Assessment of the Effect of Thermoforming Process and Simulated Aging on the Mechanical Properties of Clear Aligner Material.

Background Choosing the optimal aligner material on the market is crucial to ensure constant forces for tooth displacement. Processes like manufacturing and intraoral usage can result in the degradation of certain properties, which can affect the overall efficacy of treatment. Objective The objective of the study is to compare the surface roughness and flexural modulus of two aligner materials following the processes of thermoforming and aging. Materials and methods Two groups of 12 samples each were tested: Group 1 consisted of polyethylene terephthalate glycol (PET-G) and Group 2 of zendura-polyurethane (PU). The groups were tested at three time points: T0 - pre-thermoformed; T1 - after thermoforming; T2 - after thermoforming and aging. The surface roughness and the flexural modulus were evaluated. One-way ANOVA followed by a Bonferroni post hoc test was conducted to compare the changes within each group across the three times. An independent t-test was done to compare the values between the two groups at each time point. The statistical tests were performed using SPSS software version 26 (IBM Corp., Armonk, NY, USA). P-values >0.05 were considered statistically significant. Results There was a significant change in the surface roughness post-aging in Group 2 (p=0.03) and flexural strength within Group 1 (p=0.031) and Group 2 (p=0.06) across the three time points. Comparing the changes within the three time points in Group 1, significant changes were observed between T0-T1 (p=0.045) and T0-T2 (p=0.07). In Group 2, significant changes were observed between T0-T2 (p=0.012). Comparing the flexural strength between the two groups, significant differences were observed at T0 (p=0.012) and T1 (p=0.001). Conclusion The aging process affected the surface roughness in Zendura (PU). The thermoforming and aging process resulted in reduced flexural strength in both Zendura (PU) and Duran groups (PET-G).