In spite of the recent increase in the relevance of soft tissue facial analysis, there is an absence of reference values for some races, ethnicities, and geographic population groups. These data are required to determine deviations from standard measurements. We used a recent non-invasive 3D photography method to analyze the faces of a sample of healthy European adults with normal occlusion from southern Spain. We established anthropometric facial soft tissue reference values for this specific geographic-ethnic population. We also investigated differences between the sexes in this population.
We found clear sexual dimorphism, with statistically significant differences between male and female subjects in most facial variables that were analyzed. The male subjects had higher values in all vertical and transversal dimensions, with the exception of lower lip height, which was similar in the two groups. The male subjects also had higher values in the angular measurements of the nose. No sex differences were found in transverse upper lip prominence or transverse mandibular prominence. Only one statistically significant sex difference was found in the ratio measurements (intercantal width/nasal width, which was higher in women than in men). The rest of the measured ratios were similar in both sexes.
Planmeca ProFace™, which was used to capture facial soft tissue characteristics, is a unique 3D facial photo option available for all of Planmeca’s 3D X-ray units. The upgraded unit produces a realistic 3D photo of the face in addition to performing maxillofacial radiography. Planmeca is the first manufacturer to introduce this type of product. One imaging session generates both a 3D photo and a CBCT volume, or if required, only a 3D photo, in which case no radiation is emitted. We used the latter option in the present study. Three-dimensional photos are generated in one imaging session while the patient position, facial expression, and muscle position remain unchanged. This leads to the production of images that are perfectly compatible (technical information provided on the company website: http://www.planmeca.com/Imaging/3D-imaging/Planmeca-ProFace/).The reliability of the measurements produced by the 3D imaging capture system used was tested using the method of moments. Specifically, we compared the direct measurements (those made over the face of the patient using an electronic caliper) with the same measurements made indirectly (over the 3D images captured using Planmeca ProMax 3D ProFace® [Planmeca USA, Inc.; Roselle, IL, USA]) using the same randomly selected participants. The results indicated adequate reproducibility (mean, 1.04 mm) [10].
In our population, which consisted of European adults from southern Spain, prominent sex differences were observed in measurements of the face, mandible, and nose. These measurements were significantly larger in men than in women.
In our study, the male subjects had longer and wider faces than the female subjects. Similar results were found by Baik et al. in Korean adults [14] and by Ozdemir et al. in Turkish young adults [16]. Othman et al. also described longer faces in men than in women in a Malaysian population, although they did not include facial width measurements [15]. There are also differences between populations: Korean men have slightly longer faces than Europeans from southern Spain (face height, N-Me, 121.42 ± 6.03 mm vs. 120.40 ± 8.22 mm), while women from southern Spain have longer faces than Korean women (119.69 ± 69 mm vs. 114.41 ± 5.89 mm). Sexual dimorphism in face height was more prominent in the Korean population [14]. Our results are not comparable with those obtained in Turkish [16] or Malaysian [15] populations. This is because, in those studies, the authors considered face height as the distance from N to Gn, although they also found higher sexual dimorphism than we did. Sexual dimorphism has also been reported in a Chinese population [4], although the different methodology used makes it difficult to compare the Chinese study to ours.
Mandible width and right and left mandibular body length were also significantly larger in men than in women in our southern European sample. Similar results were found in Turkish and Korean adults, with wider mandibles in men than in women. Inter-group differences can be observed when comparing populations: Koreans men and women have the widest mandibles (measured from right to left gonion) (127.38 ± 7.43 mm in men and 118.01 ± 7.41 mm in women). They are followed by the Turkish (116.3 ± 1.26 mm in men and 110.2 ± 1.65 mm in women) and the southern Europeans in our study, who had the smallest mandible width (113.52 ± 6.23 mm in men and 107.58 ± 7.51 mm in women). These inter and intra-population differences in face and mandible size and shape may be attributed to several factors, including genetic or environmental factors, as suggested by paleo-anthropology studies [22-26].
