The effect of smiling on facial asymmetry in adults: a 3D evaluation


Share / Export Citation / Email / Print / Text size:

Australasian Orthodontic Journal

Australian Society of Orthodontists

Subject: Dentistry, Orthodontics & Medicine


ISSN: 2207-7472
eISSN: 2207-7480





Volume / Issue / page

Volume 37 (2021)
Volume 36 (2020)
Volume 35 (2019)
Volume 34 (2018)
Volume 33 (2017)
Volume 32 (2016)
Volume 31 (2015)
Related articles

VOLUME 31 , ISSUE 2 (November 2015) > List of articles

The effect of smiling on facial asymmetry in adults: a 3D evaluation

Laura J. Darby / Declan T. Millett * / Niamh Kelly / Grant T. McIntyre / Michael S. Cronin

Citation Information : Australasian Orthodontic Journal. Volume 31, Issue 2, Pages 132-137, DOI:

License : (CC BY 4.0)

Published Online: 15-August-2021



Background/aims: Mild resting facial asymmetry exists in clinically symmetrical faces, but the effect of smiling on the magnitude of overall facial asymmetry in adults has not been assessed. The aim of the present study was to use stereophotogrammetry to quantify the effect of smiling on overall facial asymmetry in Caucasian adults who presented with Class I incisor relationships and no history of orthodontic treatment.

Methods: Twenty male and 20 female Caucasians aged 18–30 years with no history of orthodontic treatment, a clinically symmetrical face and a Class I incisor relationship had 3D stereophotogrammetric images captured at rest and on natural and maximal smile (T1). The images were repeated 2–4 weeks later (T2) to assess expression reproducibility. Overall facial asymmetry scores were produced from 27 landmarks using partial Ordinary Procrustes Analysis (OPA) and assessed by an Analysis of Covariance (ANCOVA) model. A random sample of the images was re-examined two months later to calculate intraobserver landmark reproducibility.

Results: Mean landmark error was low (0.41 ± 0.07 mm). Mean overall facial asymmetry scores were not significantly gender different (p = 0.5300); therefore, the male and female data were pooled. Mean overall facial asymmetry scores for maximal (0.91 ± 0.16) and natural smile (0.88 ± 0.18) were higher than at rest (0.80 ± 0.17) (p < 0.0001) and were reproducible across (T1–T2) sessions (p = 0.3204).

Conclusions/implications: Overall 3D facial asymmetry scores for the sampled Caucasian adults with clinically symmetrical faces increased in magnitude from rest to natural and to maximal smile. Clinicians should assess overall facial asymmetry at rest and on natural and maximal smile at baseline, during treatment and as part of a core outcome assessment, particularly for cases with unilateral posterior crossbite, unilateral cleft lip and palate or skeletal asymmetry.

Content not available PDF Share



1. Zaidel DW, Cohen JA. The face, beauty, and symmetry: perceiving asymmetry in beautiful faces. Int J Neurosci 2005;115:1165-73.

2. Meyer-Marcotty P, Stellzig-Eisenhauer A, Bareis U, Hartmann J, Kochel J. Three-dimensional perception of facial asymmetry. Eur J Orthod 2011;33:647-53.

3. Naini FB, Donaldson AN, McDonald F, Cobourne MT. Assessing the influence of asymmetry affecting the mandible and chin point on perceived attractiveness in the orthognathic patient, clinician, and layperson. J Oral Maxillofac Surg 2012;70:192-206.

4. Haraguchi S, Iguchi Y, Takada K. Asymmetry of the face in orthodontic patients. Angle Orthod 2008;78:421-6.

5. Ferrario VF, Sforza C, Miani A Jr, Serrao G. A three-dimensional evaluation of human facial asymmetry. J Anat 1995;186:103-10.

6. Djordjevic J, Pirttiniemi P, Harila V, Heikkinen T, Toma AM, Zhurov AI et al. Three-dimensional longitudinal assessment of facial symmetry in adolescents. Eur J Orthod 2013;35:143-51.

7. Ercan I, Ozdemir ST, Etoz A, Sigirli D, Tubbs RS, Loukas M et al. Facial asymmetry in young healthy subjects evaluated by statistical shape analysis. J Anat 2008;213:663-9.

8. Hajeer MY, Ayoub AF, Millett DT. Three-dimensional assessment of facial soft-tissue asymmetry before and after orthognathic surgery. Br J Oral Maxillofac Surg 2004;42:396-404.

9. Ekman P, Hager JC, Friesen WV. The symmetry of emotional and deliberate facial actions. Psychophysiology 1981;18:101-6.

10. Okamoto H, Haraguchi S, Takada K. Laterality of asymmetry in movements of the corners of the mouth during voluntary smile. Angle Orthod 2010;80:223-9.

11. Houstis O, Kiliaridis S. Gender and age differences in facial expressions. Eur J Orthod 2009;31:459-66.

12. Coulson SE, Croxson GR, Gilleard WL. Three-dimensional quantification of the symmetry of normal facial movement. Otol Neurotol 2002;23:999-1002.

13. Keim RG, Gottlieb EL, Vogels DS 3rd, Vogels PB. 2014 JCO study of orthodontic diagnosis and treatment procedures, Part1: results and trends. J Clin Orthod 2014;48:607-30.

14. Kau CH, Richmond S, Zhurov A, Ovsenik M, Tawfik W, Borbely P et al. Use of 3-dimensional surface acquisition to study facial morphology in 5 populations. Am J Orthod Dentofac Orthop 2010;137:S56.e1-9.

15. Zachrisson BU. Esthetic factors involved in anterior tooth display and the smile: vertical dimension. J Clin Orthod 1998;32:432-45.

16. McIntyre GT, Mossey PA. Size and shape measurement in contemporary cephalometrics. Eur J Orthod 2003;25:231-42.

17. Weinberg SM, Scott NM, Neiswanger K, Brandon CA, Marazita ML. Digital three-dimensional photogrammetry: evaluation of anthropometric precision and accuracy using a Genex 3D camera system. Cleft Palate Craniofac J 2004;41:507-18.

18. Sawyer AR, See M, Nduka C. Assessment of the reproducibility of facial expressions with 3D stereophotogrammetry. Otolaryngol Head Neck Surg 2009;140:76-81.

19. Verzé L, Bianchi FA, Schellino E, Ramieri G. Soft tissue changes after orthodontic surgical correction of jaws asymmetry evaluated by three-dimensional surface laser scanner. J Craniofac Surg 2012;23:1448-52.

20. Sarver DM, Ackerman MB. Dynamic smile visualization and quantification: Part 2. Smile analysis and treatment strategies. Am J Orthod Dentofacial Orthop 2003;124:116-27.

21. Williamson PR, Altman DG, Blazeby JM, Clarke M, Devane D, Gargon E et al. Developing core outcome sets for clinical trials: issues to consider. Trials 2012;13:132.