|Year : 2020 | Volume
| Issue : 2 | Page : 205-211
Evaluation of the relationship between appearances of the lingual foramen on panoramic radiography and cone-beam computed tomography
O Isman1, S Kayar2, D Surmelioglu3, ME Ciftci4, AM Aktan4
1 Department of Dentomaxillofacial Radiology, Vocational High School of Health Service Gaziantep University, Gaziantep, Turkey
2 Department of Dentomaxillofacial Radiology, Okmeydanı Oral and Dental Health Hospital, Istanbul, Turkey
3 Department of Restorative Dentistry, Faculty of Dentistry, Gaziantep University, Gaziantep, Turkey
4 Department of Dentomaxillofacial Radiology, Private Practice, Gaziantep, Turkey
|Date of Submission||19-Jul-2019|
|Date of Acceptance||30-Sep-2019|
|Date of Web Publication||7-Feb-2020|
Dr. O Isman
Gaziantep University, Vocational High School of Health Service, 27310, Sehitkamil/Gaziantep
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Aim: The aim of this retrospective study is to determine the level of visibility of the lingual foramen in panoramic radiography using cone-beam computed tomography (CBCT) as a reference tool. Method: A total of 200 patients (111 females and 89 males) were included in the study. Cross-sectional CBCT images of the mandible in the midline were used to locate and define the orifice and diameter of each lingual canal that was detected. The appearance of the lingual foramen in the anterior mandible in panoramic radiography was assessed using a five-point ordinal scale. Descriptive statistics including tables and graphs were used. The correlation between CBCT and panoramic radiography findings were analyzed using Chi-square tests. Results: The lingual foramen was found to be located most frequently in the mandibular midline, above the genial tubercle (78.5%). A narrow-diameter type was found to occur most frequently (56.5%). A prominent genial tubercle was the most commonly found type (57.5%). The lingual foramen could be definitively identified in panoramic radiographs in only 8 cases (4%), while a high degree of probability was found in 25 cases (12.5%). The lingual foramen appears wider and therefore more distinctive in panoramic radiographs when the angulation of the lingual canal is less than 20° to the ground plane. Conclusions: Radiological evaluation with panoramic radiographs alone may lead to inadequate assessments prior to surgical procedures involving the anterior mandible. Clinicians may consider using three-dimensional imaging for procedures with a risk of hemorrhagic and neurosensory complications such as dental implant placement in the anterior mandible.
Keywords: Anterior mandible, cone-beam computed tomography, implant, lingual foramen, panoramic radiography
|How to cite this article:|
Isman O, Kayar S, Surmelioglu D, Ciftci M E, Aktan A M. Evaluation of the relationship between appearances of the lingual foramen on panoramic radiography and cone-beam computed tomography. Niger J Clin Pract 2020;23:205-11
|How to cite this URL:|
Isman O, Kayar S, Surmelioglu D, Ciftci M E, Aktan A M. Evaluation of the relationship between appearances of the lingual foramen on panoramic radiography and cone-beam computed tomography. Niger J Clin Pract [serial online] 2020 [cited 2020 Jul 16];23:205-11. Available from: http://www.njcponline.com/text.asp?2020/23/2/205/277867
| Introduction|| |
The anterior mandible's anatomical structures include concavity of the lingual cortex, the accessory mental, lingual canals, and extensions of the alveolar canal. Although surgical procedures such as dental implant placements, endodontic surgery, or periodontal surgery performed in the anterior region of the mandible are often accepted as being simple and uncritical,, variations in these structures or extensions of the lingual, mental canals may pose a risk of hemorrhagic and neurosensory complications.,,, Appropriate radiological assessments performed prior to surgical operations in this area may help clinicians to plan surgical procedures and reduce these complications. In the past, several studies have been performed for the purpose of identifying the morphology and the vital anatomical structures of the anterior mandible including the lingual foramen and the canals.,,, However to the best of our knowledge it is still unknown if panoramic radiography is adequate in detecting variations in the small lingual canals and their extensions.
Panoramic radiography provides a single image of the dentomaxillofacial complex including the alveolar bone, the teeth, the temporomandibular joint, and neighboring anatomical structures. Owing to the ease of use, relatively low cost, and low radiation doses, it is used extensively in all areas of dentistry. In addition panoramic radiography has some limitations since it provides 2D images and superimpositions of the structures so that it sometimes fails to visualize actual morphology.
