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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 34  |  Issue : 1  |  Page : 87-94

Correlation of pulp-to-tooth area ratio with age and gender using CBCT of maxillary central incisor and canine: A comparative study


Department of Oral Medicine and Radiology, Swami Devi Dyal Hospital and Dental College, Barwala, Haryana, India

Date of Submission09-Mar-2021
Date of Decision13-Jul-2021
Date of Acceptance21-Oct-2021
Date of Web Publication25-Mar-2022

Correspondence Address:
Dr. Aravinda Konidena
Department of Oral Medicine and Radiology, Swami Devi Dyal Hospital and Dental College, Haryana
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0019-5049.340762

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   Abstract 


Introduction: Dental age estimation of living or deceased individuals through radiographic methods are popular, among which pulp-tooth ratio is a sensitive indicator. The aim of this study was to estimate and compare age based on the pulp-to-tooth area ratio (PTR) of maxillary canines and central incisors from sagittal, coronal, and three levels on axial section from CBCT data. Methods and Materials: Sixty adults of Indian origin (31 men and 29 women) aged between 20 and 65 years visiting the Department of Oral Medicine and Radiology of our institution requiring CBCT of anterior maxilla for their diagnosis or treatment planning were included as study subjects. The sagittal, coronal, and axial images of maxillary central incisor and canine were imported to AutoCAD 2016 computer-aided drafting program. For each image, 30 and 10 points were marked on the tooth and pulp outlines, respectively, using the point tool on AutoCAD Toolbox. PTR was calculated and subjected to statistical analysis. Results: There was a declining trend in PTR with advancing age in maxillary central incisor in all sections and axial section at CEJ in canine. When the PTR values were compared, axial section at one-fourth, axial section at mid-root, sagittal and coronal sections for maxillary incisor showed significant differences between the age groups. There was no significant difference in PTR values between the genders. The best predictor for age was coronal and sagittal sections for central incisor, and sagittal section for maxillary canine. Maxillary central incisor yielded a better estimate with an SEE of 8.258 years than canine for age estimation. Conclusion: Results revealed a declining trend in PTR with advancing age in maxillary central incisor in all sections and axial section at CEJ in canine.

Keywords: Age estimation, Auto CAD, CBCT, canine, incisor, pulp-tooth ratio


How to cite this article:
Bansal V, Konidena A, Nagi R, Kataria AP, Yumnam N, Farooq F. Correlation of pulp-to-tooth area ratio with age and gender using CBCT of maxillary central incisor and canine: A comparative study. J Indian Acad Oral Med Radiol 2022;34:87-94

How to cite this URL:
Bansal V, Konidena A, Nagi R, Kataria AP, Yumnam N, Farooq F. Correlation of pulp-to-tooth area ratio with age and gender using CBCT of maxillary central incisor and canine: A comparative study. J Indian Acad Oral Med Radiol [serial online] 2022 [cited 2022 May 27];34:87-94. Available from: https://www.jiaomr.in/text.asp?2022/34/1/87/340762




   Introduction Top


Age estimation of living or deceased individuals is vital to determine the identity in cases where visual recognition is not possible.[1] An accurate estimation of age will significantly narrow the field of possible identities that will have to be compared to the remains in order to establish a positive identification.[2] Teeth are one of the strongest structures in the human body that are least affected by external factors; hence, their use in age estimation has long been recognized.[3] Dental age prediction based on quantification of morphological age-related changes of teeth such as secondary dentine deposition through histological, biochemical as well as radiological methods had gained popularity.[4] However, noninvasive methods that do not require tooth extraction or sectioning including radiographic methods had gained wider acceptance.[5]

The common practice of dental age prediction through secondary dentin deposition, using pulp-tooth area ratio through periapical or panoramic radiographs was constrained due to distortion errors.[6] Cone-beam computed tomography (CBCT) is currently being used in dentistry for various diagnostic applications, thus creating new avenues to get three-dimensional images of reasonable image quality at a low radiation dose. Thorough literature search revealed a paucity of studies evaluating teeth other than canine. However, given that maxillary lateral incisors are known to present commonly with morphological variations and any anterior tooth may be available for investigation,[7] this study was planned to compare age estimated based on the pulp-to-tooth area ratio (PTR) of maxillary central incisors and canines from sagittal, coronal and three levels on axial section from CBCT image data.


