Age Estimation Using Attrition and Pulp Cavity Size of the Mandibular First Molar in Korean Population

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Korean J Leg Med. 2025;49(1):1-6

Publication date (electronic) : 2025 February 28

doi : https://doi.org/10.7580/kjlm.2025.49.1.1

Hee-Won Kim¹, Hye-Mi Jeon², Kyung-Hee Kim³, Hye-Min Ju⁴, Soo-Min Ok⁴, Sung-Hee Jeong⁴, Yong-Woo Ahn^4,

¹Department of Oral Medicine, Pusan National University Dental Hospital, Dental Research Institute, Yangsan, Korea

²Dental Clinic Center, Pusan National University Hospital, Busan, Korea

³Department of Oral Medicine, Busan Paik Hospital, Inje University College of Medicine, Busan, Korea

⁴Department of Oral Medicine, Pusan National University, School of Dentistry, Dental Research Institute, Dental and Life Science Institute, Yangsan, Korea

Correspondence to Yong-Woo Ahn Department of Oral Medicine, Pusan National University, School of Dentistry, 20 Geumo-ro, Mulgeum-eup, Yangsan 50612, Korea Tel: +82-55-360-5233 Fax: +82-55-360-5234 E-mail: ahnyongw@pusan.ac.kr

Received 2024 October 27; Revised 2024 December 2; Accepted 2025 February 17.

Abstract

Introduction

In forensic science, age estimation is a crucial factor for identifying both living and deceased individuals, with applications across various fields, including the identification of dead bodies and the verification of survivors’ identities [1]. Among human body tissues, oral tissues exhibit age-related changes more gradually than other areas, with the teeth and jawbones showing the least individual variation [2,3]. In particular, teeth are considered reliable indicators for age estimation because they are highly resistant to physical and chemical stimuli and can remain preserved for long periods [3]. Factors used in dental age estimation include tooth eruption, exchange of primary and permanent teeth, loss of permanent teeth, degree of calcification, pulp cavity size, tooth attrition, and microstructural changes. In adults with complete tooth calcification, tooth attrition and pulp cavity size are the primary indicators of age [3,4].

Tooth attrition is a physiological process that refers to the natural wear of the cutting surfaces of the anterior teeth and the occlusal surfaces of the posterior teeth due to normal chewing. In contrast, mechanical wear beyond normal chewing, such as grinding, is referred to as abrasion. As teeth gradually wear down over time, the degree of attrition increases with age [4]. Age estimation methods using tooth wear have been reported in various studies, with Takei's method [5] being the most widely used. This method evaluates the tooth wear by dividing it into three grades: grade A (attrition parts are still separated), grade B (attrition parts are united), and grade C (dentin is exposed) [5]. Recently, Choi et al. [6] analyzed the relationship between attrition of the first and second molars and age in a Korean population aged in their 50s and 60s using the Average Stage of Attrition (ASA) method [7].

The size of the pulp cavity decreases with age due to physiological changes, particularly secondary dentin formation [4]. Patterns of secondary dentin deposition vary between teeth; in the maxillary anterior teeth, it primarily occurs on the palatal side of the pulp chamber, while in the posterior teeth, it appears on the pulp chamber floor, occlusal surface, and lateral walls [8]. This variation in pulp cavity size can provide essential clues for age estimation, and several studies have developed age-estimation equations with high explanatory power based on these patterns [9-12].

While tooth attrition-based age estimation requires a large number of teeth, pulp cavity size estimation is limited by its reliance solely on the size of the pulp cavity without considering the overall condition of the oral cavity. Therefore, the development of an age-estimation equation using both attrition and pulp cavity size may simplify future age estimation for both living and deceased individuals.

Additionally, changes in the tooth microstructure, although useful, require extraction, which makes in vivo age estimation challenging. With social changes increasing the demand for accurate age verification among the older adults, often for pension or insurance purposes, a new approach for age estimation that considers the number of teeth, attrition level, and pulp cavity size is required.

