Investigation of the cytotoxicity of thermoplastic denture base resins

PURPOSE The purpose of this study was to investigate the in vitro cytotoxicity of thermoplastic denture base resins and to identify the possible adverse effects of these resins on oral keratinocytes in response to hot water/food intake. MATERIALS AND METHODS Six dental thermoplastic resin materials were evaluated: three polyamide materials (Smile tone, ST; Valplast, VP; and Luciton FRS, LF), two acrylic materials (Acrytone, AT; and Acryshot, AS), and one polypropylene resin material (Unigum, UG). One heat-polymerized acrylic resin (Vertex RS, RS) was chosen for comparison. After obtaining extracts from specimens of the denture resin materials (Φ=10 mm and d=2 mm) under different extraction conditions (37℃ for 24 hours, 70℃ for 24 hours, and 121℃ for 1 hour), the extracts (50%) or serial dilutions (25%, 12.5%, and 6.25%) in distilled water were co-cultured for 24 hours with immortalized human oral keratinocytes (IHOKs) or mouse fibroblasts (L929s) for the cytotoxicity assay described in ISO 10993. RESULTS Greater than 70% viability was detected under all test conditions. Significantly lower IHOK and L929 viability was detected in the 50% extract from the VP (70℃) and AT (121℃) samples (P<.05), but only L929 showed reduced viability in the 50% and 25% extract from LF (37℃) (P<.05). CONCLUSION Extracts obtained from six materials under different extraction conditions (37℃, 70℃, and 121℃) did not exhibit severe cytotoxicity (less than 70% viability), although their potential risk to oral mucosa at high temperatures should not be ignored.