8 J Gandhara Med Dent Sci

July - September 2025

ORIGINAL ARTICLE

DETERMINATION OF THE FREQUENCY OF ACCESSORY MENTAL FORAMEN USING CBCT IN
PATIENTS PRESENTING TO A LOCAL TERTIARY CARE HOSPITAL

Nida Ayub 1, Yousaf Athar2, Ramsha Jalal3, Fatima Saleem4, Aneela Shabbir5, Ahmed6

ABSTRACT
OBJECTIVES
This study aimed to determine the frequency of accessory mental foramen
using CBCT in the local population.
METHODOLOGY
The cross-sectional descriptive study; Periodontology Department, Institute
of Dentistry, CMH Medical and Dental College, Lahore. Patients reporting
to the outpatient department for routine dental treatment that required a
CBCT assessment were sought. Adult dentate subjects with at least
mandibular canine to first molar teeth present bilaterally were selected.
Volumetric data from CBCT scans was used to reconstruct mandibular
images. Mental foramen was identified as the largest opening on the
mandibular buccal surface. Any additional buccal opening in the proximity of
the mental foramen was recognized as an accessory foramen. The location of
the accessory foramen concerning the mental foramen and its diameter was
noted. Data was analysed using the Statistical Package for the Social
Sciences (SPSS), version 24. Descriptive statistics were evaluated. Effect
modifiers were controlled through stratification, and a post -stratification chi-
square test was used. An Independent sample t-test was used to compare the
mean foramen diameter between males and females. A p-value of ≤0.05 was
considered significant.
RESULTS
Accessory mental foramen was observed in only 5.5% of subjects. The most
frequent location of accessory mental foramen to mental foramen was
"postero-inferior", seen in 3% of cases. No significant difference in the
incidence of accessory mental foramen was seen between males and females
(p=0.733).
CONCLUSION
Results of this study suggest it is quite possible to encounter an accessory
mental foramen during dental procedures in the Pakistan population. It is a
rare but significant anatomical variation. Care must be taken to identify such
structures during the treatment planning phase of dental surgical procedures.
KEYWORDS: Mental Foramen; Cone Beam Computed Tomography;
Mandible

How to cite this article

Ayub N, Athar Y, Jalal R, Saleem F,
Shabbir A, Ahmed. Determination of
the Frequency of Accessory Mental
Foramen Using Cbct in Patients
Presenting to A Local Tertiary Care
Hospital. J Gandhara Med Dent Sci.
2025;12(3):8-11. https://doi.org/10.37762

Date of Submission: 19-03-2025
Date Revised: 25-04-2025
Date Acceptance: 31-05-2025

2HOD, Associate Professor,
Department of Periodontology,
Institute of Dentistry, CMH Lahore
Medical College

3FCPS-II Trainee, Department of
Periodontology, Institute of Dentistry,
CMH Lahore Medical College

4FCPS-II Trainee, Department of
Periodontology, Institute of
Dentistry, CMH Lahore Medical
College

5Assistant Professor, Department of
Periodontology, Institute of
Dentistry, CMH Lahore Medical
College

6Senior Registrar, Department of
Periodontology, Institute of
Dentistry, CMH Lahore Medical
College

Correspondence

1Nida Ayub, FCPS-II Trainee,
Department of Periodontology,
Institute of Dentistry, CMH Lahore
Medical College

+92-327-7722291
nidaakhan1991@gmail.com

:
:

INTRODUCTION

Mental foramen (MeF) marks the point of exit of the
mental nerve from the mandibular canal, from where it
travels to provide sensory innervation to the mandible
and lower half of the face.1 MeF is usually circular or
slightly elliptical, occurring either amid the root apices
of the two mandibular premolars or right below the
second premolar.2 It is a solitary opening on the
anterolateral mandibular surface and is present
bilaterally.3 Openings besides the primary MeF have
been reported and are termed "accessory mental
foramina" (AMeF). It is theorised that AMeF may arise
as a result of the division of the mental nerve during the
first trimester of intrauterine development.4,5 AMeF can
be single or multiple, located unilaterally or bilaterally

