Static and Dynamic Mechanical Properties of 3D-Printable Aligner Resins: An In Vitro Study with FTIR Chemical...

Area of Science:

• Biomaterials Science
• Dental Materials Science
• Orthodontic Technology

Background:

• Directly printed aligners are a rapidly advancing area in orthodontics.
• The mechanical behavior of resins used for these aligners is not fully understood.
• This study focuses on Class IIa-certified 3D-printable resins for orthodontic aligners.

Purpose of the Study:

• To compare the static flexural behavior of five different 3D-printable resins.
• To evaluate the short-term stress relaxation properties of these resins.
• To analyze the chemical profiles using FTIR for material characterization.

Main Methods:

• Five Class IIa-certified resins (TC-85, TA-28, DCA, Clear-A V2, Ortho Flex) were 3D printed into standardized bars.
• Static flexural tests were performed at 37 °C to determine flexural stress and modulus.
• Short-term stress relaxation was measured over 30 minutes at a fixed deflection.
• Fourier Transform Infrared Spectroscopy (FTIR) was used for chemical analysis.

Main Results:

• Significant mechanical differences were observed among the five resins.
• DCA exhibited the highest flexural stress and modulus, along with the best stiffness retention.
• Clear-A V2 showed good static stiffness but intermediate force retention, while TC-85 had high stiffness with significant relaxation.
• Ortho Flex demonstrated moderate static performance and stiffness retention, and TA-28 showed the highest degree of relaxation.

Conclusions:

• The mechanical properties of directly printed aligner resins are highly heterogeneous.
• Static flexural testing alone is insufficient to predict the short-term force stability of these resins.
• Relaxation metrics are crucial and should be considered alongside static testing for selecting resins for specific clinical applications in orthodontic aligners.