|Year : 2015 | Volume
| Issue : 1 | Page : 26-32
Prediction of Facial Profile Based on Morphometric Measurements and Profile Characteristics of Permanent Maxillary Central Incisor Teeth
N Raghavendra, Venkatesh V Kamath, Krishnanand P Satelur, Komali Rajkumar
Department of Oral and Maxillofacial Pathology, Dr. Syamala Reddy Dental College, Hospital and Research Centre, Bangalore, Karnataka, India
|Date of Web Publication||29-May-2015|
Venkatesh V Kamath
Department of Oral and Maxillofacial Pathology, Dr. Syamala Reddy Dental College, Hospital and Research Institute, Munnekolala, Marathalli, Bangalore 560 037, Karnataka
Source of Support: None, Conflict of Interest: None
The computation of facial profile from dental morphometrics has been a subject of great interest in forensic odontology. The use of teeth to draw a profile and facial features is valuable in times of mass disasters when body remains are unavailable due to extreme destruction. This study aims to identify and evaluate applicable parameters in the permanent maxillary central incisors and the face of an individual. A correlation of these parameters establishes a mathematical equation that further charts a tooth-facial profile table. Thirty soft and hard tissue landmarks on the face in the frontal and the lateral profiles (using standardized photographs) and seven landmarks on the facial/labial surface of the clinical crown of the permanent maxillary central incisor (using casts of the maxilla) were identified for the study. Based on these, a set of eight horizontal and seven vertical parameters on the face and four parameters on the tooth were created for the assessment. Internal and external correlations between the two were carried out and statistically analyzed. A logistic regression was made to predict the probability of the parameters most likely to be reproduced in the creation of the facial profile, based on tooth morphometrics. The results indicated a definite correlation between the facial and the tooth parameters. Among the multiple parameters, a definite correlation in the horizontal dimension could be established between the mouth width and the mesiodistal width (MDW) of the tooth. In the vertical dimension, a definite relationship existed between the crown height of the tooth and the width of the midface (zygoma-mandible). There exist divergences in the correlation of tooth and facial parameters.
Keywords: Dental morphometrics, forensic odontology, permanent maxillary central incisor
|How to cite this article:|
Raghavendra N, Kamath VV, Satelur KP, Rajkumar K. Prediction of Facial Profile Based on Morphometric Measurements and Profile Characteristics of Permanent Maxillary Central Incisor Teeth. J Forensic Sci Med 2015;1:26-32
|How to cite this URL:|
Raghavendra N, Kamath VV, Satelur KP, Rajkumar K. Prediction of Facial Profile Based on Morphometric Measurements and Profile Characteristics of Permanent Maxillary Central Incisor Teeth. J Forensic Sci Med [serial online] 2015 [cited 2020 Oct 31];1:26-32. Available from: https://www.jfsmonline.com/text.asp?2015/1/1/26/155550
| Introduction|| |
Teeth are an excellent clinical study material in the living and nonliving populations for anthropological, genetic, and forensic investigations. Teeth play a key role in personal identification in natural and manmade disaster situations, the mass casualties normally associated with disasters since teeth are resistant to them. ,
The inverted tooth-face form matching theory is not new. Leon William (1914) hypothesized the presence of a harmony between the frontal view of the inverted central incisor and the face form. He classified the central incisor and the face forms into four basic geometrical shapes for harmonious matching. In addition, the most pleasing appearance can be achieved when the outline forms of the individual's inverted face and that of his/her maxillary central incisor are identical. 
Face and teeth measurements vary from person to person and are worthy criteria for evaluation. The use of mathematical methods helps to establish qualitative relationships between the tooth form and the facial profile of an individual.
Various studies have been done to establish a correlation between the facial profile and the tooth measurements. ,,,,, Extraction of numerical data from teeth, like morphology of the crown sizes and the facial profile, is characteristic for both males and females. In case of the absence of an individual, a single tooth could be used as an identity kit to draw the profile of a missing individual based on its dimensions. , Many attempts have been made to establish a correlation between the face and the tooth using anatomic parameters in living beings either directly in vivo or using radiographic tracings and photographs.  Conventional linear measurements have been performed using standardized hard-tissue landmarks individualized on the face in both males and females. ,,,,
A literature review indicates few studies establishing the presence of a mathematical relationship between the face and the central incisor form. An objective method applies regression analysis to find the best model, fit for the central incisor-face width relationship using a comprehensive group of anatomic parameters. 
