Age-Related Variations In Mental Foramen Location: A CBCT-Based Analysis

INTRODUCTION

Age stimation lays ital ole in forensic investigations, particularly when dealing with unidentified bodies or age-related legal disputes.^[1,2] hile traditional techniques often depend on dental development and skeletal maturity, these methods have limitations when applied to adult populations.^[3] dvanced morphometric analysis of craniofacial landmarks using imaging technologies like cone-beam computed tomography has emerged as a promising alternative.^[4] The mental foramen (MF) is a significant anatomical landmark in the mandible, position and size may undergo changes due to aging and bone remodeling processes.^[5,6] Several studies have evaluated the potential of characteristics to estimate age, although results vary due to differences in ethnicity and study design.^[7–9] CBCT offers detailed imagingallows precise measurement of these parameters.^[10]

This study focuses on analyzing the relationship between chronological age and specific distancesSM-UM (superior margin to upper margin), LM-IM (lower margin to inferior margin), UM-IM, and SM-IMusing CBCT images. The main goal is to develop regression models that predict age from these measurements, while the secondary aim is to observe how these distances vary across different adult age groups.^[11]

MATERIAL AND METHODS

RESULTS

The present study deals with forensic age estimation via assessment on CBCT scan. A total of 80 subjects, aged between 21 to 60 years, of both (female=35 and male=45) were recruited from the utpatientepartment (OPD) of Oral Medicine and Radiology (OMR), Career Post Graduate Institute of Dental Sciences and Hospital (CPGIDSH), Lucknow (U.P.), India. The subjects were randomized equally into four groups, viz. 21-30, 31-40, 41-50, and 51-60 years, having 20 subjects. The outcome measures of the study were distances (SM-UM, LM-IM, UM-IM, and SM-IM) assessed using CBCT and measured in millimetes (mm).

The primary objective of the study was to estimate the chronological age (i.e., actual age) from measurements (SMUM, LM-IM, UM-IM, and SM-IM). The secondary objective was to assess the age-wise (21-30, 31-40, 41-50, and 51-60 years) variations in .

Age-wise variations the mental foramen

The age-wise variations in mental foramen are summarized in Table 1. The mean LM-IM showed a linear increase, while SM-IM showed a linear decrease with an increase in age. The mean SM-UM and UM-IM both showed linear increase up to 41-50 years, but showed a slight decrease at 51-60 years compared to their levels at 41-50 years.

Table 1: Age-wise variations in the mental foramen.

Mental foramen	Age (years)	Mean ± SD (n=20)	F-value	P-value
SM-UM (mm)	21-30 * 31-40 * 41-50 * 51-60 *	15.71 ±2.63 17.14 ±2.79 18.91 ±2.60 18.43 ±2.79	5.64	0.002
LM-IM (mm)	21-30 * 31-40 * 41-50 * 51-60 *	9.52 ±1.61 10.12 ±2.05 10.76 ±2.04 11.20 ±2.59	2.45	0.070
UM-IM (mm)	21-30 * 31-40 * 41-50 * 51-60 *	10.53 ±1.81 11.98 ±2.24 13.40 ±2.31 13.24 ±1.88	8.27	<0.001
SM-IM (mm)	21-30 * 31-40 * 41-50 * 51-60 *	30.04 ±3.67 28.99 ±3.69 27.67 ±3.44 27.01 ±3.44	2.89	0.041

*Age-wise variations in each were summarized in Mean ± SD and compared by ANOVA (F value). P-values were calculated using One-way ANOVA followed by Tukey’s post hoc test. F Value denotes ANOVA test statistic used to check if age groups differ significantly in the measurements of the mental foramen. SU-UM: Superior border of mandible to upper margin of mental foramen, LM-IM: Lower margin of mental foramen to inferior border of mandible, UM-IM: Upper margin of mental foramen to inferior border of mandible, SM-IM: Superior border of mandible to inferior border of mandible, SD: Standard deviation

Comparing the mean of each among different age groups, ANOVA showed significantly different SM-UM (F=5.64, P=0.002), UM-IM (F=9.27, P < 0.001), and SM-IM (F=2.89, P=0.041) among the groups. However, mean LM-IM (F=2.45, P=0.070) was similar among the groups, indicating no significant difference.

Further, Tukey’s test revealed that SM-UM was significantly higher (P < 0.01 and P < 0.05) in both 41-50 and 51-60 year groups compared to 21-30 years [Table 2 and Figure 1]. Similarly, UM-IM was significantly higher (P < 0.001) in both 41-50 and 51-60 year compared to 21-30 years. In contrast, SM-IM significantly decreased (P < 0.05) in 51-60 year compared to 21-30 years.

