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The development of an anthropometric craniofacial database is a necessary multidisciplinary proposal.
The aim of this study was to establish facial anthropometric norms and to investigate into sexual dimorphism in facial variables among Kosovo Albanian adults.
The sample included 204 students of Dental School, Faculty of Medicine, University of Pristina. Using direct anthropometry, a series of 8 standard facial measurements was taken on each subject with digital caliper with an accuracy of 0.01 mm (Boss, Hamburg-Germany). The normative data and percentile rankings were calculated. Gender differences in facial variables were analyzed using t- test for independent samples (p<0.05). The index of sexual dimorphism (ISD) and percentage of sexual dimorphism were calculated for each facial measurement.
ormative data for all facial anthropometric measurements in males were higher than in females. Male average norms compared with the female average norms differed significantly from each other (p>0.05).The highest index of sexual dimorphism (ISD) was found for the lower facial height 1.120, for which the highest percentage of sexual dimorphism, 12.01%., was also found. The lowest ISD was found for intercanthal width, 1.022, accompanied with the lowest percentage of sexual dimorphism, 2.23%.
The obtained results have established the facial anthropometric norms among Kosovo Albanian adults. Sexual dimorphism has been confirmed for each facial measurement.
Craniofacial anthropometry, as an important part of anthropology and medicine, is used for determination of morphological characteristic of the head and face (1). The craniofacial region represents the most complex and special part of the body, consisting of 22 separate bones in addition to 20 deciduous and 32 permanent teeth (2). Studies of human facial morphology can impact various areas including anthropology and genetics (3). Facial morphology is an important phenotypic feature that aids in the diagnostic of several craniomaxillofacial and genetic disorders (4). Morphological characteristics in human beings are affected by ecological, biological, geographical, racial, ethnic, gender and age factors (5-9).
In order to successfully treat various deformities such as congenital facial malformation and/or post-traumatic facial disfigurements in different ethnics groups, surgeons need an access to databases based on correct anthropometric craniofacial measurements. For many ethnic and racial groups, the forensic norms have been set up where the differences among racial/ethnic groups have been proved and normative data have been developed (10). The normative data of facial measurements are necessary to a specific determination of the level of deviations from the norm. Furthermore, the normative data have significant implications for facial plastic surgeons and medical professionals whose work involves correction and analysis of different impairments, malformations or post-traumatic disfigurements of the face and head (11).
Sexual dimorphisms exist in various forms in all humans. In general, it refers to differences between males and females of the same species in terms of size, appearance, and behaviours (12). Although humans show relatively little sexual dimorphism compared with other primates, males and females still differ, on average, in many physical features of physical appearance such as height and muscle mass. In orthodontic, forensic and anthropological literature, it has been well documented that males and females differ in various aspects regarding the craniofacial complex (13). It is still believed that sexual dimorphism in the crania within a genius or species is related to sexual selection and mating preference, which has resulted in differences in physical attributes between males and females. These differences include larger, and heavier brow ridges, more robust crania, and more pronounced noses and nasal cavities in males. Females have larger eyes, smaller jaws and noses and an overall more gracile appearance (14). Characterizing sexual dimorphism of the human craniofacial complex is of interest to numerous fields, including physical anthropology, forensics, cognitive science, plastic and reconstructive surgery and orthodontics (12, 15-18). However, the largest number of studies in the literature focuses on sex differences involving the skull (15, 19, 20). A sexual dimorphism in craniofacial soft tissue has also been extensively demonstrated in adults (10, 21-25)
Many scientists recognized the importance of the research on sexual dimorphism and have since determined the usefulness of recognizing population specific traits and values (26). The genetic background determines physical qualities and characteristics and makes each population unique in its characterization as well as in sexual dimorphism (27). It is important to establish a baseline for each distinct population and to create intra-population standards of facial measurements and sexual dimorphism. At present, very limited data are available regarding the facial anthropometric norms in Kosovo Albanian population. The present study was designed to establish the facial anthropometric norms and to investigate the sexual dimorphism in facial variables among Kosovo Albanian population.
