Abstract
Invisible orthodontic aligners (IOAs) have been introduced in the orthodontic field as an innovative alternative for fixed brackets, in relation to their ability to be easily inserted/removed from the oral cavity without affecting the chewing ability and the aesthetic of the patients. The paper provides a complete physicochemical and mechanical characterization of thermoplastic materials in the form of disks used for commercial IOAs. A wide palette of specific techniques is considered, from tensile tests and dynamic-mechanical analysis, to X-Ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transformation infrared spectroscopy (FTIR-ATR) analyses and water absorption tests. The disks are investigated before and after immersion into staining beverages (red wine, coffee, nicotine and artificial saliva), in terms of colour variations, transparency, and microscopic surface modifications by means of colorimetry, UV-VIS absorbance and scanning electron microscopy (SEM). Among all the samples, polyurethane (PU) exhibited the highest crystallinity and the highest values of mechanical and thermal resistance, while the poly(ethylene terephthalate)-glycol (PETG) samples presented better transparency and less ability to absorb water. Moreover, red wine and coffee give noticeable colour variations after 14 days of immersion, together with a slight reduction of transparency.
Highlights
With an increase in the demand for adult orthodontics, the demand for invisible orthodontic appliances (IOAs) that can replace the commonly used metal brackets is increasing [1]
It is evident that EK, EP and GA samples have comparable X-Ray diffraction (XRD) patterns, and this result confirms
This paper aims to provide an overview on the physicochemical and mechanical characterization This paper aims to provide an overview on the invisible physicochemical mechanical characterization of thermoplastic disks used to realise orthodontic aligners.and
Summary
With an increase in the demand for adult orthodontics, the demand for invisible orthodontic appliances (IOAs) that can replace the commonly used metal brackets is increasing [1]. Conventional orthodontic brackets frequently increase the risk of carious lesions and cause gingivitis and periodontitis because of surrounding plaque accumulation [2]. This results in impaired oral health in addition to poor aesthetics during orthodontic treatment [3]. To remedy this problem, invisible orthodontic aligners (IOAs) have been introduced as alternatives for fixed brackets and wires. Considering the ever-growing attention in the dentistry field towards the use of invisible orthodontic aligners, further research on the thermoplastic materials used to manufacture aligners is necessary
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