In our study, all the measurements of the nose had larger values in men than in women. This was especially true of nasal width, which had a mean difference of 5.23 mm. Sexual dimorphism in nose dimensions had also been described in Malaysian adults. Malaysian men have generally longer and more prominent noses. In addition, nose height and nasal bridge length are significantly in Malaysian men (mean differences of 4.93 mm and 5.73 mm, respectively) [15]. Baik et al. [14] also found longer and more prominent noses in men than in women. In contrast, Ozdemir et al. [16] did not find sexual dimorphism in the height of the nose, the length of the nasal bridge, or the nasal root width in Turkish adults. Our southern European population had narrower noses (nasal width: 36.62 ± 3.28 mm in men and 31.15 ± 2.21 mm in women) than other racial and ethnic groups [14-16, 27-29]. In contrast, the nose height was had higher values in our group (56.94 ± 4.45 mm in men and 56.17 ± 2.83 mm in women) than in Malaysian (54.13 ± 3.61 mm in men and 49.20 mm in women) [15], Chinese (50.15 ± 4.16 mm in men and 46.93 ± 3.3 mm in women) [30], Turkish (51.9 ± 0.75 mm in men and 51.7 ± 0.58 mm in women) [16], and Korean (53.26 ± 3.46 mm in men and 48.4 ± 4.52 mm in women) [14] populations. Our results were similar to those found in white northern Italians (57.43 ± 3.93 mm in men and 54.07 ± 3.68 mm in women) [27]. A proposed explanation for sexual differences in nose dimensions is that men have higher daily energy expenditure, greater respiratory air consumption, and different body composition [22, 31].
Sexual dimorphism was also found in the ocular region in our population, with significantly higher values in men than in women for all variables analyzed. Major differences were found in biocular width (mean difference, 4.83 mm) and biorbitale width (mean difference, 4.53 mm). In the study by Othman et al. [15], only biocular width (mean difference, 4.14 mm) was significantly larger in Malay men than in Malay women. Although the main differences in biocular width were quite similar in both studies, the Malaysian subjects had higher values for both men (96.19 ± 4.64 mm) and women (92.05 ± 3.22 mm) than those found in our southern European sample (90.40 ± 4.68 mm in men and 86.58 ± 3.20 mm in women). No sexual dimorphism was found in a Korean population [14], although the linear distance ExR-ExL (what is referred to as ’upper face width’) was even higher (106.75 ± 6.13 mm in men and 104.98 ± 5.47 mm in women) in that population. There are thus large differences in the ocular area between races and ethnic groups.
All of the measurements in the orolabial were significantly larger in men than in women, with the remarkable exception of lower lip height, which did not display a significant sex difference. Similarly, no sexual dimorphism was found in the lower vermilion height in a Turkish population [16]. In our sample, philtrum width (10.62 ± 2.43 mm in men and 9.29 ± 1.95 mm in women) and mouth width (51.11 ± 4.77 mm in men and 47.34 ± 3.65 mm in women) values were similar to those found by Othman et al. [15] in Malaysians (11.84 ± 1.90 mm in men and 10.40 ± 1.14 mm in women, and 50.83 ± 3.75 mm in men and 48.00 ± 2.61 mm in women, respectively). The above authors, however, found smaller differences in mouth width between sexes (2.83 mm vs. 4.21 mm in our study). Turkish [16] and Korean [14] subjects have wider philtrums in both sexes. The widest mouths are found in white northern Italians [27] (55.71 ± 3.81 mm in men and 50.84 ± 3.83 mm in women). The narrowest mouths are found in Turks [16] (47.1 ± 0.54 mm in men and 44 ± 0.31 mm in women).
Angular and ratio measurements are difficult to compare among the published studies due to the different methodologies and variables that have been considered. In our population, nasolabial, nasomental, and transverse nasal prominence angles were significantly larger in men than in women. In contrast, transverse upper lip prominence and transverse mandibular prominence did not show sexual dimorphism. Thus, there were significant sex differences in the angular measurements of the nose between the sexes. Baik et al. [14] also did not find significant sex differences in angular measurements, with the exception of the nasal frontal angle and the transverse nasal prominence, in a Korean population. Othman et al. [15] did not find clinically significant differences between the sexes in angular and ratio measurements in Malaysians.
Among the ratio measurements in our study, only the intercantal width/nasal width ratio was significantly different between the sexes, with higher ratios in women (1.01 ± 0.11) than men (0.89 ± 0.13). In contrast, Baik et al. [14] found significant sex differences in the ratio of anterior facial height to the interzygomatic distance and that of forehead height to forehead width. However, the ratio of facial height to upper facial height relative to mandibular width was similar in both sexes, which is consistent with our study. These results suggest that there are larger differences in the sizes, rather than the shapes, of faces between men and women. The comparisons and differences with other populations reported in our study should be interpreted with caution due to the different systems used for facial evaluation, as well as in the different variables used to analyze anthropometric facial features.
Conclusions
Here we establish reference anthropometric measurements of facial soft tissues in European adults from southern Spain with normal occlusion using non-invasive 3D photography. Most of the parameters had significant sexual dimorphism. Men had higher values in all vertical and transversal dimensions, with the exception of lower lip height, which was similar in the two groups. The greatest differences between sexes were observed in measurements obtained from the face, mandible, and nose, which were significantly larger in men than in women. However, only one statistically significant sex difference was found in the ratio measurements (intercantal width/nasal width, which was higher in women than in men).