@article {16396,
	title = {The spontaneous smile in dynamic motion.},
	journal = {Am J Orthod Dentofacial Orthop},
	volume = {128},
	year = {2005},
	month = {2005 Jul},
	pages = {8-15},
	abstract = {INTRODUCTION: The purpose of this study was to record and analyze the dynamic nature of spontaneous smiles.

METHODS: Fifteen children (9 girls and 6 boys; average age, 10.5 years) were filmed with a hidden camera while they watched a funny cartoon video. Spontaneous smiles were recorded, and the video frames were digitized. Time-graphs of the measurements were constructed, and plots of the movement of the mouth points were drawn.

RESULTS: Facial measurements showed that the upper lip elevated by 28\%, relative to the rest position, and the mouth increased in width by 27\%. The corners of the mouth moved laterally and superiorly at an angle of approximately 47 degrees . Time analysis showed that the smiles developed in a staged fashion. The first stage (attack phase) was the shortest, lasting an average 500 ms. It was followed by a sustaining phase that included waxing and waning. The smile ended with a fade-out stage. The second and third stages were of variable duration and could be interrupted by the attack phase of a subsequent smile.

CONCLUSIONS: The dynamics of the spontaneous smile and the findings of this study raise concerns about the validity of a single photographic capture for esthetic assessment and treatment planning.},
	keywords = {Adolescent, Child, Facial Muscles, Female, Humans, Image Processing, Computer-Assisted, Lip, Male, Mouth, Ocular Physiological Phenomena, Photography, Smiling, Time Factors, Videotape Recording},
	issn = {0889-5406},
	doi = {10.1016/j.ajodo.2004.03.042},
	author = {Tarantili, Vicky V and Halazonetis, Demetrios J and Spyropoulos, Meropi N}
}
