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. 2025 Sep 26;25:381. doi: 10.1186/s12880-025-01921-9

Prevalence and morphometric characterization of the genial tubercle via CBCT: evidence from a Turkish population

Berke Berberoglu 1, Nagihan Koç 2,✉, Yagmur Zengin 3, Nihal Avcu 2
PMCID: PMC12465661  PMID: 41013446

Abstract

Background

The objective of this study was to assess the prevalence and morphometric characteristics of the genial tubercle (GT) in a Turkish population using cone-beam computed tomography (CBCT), by classifying the morphology of GTs and evaluating their width, height, and anatomical position, in relation to age and sex.

Methods

A total of 356 CBCT images were collected from the radiology archive at Hacettepe University Faculty of Dentistry, involving 228 female and 128 male patients aged 18 years and older. The GTs were identified and classified using multiplanar reconstruction sections. Measurements taken included the width (GT-w) and height (GT-h) of the GTs, the distance from the GTs to the apex of the mandibular central incisors (I-SGT), the distance to the mandibular base (IGT-M), and the mandibular anterior thickness (MT).

Results

The overall prevalence of GTs was found to be 90.4%, with 9.6% of patients showing no GTs present. The most frequently observed type was GT-3 (33.1%), while the least common was GT-5 (9.6%). A statistically significant relationship was found between GT types and sex, as well as age groups (p = 0.007 and p = 0.017, respectively). Measurements indicated that the GT-w, GT-h, I-SGT, and MT values for males were greater than those for females.

Conclusions

The GTs exhibited significant variation in morphology according to age and sex, with GT-3 being the most common type and detectable GTs present in over 90% of individuals. Male participants demonstrated greater GT-w, GT-h, and MT values than females. The subdivision of Type 4 into 4 A and 4B provided a more detailed radiological characterization, which may serve as a useful reference in future anatomical and clinical research. CBCT images provide detailed information regarding the morphological assessment of GTs.

Trial registration

Not applicable.

Keywords: Anatomy, Diagnostic imaging, Cone-beam computed tomography, Genial tubercle

Introduction

Genial tubercles (GTs), also known as the mental spine, genial apophysis, and spinae mentalis, are bony prominences located in the lingual region of the midline of the mandible. Although GTs are defined as four prominences surrounding the lingual foramen arranged in two pairs, they vary in number, shape, and location [1]. The significance of GTs is associated with the functions of the genioglossus and geniohyoid muscles, which are attached to these protuberances. These muscles provide the functions of the tongue and support the airway. While the geniohyoid muscle helps to breathe in by providing the upward and forward movement of the hyoid and expanding the upper airway, the genioglossus muscle prevents the tongue from closing the upper airway by helping it to contract [2, 3].

GT types vary by age, sex, and racial characteristics [4–8]. Determining the morphology and location of GTs is crucial in various medical applications, including the identification of the safe zone prior to implant surgery and the detection of mandibular asymmetry [6, 9, 10]. In addition, traumatic GT fractures that accompany mandibular fractures are important for pharyngeal airway compromise, and determining the location and morphology of the fractured tubercle may affect the decision regarding open reduction or fixation procedures [11]. Anatomical dissections have shown that branches of the submental artery may enter lingual canals located below the GT [12]. During surgical interventions, such as implant placements involving the anterior mandibular region, hemorrhage from the submental artery may extend into the submandibular and pharyngeal spaces, creating a significant risk of life-threatening airway obstruction [13]. Therefore, accurate preoperative identification of the anatomical boundaries of the GTs is essential in procedures involving this region.

GTs may remain as prominent bony prominences in the midline of the lingual sulcus as a result of excessive atrophy of the mandible in elderly and long-term edentulous patients. This prevents the peripheral sealing of the prosthesis in the anterior lingual sulcus and resulting in impaired stability. Prosthetic applications in such cases should be conducted by considering the presence of GTs in the region [8, 14].

Radiological records are used to determine age and sex in forensic dentistry practices [15]. It may be suggested that the classification of morphology, number, and location of GTs according to age and sex, as well as the determination of their distribution across populations, may be helpful parameters in forensic researches [16]. Moreover, the anterior mandible may require special clinical and radiological attention, especially in patients with obstructive sleep apnea (OSA) [17]. Genial advancement of the mandible has been shown to objectively decrease the severity of airway obstruction in patients suffering from OSA [18].

