Validation of a double-semicircular notched configuration for mechanical testing of orthodontic thermoplastic aligner materials

Yuqing Zhang; Xiaozhuang Jin; Fabio Savoldi; Jianmin Han; Ray Kai Leung Su; Alex Fok; Jiang Chen; James Kit-Hon Tsoi

doi:10.1016/j.jmbbm.2024.106543

Validation of a double-semicircular notched configuration for mechanical testing of orthodontic thermoplastic aligner materials

J Mech Behav Biomed Mater. 2024 Apr 14:155:106543. doi: 10.1016/j.jmbbm.2024.106543. Online ahead of print.

Authors

Yuqing Zhang¹, Xiaozhuang Jin², Fabio Savoldi³, Jianmin Han⁴, Ray Kai Leung Su⁵, Alex Fok⁶, Jiang Chen⁷, James Kit-Hon Tsoi⁸

Affiliations

¹ Fujian Key Laboratory of Oral Diseases, School and Hospital of Stomatology, Fujian Medical University, PR China; Dental Materials Science, Applied Oral Sciences and Community Dental Care, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China.
² Dental Materials Science, Applied Oral Sciences and Community Dental Care, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China.
³ Orthodontics, Division of Paediatric Dentistry and Orthodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China.
⁴ Central Laboratory, Peking University School and Hospital of Stomatology, Beijing, PR China.
⁵ Department of Civil Engineering, Faculty of Engineering, The University of Hong Kong, Hong Kong, China.
⁶ Division of Biomaterials, Department of Restorative Sciences, School of Dentistry, University of Minnesota, Minneapolis, USA.
⁷ Fujian Key Laboratory of Oral Diseases, School and Hospital of Stomatology, Fujian Medical University, PR China. Electronic address: dentistjiang@126.com.
⁸ Dental Materials Science, Applied Oral Sciences and Community Dental Care, Faculty of Dentistry, The University of Hong Kong, Hong Kong, China. Electronic address: jkhtsoi@hku.hk.

PMID: 38636445
DOI: 10.1016/j.jmbbm.2024.106543

Abstract

The potential of using specimens with a double-semicircular-notched configuration for performing tensile tests of orthodontic thermoplastic aligner materials was explored. Unnotched and double-semicircular-notched specimens were loaded in tension using a universal testing machine to determine their tensile strength, while finite element analysis (FEA) and digital image correlation (DIC) were used to estimate stress and strain, respectively. The shape did affect the tensile strength, demonstrating the importance of unifying the form of the specimen. During the elastic phase under tension, double-semicircular-notched specimens showed similar behavior to unnotched specimens. However, great variance was observed in the strain patterns of the unnotched specimens, which exhibited greater chance of end-failure, while the strain patterns of the double-semicircular-notched specimens showed uniformity. Considerable agreement between the theoretical (FEA) and practical models (DIC) further confirmed the validity of the double-semicircular-notched models.

Keywords: Clear aligner; Digital image correlation; Finite element analysis; Tensile strength; Thermoplastic.