Effect of Surface Treatment on Shear Bond Strength between Artificial Resin Teeth and Denture Base Resin / 대한치과재료학회지

The purpose of this study was to investigate the effect of retaining holes on the denture base, as well as primer application, on the shear bond strength of denture base resin to the denture base. Using Trubyte Biotone artificial teeth, we selected a maxillary first molar and prepared a total of 80 teeth. Each prepared tooth was polished flat using a dental bar. The polished specimens were placed in the center of a silicon mold (diameter 30 mm, height 23 mm) and were embedded with clear acrylic resin (Ortho Jet, Lang Dental, USA). Forty specimens were shaped, using Fisher bar # 701 at the central part of the alveolar surface, to form retention holes. Each denture base resin was transferred to the resin after surface treatment, as instructed by the manufacturer. The highest shear bond strength (36.2 MPa) was achieved by heat-polymerized resin, when the retention hole and the primer were applied to the artificial tooth. The lowest shear bond strength (11.8 MPa) was achieved by auto-polymerized resin, when the primer was applied to the artificial tooth. The combination of heat-polymerized resin and artificial tooth resulted in a complex fracture pattern, whereas auto-polymerized resin and artificial tooth showed an adhesive fracture pattern.

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.