Conventional techniques for imaging GTs are inadequate due to superpositions. Therefore, three-dimensional (3D) imaging methods, especially cone-beam computed tomography (CBCT), are useful in assessing their morphology. In studies on the determination of the true size of GTs, the morphology of GTs and their distance from the lower and upper edges of the mandible were measured using cadavers and/or radiologically, and their types were determined according to various populations [5, 18, 19]. Studies on the morphology and prevalence of GTs in the Turkish population are quite limited in the literature. The size and shape of GTs were examined in those studies, but no classification was made [20, 21].

The aim of this study was to evaluate the prevalence and morphometric characteristics of the GTs using CBCT in a Turkish population by classifying the morphology of GTs and assessing their width, height, and anatomical position, in relation to age and sex.

Materials and methods

A total of 1.155 CBCT images of patients who had undergone CBCT examination based on their indications between January 1, 2018, and December 31, 2020, at Hacettepe University Faculty of Dentistry, Department of Dentomaxillofacial Radiology were retrospectively evaluated. Ethical approval was obtained from the Non-Interventional Ethics Committee of Hacettepe University (Date: 05/10/2021; Protocol No: GO 21/16 − 15). The study was conducted in accordance with the Declaration of Helsinki. Informed consent was obtained from all patients for inclusion in the study. The sample size calculation was performed using the samplingbook package in R: assuming an unknown population proportion of 50%, and a 95% confidence level with tolerance approximately 5%, it was determined that at least 330 subjects should be included in this study to estimate the prevalence of each morphological type (1–5).

CBCT imaging

CBCT images were obtained using an i-CAT Next Generation scanner (Imaging Sciences International, Hatfield, PA). The exposure parameters were set at 120 kV, 5 mA, with a field of view (FOV) of 16 × 6 cm, a voxel size of 0.2 mm, and an exposure time of 26.9 s. All CBCT scans were reconstructed in three dimensions at a thickness of 0.2 mm using the integrated i-CAT Vision™ software (version 1.9.3.14).

Images from patients aged 18 years or older were reviewed. Data had to be available, the mandible had to be fully visible, and the mandibular anterior teeth had to be present. Images lacking diagnostic quality or showing a fracture line, impacted tooth, pathology, surgical scar, or deformity in the mandibular anterior region were excluded. A total of 356 images were selected for the study. Analyses were performed by two oral radiologists (BB and NK). They evaluated randomly numbered CBCT images with a slice thickness of 0.2 mm, within the same period and in separate sessions. After a two-week interval, the images were re-examined under the same conditions. Intra- and inter-observer consistency was statistically determined prior to the study.

Image analysis

CBCT images on multiplanar reconstruction sections were arranged as the bilateral zygomatic bones were at the same level on the axial plane, the right and left infraorbital foramina in the coronal plane, and the Frankfurt horizontal plane on the sagittal plane were parallel to the ground, and the midline of the image was perpendicular to the horizontal plane [7].

GTs were classified into five types according to the dry-skull classification proposed by Singh et al. [5], which was adapted for assessment on CBCT images in the present study (Fig. 1): Type 1: Both two superior and two inferior prominences are present (Fig. 1A-B). Type 2: Two superior prominences are present, with two inferior prominences that merge to form a single middle ridge (Fig. C-D). Type 3: Two superior prominences are present, and below them, the inferior prominence appears indistinct (Fig. 1E-F). Type 4: Only a single midline prominence is present. Type 4 A: A single median ridge appears in the axial and coronal sections (Fig. 1.G-H). Type 4B: A single midline prominence appears rounded-shape in the axial section (Fig. 1I). Type 5: The GT is entirely absent (Fig. 1J). In order to evaluate the morphology of GTs:

Fig. 1.