   Materials and Methods Top


Study sample selection

Sixty adults of Indian origin (31 men and 29 women) aged between 20 and 65 years who visited the Department of Oral Medicine and Radiology of our institution between June 2019 to November 2019, requiring CBCT of anterior maxilla for their diagnosis or treatment planning such as orthodontic treatment, implant placement in region of missing teeth, endodontic considerations, were included as study subjects. Subjects with missing maxillary canines or central incisors, developmental anomalies involving shape, size, structure of canine or central incisors, endodontically treated teeth were excluded from the study. CBCT images with artifacts involving the region of interest were also excluded from the study. The chronologic age of the subjects was calculated from their date of birth from a valid identity proof and was rounded off to the nearest years. The study protocol had been approved by the Institutional ethical committee [SDD/Eth/19/30] and written informed consent was taken from the participants.

Acquisition of CBCT data

CBCT images of the subjects were acquired on Sirona digital imaging system with 70–74 kV, 10 mA, and 10.8 s, with a field of view (FOV) 8 cm × 8 cm, and voxel size of 160 μm3. For CBCT evaluation, 19-inch LCD monitor with 1366 pixel × 768 pixel resolution, 800:1 contrast ratio, and Galaxis Galileos software was used. Brightness and contrast of the images were adjusted according to the need. The data of CBCT images was sliced into three dimensions. Sagittal, coronal and axial sections of central incisor at three levels: CEJ, 1/4th of root, and mid root level, were taken for both teeth. To obtain sagittal section, curved slices oriented along the curve of the maxillary arch were delineated [Figure 1]a. The cursor was oriented parallel to the long axis of the maxillary central incisor and canine to obtain the mid-sagittal plane and section so obtained was taken as sagittal section. Oblique slicing was done to obtain the mid-coronal section along the long axis of the tooth to assess the coronal section [Figure 1]b. To get the desired axial section, the longitudinal axis of the tooth from the crown tip to root apex was determined, and then the axial section of the tooth was set at CEJ, at 1/4th of root and mid root level [Figure 1]c. Similar protocol was followed for making the measurements on maxillary canine [Figure 2].
Figure 1: a) Sagittal section used for measurements, b) Coronal section used for measurement, c) Axial sections taken at CEJ for central incisor

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Figure 2: a) Sagittal section used for measurements, b) Coronal section used for measurement, c) Axial sections taken at CEJ for canine

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The images were imported to AutoCAD 2016 computer-aided drafting program (Autodesk Inc., San Rafael, CA, USA). For each image, thirty points and 10 points were marked on the tooth and pulp outlines respectively using the point tool on AutoCAD Toolbox and joined. This procedure was performed for all the five sections of each tooth. PTR was calculated for sagittal, coronal sections and 3 levels on axial sections. The measurements were repeated on a subset of sample after 10 days to assess intra-observer variability. Measurements following the same procedure on a subset of mages was carried out by a second observer to assess interobserver variability.

Statistical analysis

The data were entered into a Microsoft Excel spreadsheet. Analysis was done using Statistical Package for Social Sciences (SPSS) version 20 (IBM SPSS Statistics Inc., Chicago, Illinois, USA) Windows software program. Descriptive statistics included computation of means and standard deviations. The Mann–Whitney U test and analysis of variance (ANOVA) followed by post hoc analysis were used to compare quantitative data within two groups and three groups respectively. Multiple-step regression model (linear stepwise regression model using backward elimination) was used for prediction. Level of significance was set at P ≤ 0.05. Intra-observer (between readings taken 10 days apart) and interobserver variability (between readings taken by two observers) were evaluated by kappa statistics.


   Results Top


The mean values of PTR along with minimum and maximum values of axial sections at 3 levels, sagittal and coronal sections of both teeth are shown in [Table 1]. There was a declining trend in PTR of maxillary central incisor with advancing age. The age range of the subjects included was diverse and hence for better evaluation, the subjects were segregated further into 5 groups with an age interval of 10 years. When the PTR values were compared between different age groups, for maxillary central incisors all sections except axial sections at CEJ showed significant differences between the age groups. Further multiple intergroup comparisons are depicted in [Table 2], [Figure 3]. Scatter plot showing relation of chronological age with PTR in axial, coronal, and sagittal sections of central incisor is shown in [Figure 4].
Table 1: Comparison of PTR of different sections among the age groups using ANOVA and between canine and central incisors using Independent t-test

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Table 2: Comparison of PTR between genders for maxillary central incisor in axial, coronal and sagittal sections

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Figure 3: Bar graph showing mean PTR of maxillary central incisor in three axial, sagittal and coronal sections among different age groups