Table 2: Comparison of the difference in mean mental foramen between different age groups by Tukey test.

Comparison-Age(years)	SM-UM (mm)		LM-IM (mm)		UM-IM (mm)		SM-IM (mm)
	MD	P-value*	MD	P-value**	MD	P-value***	MD	P-value
21-30 vs. 31-40	1.43	>0.05	0.60	>0.05	1.46	>0.05	1.05	>0.05
21-30 vs. 41-50	3,20	<0.01	1.24	>0.05	2.88	<0.001	2.37	>0.05
21-30 vs. 51-60	2.72	<0.05	1.68	>0.05	2.71	<0.001	3.03	<0.05
31-40 vs. 41-50	1.78	>0.05	0.64	>0.05	1.42	>0.05	1.32	>0.05
31-40 vs. 51-60	1.30	>0.05	1.08	>0.05	1.26	>0.05	1.98	>0.05
41-50 vs. 51-60	0.48	>0.05	0.44	>0.05	0.16	>0.05	0.66	>0.05

P > 0.05 or *P < 0.05 or **P < 0.01 or ***P < 0.001 as compared to 21-30 years. P-values were calculated using One-way ANOVA with Tukey’s post hoc test. SM-UM:Superior border of mandible to upper margin of mental foramen, LM-IM:Lower margin of mental foramen to inferior border of mandible,UM-IM:Upper margin of mental foramen to inferior border of mandible,SM-IM:Superior border of mandible to inferior border of mandible,SD:Standard deviation,MD:Mean difference, Values are expressed as Mean ± SD. Differences tested using One-way ANOVA (F value). Post hoc comparisons done by Tukey’s test.

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Figure 1.

Age-wise variations in mean mental foramen. * = p < 0.05; ** = p < 0.01; *** = p < 0.001. SU-UM: Superior border of mandible to upper margin of mental foramen, LM-IM: Lower margin of mental foramen to inferior border of mandible, SD: Standard deviation, UM-IM: Upper margin of mental foramen to inferior border of mandible, SM-IM: Superior border of mandible to inferior border of mandible, ns: not significant.

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Estimation of age via the mental foramen

The estimation of age from each (SM-UM, LM-IM, UM -IM, and SM-IM) was analyzed using Pearson correlation analysis and simple linear regression analysis, and summarized in Table 3 and Figures 2 to 5 respectively. Pearson correlation analysis showed significant (P < 0.001) positive correlation of SM-UM (r=0.48), LM-IM (r=0.45), and UM-IM (r=0.59) with age. In contrast, SM-IM (r=-0.47) showed a significant (P < 0.001) negative correlation with age. This significant correlation suggests that measurements can be used to estimate age [Figure 6].

Table 3: Estimation of age from each mental foramen using Pearson correlation and simple linear regression analysis (n=80)

Mental foramen	Pearson correlation (r value)	Regression coefficient of determination (R2)	Best fit linear regression equation (y=bx+a)
SM-UM (mm)	0.48***	0.2259	y= 1.9135x + 6.7009
LM-IM (mm)	0.45***	0.2032	y= 2.4647x + 14.6540
UM-IM (mm)	0.59***	0.3509	y= 2.9845x + 3.6102
SM-IM (mm)	-0.47***	0.2177	y= -1.4947x + 82.7590

***P < 0.001. In the equation, y = age, x = mental foramen measurement, b = slope, and a = intercept. SM-UM: Superior border of mandible to upper margin of mental foramen, LM-IM: Lower margin of mental foramen to inferior border of mandible, UM-IM: Upper margin of mental foramen to inferior border of mandible, SM-IM: Superior border of mandible to inferior border of mandible.

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Figure 2.

Correlation and best-fit regression equation for SM-UM and age. SM-UM: Superior border of mandible to upper margin of mental foramen

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Figure 3.

Correlation and best-fit regression equation for LMIM and age. LM-IM: Lower margin of mental foramen to inferior border of mandible

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Figure 4.

Correlation and best-fit regression equation for UM-IM and age. UM-IM: Upper margin of mental foramen to inferior border of mandible

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Figure 5.

Correlation and best-fit regression equation for SM-IM and age. SM-IM: Superior border of mandible to inferior border of mandible

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Figure 6.

Correlation and best fit regression between mental foramen and age. SM-IM: Superior border of mandible to inferior border of mandible, SM-UM: Superior border of mandibleto upper margin of mental foramen, LM-IM: Lower margin of mental foramen to inferior border of mandible, UM-IM: Upper margin of mental foramento inferior border of mandible.

