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Comparative evaluation of physical and mechanical properties of clear aligners – a systematic review

Evidence-Based Dentistry volume 25, page 53 (2024)Cite this article

Subjects

Abstract

Introduction

The clinical effectiveness of clear aligners depends on the material properties both physical and mechanical. The purpose of this systematic review is to evaluate the physical and mechanical properties of different clear aligner materials and changes in the same during and after intra-oral use.

Methods

Search was done in five electronic databases: Pubmed, Embase, Scopus, Web of Science and Ovid individually by two reviewers. In vivo, Ex vivo and In vitro studies that evaluated the physical and mechanical properties of clear aligner materials were selected. The risk of bias assessment was performed using a modified Cochrane risk of bias tool.

Results

From the 24 articles selected, 19 evaluated a single physical property and 23 articles evaluated a single mechanical property of clear aligner materials. All domains in the risk of bias assessment showed low risk of bias except for ‘blinding of outcome’ which was unclear in almost all the selected studies. Properties such as hardness, optical properties, stiffness, and yield strength were found to be different for different clear aligner materials and were found to change with thermoforming, with intra-oral aging, and in simulated intraoral conditions. Due to heterogenicity in the parameters used to assess physical or mechanical properties a meta-analysis could not be done.

Conclusions

Properties like hardness, color, stiffness, stress relaxation and creep behavior were different for various clear aligner materials and were found to deteriorate with thermoforming and intra-oral aging. Polyurethane-based materials have a higher level of hardness and stiffness but exhibit increased creep and stress relaxation properties.

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CRD42021269597.

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Data availability

The data of this systematic review will be available on request to any one of the authors.

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Funding

Funding

The project was self-funded.

Author information

Authors and Affiliations

  1. Department of Orthodontics, Sri Ramchandra Institute of Higher Education and Research, PIN- 600116, Chennai, India

    Bhadrinath Srinivasan & Sridevi Padmanabhan

  2. Department of Applied Mechanics, Indian Institute of Technology (Madras), 600036, Chennai, India

    Sivakumar Srinivasan

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  1. Bhadrinath Srinivasan
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  2. Sridevi Padmanabhan
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  3. Sivakumar Srinivasan
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Contributions

BS: Conceptualization, methodology,Investigation, Resources, Datal Analysis, Writing the Original draft. SS: Conceptualization, Formal Analysis, Review of the draft and approving the final version. SP: Conceptualization, Methodology, Data Analysis, Review of the draft and approving the final version.

Corresponding author

Correspondence to Sridevi Padmanabhan.

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Srinivasan, B., Padmanabhan, S. & Srinivasan, S. Comparative evaluation of physical and mechanical properties of clear aligners – a systematic review. Evid Based Dent 25, 53 (2024). https://doi.org/10.1038/s41432-023-00937-w

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