In vitro evaluation of color stability of polymethelmetacrylate and nylon base polymers

Abstract

Color stability of material used for partial and complete denture bases, Provide important information on the serviceability of these material . The purpose of this study was in vitro evaluation of color stability of poly methyle metacrylate and nylon, as base of removable dentures. Material and Methods : In this study 20 samples were fabricated of PMMA (Triplex:Ivoclar Vivadent AG Schaan/Lichtenstein) and Nylon ( Bre.flex Bredent GmbH&Co KG, Senden Germany) in ordre of manufacture. The samples were evaluated in CIELAB color order system by a spectrophotometer in 3 stages: before UV exposure, after 100 hours and 200 hours UV exposure and thermocycling . Color stability of two groups was analyzed by ANOVA and t-paired stastastical tests (p< 0/05). Results : Color change in two material after 100 hours UV exposure and thermocycling was obvious (E>1) . After 200 hours UV exposure and thermocycling, brightness of two material was decreased. Chromatic change of acryl after 100 hours in "a" axis,was in direction of red chroma and after 200 hours, was in direction of green chroma and in "b" axis, after 100 hours was in direction of yellow chroma and after 200 hours, was in direction of blue chroma. Chromatic change of nylon in "a" axis was in direction of red chroma and after 200 hours, was in direction of green chroma and in "b" axis was in direction of yellow. Generally, chromatic change of acryl in comparising with nylon was moer perceptible. Conclusion : Accelerated aging affected color stabiliy of acryl and nylon but, the finaly, color change of each test material was clinically acceptable (E<3/7) Therefore, application of nylon as denture base material is possible.