Comparison of dimensional accuracy between direct-printed and thermoformed aligners

Area of Science:

• Dental Materials Science
• Orthodontics
• Biomedical Engineering

Background:

• Orthodontic aligners are widely used for teeth straightening.
• Traditional aligner manufacturing involves thermoforming plastic sheets over molds.
• Advancements in 3D printing offer potential for direct aligner fabrication.

Purpose of the Study:

• To evaluate and compare the dimensional accuracy of thermoformed aligners versus direct-printed aligners.
• To assess the trueness and precision of different aligner manufacturing methods.

Main Methods:

• Three types of aligners were manufactured from a single Standard Tessellation Language (STL) file: thermoformed (Zendura FLX™, Essix ACE™) and direct-printed (Tera Harz™).
• Dimensional accuracy was assessed by superimposing scanned aligner models onto the reference STL file using best-fit alignment.
• Measurements were taken at nine anatomical landmarks to quantify discrepancies.

Main Results:

• Direct-printed aligners exhibited a lower range of mean absolute discrepancies (0.079 ± 0.054 mm to 0.224 ± 0.041 mm).
• Root mean square (RMS) values, indicating overall trueness, were lowest for direct-printed aligners (0.140 ± 0.020 mm).
• Thermoformed aligners showed higher discrepancies, particularly Essix ACE™ (0.188 ± 0.271 mm to 0.457 ± 0.350 mm).

Conclusions:

• Direct-printed aligners demonstrated superior trueness and precision compared to both types of thermoformed aligners.
• 3D printing technology shows promise for producing highly accurate orthodontic aligners.
• This advancement could lead to improved treatment outcomes in clear aligner therapy.