title: Establishment of a new relationship between posed smile width and lower facial height: A cross-sectional study.
abstract: OBJECTIVE
  The present study is intended to add a new parameter that would be useful in orthodontic clinical evaluation, treatment planning, and determination of vertical dimension (at occlusion).
  
  
  METHODS
  Standardized videographic recording of 79 subjects during posed smile was captured. Each video was then cut into 30 photos using the free studio software. The widest commissure-to-commissure posed smile frame (posed smile width [SW]) was selected as one of 10 or more frames showing an identical smile. Lower third of the face is measured from subnasale to soft tissue menton using a digital vernier caliper. Two values were then compared. Ratio between lower facial height and posed SW was calculated.
  
  
  RESULTS
  The co-relation between smiling width and lower facial height was found to be statistically significant (P < 0.01). The ratio of lower facial height and smiling width was calculated as 1.0016 with a standard deviation (SD) = 0.04 in males and 1.0301 with an SD = 0.07 in females. The difference between the mean lower facial height in males and females was statistically significant with a t = 10.231 and P = 0.000. The difference between the mean smiling width in males and females was also statistically significant with a t = 5.653 and P = 0.000.
  
  
  CONCLUSIONS
  In class I subjects with pleasing appearance, normal facial proportions, normal overjet and overbite, and average Frankfort mandibular angle, the lower facial height (subnasale to soft tissue menton) is equal to posed SW.
authors.affiliation: Department of Orthodontics, Government Dental College, Kottayam, Kerala, India.
authors.forename: Aby
authors.initials: A
authors.lastname: Abraham
authors.affiliation: Department of Orthodontics, Government Dental College, Kottayam, Kerala, India.
authors.forename: Jinu
authors.initials: J
authors.lastname: George
authors.affiliation: Department of Orthodontics, Government Dental College, Kottayam, Kerala, India.
authors.forename: Elbe
authors.initials: E
authors.lastname: Peter
authors.affiliation: Department of Orthodontics, Government Dental College, Kottayam, Kerala, India.
authors.forename: Koshi
authors.initials: K
authors.lastname: Philip
authors.affiliation: Department of Prosthodontics, Government Dental College, Kottayam, Kerala, India.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Chankramath
authors.affiliation: Department of Endodontics, KMCT Dental College, Kozhikode, Kerala, India.
authors.forename: Dexton Antony
authors.initials: DA
authors.lastname: Johns
authors.affiliation: Department of Community Medicine, Government Medical College, Kottayam, Kerala, India.
authors.forename: Anitha
authors.initials: A
authors.lastname: Bhaskar
keywords: Lower face height; posed smile width; vertical facial proportion