Purpose: This study aimed to evaluate the effects of the color of the cast on dimensional stability of visible light-cured (VLC) trial denture bases. Materials and methods:A total of 60 VLC acrylic resin trial denture bases were fabricated on different colored casts (20 white, 20 dark blue, and 20 dark brown casts) and were divided into two groups; each group consisted of 30 casts (10 white, 10 dark blue, and 10 dark brown). The gap between the base and the cast after 24 hours was measured at different points (left crest of the ridge, midpalatal area, and right crest of the ridge) at the posterior and premolar areas for group I and after 48 hours for group II by using a stereomicroscope. Results:With brown cast, the trial denture base showed significant decrease in dimensional change in comparison with white and blue casts after 24 and 48 hours. Conclusion:The dimensional accuracy of the VLC trial denture base could be improved by using dark-colored cast during construction, to ensure accurate maxillomandibular relationship and accurate evaluation of phonetics and esthetic of wax trial dentures.

Aim: To evaluate the influence of water conditioning on the hardness and dimensional stability of polyamide denture material. Materials and methods:The samples were conditioned in a water bath according to values of temperature (4° C and 43° C) and time (700 hours). To evaluate the hardness test, samples were fabricated from polyamide and heat cured acrylic resin materials and was divided into control, cold conditioning and hot conditioning groups and hardness were measured for all groups. For dimensional stability test, forty denture bases were divided into cold conditioning and hot conditioning groups. The gaps between the denture base and the cast were measured. Results:The hardness of polyamide denture material was significantly decreased after hot water conditioning. Heat cured acrylic resin showed a significant increase in dimensional changes regarding cold water conditioning test. Conclusion:Water conditioning at 43° C could decrease hardness and increase the flexibility of polyamide denture material. Water conditioning at 4° C could increase in dimensional instability of heat cure poly (methyl methacryolate) (PMMA) denture material.Clinical significance: Use of dimensionally stable denture materials under the hot and cold condition are very important to retain the denture.