Indian Journal of Dental Research

ORIGINAL RESEARCH
Year
: 2018  |  Volume : 29  |  Issue : 2  |  Page : 155--160

Comparison of interpupillary distance and combined mesiodistal width of maxillary central incisor teeth in two ethnic groups of Northeast India: An in vivo study


Jogeswar Barman, Sangma Serin 
 Department of Prosthetics, Regional Dental College, Guwahati, Assam, India

Correspondence Address:
Dr. Jogeswar Barman
My Dentist, MRD Road, Chandmari Colony, Guwahati - 781 003, Assam
India

Abstract

Background: Anthropometric measurements of the face can be used as a guide in selecting proper sized anterior teeth. Aim: The aim of this study is to evaluate the relationship between the interpupillary distance (IPD) and the combined mesiodistal width of maxillary central incisors (MDW of MCIs) to establish their morphometric criterion and their significance in two ethnic groups of Northeast India. Methodology: A total of 120 participants consisting of 60 indigenous students each from Assam and Meghalaya in the age group of 18–25 years were selected after taking their written consent. Standardized facial frontal photographs of all the participants were taken using a digital camera in such a manner that maxillary anterior teeth were visible. The photographs were uploaded onto the computer and saved in a file. Anthropometric measurements of IPD and combined MDW of MCIs in centimeters were made using both Adobe Photoshop® 7.0 software program and manually using a digital vernier caliper on the developed photographs to a same size of 15 cm × 10 cm. Data obtained were tabulated and analyzed using Student ”t”-test and Pearson correlation test. Results: The present study reveals a positive correlation with a high degree of statistical significance between IPD and combined mesiodistal width of maxillary central incisors among all the samples irrespective of gender and ethnicity where P < 0.01. Conclusion: IPD can be used as a guide in determining the suitable mesiodistal dimension of the maxillary central incisors.



How to cite this article:
Barman J, Serin S. Comparison of interpupillary distance and combined mesiodistal width of maxillary central incisor teeth in two ethnic groups of Northeast India: An in vivo study.Indian J Dent Res 2018;29:155-160


How to cite this URL:
Barman J, Serin S. Comparison of interpupillary distance and combined mesiodistal width of maxillary central incisor teeth in two ethnic groups of Northeast India: An in vivo study. Indian J Dent Res [serial online] 2018 [cited 2021 Sep 19 ];29:155-160
Available from: https://www.ijdr.in/text.asp?2018/29/2/155/229628


Full Text

 Introduction



Esthetic tooth selection and its physiologic arrangement is a critical step to successfully restore lost structural and functional harmony by a removable dental prosthesis. Apart from teeth arrangement, facial harmony is constituted by matching of shape, mold, color, and size of teeth to that of the face. Based on these observations, a number of studies have reported that anthropometric measurements of the face can be used as a guide in selecting proper sized anterior teeth.[1] Among these anthropometric measurements, only interpupillary distance (IPD) probably remains constant and does not modify after the age of 14.[2] The variations in tooth form are a common occurrence in permanent dentition and these variations have an ethnic, forensic, and anthropological significance.[3] Further, anthropometric measurements may be variable demographically that can influence the selection of size of artificial teeth.

 Methodology



A total of 120 participants, 60 indigenous students of Assam and 60 indigenous students of Meghalaya, both male and female in the age group of 18–25 years having full complements of natural teeth (at least up to second molars) with acceptable alignments were selected. Nature of the study was explained with participant information sheet and informed consent of all the participants was obtained.

Distribution of subjects

All the 120 participants are broadly divided into two ethnic groups: Group A (Assam) and Group B (Meghalaya) consisting 60 participants in each group. All the participants in each group were further divided into male and female group.

Obtaining photographs

Photographs are taken using the digital camera (Canon IXUS 115 h 12.1 Megapixels). The camera is fixed on a camera tripod stand. The participant with the cheeks retracted is seated on a chair in an upright position and asked to look straight. The position of the camera is also standardized by holding it parallel to the face to avoid distortion. The distance between the participant and camera (i.e. the focal distance) is set at 2 feet for all the participants. Focusing is done in such a way that complete face with exposed maxillary anterior teeth is recorded in the photograph. The photographs are uploaded onto the computer. The photographs taken are also processed and printed to a size of 15 cm × 10 cm.

