Impact of Hot and Cold Drinks on Tensile Strength and Surface Roughness of Thermoformed Clear Aligners: An in vitro Study

Objective: To find the influence of hot and cold beverages on the tensile strength and surface roughness of thermoformed clear aligners. Methods: Clear aligner foil (single-layered) and Clear aligner pro+ (multi-layered) sheets were thermoformed on round models using Biostar machine, and 60 rectangular samples (30n per material) were prepared for tensile testing according to the standard test method for tensile properties of thin plastic sheeting ASTM D882-18 standard; the 30 specimens were divided into six groups: control groups, coffee at 55 55 degrees Celsius (℃), distilled water 55℃, cola 5℃, distilled water 5℃ and distilled water at 37℃ for each material. The ultimate tensile strength of all groups was measured using a universal testing machine, and the surface topography of 30 samples was examined by using atomic force microscopy before and after immersion to find alterations in the surface roughness. The data were evaluated statistically by using one-way analysis of variance (one-way ANOVA) (P < 0.05), followed by Tukey's post hoc for ultimate tensile strength, and Paired t-test (P < 0.05) was used for comparing surface roughness before and after immersion for each material. Results: The single-layered aligners had significantly higher tensile strength before and after aging than the multi-layered aligners; no statistically significant differences were found between groups within the same material; both materials showed increased surface roughness in the solutions after aging. Conclusions: The ultimate tensile strength of the aligners remains unaffected by the consumption of hot and cold drinks. However, the surface roughness of the clear aligners deteriorates when exposed to these drinks.