Evaluation of colour stability of flexible denture base resin in four commonly used food substances

The objective of this study was to evaluate the colour stability of flexible denture base resin (Valplast) in two different resin thicknesses (1-1.5 mm and 2.0- 2.5 mm) in four commonly used food substance such as coffee, tea, turmeric and sunset yellow dye. Within the limitations of the study, the following conclusions were drawn, 1. The thickness of the sample, duration of immersion of the samples, the solution used, and their interactions were significant in producing colour change. 2. Though there was an initial increase in colour difference values, there was a gradual decrease after 30 hour duration. Δ E values of the 60 hours group were lower than 10 hours and 30 hours group suggesting a gradual increase in colour stability from 30 hours to 60 hours duration. 3. The turmeric solution produced greater colour change than the other solutions (Δ E >3.3) 4. According to the National Bureau of Standards units, samples of 1 mm thickness immersed in coffee, tea and sunset yellow for 10 hours, sunset yellow for 30 hours and in coffee and tea for 60 hours showed slight colour change values.(0.5- 1.5). The samples of 1 mm thickness immersed in coffee and tea for 30 hours, sunset yellow for 60 hours and the samples of 2 mm thickness immersed in coffee, tea and sunset yellow for 10 hours, coffee, tea and sunset yellow for 30 hours, coffee, tea and sunset yellow for 60 hours showed noticeable colour change values. (1.5 – 3.0). The samples of both 1mm and 2mm thicknesses immersed in turmeric solution for 10 hours, 30 hours and 60 hours exceeded the noticeable range.(>3.0) and considered to be clinically unacceptable. The present study is an invitro study where the interaction of saliva with the food colorants was not examined. Further research is required to evaluate the colour stability in invivo situation and in longer durations of clinical use