Surface Hardness and Microbial Adhesion of Modified Polymers by Coupled-Bioactive-Glass

Methods: Poly(methyl methacrylate) (PMMA) (Palapress – Heraeus Kulzer) samples were prepared in dimensions of 65x10x3mm (ISO 1567:1999).  Samples were modified by different ratios of non-silanized and silanized Bioactive Glass Granules (BAG) (BonAlive Biomaterials). Coupling of the glass was carried out by 3-methacryloxypropyltrimethoxy silane (MPS). The samples were polished under water cooling, and divided into 9 groups. (Group 1) No glass (Control), (Group 2-5) 3-6-9-12wt% non-silanized BAG, (Group 6-9) 3-6-9-12wt% silanized BAG. For surface hardness test, samples were immersed in distilled water for 60 days and Vickers surface hardness device (HMV, Shimadzu) was used 245.2 mN 0.025 Hv force 15 seconds of three points on each sample. Statistical analysis was performed using Kruskal-Wallis ve Mann Whitney tests (p<0.05). For microbial adhesion test, samples were scaled down 5x10x3mm size. C. albicans and S. mutans were incubated in selective media and adhered on the samples in artificial saliva solution. Calculation of the microorganisms was held by Real-Time PCR (Light Cycler^® 1.5, Roche).

Results: Surface characteristics were significantly affected by the increased ratio of coupled glass (p<0.05). The highest surface hardness value was observed in Group 9 (30.4±0.87VHN), the lowest surface hardness was recorded in Group 4 (26.5±0.68VHN). For S. mutans adhesion test, the highest value was observed in Control group (3.08x10³DNA/100µL), the lowest value was recorded in Group 8 (2.20x10²DNA/100µL). For C. albicans adhesion test, the highest value was observed in Group 5 (7.84x10²DNA/200µL), the lowest values was recorded in Group 8 and Group 9 (4.0x10¹DNA/200µL).

Conclusions: Observed changes in the properties influenced by addition of BAG and silanization. Within the limitations of this study, it can be concluded that silanization procedure increases the hardness, decreases the microbial adhesion of the modified polymers.