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Figure 4: Scatter plot showing relation of age and PTR of maxillary central incisor in a) axial CEJ, b) axial one fourth, c) axial mid root level d) coronal and e) sagittal sections

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When the PTR variables of central incisor were compared between the genders, there were no significant differences noted in any of the sections as shown in [Table 2] which indicated that, the PTR values were similar in both genders. PTR values showed a negative correlation with age. Correlation coefficient lower than –0.7 implicates very strong negative correlation, values between –0.7 and –0.5 indicates a strong negative correlation, between –0.5 and –0.3 suggest moderate negative correlation while values higher than –0.3 suggest weak correlation. In this context, the strongest negative correlation in male subjects was observed in axial mid root and coronal sections, while in females, highest negative correlation was observed for axial one-fourth and sagittal sections. It was found that males showed highly significant moderate negative correlation in most sections except axial one-fourth section.

When the PTR of central incisors on various sections was regressed on chronologic age, PTR on sagittal and coronal sections emerged as significant predictors, as shown in [Table 3]a, [Table 3]b. Age estimation by maxillary central incisor by sagittal + coronal sections had higher R2. The measured R2 for sagittal and sagittal + coronal sections were 0.537 and, 0.669, respectively, indicating the highest power of combined sagittal and coronal sections over the sagittal values alone to predict age. Thereafter, by considering all the involved variables, the R2 and SEE of maxillary central incisor were measured using multiple stepwise regression analysis and were found to be 0.537 and 9.774 years on sagittal section and 0.669 and 8.258 on sagittal + coronal sections respectively. Derived regression equations to predict chronologic age in various sections for maxillary central incisor are illustrated in [Table 3]c.
Table 3:

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The differences in PTR of canine between age intervals had been shown in [Table 4], [Figure 5]. Scatter plot showing relation of chronological age with PTR in axial, coronal and sagittal sections for canine is illustrated in [Figure 6]. PTR values obtained from maxillary canines in different sections did not show any particular trend, except in axial section at CEJ, where there was a decrease in PTR with increasing age. Significant differences in PTR were noted in axial section at CEJ between the age groups. When the PTR variables of maxillary canine were compared between the genders, there were no significant differences noted in any of the sections, as with central incisor, as shown in [Table 4]. When correlated with age, PTR values of maxillary canine exhibited a weak negative correlation in most cases and strong negative correlation in females for axial mid root section. When PTR values of different sections were regressed on chronological age in maxillary canine, the best significant predictor was sagittal section with highest R2 (R2 = 0.843), with a mean error of estimation of 19.31 years as shown in [Table 5]a, [Table 5]b. Derived regression equations to predict chronologic age in various sections for maxillary canine are illustrated in [Table ]5c. Though the predictability of age derived from canine was higher than that of central incisor, the standard error of estimate from central incisor data was much smaller. Furthermore, when mean values of PTR were compared between central incisor and canine, significant difference was obtained on sagittal sections [Table 1].
Table 4: Comparison of PTR of maxillary canine between genders in axial, coronal, and sagittal sections

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Figure 5: Bar graph showing mean PTR of maxillary canine in three axial, sagittal and coronal sections among different age groups

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Figure 6: Scatter plot showing relation of age and PTR of maxillary canine in a) axial CEJ, b) axial one fourth, c) axial mid root level d) coronal and e) sagittal sections

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Table 5:

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When the primary and repeat measurements were analyzed using kappa statistics for intraclass correlation, sagittal and axial sections showed the best agreement with coefficients ranging between 0.98-0.99, while even the coronal section measurements showed very good agreement as shown in [Table 6](a). For interclass correlation primary and repeat measurements in sagittal and axial sections showed the best agreement with coefficients ranging between 0.93-0.95, while the coronal section showed good agreement [Table 6](b).
Table 6:

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   Discussion Top


Our analysis predicted that PTR is an indirect quantification of secondary dentin deposition and generally correlates well with the chronological age of the subject.[1],[8],[9],[10],[11] Declining PTR values with advancing age were observed due to secondary dentin deposition and an inverse correlation between PTR and chronological age was found, similar to the study by Cameriere et al.[10],[12] PTR values showed significant variations between the various age groups in 4 sections of maxillary central incisor but only with axial section at CEJ in maxillary canine. This may be attributed to the possibility of distinct demarcation of the pulp and the tooth outline in the CEJ section as compared to apical sections.