and are usually smaller than the main MeF. 6 For a
foramen to be termed AMeF, it must be in continuation
with the mandibular canal; otherwise, the term "nutrient
foramen" is used.2 MeF serves as an important
anatomical landmark. It is essential to evaluate the
exact position and presence of any accessory foramina
before conducting invasive surgical procedures in the
region, such as the placement of dental implants or
harvesting bone graft material, to ensure optimal
outcomes.7 However, failure to identify AMeF can also
lead to serious post-operative complications such as
hemorrhage due to the damage to the associated
neurovascular bundle and/or nerve damage leading to
altered sensations or paralysis in the chin, lower lip and
surrounding areas.8,9 Conventionally, panoramic
radiographs have been used for such an evaluation.

/jgmds.12-3.707

9 J Gandhara Med Dent SciJuly - September 2025

However, due to poor resolution, two-dimensional
images, and the superimposition of structures, accurate
identification of anatomical landmarks becomes
difficult. With the use of CBCT, the identification of
these landmarks, including AMeF, can be more
accurate and reliable, with high image resolution,
minimal distortion, and three dimensional
visualisation.10 Studies have reported a varying
prevalence of AMeF in different populations ranging
from 1% to 14%.2,8,11 Data reporting on "how
frequently one can encounter AMeF in the Pakistani
population" is rather scarce. A retrospective study done
on the local population in the Federal region reported a
4.5% prevalence of AMeF. 12 Suggesting considerable
frequency of AMeF in our population. The present
study, therefore, aimed to determine the frequency of
accessory mental foramen using CBCT in patients
presenting to a local tertiary care hospital in Lahore.
The knowledge thus gained will aid in more effective
pre-operative planning of dental surgical procedures
and enhanced provision of care to patients.

METHODOLOGY

A cross-sectional descriptive research study was
designed and conducted at the Periodontology
Department, Institute of Dentistry, CMH Medical and
Dental College, Lahore, from October 2023 to March
2024. Approval for the research was sought from the
Institute‘s ethical review committee (letter no.
646/ERC/CMH/LMC). The sample size was calculated
using the WHO calculator. With confidence level (1-α)
at 95%, the margin of error (d) at 0.05, and anticipated
population proportion (P) at 0.1223.2 a total sample
size of 165 was calculated. The target population
consisted of subjects reporting to the dental outpatient
department of CMH Lahore Institute of Dentistry for
routine dental treatment that required a CBCT
assessment (e.g., dental implant placement). Adult
dentate subjects >18 years of age, with at least
mandibular canine to first molar teeth present
bilaterally and those with high-resolution CBCT images
were included in the study. Subjects who were under-
aged <18 years, or pregnant, or those with any bone
pathology, impacted mandibular premolars, periapical
lesions associated with mandibular posterior teeth, a
history of mandibular fracture and/or mandibular
surgery for any reason, signs of bone loss in the
posterior mandible, presence of any artifacts in CBCT
images were excluded from the study. All selected
individuals were asked to sign a consent form, and their
demographic details were recorded on a proforma. A
CBCT scan of each subject was performed at the
radiology department by trained personnel using a
Carestream CS9600 (Carestream Dental LLC, Atlanta,

GA) with 120 kVp, 20 mA, and a voxel size of 0.3 ×
0.3 × 0.3 mm, with up to 14 different fields of view.
Volumetric data from CBCT scans was used to
reconstruct mandibular images in coronal, sagittal and
axial planes using the CS MAR imaging software.
Mental foramen was identified as the largest opening on
the mandibular buccal surface and in continuity with
the mandibular canal. Any additional buccal opening in
the proximity of MeF was identified as AMeF. The
location of the AMeF for MeF was noted and classified
using Ayutgar et al.’s 2 method as follows: "(i) posterior,
(ii) posterior-superior, (iii) posterior-inferior, (iv)
inferior, (v)antero-inferior, (vi) antero-superior, and
(vii) anterior". As a secondary objective, the diameter
of AMeF was also calculated. Three readings were
taken for each subject and foramen to calculate the
mean. Data were analysed using the Statistical Package
for the Social Sciences (SPSS) version 24. Descriptive
statistics were evaluated. Mean ± standard deviation
values of quantitative variables, such as age and
foramen diameter, were calculated, while frequencies
and percentages for categorical variables, like the
presence or absence of an accessory mental foramen,
were determined. Stratification was performed to
control for effect-modifying variables, such as age and
gender. A post-stratification chi-squared test of
independence was used to determine any differences
attributable to age and gender. An independent sample
t-test was used to compare the mean accessory foramen
diameter between males and females. A p-value of
≤0.05 was considered significant.

