|Year : 2018 | Volume
| Issue : 2 | Page : 70-75
Correlation between maxillary central incisor crown form and maxillary dental arch form: A Model-Based morphometric, cross-sectional study
Jayasankar Purushothaman Pillai1, Riddhi Amrutbhai Patel2, Alka M Banker3, J Rajarajeswari4
1 Department of Oral Pathology, Government Dental College and Hospital, Ahmedabad, India
2 Consultant Dental Surgeon, Shraddha Orthodontic Clinic, Bharuch, India
3 Department of Orthodontia, Goenka Research Institute of Dental Science, Gandhinagar, Gujarat, India
4 Consultant Dental Surgeon, Sai Balaji Dental Clinic, Gandhinagar, Gujarat, India
|Date of Web Publication||29-Jun-2018|
Dr. Jayasankar Purushothaman Pillai
Department of Oral Pathology, Government Dental College and Hospital, New Civil Hospital Campus, Asarwa, Ahmedabad - 380 016, Gujarat
Source of Support: None, Conflict of Interest: None
The crown form of maxillary central incisor tooth is one of the vital phenomenon for a person's esthetics. Its crown form has been compared with other anatomical parameters such as arch form and facial form. Three different classes of tooth forms which relate to square, tapered, and ovoid forms are identified. The aim of this study was to morphometrically evaluate the correlation between maxillary dental arch form and the maxillary central incisor crown form. Dentate cast models of fifty male and fifty female normal occlusion controls in the age group of 18–23 years were analyzed. The mesiodistal (MD) dimensions of the maxillary central incisors were measured at incisal (MD_I) and at gingival (MD_G) levels. The transverse widths of maxillary casts were measured at the first molar and at the first premolar levels. The measured data were statistically analyzed using the SPSS software. The MD dimensions of maxillary central incisor were significantly greater in males than females. The ratio between the two MD dimensions also varied significantly among genders. The intermolar width (IMW) and inter first premolar width (IPmW) between males and females were highly significant (P < 0.05), whereas the ratio between these two parameters in males and females was not significant (P = 0.43). Eighty-eight percentage of the participants were found to have an ovoid type of maxillary arch, while only 45% of them had the ovoid form of maxillary central incisors. The MD_I and the IMW were found to be in the ratio of 1:5.5 in both genders. The MD_G and the IPmW were in the ratio of 1:4.7 in males and 1:4.5 in females. There was a weak positive correlation between MD_I and IMW (r2 = 0.146) and between MD_G and IPmW (r2 = 0.05). No significant concordance between the maxillary central incisor crown form and the maxillary arch form was found in this study.
Keywords: Intermolar width, interpremolar width, maxillary arch, maxillary central incisor, morphometric
|How to cite this article:|
Pillai JP, Patel RA, Banker AM, Rajarajeswari J. Correlation between maxillary central incisor crown form and maxillary dental arch form: A Model-Based morphometric, cross-sectional study. J Forensic Sci Med 2018;4:70-5
|How to cite this URL:|
Pillai JP, Patel RA, Banker AM, Rajarajeswari J. Correlation between maxillary central incisor crown form and maxillary dental arch form: A Model-Based morphometric, cross-sectional study. J Forensic Sci Med [serial online] 2018 [cited 2018 Nov 16];4:70-5. Available from: http://www.jfsmonline.com/text.asp?2018/4/2/70/235444
| Introduction|| |
The morphometric analysis of the tooth, known as “odontometrics,” is a part of dental anthropology that involves the physical measurements of the tooth. It can be quantitatively expressed to assess the dimensions of other body structures and skeleton. The dimensions of teeth are shown to exhibit sexual dimorphism and racial variations., Thus, the morphometric analysis of teeth has great significance in forensic and anthropological investigations. In clinical dentistry, the tooth morphometry is assessed to standardize the tooth shape based on the other craniofacial structures for rehabilitative and esthetic reasons., The correlation between the tooth form, especially of anterior teeth and the dental arch form, has been studied earlier by several researchers ,, with varied conclusions. The dental arch form is the arch formed by the buccal and facial surfaces of the teeth when viewed from their occlusal surface [Figure 1]. The shape of the tooth is classified according to different geometric shapes and based on the orientation of the proximal surfaces inciso-gingivally., The crown form of maxillary central incisor varies according to the mesiodistal (MD) dimension, the taper of proximal surfaces, and location of contact areas. Based on House and Loop classification, there are three forms of incisors: square, ovoid, and tapering. For harmonious and balanced esthetics and functional values, it is essential that a proper or ideal proportion between teeth and the arch is maintained. This comparison between tooth and arch form not only favors the clinical dentistry, but also helps forensic odontologists in predicting the arch size when only the tooth is available. Based on the correlation between the tooth form and arch form, it is possible to predict the value of one parameter when the value of other parameter is available. The present study is aimed at investigating and establishing the relationship between the crown form of maxillary central incisor and the maxillary dental arch form.