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Simple linear regression analysis showed that each measurement significantly estimated the age with respective equations [Table 3], accounting for 22.59%, 20.32%, 35.09%, and 21.77% of the variation in age (coefficient of determination R²) for SM-UM, LM-IM, UM-IM, and SMIM, respectively.

When all four measurements together, multiple regression analysis also showed significant estimation of age (F=14.77, P < 0.001) with multiple R² = 0.44. In this analysis, SM-UM (t=2.37, P=0.020) and UM-IM (t=3.45, P=0.001) showed significant contributions to age estimation, whereas LMIM (t=0.54, P=0.590) and SM-IM (t=1.52, P=0.133) did not show significant association [Table 4].

Table 4: Estimation of age from mental foramen using multiple regression analysis (n=80)

Mental foramen	Co-efficient (b)	SE	t-value	P-value	Lower 95% CI	Upper 95% CI
SM-UM (mm)	0.93	0.39	2.37	0.020	0.15	1.72
LM-IM (mm)	0.34	0.63	0.54	0.590	-0.92	1.60
UM-IM (mm)	1.90	0.55	3.45	0.001	0.80	3.00
SM-IM (mm)	-0.54	0.36	1.52	0.133	-1.25	0.17
Intercept (a)	12.36	16.62	0.74	0.459	20.74	45.46

SE: Standard error and CI:Confidence interval. SM-IM: Superior border of mandible to inferior border of mandible, SM-UM: Superior border of mandible to upper margin of mental foramen, LM-IM: Lower margin of mental foramen to inferior border of mandible, UM-IM: Upper margin of mental foramen to inferior border of mandible.

DISCUSSION

This study assessed the potential of MF measurements on CBCT scans for forensic age estimation and found significant age-related variations. The dimensions SM-UM and UM-IM increased progressively from the 21-30 to the 41-50 year age group. These findings support the hypothesis that age-related remodeling of the mandible alters MF positioning and morphology.^[13]

Interestingly, a slight decline in SM-UM and UM-IM values in the 51-60 year group may indicate the influence of age-related bone resorption, particularly affecting cortical structures. This trend has also been observed by Singh et al.^[14], who attributed the changes to progressive alveolar bone loss and structural alteration in late adulthood.

The SM-IM showed a significant negative correlation with age, suggesting that vertical reduction in mandibular height with age could serve as a useful forensic marker. Conversely, LM-IM did not show statistically significant intergroup differences. This lack of variation may stem from individual anatomical differences or challenges in consistently identifying measurement points on CBCT images, as noted in similar studies.^[15]

The Pearson correlation analysis showed moderate but significant relationships between MF parameters and age, particularly UM-IM (r = 0.59), supporting its utility in forensic applications. Linear regression models based on these parameters could estimate chronological age with reasonable accuracy, explaining up to 35.09% of age variability for UM-IM. Although these models do not yield precise age values due to inherent biological variability, they offer valuable supplementary tools in forensic age estimation.^[16,17]

The use of CBCT significantly enhanced the precision of landmark identification and measurement, addressing limitations such as image distortion and superimposition seen in traditional radiography. The ability of CBCT to provide detailed 3D visualization of anatomical structures supports its role in forensic odontology, especially in age assessment, where millimetric accuracy is essential.^[18,19]

Multiple regression analysis revealed that SM-UM and UM-IM made statistically significant contributions to age prediction when considered together, with an overall model R² of 0.44. This highlights their combined predictive power, though the model still reflects that age estimation from MF metrics is best used as an adjunct rather than a stand-alone method.

Despite the promising results, the study has limitations. The sample size (n = 80) and age range (21-60 years) limit generalizability. Inclusion of older age groups and larger, more diverse populations would enhance the strength and applicability of the findings. In addition, factors such as dental status, bone density, and systemic health conditions were not considered, which might influence MF position.^[20]

CONCLUSION

Mental foramen dimensions measured on CBCT images exhibit significant age-related variation. Among the parameters studied, SM-UM and UM-IM increased with age, while SM-IM decreased, showing potential as age estimation indicators. The strongest correlation with age was observed with UM-IM, making it a reliable parameter for forensic assessments.

Regression models based on these metrics provide a moderate degree of age prediction and, when used in combination, improve accuracy. While these metrics cannot replace primary age estimation tools, they can serve as valuable adjuncts, particularly when other indicators are inconclusive or unavailable.

CBCT's high-resolution imaging further strengthens the reliability of MF assessment in forensic contexts, offering a practical and accurate modality for anatomical studies. Future studies involving larger and more heterogeneous populations, including subjects over 60 years, are needed to validate and refine the predictive models.

In conclusion, CBCT-based assessment of morphology is a promising supplemental tool in forensic age estimation, enhancing the reliability of age-related analysis in oral radiology and forensic dentistry.