RESULTS

Of the 165 study subjects, 43% (n = 71) were male and
57% (n = 94) were female. The mean age of the study
subjects was 39.5 ± 8.8 years (range, 24-62 years).
Accessory mental foramen (AMeF) was observed in
only 5.5% (n=9) of subjects. Only a single accessory
opening was observed in all cases. The most frequent
location of AMeF to MeF was "postero-inferior" seen
in 3% (n=5) cases, followed by anterior location seen in
1.2% (n=2) cases (Table 1). No significant difference in
the frequency of AMeF was observed between
males/females (p=0.733) and between different age
groups (<35 years vs. ≥35 years) (p=0.726) (Table 2).
Table 1: Distribution of accessory mental foramina according to

their location
Accessory Mental Foramen
Location
Posterior
Posteroinferior
Postero-superior
Inferior
Antero-inferior
Antero-superior
Superior

%Age (n)

-
3(5)
-
0.6 (1)
0.6 (1)
1.2 (2)
-

Determination of the Frequency of Accessory Mental

10 J Gandhara Med Dent Sci

July - September 2025

Table 2: Association of frequency of accessory mental foramen

with age and gender
Parameter Accessory Mental

Foramen (n)
P-value

Present Absent
Gender Male 03 68 0.73

Female 06 88
Age
Group

<35 years 03 46 0.72
≥35 years 06 110

The mean distance of AMeF from MeF was 3.12±0.11
mm. The mean diameter of the accessory foramen was
1.68±0.37 mm. No significant difference in mean
accessory foramen diameter was seen between males
and females (p=0.454) (Table 3).

Table 3: Comparison of mean diameter of accessory mental
foramina between males and females

Gender N
Accessory Mental
Foramen Diameter
Mean±SD mm

Male 03 1.54±0.58
Female 06 1.75±0.25

p-value

0.454

DISCUSSION
Typically, human mandibles have only a single,
bilateral opening for the mental nerve on the
anterolateral aspect. However, one or more additional
openings may be encountered on either side, termed as
"accessory mental foramen", which is a "rare
anatomical variation".13 Hence, planning mandibular
surgical procedures requires utmost care and attention
to detail to accurately identify the MeF and any
accessory foramina to avoid neurovascular damage in
the mental region. These anatomical variations are often
missed when only two-dimensional imaging is used;
therefore, they mandate the use of three-dimensional
imaging, such as CBCT, for accurate diagnosis.14,15 The
present study found an overall 5.5% prevalence of
accessory mental foramen. Comparable results have
been reported by Shah et al., who found AMeF in 4.5%
of the studied Pakistani population.12,11 Similarly,
Khojastepour et al. reported a 5.1% prevalence of
AMeF in the Iranian population. A slightly higher
prevalence of 7.8% AMeF has been reported by Ahmad
et al. in the Pakistani population.16 However, since the
authors analysed retrospective data from a very small
sample, selection bias may have been introduced into
their findings.17 Varying prevalences of AMeF have
been reported in different populations worldwide.
Zmysłowska-Polakowska et al. reported a 7%
prevalence in the Polish population, while Rajkohila et
al. reported an 8.85% prevalence in the Indian
population.18,19 Wei et al. reported a 10.5% prevalence
in the Chinese population, while Lam et al. quoted a
prevalence of 6.4% in the Australian population.7,8
Ayutgar et al. reported a 12.23% prevalence in the
Turkish population, which is the highest documented
prevalence.2 The present research found only single