Methods of measuring

Measurement using computer

The file containing photograph of the participant is opened using the Adobe Photoshop ® 7.0 software. The photo is kept at 15 cm × 10 cm. The ruler is selected from the view menu and kept in centimeters. The toolbox is then opened and the move tool command is selected. The measurements are made by positioning the guide from the ruler on the Y-axis by dragging with the help of the move tool. For measurement of the IPD, the guide is positioned on the mid-pupil of one eye. Again another guide from the ruler is dragged to the mid-pupil point of the other eye. The ruler on the X-axis is adjusted to zero from the first guide. The navigator on the corner of the screen gives the measurement in the scale [Figure 1]a. The same procedure is followed to measure the width of teeth. The first guide is then dragged from maximum convexity of the distal side of the right maxillary central incisor and the second guide to maximum convexity of distal side of the left maxillary central incisor, accordingly combined mesiodistal width of the maxillary central incisors were recorded [Figure 1]b.{Figure 1}

Measurement using vernier calipers on subjects' photographs

The measurements are also done manually using the digital vernier calipers (150 mm/6 inch, model no-FG-900125-CS-013) for IPD and combined mesiodistal width of the maxillary central incisor (MDW of MCI). The two end points of the vernier caliper were placed on the two mid pupils of the participant's photographs. The distance between the two points was measured [Figure 2]a. The same procedure is followed to measure the width of the teeth on each participant's photograph. The two end points were placed on the maximum convexity of the distal side of the right maxillary central incisor and on the maximum convexity of distal side of the left maxillary central incisor [Figure 2]b.{Figure 2}

Data collection and tabulation

Anthropometric measurements of all samples were recorded and tabulation done. Data, thus collected were subjected to statistical analysis.

 Results



Statistical analysis of the collected data to ascertain the correlation of IPD and combined mesiodistal width of maxillary central incisor teeth reveals the following results.

[Table 1] shows the mean IPD and mean combined mesiodistal width of maxillary central incisors with associated standard deviation among all 120 participants using both photoshop and vernier method. The statistical analysis using Student's t- test does not reveal any significant difference in the mean IPD done with photoshop and vernier methods. However, it shows statistically a very highly significant (P< 0.01) difference in the mean combined mesiodistal width of maxillary central incisors measured with photoshop and vernier methods.{Table 1}

[Table 2] with statistical analysis using Student's t- test does not reveal any significant difference in the IPD and combined MDW of MCIs among male and female participants done with photoshop and vernier methods. However, male participants had greater IPD compared to female participants.{Table 2}

[Table 3] shows that the result of the student's t- test does not reveal any statistically significant difference in the IPD among the ethnic Group A (Assam) and ethnic Group B (Meghalaya) using both photoshop and vernier method. Further, statistically no significant difference was seen in the combined mesiodistal width of maxillary central incisors among the ethnic Group A (Assam) and ethnic Group B (Meghalaya) using both photoshop and vernier method.{Table 3}

[Table 4] shows a highly positive correlation with statistical significance (P< 0.01) between IPD and combined mesiodistal width of maxillary central incisors among all the samples of males, females, and ethnic (Assam and Meghalaya) groups.{Table 4}

[Table 5a] presents regression analysis between the IPD and combined MDW of MCIs in all samples of male and female of both the ethnic groups R-square value, constant values for A and B with standard error.{Table 5a}

[Table 5b] presents the relation between the dependent variable-combined MDW of MCI and independent variable-IPD after calculating the value of the dependent variable using the linear regression equation: Y = A × X + B; where Y is dependent variable and X is independent variable and A and B are constant.{Table 5b}

 Discussion



Analysis of human face is a science and an art. It is a well-established fact that human faces differ from one another on the basis of race and ethnicity. Different anthropometric studies of facial measurements show wide variation between different ethnic groups.[4],[5],[6] However, the methods used for facial measurement based on soft-tissue references show age-related variations contrary to the IPD which is stable and reproducible. Hence, the present study was undertaken to investigate the potential relationship between the IPD and the combined mesiodistal width of the maxillary central incisors among the two selected groups of population of Northeast India.

Further, anthropometric measurements by previous investigators were either recorded directly on the anatomical landmarks, on the dental cast obtained from the impression by calipers like devices and various other techniques. There will be some amount of human error creeping into recordings. To eliminate the human error, Sellen et al.[7] used computer to accurately record the measurement. However, Habbu et al.[1] used both computer and caliper method and recorded the variation on both methods. The present study also used both computer (photoshop) and caliper (vernier) for recording the measurements.