The sample for this study included 204 students of the Dental School, Faculty of Medicine, University of Pristina. There were 101 males and 103 females ranging in age from 18 to 30 years. The study was approved by the Ethics Committee of the Dental School, Faculty of Medicine, University of Pristina, Republic of Kosovo (Reference Number: 2363/2005). In order to participate in the study, the subjects had to be native Kosovo-Albanian, all four grandparents. The participants agreed to bring birth certificates from both parents, wherein the origin of both grandparents was confirmed. In addition to that, the inclusion criteria was no facial traumas in their health history or orthodontic treatments, facial reconstruction or aesthetic plastic surgery, orthognathic surgery, or any other medical condition that might affect the structural integrity of the head and face. Furthermore, there were no family histories of any craniofacial anomalies or syndromes that involved the craniofacial complex. All subjects were screened for those criteria prior to inclusion in this study and were well informed on the purpose and the procedure of the research. Prior to the start of the study, they all provided a written informed consent Measurements were carried out by a single examiner to reduce interobserver error. To minimize the intra-observer error, each measurement was taken three times and the average of the three values was noted.
Using direct anthropometry, a series of 8 standard facial measurements by Kolar and Salter (28) was performed on each subject with digital caliper with an accuracy of 0.01 mm (Boss, Hamburg-Germany). The descriptions of all facial measurements are listed in Table 1. To minimize intra-observer error, all the measurements were taken three times and the average values were utilized for the analysis.
Normative data were obtained by administering the test for representative sample population, among Albanian males and females in Kosovo in order to establish facial anthropometric norms. Normative data were calculated by applying the methods of descriptive analysis: mean median, mode, range (maximum and minimum values) and percentiles rankings. The gender differences in the facial variables were analyzed using t test for independent samples. The statistical tests were performed with SPSS 20 (SPSS Inc., Chicago, IL, USA) and Excel 2007 (Microsoft Corporation, Redmond, WA, USA). The significance level was set up at p<0.05.
The sexual dimorphism between facial variables was analyzed using the index of sexual dimorphism (ISD):
Xm = mean value for males; Xf = mean values for females. This index indicated the level of difference between sexes. The values close to 1 indicated the lowest level of sexual difference and, by increasing the distance from 1, the level of sexual difference increased (29).
The percentage of sexual dimorphism for each measurement was calculated using the formula given by Garn and Lewis (30), as follows:
Xm = mean value for males; Xf = mean values for females.
The average facial measurements and normative data, for the Kosovo-Albanian adults, males, and females (mean, median, mode, standard deviation, range, and percentiles) are presented in Table 2 and Table 3. Decile norms were established for both, males and females for all series of eight standard facial measurements which were measured in millimeters. The median values for all facial anthropometric measurements were higher in males than in females. Table 4 shows comparison between the average facial measurements of the males and females of the Kosovo-Albanian population. All of the measurements have shown a statistically significant difference when male average measures were compared to female ones (p>0.05).
The index of sexual dimorphism (ISD) and percentage of each facial measurements were calculated and presented in Table 5. The highest ISD was 1.120 for the lower facial height, which also had the highest percentage of sexual dimorphism, 12.01%.The lowest ISD was found for the intercanthal width, 1.022, (the lowest percentage of sexual dimorphism 2.23%).