Cone-beam computed tomography (CBCT) has been established as a very useful tool for the three-dimensional (3D) examination of the anatomy and abnormalities of the jaw.,,, Despite its widespread and ever-growing use, CBCT imaging performed before surgical procedures is still not as common as panoramic radiography due to the relatively high cost, higher levels of radiation exposure, and practitioners' lack of technical expertise.
The visibility of certain anatomical structures in panoramic radiographs and CBCT images differ markedly, which may result in inadequate radiographic evaluation of the area of interest and, therefore, unexpected complications. Taking into account the different characteristics and interchangeable use of these imaging techniques, the aim of this retrospective study was to determine the level of visibility of the lingual foramen in panoramic radiography using CBCT as a reference tool. Furthermore, it seeks to determine under which circumstances the lingual foramen appears in panoramic images, so that clinicians may have a practical and accurate means of evaluating the anterior mandibular region using panoramic radiography with regard to the lingual foramen and its bony canals.
| Materials and Method|| |
This study was approved by the Gaziantep University Faculty of Medicine Ethics Committee. CBCT (Planmeca, Helsinki, Finland) and panoramic radiography (Planmeca, Helsinki, Finland) images of 800 patients who were referred to the Department of Dentomaxillofacial Radiology at Gaziantep University; Faculty of Dentistry were evaluated retrospectively.
The inclusion criteria incorporated an absence of pathological lesions in the mandible—particularly the anterior region—, good quality mandibular images, an absence of apparent atrophy of the mandible, and an absence of impacted teeth in the anterior mandible. Radiographic images with metallic or moving artifacts, low-resolution, or inadequate image quality were excluded from the study.
A total of 200 patients (111 females and 89 males) whose qualified CBCT and panoramic radiography images could be obtained were included in the study. The analyses of the CBCT images were done using built-in software (Planmeca, Romexis, Helsinki, Finland) in a Dell Precision T5400 workstation (Dell, Round Rock, TX, USA) equipped with a 24-inch Ultra Sharp LED TFT monitor (Dell, TX, USA), which displayed 2 megapixels with 0.27 pixel pitch in a darkroom. The brightness and contrast of the images were calibrated according to the image processing tool in the software to provide optimal visualization.
Panoramic radiographs were obtained using the same machine (Planmeca, Promax, Helsinki, Finland), and the standard protocol for panoramic radiography was applied in all cases. The position of the head was standardized for all patients. The Frankfurt plane was kept parallel to the horizontal plane during image acquisition and the central beam was radiated to the mandible with -7° angle relative to the horizontal plane.
Cross-sectional CBCT images of the mandible in the midline were used to locate and define the orifice and diameter of each lingual canal that was detected. Localization of the lingual foramen was categorized into six regional subgroups: Above, at the level (middle) of the mental spine, below, both above and at the level of the mental spine, both below and at the level of the mental spine, above and below the mental spine [Figure 1]. In addition, multiple lingual foramina were recorded. The diameter of the lingual foramen was categorized into three subgroups; wide, medium, and narrow [Figure 2]. The shape of the genial tubercle was also classified into four groups; concave, flat, prominent, and more prominent [Figure 3].
|Figure 1: Different locations of the lingual foramen with reference to the genial tubercle (a) above (b) at the level (middle) of the mental spine, (c) below (d) both above and at the level of the mental spine, (e) both below and at the level of the mental spine, (f) above and below the mental spine|
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|Figure 2: The classification of the bony canals of the lingual foramen according to width (a) wide, (b) medium (c) narrow diameter of the lingual foramen|
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|Figure 3: The classification of the genial tubercles according to shape a) concave, b) flat, c) prominent, d) more prominent|
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Then the appearance of the lingual foramen in the anterior mandible in panoramic radiography was assessed using a five-point ordinal scale; lingual foramen definitely absent (0), lingual foramen probably absent (1), unsure if lingual foramen is absent or present (2); lingual foramen probably present (3), lingual foramen definitely present (4) [Figure 4]. The lingual foramen angle relative to the horizontal plane was divided into six subgroups; 0-10° angle (1); 11-20° angle (2), 21-30° angle (3); 31-40° angle (4); 41-50° angle (5); and 51° angle > (6).