In the present study, the mean IPD among 60 male and 60 female participants with the photoshop method was found to be 2.8600 cm ± 0.2781 cm and 2.8467 cm ± 0.2994 cm, respectively. Furthermore, the mean IPD among 60 male and 60 female participants with the vernier caliper method was found to be 2.8083 cm ± 0.32222 cm. In both the photoshop and vernier methods of measurement, the male participants had greater IPD compared to female participants. This difference in mean values between male and female participants is consistent to a study by Sharma et al.[8] where the mean IPD was found to be 59.77 mm in males and 57.56 mm in females. This same variation was also supported in studies done by Gomes et al.[9] and Hussain et al.[10] However, in a study done by Habbu et al.,[1] the mean IPD value in males was reported as lesser than that of females. The value of the mean of the IPD was reported higher in the study done by Sharma et al.[8] than the present study. The variation in the mean values was because of difference in focusing the camera and size of the photographs which was less in the present study. The mean values found in the present study are in accordance with the study done by Habbu et al.[1]

In general, the Indian population is genetically diverse due to its geographical location and historical background, giving rise to many dental and facial variations.[4] Gender variations in the mean mesiodistal width of the maxillary central incisors (male:8.87 mm and female:8.69 mm) have also been reported by Abdullah.[11]

In a study by Sülün et al.,[12] the width of the central incisors seems to be slightly wider in male participants (8.89 mm and 8.86 mm right and left, respectively) in comparison to females (8.72 mm and 8.74 mm right and left, respectively).

In the present study, the mean combined mesiodistal width of maxillary central incisors among 60 male participants of both Group A and Group B with the photoshop method and vernier method was found to be 0.8583 cm ± 0.0.0907 cm and 0.8183 cm ± 0.10969 cm, respectively. The mean combined mesiodistal width of maxillary central incisors among 60 female participants of both Group A and Group B with the photoshop method and vernier method was found to be 0.8433 cm ± 0.0.1079 cm and 0.79 cm ± 0.10034 cm, respectively. The results of the present study are in accordance with the previous studies done by Abdullah [11] and Sülün et al.[12]

In the present study, statistically no significant difference was found in the IPD among the age groups of 18–21 years and 22–25 years done with photoshop and vernier method. Similarly, statistically no significant difference was found in the combined mesiodistal width of maxillary central incisors among the age groups of 18–21 years and 22–25 years done with photoshop and vernier methods. This may be attributed to the fact that all the participants belong to a young age group where the gross wear and tear of teeth is usually not visible.

Since ethnic differences exist between different populations, universal application of the previous research work is possible only when it is studied in all populations.[13] The present study was an attempt to analyze this relation among the Assam and Meghalayan populations only. Student “t”-test in the present study did not reveal any statistically significant difference in the IPD among the ethnic groups of Assam and Meghalaya, done with photoshop and vernier methods. Likewise, statistically no significant difference was seen in the combined mesiodistal width of maxillary central incisors among the ethnic groups of Assam and Meghalaya, done with photoshop and vernier methods. The results of this study are not consistent with the studies previously done by other researchers on the basis of ethnic populations.[7],[14]

The present study reveals a positive correlation with a high degree of statistical significance between IPD and combined MDW of MCIs among all the samples, males and females, age and ethnicity where P < 0.01. This result is supportive to the previous studies done by Habbu et al.,[1] Anitha et al.,[15] and Sharma et al.[8] The present study could also find a statistical ratio of 1: 4 between the combined MDW of MCIs and IPD which could be used as an additional clinical guide to determine the MDW of MCIs.

The limitations of the present study included the relatively small sample of individuals from ethnically diverse backgrounds. No assessment was made regarding skeletal relationships in this study. Hence, further studies must necessarily be carried out to determine if this correlation leads to different results.

 Conclusion



Within limitations, from the findings of the present study, the following conclusions were drawn:

Although the male participants had greater IPD, statistically there is no significant gender difference in the measurement of IPD and combined MDW of MCIsThere was a positive correlation between IPD and combined MDW of MCIs among all the samples of males and females, age and ethnicityIPD can be used as an additional guide in selecting suitable size of the artificial teeth as the combined MDW of MCIs and IPD maintains a ratio of 1:4 irrespective of gender and ethnicity.

Although various methods of teeth selection are used, the applicability can vary due to ethnic differences between populations. In future, studies should be carried out with greater sample size to authenticate the use of these parameters for selection and arrangement of maxillary anterior teeth.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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