Do termocycling and brushing affect stability of pet G orthodontic retainers?

Aim: To evaluate changes of surface roughness and mass of orthodontic retainer materials after exposure to thermocycling and brushing. Materials and Methods: A total number of 96 samples of polyethylene terephthalate glycol (PETG) material from four different manufacturers (Biolon- Dreve ; Erkodur A1- Erkodent ; Track A- Forestadent ; Essix C+ - Raintree Essix) were exposed to thermocycling and simulated brushing. Thermocycling was performed on Thermocycler- SD Mechatronik machine for a total number of 1500 cycles, 5-55 °C, and dwell time 13 seconds. Samples were then exposed to simulated brushing for 30 minutes with 3 different types of toothbrushes according to the number and thickness of filaments (CS 5460, CS 3960, CS 1560). Both surface roughness and mass of the samples were evaluated three times: initial, after thermocycling and after brushing. Since the data followed normal distribution, t-test and one-way ANOVA were used. Results: In all four brands, both thermocycling and brushing increased surface roughness significantly (p