The purpose of this study was to examine the effects of temperature on the viscoelastic properties of soft denture liners. The materials used were 3 acrylic-type materials (Comfortner, COE-SOFT, and PHYSIO SOFT REBASE) and 4 silicone type materials (GC RELINE Ⅱ，Mollosil plus, GC Silfy, and SOFRELINER TOUGH). The apparatus used was a modification of the instrument for impression materials in JIS. Creep measurement was performed under a 200-g load for 300 seconds for each specimen in water (23, 28, 37, and 42℃) and air (23℃). The weight change characteristics with time of soft denture liners in water were determined to examine the water’s influence. Each specimen was immersed in a constant-temperature water bath maintained at 23 or 37℃. The weight of the specimen was recorded after immersion for 0.17, 0.25, 0.5, 1, 3, 6, 12, 24, 72, 168, and 336 hours. As the results, acrylic-type materials exhibited various viscoelastic properties, but they were easily affected by water and temperature. The viscoelastic properties of silicone-type materials were more stable compared with those of acrylic materials.

The objective of this study was to determine the mechanical properties, surface characteristics, discoloration, and microbial adherence (Streptococus oralis and Candida albicans) of a new composite denture teeth containing fluoropolymers and nano silica filler before and after alkaline degradation. We experimentally produced 2 types of composite resin artificial teeth for dentures. In one type, aliphatic monomers containing fluorine were used as the matrix resin of composite resin, and macro-fillers were added as inorganic fillers. In the other type, aliphatic and aromatic monomers containing fluorine were used as the matrix resin, and nano-fillers were added as inorganic fillers. Acrylic resin was also examined as a control. All data were statistically analyzed with ANOVA and Scheffe’s test (α＝0.05). As a result, the mechanical strength of the experimentally produced composite resin artificial teeth decreased before alkaline degradation, and the hydrophobicity increased. The surface roughness (Ra) of the nano-composite resin artificial tooth material containing fluorine aliphatic and aromatic monomers was lower than 0.2 μm even if the fillers dislodged due to alkaline degradation, and coloring and adhesion of S. oralis were suppressed.

Although many dentists have not recommended using denture adhesive materials for patients wearing ill-fitting dentures, their usefulness has been reported in recent years. At the beginning of this study, the consistency and adhesive strength of four commercially available denture adhesives in water (23℃) were examined. Based on the results obtained, six experimental materials were prepared using CMC-Na and P(VM/MA), and we investigated the strength of adhesion to a PMMA plate in air or water, the elasticity or viscosity of each material, and variation of the relative strength (f(t)/f(0)) with the time determined by a stress relaxation test.
In the case of commercially available denture adhesive, the decrease in the strength of adhesion to the PMMA plate when subjected to a repeated load was marked. In the case of experimental materials, the increase of CMC-Na caused elevation of the viscosity coefficient. This indicates that the high-level adhesive strength and elasticity on repeated loading in water is maintained for a prolonged period.