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Locating the Mandibular Lingula Using Cone-Beam Computed Tomography: A Literature Review

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Journal of Clinical Medicine
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Chun-Ming Chen
Chun-Ming Chen
Chun-Ming Chen
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Hui-Na Lee at Kaohsiung Medical University Chung-Ho Memorial Hospital
Hui-Na Lee
Ying-Ting Chen
Ying-Ting Chen
Ying-Ting Chen
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Kun-Jung Hsu at Kaohsiung Medical University
Kun-Jung Hsu
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Abstract and Figures

This study aimed to review the literature on adult mandibular lingula (ML) locations and related distances determined using cone-beam computed tomography (CBCT). A search was conducted for studies on CBCT using the following databases: PubMed, Web of Science, and Embase. The search results were limited to studies published between 1970 and 2021. The inclusion criteria were the investigation of ML location, CBCT, and participants aged ≥18 years. Eligible studies were examined for the distances from the lingual tip to the anterior ramus border, posterior ramus border, sigmoid notch, inferior ramus border, and occlusal plane. Eight studies on CBCT qualified for inclusion in the study. The mean distances from the ML to the anterior ramus border were 15.57 to 20 mm. In most of these, the ML was located above the occlusal plane. No significant differences were observed in the location and related distances for the ML among patients of different sexes, ethnicities, or skeletal patterns.
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Citation: Chen, C.-M.; Lee, H.-N.;
Chen, Y.-T.; Hsu, K.-J. Locating the
Mandibular Lingula Using
Cone-Beam Computed Tomography:
A Literature Review. J. Clin. Med.
2023,12, 881. https://doi.org/
10.3390/jcm12030881
Academic Editor: Eiji Tanaka
Received: 15 October 2022
Revised: 11 January 2023
Accepted: 19 January 2023
Published: 22 January 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
Journal of
Clinical Medicine
Review
Locating the Mandibular Lingula Using Cone-Beam Computed
Tomography: A Literature Review
Chun-Ming Chen 1, 2, † , Hui-Na Lee 3, † , Ying-Ting Chen 4and Kun-Jung Hsu 1,5,*
1School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 80708, Taiwan
2
Division of Oral and Maxillofacial Surgery, Department of Dentistry, Kaohsiung Medical University Hospital,
Kaohsiung 80756, Taiwan
3Division of Conservative Dentistry, Kaohsiung Medical University Hospital, Kaohsiung 80756, Taiwan
4School of Dentistry, CEU Cardenal Herrera University, 46113 Valencia, Spain
5Department of Dentistry, Kaohsiung Medical University Hospital, Kaohsiung 80756, Taiwan
*Correspondence: kjhsu1120@gmail.com; Tel.: +886-7-2015151
† These authors contributed equally to this work.
Abstract:
This study aimed to review the literature on adult mandibular lingula (ML) locations
and related distances determined using cone-beam computed tomography (CBCT). A search was
conducted for studies on CBCT using the following databases: PubMed, Web of Science, and Embase.
The search results were limited to studies published between 1970 and 2021. The inclusion criteria
were the investigation of ML location, CBCT, and participants aged
≥
18 years. Eligible studies
were examined for the distances from the lingual tip to the anterior ramus border, posterior ramus
border, sigmoid notch, inferior ramus border, and occlusal plane. Eight studies on CBCT qualified for
inclusion in the study. The mean distances from the ML to the anterior ramus border were 15.57 to
20 mm. In most of these, the ML was located above the occlusal plane. No significant differences
were observed in the location and related distances for the ML among patients of different sexes,
ethnicities, or skeletal patterns.
Keywords:
mandibular lingula; mandibular foramen; inferior alveolar nerve block; occlusal plane;
cone-beam computed tomography; ramus surgery
1. Introduction
Identifying the position of the mandibular foramen (MF) is essential for the successful
administration of an inferior alveolar nerve block (IANB) and for avoiding damage to the
inferior alveolar neurovascular bundle during ramus surgery. Located on the medial surface
of the ramus, the MF is a bony orifice through which the inferior alveolar neurovascular
bundle enters the mandible. The mandibular lingula (ML), located above the MF, is a key
anatomical landmark for determining the position of the MF and for the orientation of the
surgeon during ramus surgery. The ML is a bone plate structure that medially limits the
MF and provides an attachment area for the sphenomandibular ligament [
1
]. Determining
the shape, position, and height of the ML is crucial for dentists and surgeons during IANBs
and ramus surgeries [
2
]. Understanding the position of the ML and the surrounding
nerves and blood vessels is critical for a successful operation, thereby preventing excessive
intraoperative blood loss and postoperative numbness in the lower lip [3,4].
In the past, determination of the morphometry of the lingula required using the dry
mandible [
5
–
10
]. Recently, cone-beam computed tomography (CBCT) has provided high
quality and accurate three-dimensional images to replace dry mandibles in morphometric
study [
11
–
14
]. Studies [
15
–
22
] have employed CBCT images to determine the shape of
the ML and measure the distances related to the ML. Although CBCT provides real-time
measurements, the results obtained using the images may be affected by the resolution used
for image processing and the applied image-recognition method. Furthermore, the ramus
J. Clin. Med. 2023,12, 881. https://doi.org/10.3390/jcm12030881 https://www.mdpi.com/journal/jcm
J. Clin. Med. 2023,12, 881 2 of 11
borders to ML distances are closely related to the horizontal and vertical reference planes
set for CBCT scans and are considerably influenced by the consistency of the reference
point. Therefore, this study reviewed articles on CBCT scans separately and explored the
differences in the relative position of the ML on the ramus and its distance from other
anatomical landmarks among patients of different sexes, ethnicities, and skeletal patterns.
