Polymethyl methacrylate (PMMA)-made prostheses used in the oral cavity were evaluated by multimodal assessment in order to elucidate the biodeterioration of PMMA. In used dentures (UD), the micro-Vickers hardness of the polished denture surface and denture basal surface was lower than that of the torn surface (p<0.05), whereas the shaved surface approximately 100 μm from the polished surface showed a similar value to the torn surface. By contrast, there were no differences among these surfaces in new resin (NR). The volatile content of UD was higher than that of NR (p<0.05). Component analysis by ATR-FTIR showed specific spectra (1,700–1,400 cm−1) only in UD. This study revealed that PMMA deteriorated during long-term use in the oral cavity in terms of hardness and volatile content with component alteration, and suggests the involvement of biodeterioration, possibly due to saliva and oral microbiota.
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