Improving Polymethyl Methacrylate Resin Using Novel Nano-Ceramic Coating

Objectives: Poly methyl methacrylate (PMMA) has been broadly used in dentistry. Unfortunately, PMMA has poor surface wear resistance, is relatively porous, and promotes adhesion of complex oral biofilms associated with oral mucositis and systemic co-morbidities. The Aim of this study is to improve the surface physical and chemical characteristics of PMMA by developing a novel, thin film, nano-ceramic coating process, and to analyze the resulting coated surface. Methods: Atomic Layer Deposition (ALD) technique was developed to deposit a titanium dioxide (TiO2) nano-ceramic thin film on PMMA. The surface wettability for both coated and uncoated PMMA was determined by water contact angle. Wear resistance was performed using a mechanical tooth-brushing device with a load of 50g for 6000 strokes after 5-month water storage. Chemical and mechanical challenge test was performed by using sonication in 3.8% sodium perborate (Polident denture cleanser) for 1 hour with aged specimens. X-ray photoelectron spectroscopy (XPS) was utilized before and after the brushing test and challenge test to analyze the PMMA surface chemical composition. The mechanical strength of coated and uncoated PMMA was measured by three-point bending with a universal testing machine (n=10). Surface microbial interactions were evaluated using C. albicans attachment and biofilm formation test. Results: Nano-ceramic TiO2 coating (30 nm-thick) was successfully deposited on PMMA at 65°C. After coating, water contact angle decreased from 67° to less than 5°, indicating formation of a super-hydrophilic surface. After brushing test, the ceramic coating remained intact. XPS analysis revealed no loss of TiO2 from coated samples following brushing and denture cleanser sonication for 1 hour. There was no statistically significant difference in mechanical strength (MPa) (Mean±SD) between PMMA (139.37±11.34) and TiO2-PMMA (160.65±37.07). C. albicans attachment decreased by 63% on the coated PMMA surface. C. albicans biofilm formation decreased by 53% on the coated PMMA surface. Conclusions: ALD is a promising technique to modify surface properties of PMMA and resulted in a stable adherent thin film. By depositing a TiO2 nano-ceramic coating, PMMA surface properties may lead to significantly reduced microorganism adhesion and easier pathogen removal from PMMA. For patients who wear dentures, reducing the oral microbial biofilm burden using a TiO2 coated PMMA surface could positively impact their oral and systemic health.