Fig. 1

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Cone-beam computed tomography images showing the examples of GT types. A, B) Type 1: Both two superior and two inferior prominences are present; C, D) Type 2: Two superior prominences are present, with two inferior prominences that merge to form a single middle ridge; E, F) Type 3: Two superior prominences are present, and below them, the inferior prominence is indistinct; G, H) Type 4 A: Single midline ridge in the axial and coronal sections; I) Type 4B: rounded-shape midline prominence in the axial section; J) Type 5: The GT is entirely absent

  • (i)

    The width (GT-w) was determined by measuring the widest horizontal distance on the axial section (Fig. 2A),

Fig. 2.

Fig. 2

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Cone-beam computed tomography images showing the measurements of GT-w: genial tubercles width in axial (A) and GT-h: genial tubercles height in cross-sectional sections (B)

  • (ii)

    The height (GT-h) was determined by measuring the vertical distances between the highest and lowest points of the GTs on the sagittal and coronal sections (Fig. 2B),

  • (iii)

    The distance between the GTs and the mandibular central incisors (I-SGT) was determined by measuring the vertical distance between the apex of the GTs on the sagittal section and the apex of the mandibular central incisors (Fig. 3A),

Fig. 3.

Fig. 3

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Cross-sectional cone-beam computed tomography images showing the measurements of I-SGT: genial tubercles to the mandibular central incisors (A); IGT-M: genial tubercles to the inferior border of the mandible (B); MT: mandibular thickness (C)

  • (iv)

    The distance between the GTs and the border of the mandible (IGT-M) was determined by measuring the vertical distance between the lowest point of the GTs on the sagittal section and the lower border of the mandible (Fig. 3B),

  • (v)

    The anterior bone thickness of the mandible (MT) was determined by measuring the horizontal distance between the most convex part of the GT on the sagittal section and the mandibular buccal cortex (Fig. 3C).

Statistical analysis

Intra-observer and inter-observer reliability were analyzed using the intraclass correlation coefficient (ICC) for quantitative measurements. The Kappa coefficient was used for categorical assessments. The sample was categorized into age groups of 18–25, 26–35, 36–45, 46–55, and 56 years and above. These intervals were chosen to provide balanced subgroup sizes and are consistent with ranges commonly used in previous studies assessing maxillofacial morphology [22–24]. Two-way analysis of variance was used to examine the main effects and interactions of age group and sex on quantitative measurements, including GT-w, GT-h, I-SGT, IGT-M, and MT. Mean ± standard deviation (sd) values were presented as descriptive statistics. Bonferroni-corrected multiple comparison test results were utilized to examine the difference in cases where the interaction term (age group*sex) was significant in two-way analysis of variance. The dependency between GT types and sex and age group was examined using the Pearson Chi-square test, as the test assumptions were met. Statistical significance was set at P < 0.05. All analyses were performed on IBM SPSS Statistics for Windows, Version 23.0 (Released 2015, Armonk, NY: IBM Corp.).

Results

A total of 356 CBCT images of patients, including 228 (64%) females and 128 (36%) males, were evaluated in the study. The age range was 18–78, and the mean age was 39.7 ± 16.5 years. All the intraclass correlation coefficients examined for inter-observer agreement in terms of the morphological measurements (GT-w, GT-h, I-SGT, IGT-M, and MT) were found to be significantly high (ICC = 0.883, 0.983, 0.965, 0.975, 0.957, respectively, all p < 0.05). The Kappa value of categorical data, including GT typing, was examined, and it was found that the inter-observer agreement was at a substantial level (Kappa = 0.765) [25].

According to GT classification, the most common type of GT was GT-3 (33.1%), which was followed by GT-2 (22.5%), GT-4 A (14.3%), GT-1 (11.8%), and GT-5 (9.6%), and the least common type was GT-4B (8.7%) (Table 1). At least one GT was detected in 90.4% of the images, while none were detected in 9.6% of them.

Table 1.

The frequency distribution of GTs and GT types in the sample

Frequency n %
Presence 322 90.4%
Absence 34 9.6%
Types
GT-1 42 11.8%
GT-2 80 22.5%
GT-3 118 33.1%
GT-4A 51 14.3%
GT-4B 31 8.7%
GT-5 34 9.6%
Total 356 100%
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The most common type of GT in males and females was GT-3, followed by GT-2, GT-4 A, GT-5, GT-1, and GT-4B in females, and GT-2, GT-4 A, GT-1, GT-4B, and GT-5 in males, respectively. A statistically significant relationship was found between sex and GT types (p = 0.007, Table 2).

