Effects of incorporation of 2.5 and 5 wt% TiO(2) nanotubes on fracture toughness, flexural strength, and microhardness of denture base poly methyl methacrylate (PMMA)

PURPOSE: The aim of this preliminary study was to investigate, for the first time, the effects of addition of titania nanotubes (n-TiO(2)) to poly methyl methacrylate (PMMA) on mechanical properties of PMMA denture base. MATERIALS AND METHODS: TiO(2) nanotubes were prepared using alkaline hydrothermal process. Obtained nanotubes were assessed using FESEM-EDX, XRD, and FT-IR. For 3 experiments of this study (fracture toughness, three-point bending flexural strength, and Vickers microhardness), 135 specimens were prepared according to ISO 20795-1:2013 (n of each experiment=45). For each experiment, PMMA was mixed with 0% (control), 2.5 wt%, and 5 wt% nanotubes. From each TiO(2):PMMA ratio, 15 specimens were fabricated for each experiment. Effects of n-TiO(2) addition on 3 mechanical properties were assessed using Pearson, ANOVA, and Tukey tests. RESULTS: SEM images of n-TiO(2) exhibited the presence of elongated tubular structures. The XRD pattern of synthesized n-TiO(2) represented the anatase crystal phase of TiO(2). Moderate to very strong significant positive correlations were observed between the concentration of n-TiO(2) and each of the 3 physicomechanical properties of PMMA (Pearson's P value ≤.001, correlation coefficient ranging between 0.5 and 0.9). Flexural strength and hardness values of specimens modified with both 2.5 and 5 wt% n-TiO(2) were significantly higher than those of control (P≤.001). Fracture toughness of samples reinforced with 5 wt% n-TiO(2) (but not those of 2.5% n-TiO(2)) was higher than control (P=.002). CONCLUSION: Titania nanotubes were successfully introduced for the first time as a means of enhancing the hardness, flexural strength, and fracture toughness of denture base PMMA.