Maintaining the cleanliness of orthodontic aligners is crucial for oral hygiene and preserving the optical properties of aligners. In this randomized clinical trial, we compared the effectiveness of different cleaning methods for the maintenance of Invisalign clear aligners. Twelve adult patients received five aligners, each worn for 10 days. The aligners were divided based on the cleaning method: tooth brushing with whitening toothpaste, vinegar, Fittydent Super Cleansing Tablets, Invisalign cleaning crystals, and only water. Scanning electron microscopy (SEM) was used to detect surface morphology changes; color changes (ΔE) were evaluated using a spectrophotometer. Fourier transform infrared spectroscopy (FTIR) with a diamond hemisphere was used to study the aligners’ chemical compositions. Nanoindentation testing was used to assess changes in the elastic modulus. SEM confirmed the effectiveness of Invisalign cleaning crystals in maintaining cleanliness, revealing a surface similar to that of the control group with no adverse effects. Color stability analysis revealed significant ΔE value differences; whitening toothpaste had significantly lower ΔE values than water and Invisalign cleaning crystals. The elastic modulus and FTIR analyses indicated no significant differences between the cleaning methods. Therefore, Invisalign cleaning crystals and whitening toothpaste are safe for aligner maintenance, showing successful and aesthetically pleasing results.

Although guidelines recommend removing aligners before eating, many patients wear them while consuming food or beverages. Understanding the response of a material to high temperatures is crucial for predicting treatment outcomes. This study aimed to assess the effects of elevated beverage temperatures on the physical and mechanical properties of Invisalign clear aligners. Sixty Invisalign aligner specimens were thermocycled and divided into four groups. The specimens in the first and second groups were immersed in coffee and tea at 57 °C, respectively, whereas the third and fourth groups consisted of raw and thermocycled specimens, respectively. Each specimen from group 1 and 2 was immersed in each solution and subsequently in artificial saliva to simulate an intermittent drinking process, which was repeated 200 times, with each immersion lasting 2 s. The elastic moduli and hardnesses of the materials were measured and compared with those of the raw and thermocycled specimens. Statistically significant differences were observed in mean hardness and elastic modulus values (p < 0.0001 and p = 0.025, respectively). The mean hardness of the raw specimens was significantly higher than those of the other three groups (p < 0.0001 each), and the elastic modulus was lower than that of the coffee group (p = 0.018) but not statistically different from those of the thermocycling and tea groups (p = 0.413 and p = 0.309, respectively). Thermocycling and exposure to beverages at 57 °C significantly decreased the hardness of Invisalign clear aligners. The coffee-exposed group exhibited an increased elastic modulus, indicating greater rigidity. Investigating the effects of increased temperature on thermoplastic materials is crucial to ensuring the durability and safety of orthodontic treatment, which directly impacts patient care.