Abstract
Background
The main arterial supply to the anterior segment of the mandible consists of a single terminal branch from the anastomosis of the left and right sublingual arteries that enter the lingual foramen and courses through the midline lingual canal (MLC). The aim of the study was to evaluate the correlation between the diameter of the MLC by cone-beam computed tomography (CBCT) and quantitative measurements of the anastomotic arterial branch as obtained by Doppler ultrasonography (USG).
Methods
A total of 24 patients (mean age, 48.4 years; range, 20–73 years) with CBCT scans were included in the study. The diameter of MLC was measured on the axial CBCT sections. The volumetric flow rate and the diameter of the artery were assessed using Doppler USG. Statistical analyses were conducted using Student’s t-test and Pearson’s correlation coefficient (r).
Results
The diameter of the MLC ranged from 0.44 to 1.52 mm. The diameter and the volumetric flow rate of the artery were 1.1–1.9 mm and 1.3–16.9 ml/min, respectively. The MLC diameter was positively correlated with both arterial diameter (r = 0.404, P = 0.05) and arterial blood-flow rate (r = 0.447, P = 0.028).
Conclusions
Doppler USG is a safe and effective method for visualizing and measuring the anastomotic arterial branch in the lingual foramen region. The diameter of the MLC on CBCT may indicate the vascularity of the interforaminal region of the mandible.
Keywords: Lingual foramen, Sublingual artery, Cone-beam computed tomography, Ultrasonography, Doppler
Background
Radiographic assessment of the anterior mandible plays a key role in planning and managing surgical approaches such as implant placement, genioplasty, bone grafting, fracture fixation, jaw resection, or cyst removal. The interforaminal region of the anterior mandible, an area between the mental foramina, is often involved in the planning of implant procedures in edentulous cases and is considered a safe space for implant placement [1]. Vascular supply to the interforaminal region of the mandible and floor of the mouth has been well described using various techniques [2]. The main arterial supply to the anterior segment of the mandible consists of a single terminal branch from the anastomosis of the left and right sublingual arteries that enter the lingual surface of the bone through the lingual foramina located in the midline, between the genial tubercles [3, 4]. Two or more foramina may be present in the midline, and their locations and diameters are variable [5, 6]. However, at least one lingual foramen provides an entrance to the midline lingual canal in more than 80% of cases. The content of the MLC remains controversial. While some authors describe it as a neurovascular bundle, others state that it is only a branch of the incisive artery.
According to Loukas et al. [7], who studied the anatomical variations of the sublingual artery in cadavers, the sublingual artery has three branches: an ascending branch that extends towards the alveolar ridge, a middle branch that anastomoses with the contralateral sublingual artery to enter the MLC, and a descending branch located beneath the MLC. The arteries supply blood to the sublingual gland, the floor of the mouth, the mylohyoid muscle, the lingual gingiva, and the mandible through the foramina [2, 7, 8].
Complications due to artery damage occur in the MLC rather than the foramen region. The literature describes many cases of severe bleeding complications during implant placement following the perforation of the lingual cortical plate and damage to the arteries, emphasizing the critical importance of a precise determination of the anatomy and its common vascular variations [6, 9–12].
Computer tomography (CT) is a preferred modality for visualizing and determining the course of vascular canals through the mandibular bone [11]. Although not routinely used as a diagnostic tool before mandibular surgeries, Doppler ultrasonography (USG) is the only method to evaluate vascular architecture and blood flow. USG allows real-time assessment and quantification of blood flow and vascularization, and therefore has the potential to determine hemorrhage risk prior to implant surgeries involving the anterior segment of the mandible [13, 14].
Only a few studies in the literature evaluated the volume and diameter of the anastomosing artery using the USG [14, 15]. Our study aims to reassess the correlation between MLC diameters measured by CBCT and the volumetric flow rate and diameter of the anastomotic arterial branch evaluated with Doppler USG.
Methods
Study registration and design
The study was conducted with the approval of Hacettepe University Clinical Research Ethics Board (date: 01.06.2021, number: 2021/12 − 11). Patients aged 18 and older who applied to the Department of Dentomaxillofacial Radiology for a CBCT scan before mandibular implant procedures were included in this study.
Patient selection criteria
The selected patients had no missing mandibular anterior teeth, congenital or acquired facial deformities, history of mandibular surgery, or pathology in the mandible anterior region. After obtaining informed consent, CBCT imaging patients were asked to undergo a USG examination. The study consisted of 24 patients (12 females and 12 males).