The present study included all reference planes used in the articles on CBCT.
2. Materials and Methods
2.1. Search Strategy
A literature search was conducted using the PubMed, Web of Science, and Embase
databases. The search results were limited to studies published between 1970 and 2021.
Results of participants aged <18 years were excluded from the review. The first search
term used was “mandibular lingula location.” These results were further examined for the
inclusion of CBCT.
2.2. Study Selection and Eligibility
Two authors of this study selected the articles using a data retrieval system. After read-
ing the titles and abstracts, the authors independently assessed the selected articles based
on eligibility criteria. The inclusion criteria were as follows: (1) Randomized controlled
trials and observational studies; (2) Research participants aged
≥
18 years. The exclusion
criteria were as follows: (1) Non-English articles; (2) Non-human studies; (3) Duplicate
articles. The authors read the full text of any article for which they could not reach a
consensus regarding eligibility. Regarding the inter-rater reliability, the kappa coefficient
was 0.890 (p< 0.05), demonstrating a high level of consistency between the two authors’
discretionary eligibility selections.
2.3. Data Extraction and Analysis of ML Location
The data were examined independently by the two authors according to the research
methodology. ML was identified as a reference landmark, and its related distances were
obtained. If the results extracted by the two authors from the same article were inconsistent,
the authors discussed the article with other authors to reach a consensus. The ML location
was determined based on relevant reference planes (Figure 1). The ML-related distances
(Figure 2) were measured using the following landmarks: lingula tip to anterior ramus
border (As: landmark (shortest distance) at the anterior border of ramus; Ai: intersection
landmark parallel to horizontal plane at the anterior border of ramus), posterior ramus
border (Ps: landmark (shortest distance) at the posterior border of ramus; Pi: intersection
landmark parallel to the horizontal plane at the posterior border of ramus), sigmoid notch
(Ss: lowest location (shortest distance) of the sigmoid notch; Si: intersection landmark
parallel to vertical plane and through lingula at the sigmoid notch), inferior ramus border
(Is: landmark (shortest distance) at the inferior border of ramus; Ii: intersection land-
mark parallel to vertical plane and through lingula at the inferior border of ramus), and
occlusal plane.
J. Clin. Med. 2023,12, 881 3 of 11
J. Clin. Med. 2023, 12, 881 3 of 11
Figure 1. Reference lines: Brown line: Frankfort horizontal plane; Green line: axial plane of ramus;
Red line: occlusal plane; Yellow line: vertical plane to occlusal plane.
Figure 2. Reference lines: Brown line: Frankfort horizontal plane; Green line: axial plane of ramus;
Red line: occlusal plane; Yellow line: vertical plane to occlusal plane. Landmarks: L: lingual, As:
landmark (shortest distance) at the anterior border of ramus; Ai: intersection landmark parallel to
horizontal plane at the anterior border of ramus; Ps: landmark (shortest distance) at the posterior
border of ramus; Pi: intersection landmark parallel to horizontal plane at the posterior border of
ramus; Ss: deepest location (shortest distance) of the sigmoid notch; Si: intersection landmark par-
allel to vertical plane and through lingula at the sigmoid notch; Is: landmark (shortest distance) at
the inferior border of ramus; Ii: intersection landmark parallel to vertical plane and through lin-
gula at the inferior border of ramus.
Figure 1.
Reference lines: Brown line: Frankfort horizontal plane; Green line: axial plane of ramus;
Red line: occlusal plane; Yellow line: vertical plane to occlusal plane.
J. Clin. Med. 2023, 12, 881 3 of 11
Figure 1. Reference lines: Brown line: Frankfort horizontal plane; Green line: axial plane of ramus;
Red line: occlusal plane; Yellow line: vertical plane to occlusal plane.
Figure 2. Reference lines: Brown line: Frankfort horizontal plane; Green line: axial plane of ramus;
Red line: occlusal plane; Yellow line: vertical plane to occlusal plane. Landmarks: L: lingual, As:
landmark (shortest distance) at the anterior border of ramus; Ai: intersection landmark parallel to
horizontal plane at the anterior border of ramus; Ps: landmark (shortest distance) at the posterior
border of ramus; Pi: intersection landmark parallel to horizontal plane at the posterior border of
ramus; Ss: deepest location (shortest distance) of the sigmoid notch; Si: intersection landmark par-
allel to vertical plane and through lingula at the sigmoid notch; Is: landmark (shortest distance) at
the inferior border of ramus; Ii: intersection landmark parallel to vertical plane and through lin-
gula at the inferior border of ramus.
Figure 2.