|Figure 1: Photograph showing the tooth form of maxillary central incisor and MD width parameters (a) , maxillary arch form and arch width parameters (b) used in the study|
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| Materials and Methods|| |
One hundred dental stone models of upper arch from the archives of an earlier invitro odontometric study done by the same principal investigator was selected for the present study. The approval from Institutional Ethical committee has been obtained for that study (GDCH-IEC-01/2013). The dental models belonged to the undergraduate dental students of Government Dental College and Hospital, Ahmedabad. The research methodologies and the potential use of their dental models were explained to the participants and written consents were obtained from them prior to taking the alginate impressions. The following inclusion criteria were followed:
- All participants aged 18–23 years
- Well-aligned maxillary dentition without any spacing or crowding in the incisor region
- Participants who had not undergone any orthodontic or restorative treatments
- Participants whose gingival and periodontal conditions were sound without any sign of inflammation.
The MD dimensions of the maxillary central incisors were measured using digital vernier caliper at incisal level [MD_I] and at gingival papilla level [MD_G] in both the right and left incisors. The transverse widths of the maxillary arch were taken at the first molar level (intermolar width [IMW]) and at the first premolar level (inter-first premolar width [IPmW]). The central occlusal pit in maxillary first molars and the distal pit on the occlusal surface of the first premolars on either side were identified as corresponding reference points on the plaster models. An ultrafine graphite pencil was used to mark the reference points. The measurements were made by a calibrated examiner, using a digital caliper (Mitutoyo ®, Digimatic, Mitutoyo Corp., Japan) accurate to 0.01 mm. All the parameters were measured twice on two different occasions with a gap of 2 weeks to 1 month by the same investigator (RP) and the measured values were tabulated in an Excel sheet. The mathematical calculation of the ratios and the descriptive statistics were done in Office Excel® 2007 (Microsoft®, Redmond, Washington, U.S). To assess the reliability of the measurements, a set of twenty measurements were taken from randomly selected models and were checked using Dahlberg's formula. It is defined as where di is the difference between the two measured values and N is the sample size. A range of 0.07–0.16 was obtained for the measured parameters, which was considered acceptable for our set of data [Table 1]. Interclass correlation coefficient was applied to the first reading and the second reading, to check the intra-observer error. The mean value of the two readings was applied for further statistical evaluation. The ratio between IMW and IPmW was calculated and the value was compared with the tooth mesiodistal ratio value.
|Table 1: Interclass correlation, Dahlberg's measurement error, and t-test on the variables to check the intra-observer reliability of the measured variables|
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The data were tabulated in Excel sheet and was transferred to the SPSS software (SPSS for Windows, Version 16.0. SPSS Inc., Chicago, IL, USA) for analysis. The normality of data for each variable was checked using Shapiro–Wilk's test and it was found that the data were normally distributed. The t-test done on the first and second measurements was not showing any significant differences between the values [Table 1]. Independent samples t-test was applied to examine the difference in each variable's measurements between genders. Pearson's correlation coefficient and regression analysis were performed to estimate the arch dimensions based on the MD dimension of maxillary central incisor. All tests were carried out with 5% level of significance using SPSS software version 16 (SPSS Inc., Chicago, IL, USA).
