Effect of nano-ceramic coating on surface property and microbial adhesion to poly(methyl methacrylate).

To improve surface properties of poly(methyl methacrylate) (PMMA) using nano-ceramic coatings and assess microbial adherence after long-term use of a chemical cleanser. Thirty-six PMMA samples were fabricated, polished and coated with a nano-thin TiO2 or mixed TiO2 /ZrO2 , with uncoated samples as controls. Six samples in each group (n = 12) were soaked in Polident denture cleaner 180 times for 30 min, while six were soaked in deionized water. Surface roughness of PMMA before and after being soaked in Polident was assessed. All samples were subsequently exposed to Candida albicans for 6 h and the adherent cells were determined by viable colony count. Two-way analysis of variance was performed for statistical analysis. No significant difference in surface roughness was noted between the uncoated and coated PMMA before soaking. After soaking, surface roughness of the uncoated PMMA increased from 0.164 to 0.532 µm (p < .05). No significant change was observed for TiO2 -coated (0.105-0.143 µm) or TiO2 /ZrO2 -coated PMMA (0.104-0.141 µm). Attachment of C. albicans to PMMA soaked in water showed significantly less attachment to both TiO2 -coated (1.4 × 103 cfu/ml) and TiO2 /ZrO2 -coated PMMA (1.6 × 103 cfu/ml) than to the uncoated PMMA (2.6 × 103 cfu/ml). After soaking in Polident, the uncoated PMMA had significantly less C. albicans attachment than coated samples. Less attachment was noted on the TiO2 /ZrO2 -coated PMMA then the TiO2 -coated samples (p < .05). Nano-ceramic TiO22 /ZrO2 coating of PMMA denture base material alters surface properties thus reduces oral microbial adhesion. It represents a promising alternative to the chemical disinfection for PMMA denture materials.

Recent Advances in Theoretical Development of Thermal Atomic Layer Deposition: A Review.

Atomic layer deposition (ALD) is a vapor-phase deposition technique that has attracted increasing attention from both experimentalists and theoreticians in the last few decades. ALD is well-known to produce conformal, uniform, and pinhole-free thin films across the surface of substrates. Due to these advantages, ALD has found many engineering and biomedical applications. However, drawbacks of ALD should be considered. For example, the reaction mechanisms cannot be thoroughly understood through experiments. Moreover, ALD conditions such as materials, pulse and purge durations, and temperature should be optimized for every experiment. It is practically impossible to perform many experiments to find materials and deposition conditions that achieve a thin film with desired applications. Additionally, only existing materials can be tested experimentally, which are often expensive and hazardous, and their use should be minimized. To overcome ALD limitations, theoretical methods are beneficial and essential complements to experimental data. Recently, theoretical approaches have been reported to model, predict, and optimize different ALD aspects, such as materials, mechanisms, and deposition characteristics. Those methods can be validated using a different theoretical approach or a few knowledge-based experiments. This review focuses on recent computational advances in thermal ALD and discusses how theoretical methods can make experiments more efficient.