Reference lines: Brown line: Frankfort horizontal plane; Green line: axial plane of ramus;
Red line: occlusal plane; Yellow line: vertical plane to occlusal plane. Landmarks: L: lingual, As:
landmark (shortest distance) at the anterior border of ramus; Ai: intersection landmark parallel to
horizontal plane at the anterior border of ramus; Ps: landmark (shortest distance) at the posterior
border of ramus; Pi: intersection landmark parallel to horizontal plane at the posterior border of
ramus; Ss: deepest location (shortest distance) of the sigmoid notch; Si: intersection landmark parallel
to vertical plane and through lingula at the sigmoid notch; Is: landmark (shortest distance) at the
inferior border of ramus; Ii: intersection landmark parallel to vertical plane and through lingula at
the inferior border of ramus.
J. Clin. Med. 2023,12, 881 4 of 11
3. Results
3.1. Study Selection and Eligibility
Using the term “mandibular lingula location” (Figure 3), 121 articles were identified
from electronic databases (PubMed, n= 53; Web of Science, n= 36; Embase, n= 32).
Regarding the mandibular lingual location and CBCT, 29 articles were identified from
electronic databases (PubMed, n= 12; Web of Science, n= 11; Embase, n= 6). After
verifying the eligibility of the selected articles, eight remained for inclusion in the study
and full-text review by the authors.
J. Clin. Med. 2023, 12, 881 4 of 11
3. Results
3.1. Study Selection and Eligibility
Using the term “mandibular lingula location” (Figure 3), 121 articles were identified
from electronic databases (PubMed, n = 53; Web of Science, n = 36; Embase, n = 32). Re-
garding the mandibular lingual location and CBCT, 29 articles were identified from
electronic databases (PubMed, n = 12; Web of Science, n = 11; Embase, n = 6). After veri-
fying the eligibility of the selected articles, eight remained for inclusion in the study and
full-text review by the authors.
Figure 3. Process flow of article selection in the mandibular lingula location using cone-beam
computed tomography.
3.2. Data Extraction and Analysis
3.2.1. ML Height
The sample size of the CBCT group ranged from 60 to 412 participants (Table 1); the
youngest participant was 18 years old and the oldest participant was 71 years old. The
occlusal plane was used as the coordinate axis for measurements in five studies [16,18–
20,22]. The mean ML height ranged from 7 to 9.08 mm [16,17,21].
Figure 3.
Process flow of article selection in the mandibular lingula location using cone-beam
computed tomography.
3.2. Data Extraction and Analysis
3.2.1. ML Height
The sample size of the CBCT group ranged from 60 to 412 participants (Table 1); the
youngest participant was 18 years old and the oldest participant was 71 years old. The oc-
clusal plane was used as the coordinate axis for measurements in five studies
[16,18–20,22]
.
The mean ML height ranged from 7 to 9.08 mm [16,17,21].
J. Clin. Med. 2023,12, 881 5 of 11
Table 1. Demographic and study characteristics in the included studies (cone-beam computed tomography: CBCT).
Author Age/Range
(Years)
Patients/Total
Sides
Axis of
Coordinates
Sex
Race
Landmarks Height of
Lingula
Anterior
Ramus to
Lingula
Posterior
Ramus to
Lingula
Sigmoid
Notch to
Lingula
Inferior
Border to
Lingula
Above
Occlusal
Plane
Below
Occlusal
Plane
Year F (Female) Right (R)
Country of Origin M (Male) Left (L)
Findik et al. [15] 19–71 years n= 96 Axial plane NA Turk Ai NA 15.57 (R) NA NA NA NA NA
2014 192 side 15.73 (L) * NA NA NA NA NA
Turkey
Sekerci and Sisman [16] Adult n= 412 Occlusal
plane Total (199 F, 213 M) Turk Ai, Pi, Ss, Ii 7.91 16.77 13.02 15.32 33.43 3.6 NA
2014 824 side F R 7 15.97 12.43 13.95 30.93 3.62 NA
Turkey M R 9.08 * 18.23 * 13.61 17.21 * 35.53 * 3.66 NA
F L 7.24 15.6 12 14.17 30.94 3.57 NA
M L 8.58 17.26 14.03 * 15.93 36.32 * 3.58 NA
Senel et al. [17] 46 n= 63 Axial plane 28 F, 35 M Turk Ai, Pi, Ss, Ii
2015 25–70 years 126 sides Total 7.8 18.5 16.9 18.1 38.3 NA NA
Turkey R 8.3 18.4 16.7 18.1 37.6 NA NA
L 7.4 18.7 17.1 18.1 39.1 NA NA
Zhou et al. [18] 26.8 n= 106 Occlusal
plane 55 F Korean Ai, Pi, Ss, Ii NA 18.3 17 15.5 30.5 5.8 1.9
2017 18–36 years 121 sides 51 M NA 18.2 18.2 * 15.7 35.3 * 6.2 0
Korea
Akcay et al. [19] Class I n= 30 Occlusal
plane Total Turk As, Ps, Ss NA NA 16.55 17.7 NA 8.12 NA
