Influence of thermoforming techniques on thickness distribution of in-office aligners: a micro-computed tomography analysis

Objectives: To evaluate the impact of three thermoforming methods on the resulting thickness of clear aligners (CAs). Materials and Methods: A sample of 30 clear aligners (CAs) from the upper jaw was produced with polyethylene terephthalate glycol and divided into three groups according to thermoforming technique: pressure thermoforming (PRT; n = 10), digital air vacuum thermoforming (DVT; n = 10), and conventional air vacuum thermoforming (CVT; n,=,10). Micro-computed tomography scans and thickness values at reference points were obtained in resulting images. Intrainvestigator reliability was assessed, and statistical analysis of data was performed with nonparametric analysis of variance tests (P < .05). Results: Thickness decrease was detected among the three groups, which showed statistically significant differences. CVT presented the lowest mean thickness of 380 µm (±72.3 µm), with teeth in the anterior region thicker overall than the first molar. Also, this group had the greatest variability. DVT recorded a mean of 429 µm (±67.2 µm), with more uniform anteroposterior thickness distribution. Meanwhile, PRT had less substantial thinning with a mean thickness of 467 µm (±81.7 µm). Conclusions: Thermoforming method influences the surface thickness of thermoformed CAs. The findings provide clinically relevant evidence to guide orthodontists in selecting thermoforming protocols that ensure aligner structural stability, thickness uniformity, and more predictable force delivery.