Facial asymmetry assessment in adults using three-dimensional surface imaging.
BACKGROUND
The use of three-dimensional (3D) surface imaging is becoming more popular and accepted in the fields of Medicine and Dentistry. The present study aims to develop a technique to automatically localise and quantify soft-tissue asymmetry in adults using 3D facial scans. This may be applied as a diagnostic tool to monitor growth and dynamic changes and to evaluate treatment outcomes.


METHODS
3D facial surface data were captured from 55 adults comprising 28 symmetrical faces and 27 asymmetrical faces using a 3dMDface system. A landmark-independent method, which compared the original and the mirrored 3D facial data, was developed to quantify the asymmetry. A Weibull distribution-based probabilistic model was generated from the root-mean-square (RMS) error data for the symmetrical group to designate a level of asymmetry which represented a normal range.


RESULTS
Statistically significant (p < 0.0001) differences in the RMS error values were found when comparing symmetrical with asymmetrical groups and a similarly significant difference was identified between the lower and the upper face of the asymmetrical group.


CONCLUSIONS
The proposed 3D imaging-based method of identifying and quantifying facial soft-tissue asymmetry was fast and effective. The Weibull distribution-based comparison of a person's asymmetry with respect to a large sample of symmetrical faces may also be used to evaluate growth, soft-tissue compensations and surgical outcomes.
Department of Orthodontics, School of Dentistry, The University of Western Australia, 35, Stirling Hwy, Crawley, Western Australia, 6009, Australia. arts_patel@hotmail.com.
Arti
A
Patel
Department of Orthodontics, School of Dentistry, The University of Western Australia, 35, Stirling Hwy, Crawley, Western Australia, 6009, Australia. syed.islam@uwa.edu.au.
Syed Mohammed Shamsul
SM
Islam
School of Mathematics and Statistics, The University of Western Australia, 35, Stirling Hwy, Crawley, Western Australia, 6009, Australia. kevin.murray@uwa.edu.au.
Kevin
K
Murray
Department of Orthodontics, School of Dentistry, The University of Western Australia, 35, Stirling Hwy, Crawley, Western Australia, 6009, Australia. mithran.goonewardene@uwa.edu.au.
Mithran S
MS
Goonewardene
D000328:Adult; D005145:Face / Q000000981:diagnostic imaging; D005146:Facial Asymmetry / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008311:Malocclusion, Angle Class I / Q000000981:diagnostic imaging; D008312:Malocclusion, Angle Class II / Q000000981:diagnostic imaging; D008313:Malocclusion, Angle Class III / Q000000981:diagnostic imaging; D061848:Optical Imaging / Q000379:methods; D010780:Photogrammetry / Q000379:methods; D010781:Photography / Q000379:methods; D011336:Probability; D012189:Retrospective Studies; D055815:Young Adult
3D surface imaging; Facial aesthetics; Facial soft-tissue asymmetry; Landmark-independent analysis; RMS distance measure; Weibull distribution