Table 2.

Distribution of GT types according to sex

GT Types Sex n % P-value*
GT-1 Female 25 11% 0.007
Male 17 13.3%
GT-2 Female 41 18%
Male 39 30.5%
GT-3 Female 84 36.8%
Male 34 26.6%
GT-4 A Female 30 13.2%
Male 21 16.4%
GT-4B Female 19 8.3%
Male 12 9.4%
GT-5 Female 29 %12.7
Male 5 %3.9
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* Pearson Chi-square test

The examination of the distribution of GT types by age groups in CBCT images indicated that GT-3 was the most common GT type in all age groups. The least common types varied by age range: GT-1 (18–35 years), GT-4B (36–45 years), GT-5 (46–55 years), and GT-4 A (56 ≤ years). The relationship between age groups and GT types was statistically significant (p = 0.017, Table 3). Table 4 provides the mean values of GT-w, GT-h, I-SGT, IGT-M, and MT.

Table 3.

GT types according to age groups

Age Groups GT Types P-value*
GT-1
n (%)		 GT-2
n (%)		 GT-3
n (%)		 GT-4 A
n (%)		 GT-4B
n (%)		 GT-5
n (%)
18–25 9 (9) 22 (22) 24 (24) 19 (19) 15 (15) 11 (11) 0.017
26–35 3 (5) 17 (28.3) 22 (36.7) 8 (13.3) 4 (6.7) 6 (10)
36–45 12 (18.2) 8 (12.1) 22 (33.3) 13 (19.7) 3 (4.5) 8 (12.1)
46–55 11 (21.2) 12 (23.1) 19 (36.5) 6 (11.5) 3 (5.8) 1 (1.9)
56≤ 7 (9) 21 (26.9) 31 (39.7) 5 (6.4) 6 (7.7) 8 (10.3)
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* Pearson Chi-square test

Table 4.

The mean, standard deviation (sd), and range of the GT-w, GT-h, I-SGT, IGT-M, MT (mm) in study groups

Parameters Mean ± sd (Range)
GT-w 6.44 ± 1.61 (1.8–11.6)
GT-h 7.57 ± 2.04 (2.2–12.8)
I-SGT 6.92 ± 3.09 (0–19)
IGT-M 6.89 ± 1.91 (1.6–13.4)
MT 14.28 ± 2.17 (8.4–21.2)
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GT-w, GT-h, I-SGT, and MT values were higher in males than in females (p < 0.001). IGT-M measurement was also found to be higher in males than in females, but this difference was not statistically significant (p = 0.070, Table 5).

Table 5.

The mean and standard deviation (sd) of the GT-w, GT-h, I-SGT, IGT-M, and MT (mm) according to sex and age groups

Age Sex (Mean ± sd) P-value
Female Male
GT-w 18–25 6.1 ± 1.71 6.8 ± 1.49 page=0.288, psex<0.001, pint=0.086
26–35 6.1 ± 1.74 6.5 ± 1.54
36–45 6.1 ± 1.39 7.4 ± 1.43
46–55 6.3 ± 1.41 7.4 ± 1.67
56≤ 6.5 ± 1.5 6.3 ± 1.8
GT-h 18–25 7 ± 1.87 7.7 ± 1.83 page=0.038, psex<0.001, pint=0.029
26–35 7.4 ± 1.88* 8.7 ± 2.14*
36–45 7 ± 2.01* 8.6 ± 2.63*
46–55 7.4 ± 2.22 7.3 ± 1.74
56≤ 7.2 ± 1.71* 9.2 ± 1.75*
I-SGT 18–25 5.7 ± 2.79 6 ± 2.18 page<0.001, psex<0.001, pint=0.247
26–35 6.5 ± 4.09 7.9 ± 3.22
36–45 6.4 ± 3.01 8.3 ± 2.8
46–55 6.6 ± 2.78 9.1 ± 2.9
56≤ 7.1 ± 2.72 8.3 ± 2.96
IGT-M 18–25 6.4 ± 1.69* 7.8 ± 2.17* page=0.789, psex=0.070, pint=0.030
26–35 6.7 ± 1.53 6.7 ± 2.13
36–45 6.8 ± 1.72 6.9 ± 1.76
46–55 6.5 ± 2.27 7.5 ± 1.92
56≤ 7.1 ± 2.03 6.7 ± 1.71
MT 18–25 13.8 ± 1.96 15 ± 2.49 page=0.732, psex<0.001, pint=0.888
26–35 13.4 ± 2.27 14.9 ± 2.32
36–45 13.9 ± 1.8 15.3 ± 2.13
46–55 13.5 ± 1.67 15.3 ± 2.37
56≤ 14.1 ± 2.2 15.2 ± 1.53
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Two-way analysis of variance p-values for main effects and interactions were presented. Bold indicated a significant effect, while (*) showed that the Bonferroni adjusted post-hoc comparison between sexes in related age groups was significant