| Results|| |
The mean MD width at the incisal third was 8.65 mm ± 0.57 in males and 8.26 mm ± 0.49 in females. The mean MD width at the cervical level was 7.77 mm ± 0.5 in males and 7.58 mm ± 0.46 in females. The values showed significant difference among genders. The ratio between MD widths at the two levels was 1.12 mm ± 0.04 and 1.09 mm ± 0.04 for males and females, respectively. The ratio also showed significant difference among genders [Table 2]. The mean IMW was significantly greater for males (47.7 mm ± 3.28) than females (45.78 mm ± 2.51). The mean IPmW also showed significant difference among male and female samples. The ratio between IMW and IPmW was almost same for both males and females and the difference was not statistically significant (P > 0.05) [Table 3]. When the IMW/IPmW value was compared with the MD width ratio, a highly significant difference was observed. The Pearson's correlation coefficient between the arch ratio and tooth ratio revealed a weak positive correlation (r2 = 0.085) for females and no correlation in males (r2 = 0.000) [Figure 2]. The correlation between MD_I and IMW showed a more positive correlation in female (r2 = 0.175) than in male samples (r2 = 0.050) [Table 4]. Overall, there was only 14.6% correlation between IMW and MD_I and almost no correlation between the tooth and arch ratios (r2 = 0.01) [Figure 3]. Thus, it suggests that the tooth form does not coincide with the maxillary arch form in this study. It was also found that the IMW was 5.5 times greater than the MD width of maxillary central incisor at incisal level. The IPmW was 4.7 times and 4.5 times greater in males and females, respectively, than the MD width of maxillary central incisor at gingival level. Based on the IMW/IPmW value, we categorized the arch form into square, ovoid, and tapered [Table 5]. Eighty-eight percentage of the participants in our study had an ovoid type of arch form followed by tapered form (9%) and square form (3%). In this study, we proposed three categories of tooth form based on the MD width ratio at two levels [Table 6] and found that 54% of the study participants had the square form of tooth, followed by 45% in the ovoid category and remaining 1% had tapered form. Based on the distribution pattern also, it was found that there was no concordance between tooth form and arch form in this study.
|Table 2: Descriptive statistics for the mesiodistal dimension of maxillary central incisor crown in males and females|
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|Table 3: Descriptive statistics for the measurements done in maxillary arch in both males and females|
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|Figure 2: Scatter plot showing the correlation between maxillary arch ratio and tooth ratio of Maxillary Central Incisor in male and female subjects|
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|Table 4: Pearson's correlation coefficient and the regression equation derived from the corresponding tooth and arch parameters in males and females and its significance|
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|Figure 3: Scatter plot showing the overall correlation between (a) IMW and MD_I; (b) IPmW and MG_G; (c) Arch width ratio and Tooth width ratio|
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|Table 5: Distribution of arch forms based on the ratio between intermolar width and inter-first premolar width in males and females|
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|Table 6: Distribution of tooth form based on the ratio between the mesiodistal dimensions among males and females|
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| Discussion|| |
There are variations in the size of teeth and width of the dental arch with relation to race, culture, and sex., The MD dimension of anterior teeth and the dental arch form have considerable implication in clinical dentistry, especially in the field of prosthodontics and orthodontics. The relationship between the tooth form and the arch form is also a subject of interest in the field of forensic anthropology and forensic odontology. The MD width of maxillary anterior teeth has been correlated with measurements in the facial anatomical landmarks such as interalar distance, intercanthal distance, interpupillary distance, and philtrum width., The proportional relationship between the bi-zygomatic width and the width of maxillary central incisor was observed in studies on Turkish  and Indian population. Earlier studies ,, have correlated the morphology of upper central incisor to facial types. There is also a positive correlation between the facial type and the dental arch width. Shahid et al. investigated the maxillary and mandibular anterior crown width/height ratio and its relation to various arch perimeters, arch length, and arch width. Their study could not establish any significant relationship between crown width and height ratio to the arch width of maxilla and mandible. In the present study, we tried to establish a relationship between the MD width ratio of the maxillary central incisor and the maxillary arch width ratio. Paranhos et al. in their study concluded that the crown morphology of maxillary central incisor has no significant association with mandibular dental arch morphology. They used digitized images of the dental models in their study. The present study compared the form of the maxillary central incisor with the maxillary arch form through morphometric analysis done directly on the study models. Ninety-seven percentage