Color Stability, Chemico-Physical and Optical Features of the Most Common PETG and PU Based Orthodontic Aligners for Clear Aligner Therapy

Abstract

It is difficult to find research papers collecting comparative results about characterization studies of clear aligners. Therefore, the aim of this paper is to provide the first comparative analysis of most commercial clear aligners, in terms of their stability towards intra-oral staining agents, their physicochemical and optical properties, as well as their water absorption behavior. Five types of aligners, characterized by different techniques, are considered: Erkodur, Essix Plastic, Ghost Aligner, Zendura, and Invisalign. The obtained results show that clear aligners are made up of PETG, semi rigid PU, and a mixture of PU and PETG, with different degrees of crystallinity which affect the transparency of each aligner. In particular, the PETG-based materials reveal the highest value of short-range order and the highest properties in terms of transparency in the visible range. After 14 days of immersion into red wine and coffee, PETG and PU-based aligners reveal a perceivable change in color (NBS values from 1.5 to 3), corresponding to a loss of transparency due to the deposition of impurities on the surface. These results are particularly marked for Invisalign, showing changes towards other colors (NBS up to 35), probably due to the thermoforming process which led to the formation of a wrinkled surface entrapping the impurities.

Polyvinylidene fluoride/polysulfone/air plasma defected hexagonal boron nitride emerging nano blends for electrostatic dissipation

“…Peaks observed at 791, 1146, and 1588 cm −1 confirmed the presence of PSF in the polymer system. These peaks were attributed to asymmetric CSC, COC and aromatic chain vibrations of PSF, respectively 50,51 . Presence of h‐BN in polymer host system was confirmed by peak appeared at 1378 cm −1 correlated to the E 2 g phonon mode 52,53 .…”

The Effects of Staining and Cleaning on the Color and Light Transmittance Changes of a Copolyester Retainer Material with Different Surface Textures

“…Since clear retainer material interactions with the oral environment can occur, resulting in plaque and calculus buildup along with bacteria buildup and retention, clear retainers must be maintained to mitigate loss of their light transmittance and maintain material integrity [ 5 , 6 , 7 , 8 , 21 ]. Color stability can also be affected by ultraviolet radiation, mouthwash, and various beverages [ 5 , 6 , 7 , 8 , 22 ]. Additionally, in the United States, 50% of Americans over 18 years old drink coffee, and coffee drinkers consume an average of three cups of coffee per day [ 23 ].…”

Degree of cure of orthodontic composite attachments underneath aligners

“…The most popular thermoplastic materials currently used for the production of clear aligners are polyester‐based: polyethylene terephthalate glycol modified (PET‐G); and polyester urethane [13]. These materials present a very low crystalline order [14], which is inversely related to the degree of transparency [15]. The PET‐G‐based aligners have been demonstrated to have lower light absorption values than the polyester urethane aligners, probably owing to differences in the chemical composition or the different thermoforming procedures applied [14].…”

“…These materials present a very low crystalline order [14], which is inversely related to the degree of transparency [15]. The PET‐G‐based aligners have been demonstrated to have lower light absorption values than the polyester urethane aligners, probably owing to differences in the chemical composition or the different thermoforming procedures applied [14]. Moreover, it has been shown that rigid and chemically inert polyurethane aligners of 0.75 mm thickness have significantly higher transmittance and lower absorbance than either PET‐G‐based aligners of 0.8 mm thickness or polyester urethane aligners of 0.75 mm thickness [16].…”