Effect of elevated beverage temperatures on the physical and mechanical properties of invisalign clear aligners: an in-vitro simulation study

TL;DR

This study shows that hot beverages can reduce the hardness and change the rigidity of Invisalign aligners, potentially affecting orthodontic treatment.

Contribution

The study experimentally demonstrates how hot beverages impact the mechanical properties of Invisalign aligners.

Findings

Thermocycling and hot beverages significantly decreased the hardness of Invisalign aligners.

Coffee-exposed aligners showed increased rigidity with a higher elastic modulus.

Raw specimens had higher hardness than all other groups.

Abstract

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.

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