DEVELOPMENT AND ASSESSMENT OF AN OBJECTIVE METHOD OF COLOR-CHANGE MEASUREMENT FOR ACRYLIC DENTURE BASE RESINS

Current standard specifications for the laboratory evaluation of dentu re base materials require subjective assessment of colour stability. T his study evaluates a new objective measurement technique for transluc ent denture base materials, by comparing quantitative data with the re sults obtained from a standard subjective method. Preliminary work on three representative commercial acrylic materials resulted in the sele ction of a white background for the quantification of colour change of these translucent materials, One half of each sample was exposed to a rtificial sunlight for 24h. The colour of both exposed and unexposed r esin was measured on the CIE La*b* stale using a photoelectric colori meter. Significant changes in the b and E* values (P<0.01) were obser ved following light exposure. Objective data for a wide range of comme rcial materials were compared with the results of a subjective evaluat ion and it was shown that a change in b of 1.5 units was discernable subjectively by eye for 100% of the cases. It is suggested that this m ethod and limit value could form the basis of a new objective colour c hange specification for polymeric dental materials.