of the participants in our study had square and ovoid types of maxillary central incisor tooth. In our sample, 66% of females had square form and 56% of males had an ovoid form of the tooth. The overall prevalence of the ovoid type of arch form, based on our proposed IMW/IPmW ratio, was 88%, which was similar to the study by Parahnos et al. None of the females in our study sample had the square form of the maxillary arch. Sellen et al. done a correlation study on the tooth, face arch forms, and palatal contour using image superimposition method and found significant correspondence between arch form and facial shape (28%), followed by arch form and tooth shape (24%). In their study sample, 32% of the cases showed dissimilarity between arch and tooth. A study by Berksun et al., using digital photographs, has shown 46% correlation between arch and tooth form. In the present study, we observed a weak positive correlation (14.6%) between the MD widths of maxillary central incisor at the incisal third with the corresponding IMW of the maxillary arch. There is no correlation between the MD tooth ratio and the arch ratio. This suggests that morphologically the maxillary arch form is not in harmony with the tooth form of maxillary central incisor. Based on the MD_I/MD_G ratio, and on the IMW/IPmW ratio, we proposed three categories of tooth forms and arch forms, namely, ovoid, square, and tapered. An earlier study  on Saudi population showed an insignificant distribution of tooth forms (P = 0.08) and a significant distribution of arch forms (P = 0.023) among male and female samples. The square and ovoid tooth forms were more predominant than the tapered form in their study, which was similar to the results of our earlier study. In the present study, we proposed a new value range of MD_I and MD_G ratios to categorize the tooth form. Similarly, the distribution of arch form in the Saudi population showed a significant difference between males and females (P = 0.023). The ovoid arch form predominated followed by square and tapered forms. In the present study, the ovoid arch form was the predominant form followed by tapered and square forms. The distribution of arch forms in the present study did not show any significance (P = 0.430) between male and female samples. Several population-based studies on the arch form were conducted to identify its ethnic and racial variations.,,,, Othman et al. compared the intercanine width/IMW ratio in maxillary and mandibular arches in both genders in two different ethnic groups and found no significant differences between genders in either ethnic groups. The ovoid form of maxillary arch was predominant in their study, and in our present study too, 88% of the samples had ovoid form of maxillary arch. Their study could not detect any significant difference in the IMW between genders, which is in contrast to the present study and to earlier studies. Othman et al. used the buccal cusp tip landmark to measure the IMW, whereas we used the central pit on the occlusal surface of the first molar on either sides to measure the IMW. In the present study, we compared the IMW width with the inter first premolar width. A study by Dungarwal et al. used premolar and molar indices from the sum of Incisors to predict the arch form in Maratha Population. They found a significant correlation between the sum of Maxillary Incisors and IPmW and not with IMW. They used the distance between the distobuccal cusp tips in Maxillary 2nd Molar for measuring the IMW. In their study, 60% males and 76.7% of females had the ovoid form of arch based on their formula. The arch ratio used to determine the arch form in our study was based on IMW and IPmW. In the present study, 88% of the arches were belonging to ovoid form which is based on the ratio between IMW and IPmW. We further correlated the arch ratio with the MD tooth ratio to check whether the arch form mimics the MD morphology of maxillary central incisors. In one of our earlier studies, we used the IMW and Inter Palatal Molar width to define normal transverse occlusion.
| Conclusion|| |
The present study was aimed to explore the possible correlation between the tooth form of maxillary central incisor and the maxillary arch form, so that predicting the arch width becomes possible when only the tooth is available, thus adding valuable information during facial reconstruction. Within the limitations of the samples analyzed in this study, the following conclusions may be drawn:
- There are significant gender-based variations in the MD dimensions of maxillary central incisor
- The ratio between the MD dimensions at two levels from the labial aspect can be used to determine the crown form
- There is a significant difference in IMW and IPmW values between male and female samples; while the ratio between the variables is not significant
- Based on the IMW and the IPmW, and the ratio between these two variables, we proposed three arch forms
- The female samples showed a better correlation between tooth width and arch width than male samples. Overall there is only 14.6% correlation between MD_I and IMW dimensions
- IMW was 5.5 times greater than the MD width of maxillary central incisor at Incisal level. The IPmW was 4.7 times and 4.5 times greater in males and females respectively than the MD width of maxillary central incisor at gingival level.
Through this study, we conclude that there was no any significant concordance between the tooth form and the maxillary arch form.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]