2019 18–37 years 60 sides 14 F NA NA 15.92 17.07 NA 7.60 NA
Turkey 16 M NA NA 17.09 * 18.24 NA 8.58 NA
Class III n= 30 Total NA NA 15.82 18.73 NA 9.91 * NA
18–36 years 60 sides 16 F NA NA 15 17.81 NA 9.89 NA
14 M NA NA 16.75 * 19.79 * NA 9.93 NA
Zhao et al. [20]n= 407 Occlusal
plane 206 F, HGA (270 sides) Chinese As, Ps, Ss, Is NA 16.77 16.42 16.22 32.37 5.03 NA
2019 20–35 years 814 sides LGA (142 sides) NA 17.18 17.05 * 16.6 33.32 * 5.21 NA
China 201 M, HGA (218 sides) NA 16.53 16.9 16.76 34.74 5.97 NA
LGA (184 sides) NA 17.63 * 17.94 * 17.64 * 36.86 * 5.88 NA
HGA (F = 270 sides) NA 16.77 16.42 16.22 32.37 5.03 NA
(M = 218 sides) NA 16.53 16.9 * 16.76 * 34.74 * 5.97 * NA
LGA (F = 142 sides) NA 17.18 17.05 16.6 33.32 5.21 NA
(M = 184 sides) NA 17.63 17.94 * 17.64 * 36.86 * 5.88 * NA
Hsu et al. [21] Adult n= 72 Frankfort Total Taiwanese Ai, Pi, Ss, Ii 8.07 19.21 15.22 20.04 31.2 NA NA
2020 144 sides horizontal 49 F 7.76 18.85 14.89 19.99 30.4 NA NA
Taiwan plane 23 M 8.73 * 19.99 * 15.93 * 20.14 32.91 * NA NA
R 8.2 19.23 15.25 20.51 31.26 NA NA
L 7.95 19.2 15.19 19.57 31.14 NA NA
Class I (n= 26) 8.24 18.86 15.36 19.74 31.28 NA NA
Class II (n= 21) 7.83 18.71 15.51 20.72 31.4 NA NA
Class III (n= 25) 8.11 20 14.83 19.77 30.95 NA NA
J. Clin. Med. 2023,12, 881 6 of 11
Table 1. Cont.
Author Age/Range
(Years)
Patients/Total
Sides
Axis of
Coordinates
Sex
Race
Landmarks Height of
Lingula
Anterior
Ramus to
Lingula
Posterior
Ramus to
Lingula
Sigmoid
Notch to
Lingula
Inferior
Border to
Lingula
Above
Occlusal
Plane
Below
Occlusal
Plane
Year F (Female) Right (R)
Country of Origin M (Male) Left (L)
Lupi et al. [22] 34.93 n= 111 Occlusal
plane Total Italian Ai, Pi, Si, Ii NA 16.96 15.28 13.87 31.2 11.22 NA
2021 18–88 years 201 sides 43 F NA 16.9 14.85 13.34 30.05 11.77 NA
Italy 68 M NA 17.05 16.04 15.01 33.06 10.87 NA
n: number of patients; NA: not available; *: statistically significant; Lingula tip to anterior ramus border. As: landmark (shortest distance) at the anterior border of ramus, Ai: intersection
landmark parallel to horizontal plane at the anterior border of ramus; Lingula tip to posterior ramus border. Ps: landmark (shortest distance) at the posterior border of ramus, Pi:
intersection landmark parallel to horizontal plane at the posterior border of ramus; Lingula tip to sigmoid notch. Ss: lowest location (shortest distance) of the sigmoid notch, Si:
intersection landmark parallel to vertical plane and through lingula at the sigmoid notch; Lingula tip to inferior ramus border. Is: landmark (shortest distance) at the inferior border of
ramus, Ii: intersection landmark parallel to vertical plane and through lingula at the inferior border of ramus.
J. Clin. Med. 2023,12, 881 7 of 11
3.2.2. Distances from Lingual Tip to Anterior Ramus Border and Posterior Ramus Border
The mean distance of the ML to the anterior ramus border ranged from 15.57 to
20 mm
[15–22]
. The mean distance of the ML to the posterior ramus border ranged from 12
to 18.2 mm [15–22].
3.2.3. Distances from Lingual Tip to Sigmoid Notch and Inferior Ramus Border
The mean distance of the ML to the sigmoid notch ranged from 13.34 to 20.72 mm
[15–22]
.
The mean distance of the ML to the inferior ramus border ranged from 30.4 to 39.1 mm
[15–22]
.
3.2.4. Distances from Lingual Tip to Occlusal Plane
Most ML locations were above the occlusal plane. Five articles reported that the ML
was above the occlusal plane, with a distance range of 3.57 to 11.77 mm [16,18–20,22].
4. Discussion
Mandibular growth is fully developed at approximately 18 years of age. Therefore,
studies were excluded from our review if the included patients were younger than 18.
The outcomes of the eligible studies for different sexes, races, and skeletal patterns are
discussed below.
4.1. ML Height
Sekerci and Sisman [
16
] observed that the ML height on the right side of the mandible
was greater in men than in women. Hsu et al. [
21
] reported that the ML height was
significantly greater in men than in women and that there were no significant differences
in the ML height between the left and right sides of the mandible. They also noted no
significant differences in ML height among patients with Class I, Class II, or Class III
malocclusion. ML height had similar dimensions in different races and skeletal patterns.