The present study aims to establish a mathematical correlation between the facial profile and the maxillary central incisor, using anatomic horizontal and facial parameters. The knowledge and assessment of the correlation established in the mathematical form is utilized to draw a facial profile identity kit to help identify the individual.
| Materials and Methods|| |
The study group comprised 100 subjects aged 18-23 years, considering the fact that this age group has the minimal attrition. Out of 100 subjects, 50 were males and 50 were females.
The inclusion criteria were:
- Full set of dentition of the maxillary and the mandibular arches up to the second molar
- Healthy periodontium
- No interdental spacing or crowding
- No restorations on the permanent maxillary central incisor
- No history of orthodontic treatment.
The exclusion criteria were:
- Evidence of gingival alteration or dental irregularities
- Apparent loss of tooth structure due to attrition, fracture, caries, or restorations
- Individuals presenting any characteristics that could alter the contour of the face and dentition.
Following informed consent, basic body parameters like age, height, and weight were recorded. The direct facial measurements were obtained from each subject while he/she was sitting in an upright position with his/her teeth in centric occlusion, lips relaxed, and with unsupported head, looking straight forward to maintain natural head position.
On the face, the proposed landmarks were established by using erasable markers, and the measurements were obtained using inelastic thread and later transferred to a standardized long metallic ruler to calculate the distance. [Table 1] elaborates the proposed landmarks. [Figure 1] and [Figure 2] show the marking on a male subject included in the study in the frontal and the lateral views, respectively. Standard facial photographs were taken of each subject in the frontal and lateral views using a Canon EOS 500 (Nikon cool pix 5100 12 mega pixel camera, Nikon Inc., 1300 Walt Whitman Road, Melville, New York 11747-3064 USA) 8 megapixel digital camera attached with a ring flash. Superimposition of the landmarks was done in both the views. A digital grid was created joining the selected points and a lattice framework was produced using Adobe Photoshop v. 6 software. The idea behind this exercise was to simulate the creation of a "digital skeleton" on which the facial features of the individual could be superimposed [Figure 1]b and [Figure 2]b.
|Figure 1: (a and b) Consented photographs of a male subject included in the study showing the landmarks on the face and the grid framework derived from connecting the same. Frontal view|
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|Figure 2: (a and b) Consented photographs of a male subject included in the study showing the landmarks on the face and the grid framework derived from connecting the same. Lateral view|
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For the tooth measurements, impressions of the upper arches were made using irreversible hydrocolloid (alginate) material and dental stone casts of the same were obtained. The landmarks were marked using the proposed standard points as elaborated in [Table 2]. The outline tracing of the parameters is shown in [Figure 3]. [Table 3] lists the four parameters chosen for the incisor to correlate with facial measurements. The calibrations were recorded using digital vernier calipers (Aerospace Ltd., Bengaluru, Karnataka, India) [Table 2] and [Table 3]. Both the facial and the dental measurements were transferred on to a Microsoft Excel sheet and subjected to statistical analysis (SPSS version 15, Developed from IBM software).
|Table 1: List of facial and tooth landmarks selected for the evaluation |
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|Table 3: Composite average measurements of all the parameters of males and females in vertical parameters with statistical analysis |
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|Figure 3: Photographs of cast and tooth of the subject included in the study showing the landmarks|
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The Mann-Whitney U test, a nonparametric test of the null hypothesis that two populations are the same against an alternative hypothesis, especially that a particular population tends to have larger values than the other, was utilized to analyze the gender differences between the set of parameters. 
Spearman's rank correlation coefficient or Spearman's rho was used for measuring the statistical dependence between the parameters. This test assesses how well the relationship between the two variables can be described as a monotonic function. If there are no repeated data values, a perfect Spearman correlation of + 1 or -1 occurs when each of the variables is a perfect monotone function of the other. 
