Micro-computed tomography evaluation of aligner thickness and gap width after thermoforming process: A comparative study of three different materials

Objectives: The objective of this study was to assess the clear aligner thickness and gap width after thermoforming process among three different materials. Material and Methods: Three different aligner materials, each comprising nine samples, were adapted to standardized three-dimensional-printed dental casts. High-resolution micro-computed tomography was employed to evaluate each sample. Two-dimensional (2D) quantitative analysis was conducted to assess aligner thickness and gap width. The analysis focused on the influence of three independent variables: tooth type (central incisor, canine, and molar), 2D reference point location, and aligner material. Statistical analysis was performed using analysis of variance followed by Tukey’s post hoc test for multiple comparisons. Results: Tooth type, dental region, and aligner material significantly influenced both gap width and aligner thickness. Among the materials tested, polyurethane (PU) exhibited the greatest variations in both parameters. In contrast, polyethylene terephthalate glycol (PET-G) and multilayer PU (MLPU) showed no statistically significant differences in either gap width or aligner thickness. Conclusion: PU demonstrated the highest variability in gap width and aligner thickness, indicating less precise adaptation and greater gap formation compared to PET-G and MLPU.