CBCT imaging
CBCT images were obtained using an i-CAT Next Generation scanner manufactured by 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.
Axial images were saved in the standard clinical Digital Imaging and Communications in Medicine (DICOM) format, and measurements were performed using the Radi-Ant DICOM viewer by a single calibrated examiner (NK). The presence and location of the MLC were evaluated on multiplanar sections (Fig. 1). The diameter of the MLC was measured on axial sections at the widest point of the mandibular entrance. The CBCT images were examined on a 24-inch LCD monitor with a resolution of 1920 × 1080 (Dell, Round Rock, TX, USA) in dim lighting conditions.
Fig. 1.
Axial (a) cone-beam computed (CBCT) image showing the midline lingual canal (MLC). Coronal (b) CBCT image showing the lingual foramen. Sagittal CBCT (c) image showing the entrance of the MLC
Doppler ultrasonography
Ultrasonographic examination and data collection were performed by the same examiner. During the examination, patients were placed in the supine position with the head overextended and the chin positioned forward and upward. Portable ultrasound equipment (Versana Active, GE Healthcare, USA) equipped with a 6–13 MHz wideband linear array probe (L12-6-RS; GE Healthcare, USA) was used. The probe was positioned transversely over the submental region.
A musculoskeletal preset was selected for grayscale B-mode imaging. Gain, focus, and depth were adjusted individually for each patient. Doppler sensitivity was optimized for low-flow detection using a Doppler frequency of 6.3 MHz. The lowest wall filter was applied, excessive probe pressure over the scanning area was avoided, and pulse repetition frequency was adjusted as needed to optimize Doppler signal acquisition.
The right and left terminal branches of the sublingual artery were identified and traced to the midline, where their anastomotic connection (Fig. 2) in the lingual foramen region was evaluated. Spectral Doppler measurements were obtained from this midline anastomotic arterial segment using a 1-mm sample volume positioned within the vessel and angle correction set at 60° along the vessel axis. Blood volume flow was automatically calculated by the ultrasound system software after manual measurement of the target vessel diameter, which was performed by placing two electronic calipers perpendicular to the inner vessel walls on transverse images. Accordingly, a single arterial diameter (mm) and a single volumetric flow rate (ml/min) were recorded for each patient (Fig. 3) [14].
Fig. 2.
Color Doppler ultrasonographic image of demonstrating the anastomotic artery (arrow) in the lingual foramen region
Fig. 3.
Spectral Doppler ultrasonographic evaluation of the anastomotic arterial branch. The upper panel shows the target vessel and diameter measurement, while the lower panel demonstrates the arterial waveform used for automatic volumetric flow calculation
Statistical analyses
Statistical analysis was conducted using MedCalc Statistical Software version 20.018 (MedCalc Software Ltd, Ostend, Belgium). Differences in CBCT and Doppler ultrasonographic measurements according to sex were analyzed using the independent samples t-test. Correlations between MLC diameter, arterial diameter, and volumetric flow rate were assessed using Pearson’s correlation analysis. Categorical variables were expressed as frequencies and percentages, while numerical variables were presented as mean ± standard deviation. A p-value of less than 0.05 was considered statistically significant. To assess intra-observer reliability, the same examiner repeated the CBCT-based measurements of MLC diameter and the ultrasonographic measurements of artery diameter after a two-week interval. Intra-observer agreement was evaluated using the intraclass correlation coefficient (ICC).
Results
The intra-observer agreement for CBCT and Doppler measurements revealed good ICC values (ICC = 0.86; 95% CI: 0.81–0.92 and ICC = 0.83; 95% CI: 0.76–0.88, respectively). The mean age of the patients included in this study was 48.4 ± 15.6 years (range 20–73 years). Age distribution was similar among male and female patients (50 ± 15.6 and 46.7 ± 16.2 years, respectively; t = -0,508, P = 0.616).
There was no significant difference between genders regarding the diameter of MLC on CBCT (P = 0.117), the diameter of the artery on USG (P = 0.710), or the Doppler values (P = 0.492; Table 1).
Table 1.