Discussion

GTs are classically defined as four prominences arranged in pairs in the lingual region of the midline of the mandible [26]. Despite seemingly being a minor anatomical landmark of no clinical significance, GTs provide several crucial roles in the patient’s functions. The role of the structures as attachment sites for the genioglossus and geniohyoid muscles is to provide stability and support for the tongue’s movements, aiding in speech, deglutition, and other oral functions. The consistent functioning and contraction of the muscles lead to the greater prominence of GTs by pulling the bone. The presence and size of GTs can influence treatment planning, especially when considering the stability of the lower dentures. In patients with severe alveolar ridge atrophy, it may appear as a prominent bony projection, potentially causing denture instability and, in extreme cases, leading to fracture of the structure itself [8, 27].

The sample in this study was predominantly female (64%), which differs from other studies where this proportion ranged between 50% and 60% [4, 28]. Additionally, Araby et al. [7] observed GTs in a sample consisting 69.4% of men, which contrasts with the sample in the present study. Therefore, the low number of male subjects may have affected the overall results and comparability of the present study. A statistically significant association was observed between GT types and age groups (p = 0.017) in the present study, indicating that the distribution of GTs varied with age.

The prevalence and shape characteristics of the GTs have been studied in the literature, mostly through osteological studies [1, 5, 16, 29–33]. Limited research has also been conducted using radiological examinations [4, 7, 34, 35]. A notable methodological distinction of our study is the subdivision of Type 4 GTs into 4 A and 4B subtypes, following the cadaveric classification of Singh et al. [5]. While previous radiological studies did not make this distinction, our approach provides a more detailed assessment of the GT morphology [4, 7, 35]. It should be considered that the absence of Type 4 subtypes in previous radiological studies may not necessarily indicate the absence of these subtypes in those populations; rather, it could reflect a methodological variation.

Oda et al. [26] and Barbosa et al. [4] reported similar findings regarding GT shape and number in studies with comparable sample sizes and populations: both identified two upper tubercles as the most common pattern and four tubercles as the least common. Similarly, Jawahar et al. [21] found the two-tubercle pattern to be most frequent, but reported the single-tubercle pattern as least common. In this study, GT-3 (33%) was the most prevalent type, while GT-5 (absence of GTs; 9.6%) was the least observed. The prevalence of GT-4 (23%) is also consistent with previous radiological studies [4, 7, 21]. Variations in the most common GT morphology across studies likely reflect underlying racial or methodological differences; however, the absence of GTs remains rare according to current data [4, 7, 21, 26].

There was limited research on the prevalence of GTs by sex [7, 33, 35]. In the present study, the presence of GT was found to be higher in males (96.1%) than in females (87.3%), which is consistent with the studies by Jawahar et al. [35] and Nirmale et al. [33]. However, Araby et al. [7] reported that there was no significant difference between sex and GT types. Hu et al. [16] investigated the morphological characteristics of dry mandibles from 102 Korean individuals and evaluated 13 non-metric mandibular traits to determine their effectiveness in sex estimation. Analysis of the inferior GTs revealed sex-related trends: sharp fusion occurred more frequently in males (36.1%) and dull fusion in females (48.5%). Due to the considerable overlap observed between the male and female distributions, evaluating the GT alone yields limited accuracy for sex estimation, but it may provide supportive information in forensic anthropology when combined with other non-metric mandibular features, including chin shape and the contour of the lower border.