4.2. Anterior Ramus Border to Mandibular Lingula Distance (ARL Distance)
The reported distance of the ML from the anterior ramus border differed considerably
between studies. Findik et al. [
15
] reported a mean distance of 15–16 mm, whereas Hsu
et al. [
21
] reported a distance of 18–20 mm. These inconsistencies arose because each study
used different reference points and planes (horizontal and vertical). Findik et al. [
15
] directly
measured the ML distance from the anterior ramus border using the axial plane as the
reference plane, thereby obtaining the lowest measurement results. Other studies [
16
,
18
,
20
]
that used the occlusal plane as the reference plane obtained measurement results larger
than those of Findik et al. [15] but smaller than those of Hsu et al. [21], who measured the
distance using the Frankfort horizontal plane as the reference plane.
Several studies [
17
,
18
,
21
,
22
] reported no significant differences between the sexes or
between the left and right sides of the mandible. However, Findik et al. [
15
] reported
that the distance between the ML and the anterior ramus border on the left side of the
mandible was significantly greater than that on the right side. Hsu et al. [
21
] reported that
the distance of the ML from the anterior ramus border was significantly greater in men
than in women but observed no significant differences in the distance of the ML from the
anterior ramus border in patients with different skeletal patterns. However, Zhou et al. [
18
]
reported that the ML distance from the anterior ramus border was significantly greater
in men with a low gonial angle (LGA) than that in men with a high gonial angle (HGA).
Among the distances to the lingual, the anterior ramus border to the lingula distance is
more important than the posterior border to the lingual distance.
For clinical application, we recommend using the occlusal plane as a reference plane.
The measured landmark is a plane running parallel to the occlusal plane, which runs
through the ML and intercepts the anterior ramus border. This method should result in
more accurate administration of IANB and avoid damage to the inferior alveolar neurovas-
cular bundle during ramus surgery.
J. Clin. Med. 2023,12, 881 8 of 11
4.3. Posterior Ramus Border to Lingula Distance
Some studies [
16
,
18
–
21
] stated that the distance between the ML and the posterior
ramus border was significantly greater in men than in women, except for Lupi et al. [
22
],
who observed no significant differences between the sexes. Sekerci and Sisman [
16
] pro-
posed that the distance between the ML and the posterior ramus border is significantly
greater on the left side of the mandible in men than that on the left side of the mandible in
women. Seneal et al. [
17
] and Hsu et al. [
21
] noted no significant differences in the distance
between the ML and the posterior ramus border on the left and right sides of the mandible.
Hsu et al. [
21
] also observed no significant differences between participants with different
classes of malocclusions. However, Zhou et al. [
20
] reported that the distance between the
ML and the posterior ramus border was significantly greater in men with LGA than that in
men with HGA, in women with LGA than that in women with HGA, in men with LGA
than that in women with LGA, and in men with HGA than that in women with HGA.
Participants of different races, ages, and sexes were recruited in each of the aforemen-
tioned studies [
15
–
22
]. The use of different reference planes, including the occlusal plane,
Frankfort horizontal plane, and axial plane, resulted in considerable differences in the
measured distances. Regarding the various landmarks at the posterior ramus border, we
suggest that the occlusal plane is a better reference plane to set both landmarks of anterior
and posterior ramus borders.
4.4. Sigmoid Notch to Lingual Distance
Regarding the distance from the ML to the sigmoid notch, Lupi et al. [
22
] reported
that the lowest mean distance was 13.34 mm in women. However, the measurements
were not performed using the lowest point of the sigmoid notch. Instead, the authors
measured the distance vertical to the occlusal plane from the lingula tip to the sigmoid
notch, thereby obtaining a lower value. Lupi et al. [
22
] and Hsu et al. [
21
] reported no
significant differences between sexes. Seneal et al. [
17
] and Hsu et al. [
21
] observed no
significant difference between the left and right sides of the mandible. Hsu et al. [
21
]
reported no significant differences in the distance between the ML and sigmoid notches in
patients with different skeletal patterns. However, Akcay et al. [
19
] noted that the distance
between the ML and the sigmoid notch was significantly greater in men with Class III
malocclusion than that in women with Class III malocclusion. However, there were no
significant differences in the distance of the ML from the sigmoid notch in men and women
with Class I malocclusion. Zhou et al. [
18
] observed that the distance between the ML and
the sigmoid notch was significantly greater in men with LGA than in those with HGA.
Moreover, the number of men with LGA and HGA was greater than the number of women
with LGA and HGA. For consistency, we recommend that the measured landmark be the
lowest point of the sigmoid notch.
4.5. Inferior Ramus Border to Lingula Distance
Among all studies, Senel et al. [
17
] reported the greatest distance (38.3 mm) of the
ML from the inferior ramus border. This result can be attributed to the reference plane
used by Senel et al. [
17
]. Several articles [
16
,
18
,
20
,
21
] reported that the distance between
the ML and the inferior ramus border was significantly greater in men than in women.
