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

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

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 1 8-30 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.

Original languageEnglish
Pages (from-to)132-137
Number of pages6
JournalAustralian Orthodontic Journal
Volume31
Issue number2
Publication statusPublished - Nov 2015

Fingerprint

Smiling
Facial Asymmetry
Incisor
Orthodontics
Photogrammetry
Malocclusion
Cleft Lip
Cleft Palate
Therapeutics
Outcome Assessment (Health Care)

Keywords

  • Adolescent
  • Adult
  • Anatomic Landmarks
  • Chin
  • Facial Asymmetry
  • Female
  • Forehead
  • Humans
  • Image Processing, Computer-Assisted
  • Imaging, Three-Dimensional
  • Lip
  • Male
  • Malocclusion, Angle Class I
  • Nose
  • Observer Variation
  • Orbit
  • Photogrammetry
  • Reproducibility of Results
  • Smiling
  • Young Adult

Cite this

Darby, L. J., Millett, D. T., Kelly, N., McIntyre, G. T., & Cronin, M. S. (2015). The effect of smiling on facial asymmetry in adults: a 3D evaluation. Australian Orthodontic Journal, 31(2), 132-137.
Darby, Laura J. ; Millett, Declan T. ; Kelly, Niamh ; McIntyre, Grant T. ; Cronin, Michael S. / The effect of smiling on facial asymmetry in adults : a 3D evaluation. In: Australian Orthodontic Journal. 2015 ; Vol. 31, No. 2. pp. 132-137.
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abstract = "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 1 8-30 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.",
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Darby, LJ, Millett, DT, Kelly, N, McIntyre, GT & Cronin, MS 2015, 'The effect of smiling on facial asymmetry in adults: a 3D evaluation', Australian Orthodontic Journal, vol. 31, no. 2, pp. 132-137.

The effect of smiling on facial asymmetry in adults : a 3D evaluation. / Darby, Laura J.; Millett, Declan T.; Kelly, Niamh; McIntyre, Grant T.; Cronin, Michael S.

In: Australian Orthodontic Journal, Vol. 31, No. 2, 11.2015, p. 132-137.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The effect of smiling on facial asymmetry in adults

T2 - a 3D evaluation

AU - Darby, Laura J.

AU - Millett, Declan T.

AU - Kelly, Niamh

AU - McIntyre, Grant T.

AU - Cronin, Michael S.

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N2 - 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 1 8-30 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.

AB - 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 1 8-30 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.

KW - Adolescent

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KW - Image Processing, Computer-Assisted

KW - Imaging, Three-Dimensional

KW - Lip

KW - Male

KW - Malocclusion, Angle Class I

KW - Nose

KW - Observer Variation

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KW - Reproducibility of Results

KW - Smiling

KW - Young Adult

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JF - Australian Orthodontic Journal

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Darby LJ, Millett DT, Kelly N, McIntyre GT, Cronin MS. The effect of smiling on facial asymmetry in adults: a 3D evaluation. Australian Orthodontic Journal. 2015 Nov;31(2):132-137.