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The ability of poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (PVBVA) to consolidate Fir wood was studied in terms of the surface and mechanical properties’ changes. Two variables were considered to treat the wood: (i) the concentration (5 and 10 wt.%) of PVBVA solutions and (ii) the method of application (brushing and immersion). The presence of PVBVA on the wood surfaces was confirmed by infrared spectroscopy. Surface roughness measured by optical profilometry did not reveal changes in the topography of the samples, and appropriate visual appearance was confirmed. Contact angle measurements showed that a droplet of the 10%-PVBVA solution needed ~50 s to reach the same contact angle decreasing rate as that measured for the 5%-PVBVA solution, suggesting there was some kind of induction time till the spreading process was no longer controlled by the viscosity, but by the solution-wood interactions. Water contact angle (WCA) measurements proved a more hydrophobic surface of the PVBVA-treated samples, compared to untreated wood. Mechanical characterization of the samples was done macroscopically by a three-point bending test and locally by the Shore D and Martens hardness (MH). Only results from MH experiments provided comparative results, indicating that treatment with PVBVA solutions increased wood hardness locally, being enhanced with solution concentration. The best surface mechanical properties were obtained for the samples immersed in the 10%-PVBVA solution.

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Background and Aim: Due to the increasing use of restorative materials, finding a suitable material with low adhesion rate and colonization of pathogenic Streptococcus mutans has a significant importance. The purpose of this study was the comparison of the adhesion rate of Streptococcus mutans to "Nano-hybrid composite" and "Amalgam" at 1, 3, and 7 day intervals. Methods and Materials: In this experimental study, 72 samples of Amalgam and composite resin were placed in two equal groups and exposed to bacterial suspension holding 1× 10 6 cell/ml and after three time periods of 1, 3, and 7 days, the restorative material samples were suspended in 1cc of physiologic serum, and 100µl of the suspension was cultured on Blood Agar medium. After 48 hours the number of Streptococcus mutans colonies were counted. The data were analyzed by T-test. Results: The mean and standard deviation of Streptococcus mutans colonies adhered to Nano-hybrid composite resin at 1, 3, and 7 day intervals were measured 12.7±2.3, 1.5±2.12 and zero colonies, respectively. Adherence of Streptococcus mutans to composite resin during these three days, showed a significant statistical difference (p<0.005). The mean and standard deviation of colonies, which adhered to Amalgam at 1, 3 and 7 day intervals were 32±7.01, 18.8±3.8 and zero colonies, correspondingly. The adherence of Streptococcus mutans to Amalgam during these three days showed a significant statistical difference (p<0.001). The comparison between Amalgam and composite resin showed that the adherence of Streptococcus mutans to composite resin was lower during the first and the third day and the results were statistically significant (p<0.001). Conclusion:The result of this study showed that adhesion of Streptococcus mutans to Nano-hybrid composite is lower than the adhension to Amalgam. Conclusion:The results indicated that adhesion of Streptococcus mutans to Nano-hybrid composite is lower than the adhesion to Amalgam.