CBCT and Doppler measurements according to sex
| Female | Male | t* | P | |
|---|---|---|---|---|
| Number | 12 | 12 | ||
| Diameter of MLC (mm) | 0.81 ± 0.28 | 1 ± 0.29 | 1.63 | 0.117 |
| Diameter of the artery (mm) | 1.47 ± 0.20 | 1.44 ± 0.19 | 0.37 | 0.710 |
| Blood volume flow (ml/min) | 7.82 ± 4.21 | 8.95 ± 3.69 | 0.69 | 0.492 |
CBCT Cone beam computed tomography, mm Millimeter. *t-test
The diameter of the MLC measured by CBCT ranged from 0.44 to 1.52 mm (mean 0.92 mm ± 0.32). The artery diameter on USG ranged from 1.1 to 1.9 mm (mean 1.46 ± 0.19 mm). The blood volume flow rates obtained by USG ranged from 1.3 to 16.9 ml/min (mean 8.39 ± 3.92 ml/min).
The CBCT-measured MLC diameter was positively correlated with both the arterial diameter (r = 0.404; Fig. 4) and the blood volume flow rate (r = 0.447; Fig. 5) determined by Doppler USG (Table 2).
Fig. 4.
Correlation between the diameter of the midline lingual canal (MLC) and the diameter of the anastomotic artery
Fig. 5.
Correlation between the diameter of the midline lingual canal (MLC) and the volumetric flow rate of the anastomotic artery
Table 2.
Correlation between the diameter of the MLC on CBCT and Doppler measurements
| Variables | N | Diameter of MLC | P |
|---|---|---|---|
| Pearson correlation Coefficient (r) | |||
| Diameter of the artery (mm) | 24 | 0.404 | 0.050 |
| Blood volume flow (ml/min) | 24 | 0.447 | 0.028 |
CBCT Cone beam computed tomography, MLC Midline lingual canal, mm Millimeter, ml Milliliter, min Minute
Discussion
The midline lingual foramen is a constant feature of the anterior mandible and includes an intraosseous portion known as the MLC, which contains a blood vessel [7, 16]. The clinical importance of this vascular bone canal becomes even more evident as its perforation during surgery may lead to bleeding and life-threatening conditions [17–20].
The purpose of this study was to assess the correlation between the diameter of the MLC as measured by CBCT and the diameter of the artery and its blood volume flow rate, as analyzed by Doppler USG. The present study demonstrated a statistically significant moderate positive correlation between the diameters of the MLC and the anastomotic arterial branch in the lingual foramen region. This finding is consistent with the research by Lakha et al. [15], which was the only relevant study found in the literature.
The midline lingual foramen and the vascular content of the lingual canal have been investigated in both anatomical and radiological studies [3, 7, 9, 15, 21, 22]. Previous reports have shown that the lingual foramen and canal are common findings in the anterior mandible, although their dimensions may vary depending on population characteristics and imaging methodology. In CT- and CBCT-based studies, canal diameters have been reported to range from 0.3 to 1.22 mm [15, 21, 22]. In the present study, the mean MLC diameter was 0.92 ± 0.32 mm (range, 0.44–1.52 mm), which is consistent with the existing literature.
Lustig et al. [14], who performed Doppler ultrasonographic evaluation of the artery in the lingual foramen region, reported an arterial diameter ranging from 0.18 to 1.8 mm, with a mean of 1.41 ± 0.34 mm. Lakha et al. [15] evaluated the MLC diameter using CBCT, as well as the diameter of the artery and blood flow entering the foramen using USG, in 10 dentate and 10 edentulous subjects. They reported a positive correlation between the diameters of the MLC and the anastomotic arterial branch, regardless of dentition status (r = 0.29). In the present study, all participants were dentate. The diameter of the artery ranged from 1.1 to 1.9 mm, with a mean of 1.46 ± 0.19 mm. A statistically significant positive correlation was observed between the MLC diameter measured on CBCT and the arterial diameter assessed by USG (r = 0.404, P = 0.05). The differences between our findings and those of Lustig et al. [14] and Lakha et al. [15] may be related to differences in population characteristics, particularly age distribution and dentition status.