In this study, the GT-w was measured as 6.44 ± 1.61 mm, aligning with most radiological studies [4, 7, 10, 21, 35, 36] and the osteological study by Yin et al. [37]. Higher values were reported by Jung et al. [19], while Hueman et al. [38] and Lopes et al. [34] reported lower values. Unlike the others, the latter evaluated CBCT scans of individuals with cleft lip and palate, as well as two different associated syndromes. In addition, findings from comparative studies demonstrate a correlation between tomographic and cadaveric measurements, as well as the accuracy of CBCT in reflecting the GT anatomy [37, 38]. Therefore, it is possible to suggest that the GT is located on a sharp projection, which makes it easier to identify than points on broad curves. As a result, identifying the GT on CBCT images is straightforward [10]. Sexual dimorphism was observed in the GT-w measurements, with females exhibiting smaller values (6.20 ± 1.56 mm) compared to males (6.85 ± 1.62 mm), consistent with previous studies [4, 36]. In contrast, some studies have reported no differing patterns, indicating variability in the literature [19, 21, 28, 39]. The CBCT study conducted by Fırıncıoğluları et al. [20] demonstrates that OSA patients have smaller GT-w values compared to non-OSA patients, suggesting an association between airway collapse and the GT dimension. However, further research is necessary to elucidate the relationship between genioglossus muscle activity and GT-w.

The results of our study in terms of GT-h measurements (7.57 ± 2.04 mm) were similar to those reported by Araby et al. [7], Wang et al. [28], Kim et al. [18], Lopes et al. [34], Jung et al. [19], and Kolsuz et al. [21], likely due to the comparable methodologies used across these studies. However, there are discrepancies with the results of the cadaveric studies [37, 38]. When GT-h measurements were examined by sex in our study, we found the value was higher in males (8.23 ± 2.10 mm) compared to females (7.16 ± 1.09 mm), which was consistent with the studies by Yin et al. [37], Jun et al. [40], Nejaim et al. [39], Unal et al. [36], Barbosa et al. [4], and contrary to Kolsuz et al. [21]. Based on the current findings, males generally exhibit longer GTs; however, a clear dimorphic pattern is not evident because both sexes share an overlapping range of GT-h values [4]. Kim et al. [18] investigated the attachment sites of the geniohyoid, genioglossus, and digastric muscles to the mandible in fifty-three fresh cadavers. The results demonstrated that the combined height of the genioglossus and geniohyoid muscles was significantly greater than that of the GT. The findings indicate that the muscle fibers of the genioglossus and geniohyoid extend beyond the superior and inferior boundaries of the GT, as identified on CT scans. Additionally, the tubercles visualized on CT may not correspond precisely to the actual muscle attachment sites on the mandible. Future studies are needed to clarify the relationship between GT morphology and the attachments of the muscles.

The mean value of I-SGT measurements in this study was 6.92 ± 3.09 mm. This result is consistent with radiological findings reported by Mintz et al. [41], Barbosa et al. [4], Jung et al. [40], and Kolsuz et al. [21]. However, it is lower than the values reported by Araby et al. [7], Wang et al. [28], and those observed in cadaveric studies [37, 42]. It is important to note that a distance of at least five mm between the apex of the mandibular teeth and the osteotomy line is necessary to prevent neurovascular devitalization of teeth during horizontal osteotomy in genioglossus advancement surgery for OSA treatment [17, 43]. Therefore, determining the variations in I-SGT is essential; CBCT should be used for precise measurement of the distance between the apex of the mandibular central incisors and the upper limit of GT. The results of this study support the use of I-SGT data measured with CBCT as a guide in OSA surgery, as these images are convenient for dental clinics and offer more advantages than CT.

