Effects of Different Head Positioning Methods on Facial Soft Tissue Analysis Using Stereophotogrammetry

Abstract

The purpose of this study was to compare the sagittal tilt of the head in different head positioning techniques using an inclinometer and facial stereophotogrammetric measurements. The study was carried out in 45 participants (26 female, 19 male). Participants' head positioning was obtained with dynamic walking, Frankfort horizontal plane (FHP'), self-balance plus mirror, and subjective photographic positioning methods. All pitch values were recorded by an inclinometer and stereophotogrammetric images were obtained. Facial analysis included distances of the glabella (G'), pronasale (Pn), soft tissue A point (A'), upper lip (Ls), lower lip (Li), soft tissue B point (B)', and soft tissue pogonion (Pog') to the true vertical line (TVL) and face height and lip length measurements. Participants' head positions were observed to be more forward in the FHP' head positioning technique compared with other methods, whereas a more backward head position was recorded with subjective head positioning, and the difference was significant (P<.001). There were no relevant differences in pitch values between the self-balance plus mirror and dynamic walking methods. G'-TVL (P<.000), Pn-TVL (P<.029), A'-TVL (P<.039), Ls-TVL (P<.001), Li-TVL (P<.037), B'-TVL (P<.003), and Pog'-TVL (P<.000) in the profile view and face height, lower face height, and lower lip length values in the frontal view (P<.001) differed significantly by head positioning method. The dynamic walking and self-balance plus mirror head positioning methods offered similar and advisable natural head position results, whereas FHP' head positioning was questionable for an accurate determination of natural head position. Facial soft tissue measurements, such as face height, lower face height, lower lip length, and projection of structures such as the G', Pn, lips, and chin, varied based on head positioning method.