Comparative evaluation of physicochemical and microbial adhesion on thermoplastic aligner sheets

Background The In-House clear aligner system has gained popularity with the advent of easily accessible In-House aligner fabrication setups. Presently, there are numerous commercially available thermoplastic aligner sheets on the market.Objectives To assess physicochemical properties, mechanical properties and microbial biofilm formation on three thermoformed commercially available clear aligner materials.Methodology Polyethylene Terephthalate Glycol, Polyethylene Terephthalate Copolymer and Polyurethane (PETG, PETC and PU) were tested for X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR-ATR), UV–vis spectroscopy contact angle and tensile strength. Further, the aligner biomaterials were tested with microbial assays to assess biofilm formation.Results PETC demonstrated the lowest degree of crystallinity by exhibiting the highest full-width at half maximum. FTIR spectra showed the presence of – NHCOO – groups in PU, with hydrogen bond; this may enhance surface polarity and promote the adsorption of pigments. DSC results indicated that all three thermoplastic aligner materials could withstand the rise in temperature generated during thermoforming and intraoral temperature variations. UV absorption spectra of PETG, PETC and PU showed a similar pattern of absorbance. Contact angle measurements indicated the hydrophobic nature of the materials. Additionally, mechanical testing demonstrated the stiffness of the material in the order of PU > PETG > PETC. During the microbial evaluation, PETC exhibited the least biofilm adhesion compared to both PETG and PU.Conclusions Based on the combined thermal, mechanical and biological performance, PETC may be regarded as a promising candidate for In-House aligner fabrication; however, further clinical validation is required.