The present study demonstrated a statistically significant positive correlation between MLC diameter and the blood volume flow rate of the anastomotic artery (r = 0.447, P = 0.028). In our sample, blood-flow values ranged from 1.3 to 16.9 ml/min, with a mean of 8.39 ± 3.92 ml/min. These findings are consistent with those of Lakha et al. [15], who also reported a positive correlation between CBCT-based MLC diameter and Doppler USG-derived volumetric flow rate (r = 0.447, P = 0.048), with similar flow measurement values (mean, 8.58 ± 4.02 ml/min; range, 2.8–17 ml/min). By contrast, Lustig et al. [14] reported substantially lower blood-flow values (mean, 2.92 ± 3.19 ml/min; range, 0.7–3.7 ml/min). This difference may be related to variations in study population characteristics, particularly age distribution and overall sample composition.
From a technical perspective, CBCT and Doppler USG provide different but complementary information. CBCT is particularly valuable for visualizing osseous anatomy, including the location, course, and diameter of bony canals and foramina, and therefore plays an important role in preoperative implant planning in the anterior mandible [22, 23]. In contrast, Doppler USG offers real-time evaluation of vascular structures and blood flow characteristics without ionizing radiation [24]. While CBCT can identify the osseous conduit, ultrasonography can demonstrate the arterial content and its flow behavior. This complementary imaging approach may also be relevant more broadly in maxillofacial diagnosis. Accordingly, the present study highlights how these two modalities may be integrated when both hard-tissue anatomy and vascular information are clinically important.
In the present study, the MLC was identified in all patients, and the anastomotic arterial branch in the lingual foramen region could be localized using ultrasonography. Doppler USG appears to be a useful method for assessing blood-flow characteristics in this region. Since perforation of the lingual canal during surgery may result in severe hemorrhagic complications, careful preoperative evaluation of the MLC is important in procedures involving the anterior mandible.
This study has certain limitations. First, the sample size (n = 24) was relatively small and may not have been sufficient to fully capture anatomical variability in the vascular architecture of the anterior mandible. In addition, the single-center design and inclusion of a convenience sample may limit the external validity and generalizability of the observed correlations. Therefore, the results should be interpreted as preliminary. Moreover, although Doppler USG offers real-time flow assessment, it remains operator-dependent and is subject to variability related to insonation angle, probe pressure, and patient positioning. All measurements were performed by a single calibrated examiner; however, the absence of interobserver reliability analysis limits reproducibility validation, and examiner-related bias cannot be completely excluded.
In addition to these limitations, certain methodological constraints should also be acknowledged. Additionally, the CBCT-based measurement of the MLC on axial sections may not have fully represented the complex three-dimensional morphology of the canal. Only dentate individuals were included in the study population. While this approach provided a more homogeneous sample, it limits extrapolation of the findings to edentulous patients, in whom alveolar bone resorption may substantially alter canal visibility and vascular patterns. Future studies with larger study populations, combined with volumetric analysis or micro-CT validation, may provide more comprehensive anatomical correlations.
Conclusions
The diameter of the MLC on CBCT may provide indirect information about the vascular characteristics of the interforaminal region of the mandible Doppler USG is a safe and effective method for visualizing and measuring the anastomotic arterial branch, which supplies the main blood flow to the anterior region of the mandible. By assessing this artery, Doppler USG can help identify the risk of hemorrhage, particularly in cases with complex vascular structures. Therefore, incorporating Doppler USG into the preoperative evaluation of the lingual foramen region may be beneficial for surgical procedures involving the anterior mandible, such as genioplasty, implant placement, and bone grafting.
Abbreviations
- MLC
Midline lingual canal
- USG
Ultrasonography
- CBCT
Cone-beam computed tomography
- CT
Computed tomography
- DICOM
Digital imaging and communications in medicine
- ICC
Intraclass correlation coefficient
- MHz
Megahertz
- mm
Millimeter
- min
Minute
- ml
Milliliter
Authors’ contributions
NK designed the study, collected the data, and wrote the main manuscript. NK and SD analyzed and interpreted the data. All authors read and approved the final manuscript.
Funding
This research was conducted as part of a project supported by Hacettepe University Scientific Research Projects Coordination Unit (TAY-2022-20121).
Data availability
All data generated or analyzed during this study are included in this published article [and its supplementary information files].
Declarations
Ethics approval and consent to participate
The study was conducted in accordance with the Declaration of Helsinki and was approved by the Clinical Research Ethics Board of the University of Hacettepe (protocol code: KA-180115; date of approval: 01.06.2021).
Informed consent was obtained from all subjects involved 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
All data generated or analyzed during this study are included in this published article [and its supplementary information files].