Comparison of Color Changes of Vacuum Formed Retainers Made from PET-G Material: An in-vitro Study

Aim: Polyethylene terephthalate glycol (PET-G) materials are frequently used in dental practice. Most vacuum formed retainers (VFRs) and trays for bleaching agents are made from PET-G materials. The aim of this in vitro study was to evaluate the color stability of different branded VFRs, made from PET-G material, in various beverages. Materials and Methods: Two different PET-G materials, Atmos (American Orthodontics, Washington, USA) and Duran (Scheu Dental, Iserlohn, Germany) were tested after thermoforming over a metal casting model of 15 mm diameter and 6 mm height for color stability. Ten samples from each brand were immersed in four different beverages (water, tea, coffee, and coke), and a total of 80 samples were evaluated on the 7th and 14th days using a spectrophotometer. Color changes were evaluated based on the L*,a*,b* color system, according to Commission Internationale de l'Eclairage (CIE). One-way ANOVA was used for ∆E. Student’s t-test and Bonferroni tests were applied to compare the variables. The level of statistical significance was set at P < .05 Results: There were statistically significant differences between Atmos and Duran. (P < .001). Duran showed significant color changes with tea, coffee, and water (p< 0.05) while Atmos were more resistant to discoloration. Conclusion: It was observed that different PET-G materials showed varying performance against discoloration. Duran was more prone to discoloration compared with Atmos. Tea had the greatest discoloration effect on all groups.