Mouth Width and Cupid’s Bow Estimation in a Southern African Population

Abstract

Standards for estimating mouth width and Cupid’s bow width in craniofacial approximation and superimposition are limited. Currently, the only guideline for mouth width, using direct skeletal references, is a general rule indicating a 75% inter‐canine to mouth width ratio. The philtrum, which closely corresponds to the Cupid’s bow, is said to be equal to the inter‐superior prominences of the maxillary central incisors. This study tested these guidelines against newly generated regression models and mean values. Cone‐beam CT scans of 120 black and 39 white southern African adults were used. Comparative hard and soft tissue measurements were taken using a 3D DICOM viewer. Regression equations accounting population, sex, and approximate age variables (20–39 and 40+ years), utilizing maxillary inter‐canine width to estimate mouth width and maxillary central–lateral incisor junction width to estimate Cupid’s bow width, performed statistically best. The regression models were more reliable than existing standards in validation tests.

Visualising trends in dentition to lip mouth morphology using geometric morphometrics

“…Using geometric morphometrics, it was found that age significantly (p < 0.0001) impacted mouth morphology, affecting all population and sex groups in a similar way (Fig 2). This study delivered a unique wireframe visual that demonstrates the impact of age on soft and hard tissue mouth shape, which is largely consistent with metric descriptions previously reported by authors [14,[18][19][20]23,24,[36][37][38]. The identified age-related lip-thinning, reduction in teeth height, and increase in mouth width, are well recognised in published literature [14,[18][19][20][36][37][38].…”

“…These results more closely correspond to this study (males = 56.2 mm, SD 4.8; females = 53.7 mm, SD 4.6). All these findings consequently suggest that population specific regression [i.e., 20,23,24], supported by the morphometric guides generated in this study, are currently needed to assist with mouth approximation.…”

“…The mean wireframe templates generated (Fig 6), with reference to the PCA and CVA findings (Figs 3, 4 and 5), and metric guides that empirically indicate hard and soft tissue landmark relationships (Table 4), deliver novel shape data that is intended to substantiate and dynamically support existing linear approaches to mouth estimation [i.e., 20,21,[23][24].…”

“…Other sources state that the mouth corners should be positioned inferior to the infraorbital foramina [22]. Sets of regression formulae have also been developed to assist in lip height and mouth width estimation [20,23,24]. Much of the aforementioned guidelines were obtained from cadaver data, or from faces that were recorded in supine positions.…”

“…It utilised an adult South African sample, which predominantly represented black individuals (Sub-Saharan African ancestry), and a small white sample (European ancestry; limited by scan availability). The shape patterns identified are intended for use in conjunction with pre-existing regression equations [e.g., 23,24].…”