Comparison of the effect of different polishing methods on the fluoride release, surface roughness and bacterial adhesion of the newly developed restorative materials

Fluoride-releasing dental materials which are frequently used in pediatric dentistry, prevent carious formation providing the maintenance of low and constant level fluoride in the saline, microbial dental plaque and surronding dental tissue. Studies are continue to improve the properties and resolve the limitations of fluoride releasing dental materials. Applying proper finishing and polishing materials is necessary to obtain successful and long-lasting restorations. There are many manufactured finishing and polishing systems for this purpose. The aim of this study was to evaluate the effect of two different polishing systems (Sof-Lex™/3M ve Enhance®/PoGo™/Dentsply) on the fluoride release, surface roughness and bacterial adhesion of five different restorative materials (BEAUTIFIL®II/Shofu, GCP Glass Fill/GCP, AmalgomerTM CR/Advanced Health Care, Dyract® XP/Dentsply, GC Fuji IX GP®/GC). This study was carried out on five different restorative materials, three hundred and fifteen specimen were used. 8 mm diameter and 2 mm height twenty-one specimens of each material were prepared for fluoride release and bacterial adhesion experiment, 10 mm diameter and 2 mm height twenty-one specimens were prepared for surface roughness experiment. The twenty-one specimens from each material were divided into three groups for all experiments. First group (n=7) were polished with Sof-Lex™ and the second group (n=7) were polished with Enhance®/PoGo™. The control group (n=7) received no polishing treatment after being cured under the Mylar strip. The specimens were placed in plastic test tubes containing 3 ml of de-ionized water and were put into an incubator at 370C. Fluoride release was determined at 1st, 2nd, 3rd, 7th,14th,21st and 28th days with using a fluoride ion-selective electrode connected to an ion analyzer. Surface roughness measurements were carried out by using "Mahr Perthometer M1" surface roughness-measuring instrument. Three measurements in different directions were recorded for every specimen for each group, and the mean Ra value was determined for each specimen. For bacterial adhesion experiment, every specimen for each group was packed up separately and sterilized with hydrogen peroxide gas plasma sterilization. The specimens were incubated with sterilized saliva to stimulate the formation of an acquired salivary pellicle After formation of pellicle, bacterial suspension which was prepared from S. mutans culture was added to specimens and incubated 4 hours at 37°C. S. mutans density on the surface of materials was measured with spectrophotometre. The statistical analysis was performed with NCSS 2007 software program. Data were analysed by using the descriptive statistical methods (mean average, standart deviation, median, interquartil range). Newman Keuls and Tukey multiple comparison tests were also performed. The level of significance was set at p<0,05. Fluoride release seen in resin-based materials, were significantly less than non-resin-based materials. The highest amount of fluoride release was obtained from the Sof-Lex™ subgroup of glass carbomer (GCP Glass Fill) material group for all the measurement days. Control subgroup of giomer (Beautifil II) released more fluoride than other subgroups. Fluoride release from Sof-Lex™ subgroup of glass carbomer (GCP Glass Fill) and ceramic reinforced glass ionomer cement (Amalgomer CR) materials was significantly higher than Enhance®/PoGo™ and control subgroups and the difference was statistically significant (p<0.05). The fluoride release from control subgroup of compomer (Dyract XP) was less than the other subgroups. The amount of fluoride release from the subgroups comprising two polishing systems of conventional glass ionomer cement (Fuji IX) was significantly more than the control subgroup and the difference was statistically significant (p<0.05). When both polishing systems were applied on the surface of conventional glass ionomer cement (Fuji IX), the fluoride release significantly increased and the difference was statistically significant (p<0.05), but there was no significant difference between two polishing subgroups (p>0.05). The highest surface roughness value was observed in the control subgroup of GCP Glass Fill material, the lowest surface roughness value was observed in the control subgroup of Dyract XP material. The surface roughness value of control subgroups of the material groups except GCP Glass Fill material was less than the other subgroups comprising polishing systems and the difference was statistically significant (p<0.01). Among the Sof-Lex™ and Enhance®/PoGo™ subgroups of the material groups, the highest surface roughness value was observed in the Enhance®/PoGo™ subgroup of Amalgomer CR material. The highest bacterial density was observed in the Enhance®/PoGo™ subgroup of the Amalgomer CR material. There was not statistically significant difference in terms of bacterial density values on the surface of the Amalgomer CR material group between control and Sof-Lex™ subgroups (p>0.05). Among the Enhance®/PoGo™ subgroup of all material groups, the bacterial density on GCP Glass Fill material was significantly less than Beautifil II and Amalgomer CR materials and the difference was statistically significant (p<0.05), the bacterial density on Amalgomer CR material was significantly higher than GCP Glass Fill, Dyract XP and Fuji IX materials and the difference was statictically significant (p<0.05). As a conclusion, effects of polishing systems used for restorative materials on fluoride release, surface roughness and bacterial adhesion are related with structural factors of materials and polishing instrument must be selected according to the material's structure.