In an attempt to explore the relationship between the parameters, multiple regression analysis was employed. The idea was to see if there existed a statistical basis for a relationship between the tooth and the facial parameters, and whether this relationship was predictive and reproducible.
| Results|| |
Thirty landmarks on the frontal and lateral portions of the face and seven landmarks on the labial surface of the permanent maxillary central incisor were identified for inclusion in this study [Table 1]. The landmarks that were identified included both hard and soft tissues. Based on these landmarks, a set of eight linear parameters was outlined in the horizontal profile and seven in the vertical profile of the face and four parameters related to the tooth [Table 2]. In the frontal profile, the horizontal parameters were further subdivided into upper, middle, and lower thirds. The upper third of the face extended from the line joining the frontal prominences (1a-1b) to the line joining the right and the left frontozygomatic sutures (2a-2b). The middle third extended from the latter to the line joining the right and left tragi of the ears passing through the nasal alae (15a-9a-9b-15b). The lower third of the face extended from the latter to the line joining the right and left gonia passing through the midpoint of the chin (menton) (16a-14-16b). The composite average measurements of the 100 subjects related to the above parameters are presented in [Table 4].
|Table 4: Composite average measurements of the parameters of face and tooth in the subjects |
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A gender-wise analysis of the composite measurements interestingly revealed a male predomination. Almost all the figures were more in males than in females, and the difference in measurements was statistically significant as determined by the Mann-Whitney U test. Out of a total of 19 parameters in the face and the tooth, only five failed to pass the statistical significance mark in spite of being numerically more in males. All the parameters in the vertical profile of the face were significantly more in males as compared to females.
Spearman's correlation coefficient test was done to identify any correlation that may exist between the face and the tooth in both the horizontal and vertical parameters of both males and females.
The correlation between the tooth parameters was statistically significant to the width of the mouth in the horizontal facial profile (13a-13b) [Table 5]. In the vertical profile, the tooth parameters were statistically correlated to the width between the zygomatic prominence and the base of the mandible (8a-17a, 8b-17b). The complexity of the interrelation between the parameters is probably reflected in these findings [Table 6].
|Table 5: The ratio obtained between vertical parameters of the face and tooth |
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|Table 6: Spearman's rho of horizontal and vertical parameters between the face and the tooth |
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From the above results, we tried to see if we could predict 13a-13b (R-L) values from the values of 18a-18b, 19a-19b, and 20a-20b. Since there were multiple predictor parameters, multiple regressions were employed. [Table 7] indicates that 13a-13b (R-L) values decrease by 0.085 for a unit increase in 18a-18b-inscisal edge (P = 0.778, NS), increase by 0.144 for a unit increase in 19a-19b-middle one-third (P = 0.478, NS), and increase by 0.162 for a unit increase in 20a-20b-cervical one-third (P = 0.538). In the vertical parameters, the clinical crown height (21-22) was significantly correlated with the facial parameter (8a-17a, 8b-17b).
|Table 7: Statistical analysis of the most probable parameters in the vertical and the horizontal dimensions that can be correlated to tooth parameter (Spearman's rho and multiple regression analysis) (for explanation see text) |
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From the above results, an attempt was made to predict the facial parameter (8a-17a, 8b-17b) values from the crown height. Since there was a single predictor (crown height), simple regression was employed. The results revealed that values of the parameter (8a-17a, 8b-17b) increase by 0.023 for a unit increase in the crown height (P = 0.077, NS) as shown in [Table 7].
The basic idea of the present study was not only to assess the relationship between the parameters of the tooth and the face but also to derive a working relationship whereby facial dimensions could be recreated based on the tooth measurements. A ratio between the two was computed and a table created as a sort of a "ready reckoner" to derive facial dimensions from the tooth form [Table 5] and [Table 8].
|Table 8: The ratio obtained between horizontal parameters of the face and tooth |
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[Figure 1]b and [Figure 2]b depict the "grid," digitally created by joining the landmarks in the horizontal and facial profiles, respectively. This forms the base on which the facial profile could be created. We attempted an exercise to prospectively match the tooth and the facial dimensions and recreate the grid. The tooth measurements from the same subject were then converted into facial dimensions using the ratios obtained in [Table 5] and [Table 8], and the result was an accurate superimposition of the grid. This verification of the dimensions was interesting and probably significant in the identification of the individual.
| Discussion|| |
The permanent maxillary central incisor provides an illusion of being the largest tooth in the mouth, making it one of the most dominant tooth in the anterior segment of the upper arch. ,,
Attempts at correlation of the maxillary central incisor with the facial profile have been made in the past and have yielded mixed results. Kassab (2004)  analyzed 100 individuals and directly measured the facial and the tooth dimensions using digital vernier calipers. The facial forms were grouped into square (euryproscopic), long and narrow (leptoproscopic), and ovoid (mesoproscopic). In leptoproscopic facies, the mesiodistal width (MDW) of the central incisor was found to be related to the intercanthal and the philtrum widths in males. In mesoproscopic facies, the width of the central incisor was found to be significantly correlated to the interzygomatic width of the face.
