Unveiling the resilience of aligner materials: Comparative analysis of mechanical properties across thermoforming and saliva exposure

• Author Details:   
• Mridula Trehan
• A Annie Maxwell ^*
• Anurag Tiwari
• Ashish Kumar
• Anamika Jakhar

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Background: Clear aligners have become a preferred choice in orthodontics, offering aesthetic and functional advantages over traditional fixed appliances. However, their clinical performance depends on the mechanical properties of the materials, which can degrade during thermoforming and intraoral exposure.

Objective: To evaluate and compare the mechanical properties of two aligner materials—CA PRO+ and ERKODUR AL—under three conditions: pre-thermoforming, post-thermoforming, and post-saliva exposure.

Materials and Methods: An in-vitro study was conducted using 96 samples, equally divided between CA PRO+ and ERKODUR AL. Samples were tested for tensile yield stress and elastic modulus before thermoforming, after thermoforming, and following seven days of saliva exposure at 37°C. Testing was performed using an INSTRON Universal Testing Machine per ASTM D638 standards. Statistical analysis included one-way ANOVA and Tukey’s HSD for post-hoc comparisons.

Results: Both materials exhibited significant reductions in tensile yield stress and elastic modulus across the three conditions (p < 0.05). CA PRO+ showed a total tensile yield stress reduction of 15.9% (from 50.24 MPa pre-thermoforming to 42.25 MPa post-saliva exposure), while ERKODUR AL showed a similar decline of 15.9% (from 52.44 MPa to 44.05 MPa). The elastic modulus decreased by approximately 16% for both materials during the same period.

Conclusion: Thermoforming and intraoral simulation significantly degrade the mechanical properties of aligner materials, potentially impacting their clinical performance. Material selection and optimization of thermoforming processes are crucial to improving the durability and efficacy of aligners.