|Figure 4: Different visibility levels of the lingual foramen in panoramic radiography a) lingual foramen definitely absent (0), b) lingual foramen probably absent (1), c) unsure if lingual foramen absent or present (2), d) lingual foramen probably present (3), e) lingual foramen definitely present|
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Descriptive statistics including tables were used. In order to test the degree of agreement between repeated analyses, kappa (k) coefficient values were employed to assess intraexaminer reliability in reaching a correct and reproducible diagnosis. The correlation between CBCT and panoramic radiography findings was analyzed using Chi-square tests. SPSS (version 16; Inc, Chicago, Illinois) was used for all analyses and a P value of less than 0.05 was considered statistically significant.
| Results|| |
Of the 200 patients (111 females and 89 males) included in the study, CBCT cross-sectional images confirmed that 184 patients had one lingual canal (92%). Two branches of the lingual canal in the mandibular anterior midline region were identified in 16 patients (8%). The lingual foramen was found to be located most frequently in the mandibular midline, above the genial tubercle (78.5%) followed by below (7.5%) and at the level of the genial tubercle (6%). [Table 1] shows the distribution of the localization of the lingual foramen in the mandibular midline.
|Table 1: The distribution of the locations of the lingual foramen with reference to the genial tubercle|
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Of the three subcategories of lingual canal diameters, the narrow-diameter type was found to be the most frequent (56.5%), followed by the medium-diameter (24.5%). [Table 2] illustrates the distribution of the diameter of the lingual foramen among patients. A prominent genial tubercle was the most commonly found type (57.5%), followed by the more prominent type (21.5%) and the flat type (20.5%). The concave type was the least common (0.5%). [Table 3] summarizes the distribution of the shape of the genial tubercle in the mandibular midline region.
[Table 4] illustrates the appearance levels of the lingual foramen in panoramic radiographs. The lingual foramen could be definitely identified in only 8 cases (4%), while a high degree of probability was seen in 25 cases (12.5%). Postulating that definitive or probable detection is a threshold for identification in panoramic radiography, the lingual foramen could not be identified in panoramic radiographs in 167 cases (83.5%).
|Table 4: The distribution of the visibility of the lingual foramen on panoramic radiography|
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Looking at the lingual foramen angle relative to the horizontal plane, statistically significant differences (p: 0.000 and p: 0.001, respectively) were found for subgroups 1 and 2. [Table 5] shows relationships between the angle, diameter, and localization of the lingual foramen on the CBCT cross-sectional images and the delineation of the lingual foramen in panoramic radiography were found to be statistically significant (p < 0.05). The findings of the present study also indicate that the lingual foramen appears wider, and therefore more distinctively in panoramic radiographs when the angulation of the lingual canal is less than 20° to the ground plane.
|Table 5: The correlation of the visibility of the lingual foramen on panoramic radiography and angulation of the lingual canal, width and localization of the LF|
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The kappa(k) coefficient value of intraexaminer reproducibility was 0.89, while that for interexaminer reproducibility was 0.79.
| Discussion|| |
The interforaminal region of the mandible is generally assumed to be a safe region for surgical procedures including for the placement of implants. However, a number of authors have previously reported serious complications, such as life-threatening hematoma in the floor of the mouth due to injury to the lingual vessels, following implant placement in the mandibular anterior region., Taking into consideration the fact that panoramic radiography is a widely used method for presurgical evaluation in implant dentistry, the present study aimed to determine the visibility of the lingual foramen and neighboring structures in panoramic radiography. A further aim was to help clinicians avoid complications by providing a better understanding of the lingual foramen anatomy focusing on its position, location, and diameter in presurgical radiographic analyses.
A number of authors have previously reported computed tomography (CT) findings of median and/or lateral lingual canals., Since the purpose of the present study was to correlate the appearance of the lingual foramen in panoramic radiography and CBCT scans, and to define its delineation in panoramic radiography, the region of interest was determined as being the median lingual foramen in the anterior mandibular midline. Jacobs et al. had previously reported that the lingual foramen could be identified in panoramic radiography in 71% of cases while 12% had adequate visibility. In a similar study by Jalili et al., the lingual foramen could be clearly identified in panoramic radiographs in only 6% of cases. According to the results of the present study, a score of 5 indicating that the lingual foramen was definitely present in panoramic radiography could only be confirmed in 4% of patients, while a score of 4 indicating the probable presence of the lingual foramen in panoramic radiography was observed in 12.5% of patients. Despite minor differences in percentage distributions, these findings of the visibility of the lingual foramen in panoramic radiography were in conformity with previous studies., These differences may be explained by the different scales utilized for the radiographic examination. On the other hand, CT-based evaluations of the lingual foramen detailed in previous studies have revealed a high prevalence ranging from 82% to 100%.,,, As was found in previous studies,,, with CT the lingual foramen could be observed in all patients in the present study.