In the present study, quantitative data of the facial area measures were collected in typical individuals among Kosovo Albanian adults. The widespread variability in the human face confirms its individuality. The measurements selected for this study consisted of eight measurements which were performed for development of a suitable figure of the facial complex morphological configuration. The methodology and inclusion criteria were selected to develop facial normative values that can assist in future analysis, diagnosis, and planning of correction of different impairments, orthognathic surgery or orthodontic treatment, malformations or post-traumatic disfigurements of the face for Kosovo Albanian adults. Adults of both sexes 18 to 30 years of age were included in this study. Farkas et al., have established a data base of anthropometric measurements made on the face, using the method of manual anthropometry among twenty-five different population, which were considered over a hundred ratios and they also made comparisons which are presented in Tables 6 and 77 (10). So far there has not been any study of differences between the sexes for the Kosovo Albanian population. Therefore, our results are compared with that database.
The most exposed to image judgment and situated between the face is endocanthion, which represents one out of many horizontal measurements of facial areas - intercanthal width (en-en). Our normative data for the en-en value was found to be similar to the North American White (NAW) and the Caucasian groups from Europe: Hungarian, Slovak, Slovenian, Turkish for both sexes, and to Bulgarian males; from Middle Eastern: Egyptian and Indians. The normative data lower than ours were found among Azerbaijan, Czech, Croatian, Greeks, Italian, Polish, Portuguese, Iranian, for both males and females, and for Bulgarian females. Higher values than ours for the en-en were found among Russian, Singaporean Chinese, Vietnamese, Thai, Japanese, Angolan, Zulu and Afro-American population of both sexes, and among Indian males.
Furthermore, our normative data for morphological facial height (n-gn) were similar to those belonging to Italian and Portuguese males, Singaporean Chinese females and both sexes of Afro-Americans. The higher values than ours for the n-gn were found among Greek and Portuguese females and among Iranian and Turkish, both females, and males. Additionally, lower normative data than ours, for both sexes, were found among NAW, Azerbaijan, Bulgarian, Czech, Croatian, German, Hungarian, Polish, Russian, Slovak, Slovenian, Egyptian, Indian, Vietnamese, Thai, Japanese, Angola and Zulu, Italian females, and Greek and Singaporean Chinese males.
Thus, our normative data for the lower facial height (sn-gn) were found to be similar to those belonging to NAW and Italian population, for both sexes as well as for Singaporean Chinese, Thai, and Zulu males. The lower data were found among Azerbaijan, Bulgarian, Croatian, Germans, Greek, Hungarian, Polish, Portuguese, Russian, Slovak, Slovenian, Turkish, Egyptian, Indian, Japanese and Angola population of both genders as well as for Czech and Vietnamese males and Thai females. Higher normative data than ours were found among Iranian and Afro-American population of both genders as well as among Czech and Singaporean Chinese females.
The normative data for the maximum facial width (zy-zy) were found to be similar only to German females. In Asian ethnic groups, the maximum facial width was extremely wider in both sexes of Indians, Singaporean Chinese, Vietnamese, Thai and Japanese population groups than in Kosovo Albanian population. The wider maximum facial width was found among NAW, Azerbaijan, Bulgarian, Czech, Croatian, Hungarian, Italian, Polish, Russian, Slovak, Slovenian, Iranian, Turkish, Egyptian, Afro-American population of both sexes; also Greeks and Zulu females and among German males. The narrow maximum facial width was found among Portuguese females and males as well as Greek and Zulu males.
Additionally, the nasal height (n-sn), was found identical to those of normal range among Azerbaijan, Greek, Hungarian, both males and females; Bulgarian, Czech, German, Italian, Polish, Slovenian, Singaporean Chinese females and Egyptian males. The nasal height was found greater than ours among Portuguese, Turkish, Iranian and Japanese individuals of both sexes; and Italian and in Slovenian males. In contrast, a shorter nasal height than in our population was found among NAW, Croatian, Russian, Slovak, Indians, Vietnamese, Thai, Angola, Zulu, and Afro-American males and females, also Bulgarian, Czech, Germans, Polish and Singaporean Chinese males and Egyptians females.