However, Lupi et al. [
22
] reported no significant differences in the distance between the
ML and the inferior ramus border between the sexes. Seneal et al. [
17
] and Hsu et al. [
21
]
noted no significant differences in the ML distance from the inferior ramus border between
the left and right sides of the mandible. Hsu et al. [
21
] observed no significant differences
in the distance between the ML and the inferior ramus border in patients with different
classes of malocclusion. However, Zhou et al. [
18
] reported that the distance between the
ML and the inferior ramus border was significantly greater in men with LGA than that
in men with HGA, and in women with LGA than that in women with HGA. Moreover,
the number of men with LGA and HGA was greater than the number of women with
LGA and HGA. In each of the aforementioned studies, participants of different ethnicities,
J. Clin. Med. 2023,12, 881 9 of 11
ages, and sexes were recruited. Different reference planes, sigmoid notch landmarks, and
inferior border landmarks were used, resulting in considerable differences in the measured
distances. Tracing an obvious notch at the inferior border of the mandible is not always
possible. Therefore, we recommend identifying two landmarks: (1) Setting a plane through
the ML vertically to the occlusal plane and intercepting the inferior border; (2) Setting a
plane from the lowest point of the sigmoid notch through to the inferior border.
4.6. Lingula to Occlusal Plane Distance
Akcay et al. [
19
] reported the distance of the ML from the occlusal plane as 8–10 mm,
whereas Lupi et al. [
22
] reported this distance as 10–12 mm. There were no significant
differences in the distance of the ML from the occlusal plane between the sexes or between
the left and right sides of the mandible. Akcay et al. [
19
] reported that the distance
between the ML and the occlusal plane was significantly greater in patients with Class III
malocclusion than that in those with Class I malocclusion. Zhou et al. [
18
] reported that
this distance was higher in men with LGA than that in women with LGA, and in men with
HGA than that in women with HGA. Lingula-to-occlusal plane distance is more important
than other distances in terms of administering an IANB and performing ramus surgery.
CBCT is a useful tool for identifying ML morphology, location, and relation to the occlusal
plane to avoid damage to the neurovascular bundle.
4.7. Clinical Relevance and Limitations of the Study
Numerous studies [
15
–
26
] have been conducted on the position of the ML and have
presented different results. CBCT images were affected by the resolution used for image
processing. Moreover, the varied settings for different reference planes and points may
have influenced the results of the study. Regarding clinical relevance, the occlusal plane is
the preferred reference plane to identify the ML and MF to prevent injury to the inferior
alveolar neurovascular bundle.
The limitations of this literature review were as follows: (1) Varied reference planes;
(2) Rare reports of edentulous people; (3) Imbalance in the age distribution of the population;
(4) Racial distribution disequilibrium of the population. For clinical applications, we
recommend using the occlusal plane as the reference plane in future studies. However,
there should be modifications to the occlusal plane if the patient is edentulous. Furthermore,
future studies should include a sample distribution that considers the age and race of the
study population.
5. Conclusions
Differences in age, race, and sex of participants, and in reference planes and points may
have generated different measurement results. Significant differences were observed in the
ML height between patients of different sexes and races and of those with different skeletal
patterns. In most studies, the ML was located above the occlusal plane. In addition, most
studies reported no significant differences in the distance of the ML to the anterior ramus
border, posterior ramus border, sigmoid notch, or inferior ramus border among patients of
different sexes and races and among those with different skeletal patterns. Additionally, the
distances of the ML to the anterior ramus border, posterior ramus border, sigmoid notch,
and inferior ramus border were significantly greater in patients with LGA than those in
patients with HGA.
Author Contributions:
Conceptualization, K.-J.H., C.-M.C. and H.-N.L.; methodology, Y.-T.C.;
writing—original draft preparation, K.-J.H.; writing—review and editing, C.-M.C. and H.-N.L. All
authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement:
Not applicable for studies not involving humans or animals.
Informed Consent Statement: Not applicable.
J. Clin. Med. 2023,12, 881 10 of 11
Data Availability Statement: Not applicable.
Conflicts of Interest: The authors declare no conflict of interest.
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Dimension and Location of the Mandibular Lingula: Comparisons of Gender and Skeletal Patterns Using Cone-Beam Computed Tomography
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Since the IAN enters the MF at the Li position, an understanding of the structures surrounding the Li and MF is therefore crucial. As surgical treatment for mandibular prognathism, the mandibular setback procedure is usually conducted using two techniques: intraoral vertical ramus osteotomy (IVRO) and sagittal split ramus osteotomy (SSRO). The procedure of IVRO extends from the sigmoid notch, vertically behind the Li and MF, to the inferior border of the mandible. The horizontal procedure of SSRO is performed above the Li and cuts through the medial cortex of the ramus. The position of the Li can determine the surgical procedures, denote injury of IAN vascular bundles, and reveal the presence of lower lip numbness. This description demonstrates that the location of the Li is very important for ramus surgery. This study investigated the Li and its relationship among three different types of skeletal patterns. 2. Materials and Methods A total of 144 rami (72 patients; 23 men and 49 women) were included. The participants were further categorized into three groups according to their skeletal patterns (specifically, the A point–nasion–B point [ANB] angle): Class I (0° < ANB < 4°), Class II (ANB ≥ 4°), and Class III (ANB ≤ 0°). Based on the A point–nasion–B point angle, participants were classified into skeletal Class I (26 individuals), skeletal Class II (21 individuals), and skeletal Class III (25 individuals) according to Riedel’s classification [3]. Cone-beam computed tomography (CBCT) was conducted at the Department of Dentistry, Kaohsiung Medical University Hospital. Patients with the following conditions were excluded: (1) cranial or facial cyst or tumor, (2) innate cranial or facial deformities, and (3) trauma or surgery on the cranial or facial skeleton. CBCT was conducted with the calibration of three-dimensional (3D) positions on the skull. The Frankfort horizontal (FH) plane was defined as the plane connecting the right orbitale and porion on both sides. CBCT images were imported using Digital Imaging and Communications in Medicine into RadiAnt DICOM Viewer (version 4.6.9, Medixant, Poznan, Poland). The function of 3D image reconstruction was also used by extracting the ramus for 3D reconstruction. Subsequently, CBCT NNT Viewer was run to adjust the FH planes to a horizontal position. The following landmarks were identified (Figures 1 and 2): tip of the Li, external oblique ridge (EOR), internal oblique ridge (IOR), posterior border of the ramus (PBR), inferior border of the ramus (IBR), sigmoid notch (Sm), and mandibular foramen (MF). The distances were measured as follows: (1) Li-EOR: distance from the Li to the EOR, (2) Li-IOR: distance from the Li to the IOR, (3) Li-PBR: distance from the Li to the PBR, (4) Li-IBR: distance from the Li to the IBR, (5) Li-Sm: distance from the Li to the Sm, (6) Li-hMF: horizontal distance from the Li to the MF, and (7) Li-vMF: vertical distance from the Li to the MF.
