements showed a statistically significant difference (p<0,01). After glaze application surface roughness measurements were lower than the measurements which were taken after the polishing procedure and the difference was statistically significant for all material groups (p<0,001).The thirty specimens which were prepared for surface hardness experiment were divided into three groups. First group (n=10) of specimens were coated with G-COAT PLUS and the second group were coated with Easy Glaze (n=10). The remaining group (n=10) were left uncoated. The specimens were stored in distilled water at 370C for 24 hours. After 24 hours all the specimens were polished in the presence of water with 1200 grit silicone carbide paper in order to obtain a flat polished surface without any of the glaze material. Five indentations were taken from the each specimen surface. Then specimens were maintained under same conditions and same procedures were taken place at the 7th day. Surface hardness measurements were carried out by using ?Buehler Hardness Testing Machine? surface hardness-measuring instrument. In EQUIA group there was a statistically significant difference between the surface hardness values of G-COAT PLUS coated and uncoated EQUIA specimens and Easy Glaze coated and uncoated specimens at the 24th hour and 7th day (p<0,05, p<0,001). Also, between G-COAT PLUS coated KETAC N100 and Easy Glaze coated Ketac N100 groups at the 24th hour and 7th day surface hardness values a statistically significant difference was determined (p<0,01, p<0,05).The statistical analysis were performed with NCSS 2007 software program. Data were analysed by using the descriptive statistical methods (mean average, standart deviation, median, interquartil range). Friedman, Kruskal Wallis, Dunn?s multiple comparison, Mann-Whitney-U and Wilcoxon tests were also performed. The comparisons were considered significant at p<0,05.As a conclusion, all materials released fluoride at the beginning, however during the experiment the fluoride release of each materials were decreased to ?0? at different test days. Glaze materials significantly decreased the fluoride release. Surface roughness values of all materials were observed a significant decrease after glaze applications (p<0,05). Statistically significant increase was observed at the surface hardness values of coated EQUIA, Ketac N100 and Vertise Flow materials during the 24th hour and 7th day measurements (p<0,05).Key words: Glass ionomer cement, resin based surface coatings, fluoride release, surface roughness, surface hardness.