بررسي مقايسه اي تغييرات ابعادي خطي دو نوع آكريل سرماسخت ايراني و خارجي

Comparison of linear dimensional changes of two cold - cure acrylic resins

Background and Aim: Cold - cure acrylic resins are commonly used for making interim prostheses, orthodontic appliances, denture repairs and special trays. Acrylic resins exhibit certain unavoidable changes that may affect on appliances accuracy. The aim of this study was to compare the linear dimensional changes of two cold - cure acrylic resins: Acropars and Meliodent. Materials and Methods: In this experimental laboratory study, twenty specimens in two groups of ten were made by Acropars OP and Meliodent acrylic resins according to the manufacturerʹs instructions. Dimensional changes were measured at 24, 48 and 72 hours after setting by a digital collis. The results were analyzed using t - test, t - paired test and repeated measure ANOVA. Results: In Acropars OP specimens, the difference between 48 hours and 72 hours (96.20±0.20 vs. 96.33±0.17) was significant (P3=0.006) but the differences between 24 (96.20±0.25) and 48 hours (P1-0.958) and between 24 and 72 hours (P2=0.123) were not significant. In Melidoent specimens, the differences between all 3 days (0.37±0.47, 0.15±0.28 and 0.18±0.24) were significant (P1=0.005, P=0.001 and P3=0.005). Moreover, the differences between Acropars and Meliodent acrylic resins on all three days (first:95.82±0.25, second: 96.05±0.11 and third 96.15±0.10) were significant (P=0.003). The differences between mean groups and metallic dye, after three days, were significant in Meliodent group (P=0.000), but in significant in Acropars group (P=0.774). Conclusion: Meliodent self-cure resin had considerable dimensional changes when compared to Acropars resin. Maximum differences between these two types of acrylic resins was in the first 24 hours and the minimum difference was at 48 hours after polymerization.