K. Dalaie, Katayoun Talebi Rafsanjan, Hanieh Nojehdehian, Zahra Namazi
{"title":"Physical and chemical changes of clear aligners after thermoforming and intraoral exposure","authors":"K. Dalaie, Katayoun Talebi Rafsanjan, Hanieh Nojehdehian, Zahra Namazi","doi":"10.25259/apos_169_2023","DOIUrl":null,"url":null,"abstract":"\n\nThis study assessed the physical and chemical changes of clear aligners after thermoforming and intraoral exposure.\n\n\n\nThis ex vivo study evaluated raw sheets, thermoformed sheets, and aligners used for 2 weeks from two commercial brands of Erkodur and Shinseki (n = 8 in each group). The surface hardness (by the Vickers hardness test), thickness (by a digital caliper), and glass transition temperature (Tg) (by differential scanning calorimetry) of the specimens were measured, and they underwent X-ray diffraction (XRD) to assess their degree of crystallinity and attenuated total reflectance-Fourier-transform infrared spectroscopy (ATR-FTIR) for analysis of their molecular composition. Data were analyzed by one-sample, paired and independent t-tests, and Mann–Whitney U and Wilcoxon signed-rank tests (alpha = 0.05).\n\n\n\nThe XRD and ATR-FTIR spectra of Erkodur and Shinseki aligners matched those of polyethylene terephthalate glycol polymer and did not change after thermoforming or intraoral exposure. Unlike intraoral exposure (P > 0.05), thermoforming significantly decreased the hardness of both brands of aligners (P < 0.05). Intraoral exposure significantly decreased the thickness of Erkodur aligners at some points and significantly increased the thickness of Shinseki aligners (P < 0.05). Thermoforming significantly decreased the Tg of both brands of aligners (P < 0.05). Intraoral exposure significantly decreased the Tg of Erkodur and increased the Tg of Shinseki aligners (P = 0.000).\n\n\n\nErkodur and Shinseki aligners showed high chemical and structural stability after thermoforming and 2 weeks of intraoral exposure. However, thermoforming affected the thermal and physical properties of both brands of aligners. Erkodur aligners had higher dimensional stability than Shinseki aligners.\n","PeriodicalId":42593,"journal":{"name":"APOS Trends in Orthodontics","volume":null,"pages":null},"PeriodicalIF":0.5000,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"APOS Trends in Orthodontics","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.25259/apos_169_2023","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"DENTISTRY, ORAL SURGERY & MEDICINE","Score":null,"Total":0}
引用次数: 0
Abstract
This study assessed the physical and chemical changes of clear aligners after thermoforming and intraoral exposure.
This ex vivo study evaluated raw sheets, thermoformed sheets, and aligners used for 2 weeks from two commercial brands of Erkodur and Shinseki (n = 8 in each group). The surface hardness (by the Vickers hardness test), thickness (by a digital caliper), and glass transition temperature (Tg) (by differential scanning calorimetry) of the specimens were measured, and they underwent X-ray diffraction (XRD) to assess their degree of crystallinity and attenuated total reflectance-Fourier-transform infrared spectroscopy (ATR-FTIR) for analysis of their molecular composition. Data were analyzed by one-sample, paired and independent t-tests, and Mann–Whitney U and Wilcoxon signed-rank tests (alpha = 0.05).
The XRD and ATR-FTIR spectra of Erkodur and Shinseki aligners matched those of polyethylene terephthalate glycol polymer and did not change after thermoforming or intraoral exposure. Unlike intraoral exposure (P > 0.05), thermoforming significantly decreased the hardness of both brands of aligners (P < 0.05). Intraoral exposure significantly decreased the thickness of Erkodur aligners at some points and significantly increased the thickness of Shinseki aligners (P < 0.05). Thermoforming significantly decreased the Tg of both brands of aligners (P < 0.05). Intraoral exposure significantly decreased the Tg of Erkodur and increased the Tg of Shinseki aligners (P = 0.000).
Erkodur and Shinseki aligners showed high chemical and structural stability after thermoforming and 2 weeks of intraoral exposure. However, thermoforming affected the thermal and physical properties of both brands of aligners. Erkodur aligners had higher dimensional stability than Shinseki aligners.