Moreover, the nasal width (al-al) was found to be similar to both sexes of Bulgarian, Czech, Croatian, Greek, Hungarian, Russian, Slovenian, Turkish, and Indian Azerbaijan and Polish females and Portuguese males. In Asian ethnic groups, the nasal width was extremely wider in both sexes of Singaporean Chinese, Vietnamese, Thai and Japanese population, also among Angola, Zulu, and Afro-American population. The slimmer value of nasal width was found among both sexes of NAW, German, Italian, Slovak, Iranian and Egyptian population as well as Portuguese females and Azerbaijan and Polish males.
The mouth width (ch-ch) was identical to that of the NAW, Azerbaijan, Czech, Slovenian, and Slovakian females, and Italian and Indians males as well as both sexes of German, Greek, Polish and Russian population. Significantly greater ch-ch were found among NAW, Azerbaijan, Czech, Slovenian, Slovakian and Turkish males, both sexes of Hungarian, Angola, Zulu, and Afro-American population. Significantly smaller ch-ch values were found among both sexes of Bulgarian, Croatian, Portuguese, Iranian, Egyptian, Singaporean, Chinese, Vietnamese, Thai, and Japanese population as well as Italian, Turkish and Indian females.
Our normative data regarding mandibular width (go-go) were found to be similar to those for Azerbaijan females and Czech, Turkish, Thai and Vietnamese males. Significantly smaller go-go compared to one belonging to our population was found among both sexes of NAW, Bulgarian, Croatian, German, Greek, Hungarian, Polish, Portuguese, Russian, Slovenian, Iranians, Egyptian, Indian, Singaporean, Chinese, Angola, Zulu, and Afro-American population as well as Turkish females and Azerbaijani males. Significantly wider go-go was found among both sexes of Italian, Slovak and Japanese population, also among Czech, Thai, and Vietnamese females. Therefore, our normative data showed the smallest differences with Caucasian groups of Europe and North American white population, following the Middle East, Asian and African population, as expected.
Our findings reflect the influence of genetic and environmental factors that contribute to the differences observed in facial dimensions within and between human populations (31, 32). Several researchers have proposed that genetic factors exert substantial influence on the variation observed in the shape and configuration of the human face (33-35).
The proportion and type of genetic control varies between individuals and groups, which may account for the morphological differences noted between populations (31). Environmental factors may also contribute to differences in facial features among populations. It has been observed that climate could influence facial height and width, as well as nasal height and cranial width in Northeast Asian populations (36, 37).
The result of this study indicated that most features of the human face show strong evidence of sexual dimorphism. Our results reveal that strong sexual dimorphism is present in most of facial measurements. All eight facial measurements; en-en, n-gn, sn-gn, zy-zy, n-sn, al-al, ch-ch and go-go showed that there were significant differences between males and females. The presence of strong sexual dimorphism of facial measurements reported in this study was supported by the results of the ISD. The ratios of male/female values were greater than one for all measurements. It indicated that male facial variables were larger than female ones in all dimensions. The highest ISD was found for the lower facial height and the lowest was found for the intercanthal width.
However, we were unable to identify any published data documenting the levels of sexual dimorphism. Gender differences in the craniofacial region were mainly expressed in size, not in shape, facial width 4.01%, morphological facial height 3.77% and mandibular width 5.29% (38). Sexual dimorphism of facial skeletal structures is well described in modern humans. In European populations, the average male facial length and width dimensions are up to 6% larger than female dimensions (39). Most mandible dimensions are 5-13% larger (40-42). Our results, regarding the percentage of sexual dimorphism are found to be similar to the facial length and width of European population.
The obtained results have established the facial anthropometric norms among Kosovo Albanian adults. Significantly higher facial values were present in males than in females. The clinical norms presented in this study will be useful in anthropology, forensic medicine, and can be used as local standards for diagnostics and planning of correction of different impairments, malformations or post-traumatic aberrations of the face and the orthognathic surgery treatment.
The authors wish to express appreciation to the passionate and patient students who took part in this study.
Competing interests: The authors declare that they have no competing interests.