Facial asymmetry and chewing sides in twins

Authors

  • Elina V. Heikkinen a Research Unit of Oral Health Sciences, Department of Orthodontics, University of Oulu, Oulu, Finland
  • Ville Vuollo a Research Unit of Oral Health Sciences, Department of Orthodontics, University of Oulu, Oulu, Finland; b Medical Research Center Oulu, Oulu University Hospital, Oulu, Finland
  • Virpi Harila a Research Unit of Oral Health Sciences, Department of Orthodontics, University of Oulu, Oulu, Finland; b Medical Research Center Oulu, Oulu University Hospital, Oulu, Finland
  • Antanas Sidlauskas c Clinic of Orthodontics, Lithuanian University of Health Sciences, Kaunas, Lithuania
  • Tuomo Heikkinen a Research Unit of Oral Health Sciences, Department of Orthodontics, University of Oulu, Oulu, Finland; b Medical Research Center Oulu, Oulu University Hospital, Oulu, Finland

DOI:

https://doi.org/10.1080/00016357.2021.1985166

Keywords:

Facial asymmetry, 3D imaging, preferred chewing side, twin study

Abstract

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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Published

2022-04-03