In a recent Indian study, the outline forms of the face and the maxillary central incisor were compared using digital photographs.  The authors attempted evaluation using a visual analysis and William's method. They found a correlation greater than 50% between the tooth and the facial forms by the visual method and 31.5% correlation by the William's method. Interestingly, no sexual dimorphism was noted in the outline forms of the tooth and the face.
The present clinical study aimed to assess and obtain a relationship between the facial and the tooth forms of the maxillary central incisor in both the genders, with certain horizontal and vertical parameters. The identification of these parameters and the morphometric measurements derived therein render objectivity to the exercise, making it mathematically sustainable and reproducible.
We found a statistically significant sexual dimorphism in the tooth and facial measurements, with the mean value of all the parameters considered individually being more in males than in females. This is probably attributable to the heavier and stronger physique of males in comparison to females.
Due to the multiplicity of the parameters employed, statistical significance between the tooth and the facial measurements was not universally forthcoming. A similar observation has been recorded in the previous studies employing multiple parameters.
There was a definite positive correlation between the width of the mouth (6a-6b) and the horizontal parameters of the teeth (18a-18b, 19a-19b, 20a-20b), in which the MDW at the middle one-third of tooth (19a-19b) of the central incisor showed the greatest statistical correlation. There was no significant correlation obtained between the other horizontal parameters of the face and that of the tooth.
In vertical parameters, the value for the lower facial height was in accordance with the value obtained in previous studies.  Also, the vertical parameter, the middle-lower one-third of the face in the frontal profile 8a-17a, 8b-17b showed a positive correlation to the clinical crown height. There was a statistically significant relation achieved between the mean values of all the vertical parameters in males and females. There is scarcity of data in the previous literature supporting this correlation.
Statistically significant relations could not be observed for ratios of the horizontal and the vertical parameters, and mean values of the face and the tooth between males and females; however, they could be numerically correlated.
The study results reveal the fact that the horizontal parameters of the face are definite indicators for prediction of the tooth form. In an analysis of 100 Turkish students, the dental proportions of the maxillary anterior teeth were matched to their facial proportions. Significant gender differences in the dimensions of the central incisors and canines were observed. The authors also found proportional relationships between the bizygomatic width and the width of the central incisor, and the interalar and the intercanine widths in women.  In a similar study, in a population of 2,000 adults of Zenica (Bosnia and Herzegovina), the authors found a definite male predomination of parameters in the central incisor tooth form. Correlation of the horizontal parameters of the face and the tooth did not reveal statistically significant relations. 
This study, additionally, did not find any direct relationship in the combination of the vertical and the horizontal parameters with that of the tooth. Ethnicity, developmental factors, geographical influences, and genetics play a role in the establishment of the unique identity of an individual. Attempts to correlate the common factor among them to establish a baseline between the tooth and the facial forms are often disappointing. As was observed in the previous studies, we had limited success in identifying the correlation between the tooth and the facial forms. As an overview, broad categorizations of the tooth and facial forms might be perceived to be related and reproducible but when analysis of the finer aspects and the parameters is attempted, there is a wide divergence.
| Conclusion|| |
There is a definite relationship between the morphometrics of the tooth and that of the face, with the horizontal parameters being better predictors. A relationship was found between the width of the mouth and the MDW of the central incisor; the mouth width values decrease by 0.023 units with the increase of MDW of the central incisor at the incisal edge and increases in definite units with the increase of MDW at the middle one-third and the cervical one-third. However, very less vertical parameters could be correlated to the clinical crown length.
There was a significant sexual dimorphism observed in our results except for the few horizontal parameters. The vertical parameters of the tooth and the face do show gender variability as well as a correlation to each other. Probably the creation of better algorithms and larger sample surveys may throw more insights and allow the correlation to be done on a mathematical model.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]