Comparison of Optical Properties of Clear Aligners Before and After In-vivo Aging

Introduction: There is a rising demand for clear aligners among orthodontic patients and after the expiry of Invisalign patent many indigenous aligners have been introduced in several part of the globe including India. The major advantage of the aligners is its invisibility which is attributed to its unique optical properties. The optical properties vary between different aligners and any changes in the optical properties during the clinical use is an important factor to be considered. Aim: To evaluate and compare the optical properties of three different types of indigenous clear orthodontic aligners before and after in-vivo aging. Materials and Methods: A prospective clinical study was conducted in the Department of Orthodontics and Dentofacial Orthopedics, SRM Dental College, Chennai, Tamil Nadu, India, August 2021 to December 2021. Total 36 volunteers participated in the study and were divided into three study groups. In group A subjects had Clearbite aligners (JJ Orthodontics Pvt. Ltd, Thrissur, Kerala), group B had Dentcare clear aligners (Dent Care Dental Lab Pvt. Ltd. Ernakulum, Kerala) and group C had Smile aligners (smile aligners Inc. Mumbai, Maharashtra). Polyvinyl siloxane impression of the maxillary arch was obtained and sent for the fabrication of two sets of clear aligners. One set of aligners were used to measure absorbance and transmittance before invivo aging and another set after an intraoral use of 14 days. The measurement of absorbance and transmittance were made at the wavelength range of 400-700 nm using a Shimadzu UV-3600i Plus UV-Vis-NIR spectrophotometer. Intergroup and intragroup comparisons were done using Independent sample t-test and One way ANOVA. Results: In all the three groups of aligners evaluated, an increase in the absorbance values was noted at all the wavelengths after in-vivo aging but the increase was not statistically significant (p-value >0.05). Transmittance values of group A samples reduced after in-vivo aging but not significantly, whereas group B values reduced significantly between 400-440 nm (p-value <0.05) and group C values reduced significantly between 400-460 nm and 680-700 nm (p-value <0.05). Intergroup comparison of the mean absorbance and transmittance values of the group A, B and C samples before and after in-vivo aging showed no significant difference at all wavelengths (p-value >0.05). Conclusion: The absorbance and transmittance values of all the three indigenous aligners did not change significantly after invivo aging at most of the evaluated wavelengths.