This study aimed to address the limitations of existing age-estimation methods by combining tooth attrition and pulp cavity size to enhance accuracy in adults. By examining pulp cavity changes across attrition grades, we sought to determine whether a more precise approach was possible.

Materials and Methods

2. Measurements

Clinical photographs were reviewed, and panoramic radiographs were saved in Digital Imaging and Communication in Medicine (DICOM) format through the Picture Archiving and Communication System for grade C teeth with exposed dentin following Takei's method [5]. The DICOM files were adjusted for size, brightness, and contrast using Adobe Photoshop 2024 (Adobe Systems Inc., San Jose, CA, USA) to ensure measurement accuracy. A line was drawn from the lingual groove to the root branch, and the image was rotated to align with this line using the ‘straighten’ tool. In the edited image, measurements were taken as described by Jeon et al. [9], including dimensions AB, a-b, C-D, and c-d (Fig. 1).

Fig. 1.

Measurements performed on a panoramic radiograph of a mandibular first molar by using Adobe Photoshop 2024 program. A, start of the lingual groove; B, apex of the furcation; a, superior point where line A-B meets the pulp cavity; b, inferior point where line A-B meets the pulp cavity; C, left point where the vertical bisector through A-B meets the tooth; D, right point where the vertical bisector through A-B meets the tooth; c, left point where the line connecting C-D meets the pulp cavity; d, right point where the line connecting C-D meets the pulp cavity.

To minimize measurement errors due to radiographic distortion, we calculated two ratios as described by Jeon et al. [9]: the pulp chamber height ratio (PCHR; a-b/A-B) and pulp chamber width ratio (PCWR; c-d/C-D). All tooth measurements were repeated by the same observer after two weeks to assess reliability.

Results

A total of 118 panoramic images of mandibular first molars, including teeth with exposed dentin, were selected. Intraobserver reliability showed significant agreement (ICC>0.6). The independent-sample t-test indicated no significant sex-based differences in the PCHR and PCWR (Table 1).

Table 1.

Results of independent-sample t-test according to sex

Both PCHR and PCWR exhibited a significant negative correlation with age in both men and women, with PCWR showing a stronger correlation than PCHR. The highest correlation between PCWR and age was observed in women (r=-0.606) (Table 2).

Table 2.

Pearson's correlation coefficients (r) between chronological age and ratios of measurements from panoramic radiographs for the pooled sample, and each group

Simple regression analyses revealed that PCWR provided age estimation equations with higher explanatory power than PCHR for both men and women. The results of studies using either the PCHR or PCWR alone indicated low correlations, suggesting that both variables should be used together (Table 3).

Table 3.

Simple regression analysis between age and each ratio of measurements

The following age estimation equation was derived from the full sample:

Estimated age (attrition grade C)=

126.700-153.413×(PCHR)-118.073×(PCWR)

The highest coefficient of determination was found when both the PCHR and PCWR were applied to the male sample (R²=0.546) (Table 4), with consistent explanatory power across sex-specific and combined samples.

Table 4.

Multiple regression equations for estimating age (yr) using independent ratios of measurements on panoramic radiographs

Discussion

In Korean society, age verification is required for various social programs, and many individuals request age assessments due to discrepancies between their actual age and recorded age. Under the Elderly Welfare Act, age certificates are often necessary for legal processes such as extending retirement age, receiving social security benefits early, or receiving welfare benefits [13,14].

Teeth, as the hardest structures in the human body, play a crucial role in age estimation. However, relying on a single indicator is challenging due to continuous physiological changes [4]. While tooth attrition and pulp cavity size serve as age markers in midlife, other indicators such as the loss of permanent teeth become significant in old age [4].

Tooth attrition is generally accepted as a physiological sign of aging. In 1984, Takei [5] estimated the age of 1,000 patients aged 20 years and older by categorizing teeth into five stages based on their degree of attrition, loss, caries, and treatment status; however, this is not accurate in individuals with multiple missing teeth, as it applies the overall oral condition and the entire tooth to estimate age, and it lacks a basis for excluding patients with abnormal wear patterns.