Yang et al.,[13] in their study stated that in young individuals, the shape of tooth mainly changes with the deposition of enamel, dentin, and cementum and the closure of apical foramen whereas for adults shape of the tooth is primarily influenced by the secondary dentin deposition. As our sample was between 20 and 65 years, teeth selected were less influenced by morphological variations and pulp tooth ratio decreased with increasing age by secondary dentin formation on inner surface of pulpal walls. In our study, more variations in PTR values were seen in older age groups above 50 years, which could be due to influence of periodontitis, increased occlusal stresses, hormonal alterations, etc., resulting in reduction of pulpal volume.[14]

There was no gender variation in PTR in this study for both teeth, which was in accordance with the study carried out by Gulsahi et al.[8], Cameriere et al.[12] and Singaraju S et al.[15] This could be explained by the assumption that dentin deposition pattern is same for both females and males after completion of pubertal growth spurt and subjects included were in age range of 20 to 65 years, wherein most of the teeth except third molars would have completed their developmental process.[16] In this study, all the PTR values except at axial one-fourth for central incisor in males showed significant correlation with age similar to Gulsahi A et al.[8] In females, we found statistically significant correlation of PTR in all sections except axial CEJ section. PTR values of canine showed significant correlation only at mid-root level in females similar to Rai A et al.[1] We found the strongest correlation for males in axial mid root and coronal sections of central incisor, while for females, highest negative correlation was observed for axial one fourth and sagittal sections. While Rai A et al.[1] and Haganifar S et al.[11] found significant correlations with axial sections alone, Lee SM et al.[17] found significant correlations between sagittal PTR and age than axial section. The differences could be due to the variation in methodology used and population studied as genetic factor influences secondary dentin formation.

Star et al.[18] found higher correlation for the maxillary incisors and they assumed that it could be a result of inclusion of relatively a smaller number of canines in comparison to incisors. Similarly, in this study maxillary central incisor yielded better age correlation than maxillary canine; although equal number of canines and central incisors were evaluated, maxillary central incisors showed a lesser SEE of 8.258 years than 19.31 years for canine. Effect of factors such as tooth wear could not be excluded in this study. Kumar et al.[19] reported that the maxillary anterior showed the lowest incidence of tooth wear score. On the contrary, Pigno et al.[20] had shown more incidence of attrition in maxillary canines which may be attributed to maximum force exerted on canine during chewing and lateral jaw movements mainly in individuals with canine guided occlusion. This may be one of the reasons for the higher standard error of estimate obtained with canine in this study.

In this study, sagittal and coronal sections put together yielded a better fit on regression models for central incisor, while sagittal parameter gave the best fit for canine. PTR correlation in sagittal plane is most anticipated given the buccopalatal orientation of pulp chamber and pattern of secondary dentin deposition. It also can be deduced that obtaining PTR in multi-planar sections would yield a better correlation with age, thus clearly indicating the superiority of using CBCT for evaluating age using PTR. This study used multiple stepwise regression model to derive the best predictor for age. It was found that standard error of estimate was 8.258 years for maxillary central incisor which was within an acceptable limit of 10 years of forensic medicine, while it was 19.31 years for canine, which makes it unsuitable for age prediction. Our results were similar to Gulsahi A et al.[8] and Haganifar S et al.[11] This may be explained by possibility of greater attrition on canine than central incisor due to canine-guided occlusion, which was not taken into consideration. In this study intra-observer variability showed good agreement of 0.98-0.99 between measurements, indicating high reproducibility of measurements and accuracy of method used, similar to the study done by Gulsahi A et al.[8]

The limitations of our study were small sample size and use of pulptooth area ratio. Therefore, to validate our findings, further studies on multiple teeth using better methods of age determination with CBCT should be carried out on large population taking into account environmental, gender and geographical variations. Although majority of studies are in agreement with our results suggesting a better correlation of age with maxillary central incisor, further studies should be focused on the maxillary canine chiefly in the young population to predict it as a reliable biomarker of age.


   Conclusion Top


There was a declining trend in PTR with advancing age in maxillary central incisor in all sections and axial section at CEJ in canine. PTR was not gender dependent. The best predictor for age was coronal and sagittal sections for central incisor, and sagittal section for maxillary canine. Stronger correlations were obtained between age and PTR were found with maxillary central incisor than canine.

Human rights statement and informed consent

All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1964 and later versions. Informed consent was obtained from all patients for being included in the study.

Animal rights statement

This article does not contain any studies on animal subjects performed by any of the authors.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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