ABSTRACTBackground:Loss of teeth could impact on the mastication efficiency. To overcome this problem, the patient can wore denture or prosthesis. One of thematerials to made denture base is Valplast® and Lucitone® FRS™. Denture base material was likely to absorbed various of contaminants such as tar that were contained in cigarettes. It became a factor of discoloration on denture base. Purpose: To determine whether there was a color change of the nylon thermoplastic resin after exposed to cigarette smoke. Methods:This type of research was true experimental with post-test only and control design, the number of samples that used were 24 pieces consisting of four groups, two of them were Valplast®, one group exposed to smoke and others were not exposed to smoke and the other two groups were Lucitone® FRS™, one group were exposed to smoke and others were not exposed to smoke. Result:There were significant differences between the group of Valplast® that exposed to smoke with the group of Valplast® that not exposed to smoke of 0.000 (p<0.05) and between the group of Lucitone® FRS™ that exposed to smoke with the group of Lucitone® FRS™ that not exposed to smoke of 0.000 (p<0.05) as well as between the group of Valplast® that exposed to smoke with the group of Lucitone® FRS™ that exposed to smoke of 0.000 (p<0.05).Conclusion: There were changed of color in the nylon thermoplastic resin after exposed to cigarette smoke.Keywords: Nylon thermoplastic resin, Discoloration, Cigarette smoke.