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Measurement of mandibular lingula location using cone-beam computed tomography and internal oblique ridge-guided inferior alveolar nerve block
Article
Full-text available
  • Jun 2019
Objectives: Inferior alveolar nerve block (IANB) is the most frequently used treatment for mandibular molars. Successful IANB requires insertion of the dental needle near the mandibular foramen. In this study, we aimed to analyze the anatomic location of the mandibular lingula and evaluate the effects of internal oblique ridge (IOR)-guided IANB. Materials and methods: The location of the mandibular lingula was measured using cone-beam computed tomography images of the mandibles obtained from 125 patients. We measured the distances from the occlusal plane to the lingula and from the IOR to the lingula in 250 mandibular rami. Based on the mean of these distances, alternative anesthesia was carried out on 300 patients, and the success rate of the technique was evaluated. Results: The mean vertical distance was 8.85±2.59 mm, and the mean horizontal distance was 14.68±1.44 mm. The vertical (P<0.001) and the horizontal (P<0.05) distances showed significant differences between the sex groups. The success rate of the IOR-guided technique was 97.3%. Conclusion: IANB-based location of mandibular lingula showed a high success rate. From this study, we concluded that analysis of the anatomic locations for mandibular lingula and IOR-guided IANB are useful for restorative and surgical dental procedures of the mandibular molars.
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Imaging study on relationship between the location of lingula and the Gonial angle in a Chinese population
Article
Full-text available
  • Apr 2019
  • SURG RADIOL ANAT
Purpose The purpose of this study was to investigate the Gonial angle in relation to the position of the lingula using computerized image analysis to guide the oral surgeons to prevent injury to the inferior alveolar nerve and peripheral blood vessels during surgery. Methods We measured Gonial angle sizes of bilateral rami and the distances from the lingula tip to the mandibular notch (LN), the anterior (LA) and posterior (LP) margin of the mandibular ramus, the mandibular base (LB) and the occlusive plane (h) in 407 Chinese adults with CBCT. Results In males, the mean distance of LN was 17.64 mm in the low Gonial angle group while 16.76 mm in the high Gonial angle group, which was significantly different between two groups (P < 0.001). The distance of LA in LGA group was obviously longer than that in HGA group (P < 0.001). The mean distance LP of men was 17.94 mm in LGA group while 16.9 mm in HGA group (P < 0.001). In females, the mean distance of LB in LGA group was 33.32 mm and 32.37 mm in HGA group (P < 0.01). Conclusion We discovered that the segment of the mandibular branch, between the mandibular lingula and the mandibular angle, was obviously smaller in the HGA group than that in the LGA group.
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Location and shape of the mandibular lingula: Comparison of skeletal class I and class III patients using panoramic radiography and cone-beam computed tomography
Article
Full-text available
  • Sep 2018
Purpose The aim of this study was to compare the location and the shape of the mandibular lingula in skeletal class I and III patients using panoramic radiography and cone-beam computed tomography. Materials and Methods The sample group included 190 skeletal class I patients and 157 class III patients. The location of the lingula in relation to the deepest point of the coronoid notch was classified into 3 types using panoramic radiographs. The shapes of the lingulae were classified into nodular, triangular, truncated, or assimilated types using cone-beam computed tomographic images. The data were analyzed using the chi-square test. Results The tips of the lingulae were at the same level as the coronoid notch in 75.3% of skeletal class I patients and above the coronoid notch in 66.6% of class III patients. The positions of the lingulae in relation to the deepest point of the coronoid notch showed statistically significant differences between class I and class III patients. The most common shape was nodular, and the least common was the assimilated shape. Although this trend was not statistically significant, the triangular shape was more frequently observed in class III patients than in class I patients. Conclusion The locations and the shapes of the mandibular lingulae were variable. Most of the lingulae were at the same level as the coronoid notch in skeletal class I patients and above the coronoid notch in skeletal class III patients. The nodular and assimilated-shaped lingulae were the most and the least prevalent, respectively.