unilateral AMeFs, i.e., only a single unilateral
accessory opening was observed in all subjects. Ahmad
et al. have also reported unilateral occurrence of AMeF
in a Pakistani study cohort.16 Literature, however,
reports AMeF occurring in varying numbers across
different races and ethnicities. A study conducted in the
Australian population reported 1% of cases showing
three AMeF, and one case in particular exhibiting 05
AMeF, with three on one side of the mandible and two
on the other side.8 Likewise, Ayutgar et al. have also
reported several AMeF ranging from 01-03 with both
unilateral and bilateral occurrences.2 In the present
study, the most frequently encountered position of
AMeF was postero-inferior to MeF. This finding is
endorsed by Ayutgar et al. , who also reported postero-
inferior as the most common location of AMeF
concerning MeF.2 Similar findings have been reported
by Rajkohila et al., Noruzi et al. and Li et al.19,20,21
Likewise, Aljarbou et al. reported "posterior and
inferior to MeF" as the most frequent location of AMeF
in the Saudi population.5 Contrary to our findings, Wei
et al.7 and Li et al.21 reported posterosuperior as the
most prevalent location of AMeF. In contrast, Yoon et
al.6 reported that the anterosuperior location is the most
prevalent site of AMeF. These differences may be
attributed to the differences in ethnicity, age, and
gender, as well as the status of dentition of the study
sample. No difference was observed in the incidence of
AMeF between males and females in this study.
Although a majority of the subjects presenting with
AMeF were female, association of AMeF frequency
and gender was not statistically significant (p=7.33),
This finding is endorsed by that of Zmysłowska-
Polakowska et al.18, Ayutgar et al.,2 Lam et al.8, Noruzi
et al.20 and Yoon et al. 6 Contrarily, Aljarbou et al.5, Li
et al.21 and Direk et al.9 reported a greater frequency of
AMeF in men. Like all other AMeF parameters,
variation in this finding may also be due to differences
in the study population. The present study attempted to
determine the frequency of AMeF in the local
population. The study did not collect data
retrospectively; rather, it targeted prospective patients
who reported for routine dental treatment that required
a CBCT scan. Hence, unnecessary exposure of patients
to radiation (by advising CBCT for the sole purpose of
this study) was also eliminated. Additionally,
prospective data collection helped eliminate selection
bias, a major drawback of retrospective data.17 The key
shortcoming of the study is its relatively small study
sample. Further studies on a larger scale involving a
diverse sample are suggested.

LIMITATIONS

This study has certain limitations. Firstly, the sample

Determination of the Frequency of Accessory Mental

size was relatively small and limited to a single

11J Gandhara Med Dent SciJuly - September 2025

institution, which may affect the generalizability of the
findings to the broader Pakistani population. Secondly,
the cross-sectional design does not allow for
longitudinal assessment or correlation with clinical
symptoms. Thirdly, potential inter-observer variability
in CBCT image interpretation may influence the
identification of accessory mental foramina. Lastly, the
study did not account for ethnic or regional variations
within the local population, which may play a role in
anatomical differences.

CONCLUSIONS
Results of this study suggest it is quite possible to
encounter an accessory mental foramen (AMeF) during
dental procedures in the Pakistan population. AMeF is a
rare but significant anatomical variation. Care must be
taken to identify it during the treatment planning phase
of dental surgical procedures to avoid iatrogenic
damage to anatomical structures.

CONFLICT OF INTEREST: None

FUNDING SOURCES: None
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Determination of the Frequency of Accessory Mental

Nida Ayub - Concept & Design; Data Acquisition; Data
Analysis/Interpretation;; Drafting Manuscript; Final Approval
Yousaf Athar - Concept & Design; Data Acquisition; Drafting

Ramsha Jalal - Concept & Design; Data Acquisition; Data

Fatima Saleem - Concept & Design; Data Acquisition; Data
Analysis/Interpretation; Drafting Manuscript; Final Approval
Aneela Shabbir - Concept & Design; Data Acquisition;

Ahmed - Concept & Design; Data Acquisition; Drafting

Manuscript; Critical Revision; Supervision; Final Approval

Analysis/Interpretation; Drafting Manuscript; Final Approval

Drafting Manuscript; Critical Revision; Final Approval

Manuscript; Final Approval

AUTHORS CONTRIBUTION

The authors accept responsibility for all aspects of the work
and will ensure that any concerns regarding the accuracy or
integrity of any part are properly investigated and resolved.