University of Oulu

Elina V. Heikkinen, Ville Vuollo, Virpi Harila, Antanas Sidlauskas & Tuomo Heikkinen (2022) Facial asymmetry and chewing sides in twins, Acta Odontologica Scandinavica, 80:3, 197-202, DOI: 10.1080/00016357.2021.1985166

Facial asymmetry and chewing sides in twins

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Author: Heikkinen, Elina V.1; Vuollo, Ville1,2; Harila, Virpi1,2;
Organizations: 1Research Unit of Oral Health Sciences, Department of Orthodontics, University of Oulu, Oulu, Finland
2Medical Research Center Oulu, Oulu University Hospital, Oulu, Finland
3Clinic of Orthodontics, Lithuanian University of Health Sciences, Kaunas, Lithuania
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.1 MB)
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Language: English
Published: Informa, 2022
Publish Date: 2021-11-22


Objective: To resolve how the preferred chewing side (PCS) affects facial asymmetry in twins, whether there are differences between monozygotic (MZ) and dizygotic (DZ) twins, and whether the twins with PCS have more asymmetric faces compared to symmetrically chewing twins.

Material and methods: The study included 106 Lithuanian twin pairs of the same sex, 59 MZ and 47 DZ pairs. The data were analysed from facial 3D images and manually added landmarks. 3D images were analysed by Rapidform2006 software and statistical analyses were done by using the R software environment version 4.1.0.

Results: The contralateral effect of PCS and larger chin side was dominant among right and non-right side chewing twins. Being female increased the whole face symmetry.

Conclusion: The volume of the chin becomes larger on the side opposite to the twins’ habitual chewing side. As the results are quite similar in both twin types, functional factors are more prominent than heredity.

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Series: Acta odontologica Scandinavica
ISSN: 0001-6357
ISSN-E: 1502-3850
ISSN-L: 0001-6357
Volume: 80
Issue: 3
Pages: 197 - 202
DOI: 10.1080/00016357.2021.1985166
Type of Publication: A1 Journal article – refereed
Field of Science: 313 Dentistry
Funding: This work was supported by the EOS (European Orthodontic Society) grant.
Copyright information: © 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of Acta Odontologica Scandinavica Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.