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Anatomical study of the location of the antilingula, lingula, and mandibular foramen for vertical ramus osteotomy
Article
Full-text available
  • Dec 2018
Background The purpose of this study was to identify the location of the antilingula, lingula, and mandibular foramen in Korean cadavers and to promote safe and accurate surgery without damage to the inferior alveolar neurovascular bundle (IANB) when performing a vertical ramus osteotomy (VRO). Methods This study was conducted on the dried mandibles of 20 adult cadavers. Digital calipers were used to measure the distances from the anatomical reference points (antilingula, lingula, and mandibular foramen). Result The antilingula was located at the anterior 44% and superior 31% in the ramus. The lingula was located at the anterior 55% and superior 30% in the ramus. The mandibular foramen was located at the anterior 58% and superior 46% in the ramus. Regarding the positional relationship with the antilingula, the lingula was located 0.54 mm superior and 4.19 mm posterior, and the mandibular foramen was located 6.95 mm inferior and 4.98 mm posterior. The results suggested that in order to prevent damage to the IANB, osteotomy should be performed in the posterior region of ramus at least 29% of the total horizontal length of the ramus. Conclusion Using only the antilingula as a reference point is not guaranteed to IANB injury. However, it is still important as a helpful reference point for the surgeon in the surgical field.
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The variable position of the inferior alveolar nerve (IAN) in the mandibular ramus: a computed tomography (CT) study
Article
Full-text available
  • Jun 2018
  • SURG RADIOL ANAT
Introduction: This study was designed to quantify the important anatomical landmarks and the path of the inferior alveolar nerve (IAN) within the human mandibular body and ramus, in particular with reference to the bilateral sagittal split osteotomy (BSSO). Materials and methods: Four hundred and eleven CT scans were studied, 299 of these were involved in determining the position of lingula; and 230 were involved in determining the course of IAN in the mandibular molar region, namely from the mesial of the mandibular first molar to the distal of the mandibular second molar; 118 were involved with both measurements. Results: On average, the lingula was located 17.0 ± 2.2 mm from the external oblique ridge; 11.6 ± 2.0 mm from the internal oblique ridge; 17.2 ± 2.7 mm from the sigmoid notch; and 15.6 ± 1.9 mm from the posterior border of the mandible. The course of the IAN in the mandibular molar region was found to descend vertically from the distal of the mandibular second molar (7) to reach its lowest point between the first and second molars (6 and 7), and then ascend towards the mesial of the first molar (6). Horizontally, the IAN was found to traverse medially between the distal of the 7 and the middle of the 7, and then changes its path laterally towards the mesial of the 6. Conclusion: Precise knowledge of the individual's position of the IAN will help surgical planning.
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Anatomical review of the mandibular lingula for inferior alveolar nerve block
Article
  • Nov 2020
The purpose of this study was to perform a review of the literature related to the anatomy of the mandibular lingula and to provide information to improve the execution of effective anesthesia of the inferior alveolar nerve in clinical practices of the mandible. Prognathic mandibles have a lingula that is located more posterior and superior than non-prognathic mandibles. Most of the lingula is located above the occlusal plane, but it is occasionally located at or below the occlusal plane. The lingula of the triangular shape was generally located slightly more superior and posterior than other shapes. The mandibular lingula is an important anatomical landmark, and accurate information for exact lingula features is required during inferior alveolar nerve block anesthesia. Proper evaluation of the lingula is key to effective anesthesia and decreases the failure rate of the inferior alveolar nerve in clinical practices of the mandible.
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Location of the Mandibular Lingula: Comparison of Skeletal Class I and Class III Patients in Relation to Ramus Osteotomy Using Cone-Beam Computed Tomography
Article
  • Aug 2019
Introduction: The aim of the study was to analyze the anatomic location differences of the mandibular lingula (ML) between dentoskeletal Class I and Class III patients, also between genders to obtain information that could be useful for sagittal split ramus osteotomy (SSRO) and other interventions in mandibular ramus. Methods: This study was conducted on cone-beam computed tomography (CBCT) images of 30 skeletal Class I (16 males and 14 females) patients aged between 18 to 37 years and 30 skeletal Class III (14 males and 16 females) patients aged 18 to 36 years. Results: Statistically, the mean distance of the ML from the occlusal plane in skeletal Class III patients (9.91±3.16mm) was found to be greater than Class I patients (8.12±2.95mm). The mean distance between the posterior border of ramus and the ML was found to be statistically lower (15.82±1.80mm) compared to Class I patients (16.55±1.67mm) but the mean distance from the anterior ramus was not found statistically significant. In both groups, the mean distance between the ML and posterior ramus was statistically greater in males. The mean distance from mandibular notch to ML was significantly greater in Class III patients (18.73±2.89mm) compared to Class I patients (17.70±2.65mm) (P<0.05). The most commonly encountered shape was the nodular type in both groups. The second most common type was truncated in Class I patients and triangular in Class III patients. Conclusions: The ML is an important landmark for mandibular ramus surgery and inferior alveolar nerve block (IANB). The anatomic data provided by this study may help surgeons to reduce complications when performing mandibular ramus osteotomies and dentists to increase the success rates of IANB.
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