A number of authors have previously investigated the location of the mandibular lingual canal in CT examinations., Sekerci et al. identified 12 different locations for the lingual foramen on CBCT cross-sectional images. They found that the most common type found in the midline of the symphysis was a single lingual foramen located above the genial tubercle followed by two lingual foramens (one located above and the other located below the genial tubercle), and a single lingual foramen located below the genial tubercle. In addition, other researchers have also shown that the most frequent location of the lingual foramen was above the genial tubercle, which conforms with the findings of the current study.
Despite the detection of a single lingual foramen in the midline area in most cases (184 patients - 92%), multiple foramina were also observed in a considerable number of patients (16 patients - 8%) in this study. This finding is also comparable data from previous research, which reveals a higher frequency of a single lingual foramen.,,
Previous studies reporting on the diameter of the lingual canal show that it may range from 0.18 to 3 mm.,,,,,, Wang et al. reported that wider canals with a diameter of ≥1 mm in the midline area were detected in 13.2% of patients included in their study. In the current study, the diameter of the lingual foramen in the midline area was categorized into three subgroups described as wide, medium, and narrow. The results showed that a narrow lingual foramen was the most frequently encountered type followed by the medium type, while lingual foramen with a wide diameter was the least common. In the present study, further measurements of the diameter of the lingual foramen could not be performed due to software limitations, which did not allow for precise measurements of lengths less than 1 mm. Nevertheless, the findings in this study of categorical outcomes may help clinicians gain a better understanding and awareness of the diameter of the lingual foramen, and therefore may aid in dental implant placement and other surgical procedures including those affecting the anterior mandible.
Genial tubercles are small bony prominences on the lingual sight of the mandible in the midline region of the symphysis and, in the literature, they are commonly reported to be located at the same level or just below the lingual foramen. In this study, the most frequently encountered type of genial tubercles was the prominent type, followed by more prominent, and flat types. When interpreting radiological findings in the lingual aspect of the anterior mandible, the fact that the radiopaque areas around the lingual foramen may not necessarily represent genial tubercles should be taken into consideration. Baldissera and Silveira had previously suggested that there was no relationship between the genial tubercles and the cortical sites around the lingual foramen and, concluded that the radiopaque ring image around the lingual foramen represents the canal cortical wall and not the projection of the genial tubercles. Keeping the distinction of these anatomical entities in mind, a conscious effort was made in the present study to accurately identify the location and protrusion levels of the genial tubercles.
It has been previously suggested that the incisive canal could be better imaged with a straighter neck position during downward tipping of the jaw, with less overlapping of the cervical spine. However, the X-ray beam is inclined slightly upward in panoramic radiography (7-8°), leading to misinterpretations due to a certain amount of distortion of the actual mandibular anatomy. Previous studies have shown that the degree of corticalization of the lingual canal may also play a significant role in visibility, and better visualization of the mandibular canal with less superimposition and better contrast values between the canal and the surrounding bone can be achieved by a 5° downward tipping of the mandible based on the Frankfurt plane. In this study, lingual canals with angulations less than 20° to the ground plane were found to be able to be observed more distinctly. Therefore, it is proposed that the visibility of a lingual canal is affected not only by the degree of corticalization but also by its angulation. The X-ray beams parallel to the long axis of the lingual canal may result in a better contrast between the canal and its surrounding bone, and therefore better visibility.
Although several studies have previously reported on the appearance of the lingual foramen in CT, CBCT, panoramic and periapical examinations,,,,, to the best of our knowledge, the present study is the first one to evaluate and report on the relationship between delineation of the lingual foramen on panoramic radiographs and CBCT cross-sectional images. Therefore, its findings may play an important role and aid clinicians in understanding the correlation of the radiographic appearance of the lingual foramen and its canals obtained from two commonly used imaging techniques.
In conclusion, the visibility of the lingual foramen and neighboring anatomical structures in panoramic radiographs and CBCT images differ markedly, and panoramic radiography fails to provide conclusive findings. Radiological evaluation with panoramic radiographs alone may lead to inadequate assessments prior to surgical procedures involving the anterior mandible. Clinicians may consider using three-dimensional imaging for procedures with a risk of hemorrhagic and neurosensory complications such as dental implant placement in the anterior mandible.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]