Analysis of orthodontic aligner biocompatibility: leachable compounds of different aligner materials.

Objectives: the aim of this study was to clarify the biocompatibility of different tooth repositioning splints (aligners). This included the characterization of the volatile fraction by headspace solid phase microextraction coupled to gas chromatography mass spectrometry, simulation of leachable organic compounds using artificial saliva and the quantitation of bisphenol A and bisphenol S after extraction.

Methods: Four different aligners were characterized in this study, these included two splints with novel shape memory properties: a printable aligner made of the resin Tera Harz TC-85 DAC (Graphy Inc., South Korea) and a self-manufactured SMP-Aligner consisting of the components polypropylene carbonate and thermoplastic polyurethane. The other two aligners were conventional, thermoformable aligners: CA® Pro Clear Aligner (Scheu Dental GmbH, Germany) and Erkodur-al (Erkodent Erich Kopp GmbH, Germany).

Results: no BPA was found in all four samples after 72 h. BPS was found in one Aligner. The most leachable compounds were found in the samples of the SMP- and the direct printed Graphy-Aligner. Most of the compound release occurred during the first 24 h.

Conclusions: the cumulative exposure effect from aligner wear should be carefully considered, although the current research indicates that the levels of leachable compounds are generally low.