The mean value of IGT-M measurements in the present study (6.89 ± 1.91 mm) aligns with findings reported by Jung et al. [40] and Wang et al. [28], who also measured the distance from the lowest point of the genial tubercle to the lower border of the mandible. However, other studies using the same methodology, including those by Araby et al. [7], Jawahar et al. [35], Jung et al. [40], and Yin et al. [37], have reported differing results. These discrepancies may be attributable to variations in population-based anatomical characteristics. Yin et al. [37] reported a strong correlation between initial IGT-M measurements on cadavers and subsequent spiral CT images of the same specimens. IGT-M relates to the inferior horizontal osteotomy landmark during genioglossal advancement [19]. To avoid mandibular fracture, the lower horizontal box osteotomy cut should be over 10 mm above the mandibular inferior border [44]. Others suggest this cut be 5–6 mm above this border [45]. The mean IGT-M in this study was 6.89 ± 1.91 mm, suggesting an insufficient bone height. The inferior bone cut should be planned based on measurement, given the variable GT position. Furthermore, the study of Suthakar et al. [46], on the CBCT scans of 100 dentulous and 40 edentulous patients, demonstrated that the height from the GT to the base of the mandible is significantly correlated with the height from the lingual alveolar crest to the base of the mandible, suggesting GT is a reliable reference for assessing mandibular ridge resorption.

Genioglossus advancement should be maximized, as it depends on mandibular thickness at the fixation point [28]. The mean MT measurement was 14.28 ± 2.17 mm, with males exhibiting greater thickness (15.13 ± 2.18 mm) than females (13.76 ± 2.00 mm), consistent with previous studies [4, 21, 28, 37, 38, 40]. Wang et al. [28] and Jung et al. [40] demonstrated that class I male subjects had thicker anterior mandibles than class II female subjects. In contrast, Kolsuz et al. [21] indicated that Class III patients have a thicker MT than Class I and Class II patients. These findings suggest that male patients have an advantage in terms of the maximal amount of genioglossus advancement.

This study has several limitations. This study presents a radiologic adaptation of a classification system initially developed using dry skulls. Although CBCT effectively delineates osseous landmarks, imaging parameters such as voxel size, reconstruction kernel, and scatter or beam-hardening can reduce the clarity of axial margins. These factors may have influenced the ability to distinguish between closely related subtypes, such as 4 A and 4B. Furthermore, GTs were not visible in approximately 10% of cases; possible underlying causes, such as biological variation, bone resorption, image resolution, or observer-related factors, were not systematically examined. The study consisted only of individuals from a Turkish population, which may limit the generalizability of the findings to other ethnic or racial groups. In addition, although gender-based differences in GT dimensions were observed, mandibular size was not considered as a covariate; therefore, the interpretation of the observed gender-based differences in GT dimensions should be approached with caution. Further research is needed to establish functional relationships between GT morphology and muscle attachment patterns or clinical function, as these aspects were not assessed in this study.

Conclusions

In this CBCT-based study of a Turkish population, the GTs exhibited significant variation in morphology according to age and sex, with GT-3 being the most common type and detectable GTs present in over 90% of individuals. Male participants demonstrated greater GT-w, GT-h, and MT values than females. The subdivision of Type 4 into 4 A and 4B provided a more detailed radiological characterization, which may serve as a useful reference in future anatomical and clinical research. CBCT should be considered the preferred method for evaluating GT morphology in both research and clinical settings.

Abbreviations

GT

Genial Tubercle

CBCT

Cone-Beam Computed Tomography

GT-w

Genial Tubercle Width

GT-h

Genial Tubercle Height

I-SGT

Incisor to Superior Genial Tubercle

IGT-M

Inferior Genial Tubercle to Mandibular Base

MT

Mandibular Anterior Thickness

ICC

Intraclass Correlation Coefficient

CT

Computed Tomography

OSA

Obstructive Sleep Apnea

SD

Standard Deviation

3D

Three-dimensional

Author contributions

BB: Protocol/project development, Data collection, Data analysis, Manuscript writing/editing. NK: Protocol/project development, Data collection, Data analysis, Manuscript writing/editing. YZ: Data analysis, Manuscript writing/editing. NA: Protocol/project development, Manuscript writing/editing, Manuscript writing/editing.

Funding

There is no funding source.

Data availability

The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

The study protocol was approved by the Non-Interventional Ethics Committee of Hacettepe University (Date: 05/10/2021; Protocol No: GO 21/16 − 15), and in accordance with the Declaration of Helsinki. Informed consent was obtained from all patients for being included in the study.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.

Footnotes

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request.

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