Polymethylmethacrylate Denture Base Layering as a New Approach for the Addition of Antifungal Agents

Purpose To introduce a new technique, denture base layering, for the addition of titanium dioxide nanoparticles (TiO(2)NPs) to polymethylmethacrylate (PMMA) and to investigate the effects of the layering technique on Candida albicans (C. albicans) adhesion and on surface roughness, hardness, translucency, and flexural strength. Materials and methods In total, 210 heat-polymerized acrylic resin specimens were prepared as discs (15 x 2 mm) for testing C. albicans adhesion (n = 70) and surface roughness, hardness, and translucency (n = 70); and as acrylic plates (65 x 10 x 2.5 mm) for testing flexural strength (n = 70). Specimens were divided into 4 groups: control (n = 30), one-layer (n = 60), double-layer (n = 60), and dotted-layer (n = 60) according to the packing and layering technique. Each group was divided according to the concentration of TiO(2)NPs 1% and 2.5% (n = 10). The control group comprised one layer of unmodified resin. The one-layer group comprised one layer of a mixture of PMMA/TiO(2)NPs packed conventionally. The double-layer group consisted of two different layers packed in two steps, as follows: unmodified resin first, followed by a continuous thin layer of the PMMA/TiO(2)NPs mixture. Similarly, the dotted-layer group consisted of two different layers packed in two steps, as follows: unmodified resin first, followed by a thin layer of the PMMA/TiO(2)NPs. However, the second mixture was added in a dotted manner. The direct culture method for C. albicans adhesion before and after ultraviolet light activation, and surface roughness, hardness, translucency, and flexural strength were measured. An analysis of variance and Tukey's post hoc test were used for data analysis (alpha = 0.05). Results The addition of TiO(2)NPs reduced C. albicans adhesion (p < 0.001). However, no significant difference was found between both concentrations within the same group before and after ultraviolet light activation (p > 0.05), except in the 1% dotted-layer (p = 0.022). Surface roughness and hardness were not affected by the additions of different concentrations of TiO(2)NPs (p = 0.905) and (p = 0.059), respectively. Translucency was significantly reduced in all the groups (p < 0.001) except in the 1% dotted-layer (p = 0.332). Flexural strength decreased as the TiO(2)NPs concentration increased, with the greatest reduction in strength observed in the one-layer group (p < 0.001). Conclusions The double and dotted layering techniques were effective in reducing C. albicans adhesion, without affecting surface roughness, hardness, or flexural strength. However, translucency was reduced in all the groups, except the 1% dotted-layer group.