In 2000, Kim et al. [15] evaluated 16 permanent molars and divided them into eight stages of tooth wear, demonstrating high accuracy, but limitations in excluding patients with missing or restored molars. In 2007, Yun et al. [16] conducted a large-scale study that included a variety of dental conditions, including caries and restorations, and found that accuracy increased with the number of remaining teeth. In addition, the process of tooth attrition is influenced by a variety of factors, including diet, mastication, bite force, geographic location, and status of the antagonist teeth, making it unreliable to estimate age based solely on tooth attrition.

The formation of secondary dentin begins after dentinogenesis and progresses throughout life along the pulpal surface of the primary dentin, hence the continuous pulp cavity loss observed with increasing age [8,17]. In 1985, Ikeda et al. [18] introduced an index called the Tooth Coronal Index (TCI) using changes in the size of the pulp cavity as a function of secondary dentin accumulation on radiographs. In 1993, Drusini [19] measured TCI on panoramic radiographs and found a high correlation with age.

In 1995, Kvaal et al. [20] measured the pulp size on periapical radiographs of the incisors, canines, and premolars in adults and found strong correlations ranging from 0.56-0.76. In 2015, Jeon et al. [21] derived an age estimation equation with a negative correlation, considering the decrease in the size of the pulp cavity in mandibular first molars in Koreans, and in 2018, they confirmed a higher correlation (R²=0.660-0.730) using the PCHR and PCWR [9].

In this study, Takei's tooth classification [5] was used to evaluate teeth with exposed dentin corresponding to group C, and the error was minimized using the PCHR and PCWR metrics from Jeon et al. [9]. The intraobserver reliability showed sufficient agreement, with an ICC>0.6.

The independent-sample t-test showed no significant differences in PCHR and PCWR by sex, indicating that sex does not significantly influence the size of the pulp cavity, which is consistent with previous studies (Table 1) [9,19]. Pearson's correlation analysis showed that both the PCHR and PCWR were negatively correlated with age, with PCWR showing a stronger negative correlation than PCHR, suggesting that the width of the pulp cavity may be a more important indicator of age (Table 2).

The correlation coefficient for PCWR was the highest in the female sample (r=-0.606), suggesting that the decrease in pulp cavity width with increasing age may be more pronounced in women. In a simple regression analysis using PCHR and PCWR, PCWR had higher explanatory power than PCHR. This indicates that pulp cavity width may be a more reliable variable for age estimation than pulp cavity height. Notably, the correlation was the highest when the PCWR was applied to females (Table 3).

Multiple regression analyses using both PCHR and PCWR consistently produced high correlations in the overall sample and in the male and female groups. The highest coefficient of determination was found in the male sample (R²=0.546), indicating that using both variables simultaneously can not only lower the standard error of age estimation but also significantly improve the accuracy and reliability of age estimation (Table 4).

Using attrition and pulp cavity size variations for age estimation has the advantage of being straightforward, noninvasive, and simple [22]. The present study evaluated grade C teeth with exposed dentin based on Takei's method [5] and combined it with Jeon's method [9] to derive an age estimation equation with higher explanatory power. As a result, we presented an equation with a higher correlation than those in previous studies (Table 4).

As society becomes more complex and interest in welfare benefits increases, finding the correct age will continue to be a subject of interest, and it is natural for forensic odontologists, who have the primary responsibility for age estimation, to seek new and more accessible methods. The combined approach of attrition and pulp cavity size using panoramic radiographs of the mandibular first molars is simple and relatively accurate for age estimation in Korean adults and is expected to be clinically useful.

This study included patients who visited our department, most of whom were in their 50s or older. Most patients present with existing fillings or pathological conditions after implant or crown restoration. As a result, normal mandibular first molars are rare, and the number of patients classified as grade A or B is extremely limited. Consequently, this study focused solely on group C. Despite the limitations posed by the small sample size, this research is expected to serve as a cornerstone for developing future age estimation methods that incorporate both pulp cavity measurements and tooth attrition levels. We look forward to further research on improved methods that can overcome the shortcomings of the sole method of evaluating attrition and identifying pulp cavity size.

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