CBCT Evaluation of Lingual Foramen and its Anatomic Variations in Northeast Indian Population

ABSTRACT

Background:

The identification of nearby neurovascular structures is a vital part of dental implant treatment planning. Commonly two implants are placed in the mandibular inter foraminal region to support the overdenture. Placing dental implants in this region is considered relatively safe. The purpose of this study was to employ cone beam computed tomography (CBCT) on a representative sample of Northeast Indians to find out the location and distribution of lingual foramen in the anterior mandible.

Study Design:

A total of 104 CBCT scans were performed using the Cranex 3D CBCT system. Three Oral and Maxillofacial Radiologists agreed on a visibility grade for assessing the lingual foramen using a 3-point scale. The number and presence of foramina were noted. On cross-sectional pictures, the distance in millimeters between the crest of the alveolar ridge and the superior cortical margin of the foramen was determined. Furthermore, the analysis of the distribution of lingual foramina in terms of frequency and percentages was performed.

Results:

Scan results showed that the lingual foramen was clearly visible in 65.4% of cases, somewhat visible in 12.5% of scans, and not visible at all in 22.1% of cases. Half of the people in the study had two foramina, whereas 27.9 percent had one and 22.1 percent had none. The mean distance from the crest of the alveolar ridge was 10.84 mm in males whereas 9.91 mm in females

Conclusion:

The Northeast Indian population exhibits an unusually high prevalence of lingual foramen in the anterior portion of the mandible. This research will aid in the precise pre-operative identification of the position and number of lingual foramina prior to surgical treatments involving the midline of the mandible.

INTRODUCTION

Implant-supported overdentures derive support from two implants placed in the mandibular inter foraminal region. There is a high level of confidence in the safety of using implant fixtures in this region.[1] Understanding where nearby nerves and blood vessels are located is essential for safe dental implant surgery. However, multiple studies conducted worldwide have revealed that potential surgical complications might lead to altered neurosensory perceptions and bleeding of the floor of the mouth. These hazards could have potentially fatal consequences.[2,3] Mandibular anterior intraoral periapical radiographs acquired by the intraoral bisecting angle technique might sometimes reveal a radiolucent pit (lingual foramen). This effect is only visible when the direction of the X-ray beam impinging on the specimen is perpendicular to the opening of the foramen. The lingual foramen is a bony opening on the floor of the mouth through which the mylohyoid and sublingual arteries enter.[4] When planning implants or other surgical treatments, the front mandibular midline is often overlooked. Due to an increase in the number of people seeking implants, there is a pressing need for baseline data on the variations in major anatomical features across different populations. The purpose of this investigation was to identify the lingual foramen in a representative sample of Northeast Indians and to calculate its frequency and percentage of the occurrence.

SUBJECTS AND METHODS

We did a cross-sectional study here at our institution with clearance from the institutional ethics review board (ethics certificate number. HCDSH/ADM/BNF/2020/231, dated 27.01.2020). All needed steps from the Declaration of Helsinki were taken. After conducting a convenience sample survey of the dental records department, we randomly selected 200 CBCT images. A total of 100 samples each from males and females, spanning January 2020 through February 2022 were selected. The correct sample size was calculated using the OPEN Epi programe. Each and every one of those 3D pictures were taken using a large (FOV). The height and width of the large FOV are 61 mm and 78 mm, respectively. Using a picture intensifier indicator, 120 kbp, 8 Mama, a voxel size of 0.25 mm 3, and a sweep duration of the 20s, the digitized images were obtained using a Cranex 3D CBCT Machine (Soredex, variation 5.2, PaloDEx Gathering Oy, Finland). Three-dimensional models were reconstructed and processed on a server Workstation (Dell Precision, Model T5810XL). For this research, we used Cyber Med’s (Finland) version 5.2 of their On Demand 3D TM Dental program. Images were seen on a Dell 21-inch display with the lights off. Sagittal slices were given the greatest attention, however, all orthogonal views of the CBCT scans were studied. Written informed consent was taken from every patient for the usage of scan data for research study purposes before the scans were taken. Only 104 healthy dentate adult patients (67 male/37 female) aged 10-80 years old who underwent CBCT scan of the mandibular region for implant planning or wisdom teeth assessment were included in the study, patients with pathologic diseases affecting the anterior mandible, such as syndromes and delayed tooth eruption and scans with radiographic artifacts (n = 96) were excluded. Scan-derived cross-sectional images of the lingual foramen were graded on a three-point scale for their visibility (definitely visible, moderately visible, and definitely not visible).[5] Three experts in oral and maxillofacial radiology came to a unanimous decision on the visibility assessment. The radiologists performed the evaluation twice. The number of lingual foramina present was also noted. The lingual canal’s location was determined by calculating the vertical distance between the alveolar crest and the superior cortical boundary of the foramen magnum (the superior foramina in case of two). The percentage and frequency of lingual foramina were determined. Both sexes were compared on a range of other metrics, including canal visibility, canal number, and canal location.

Using SPSS (IBM Corp., Armonk, NY) and Microsoft Office Excel (Redmond, WA), we performed a statistical analysis of the data we collected and then tabulated the results to the nearest whole number and first decimal place. Data were analyzed using descriptive statistics, and parameters were rated using means and standard deviations. We used the Student’s t-test to evaluate the significance of differences between continuous variables and the kappa statistic to evaluate the significance of differences between categorical variables.

RESULTS

A total of 104 CBCT scans were analyzed during this study. Lingual foramen was definitely visible in 65.4% (n = 68), moderately visible in 12.5% (n = 13), and definitely not visible in 22.1% (n = 23) of the patients [Table 1]. The overall percentage of foramina visible in our study was 77.9%. The percentage of visibility of foramen is slightly higher in females i.e. 78.4% than in males i.e. 77.7% [Table 2 and Figure 1].

Table 1.

Overall frequency and percentage of lingual foramen

Visibility of foramen
	Frequency	Percentage
Definitely Not Visible	23	22.1
Moderately Visible	13	12.5
Definitely Visible	68	65.4
Total	104	100.0

Table 2.

Frequency and percentage in males and female

Visibility of foramen
Gender	Frequency	Percentage
Male
Definitely Not Visible	15	22.4
Moderately Visible	6	9.0
Definitely Visible	46	68.7
Total	67	100.0
Female
Definitely Not Visible	8	21.6
Moderately Visible	7	18.9
Definitely Visible	22	59.5
Total	37	100.0

Figure 1.

Axial section depicting the lingual foramen

Amongst 104 CBCT scans investigated, 50% (n = 52) had two foramina, 27.9% (n = 29) had one foramen and 22.1% (n = 23) had no foramen [Table 3].

Table 3.

Frequency and percentage of number of foramen visible

Number of foramen
	Frequency	Percentage
0	23	22.1
1	29	27.9
2	52	50.0
Total	104	100.0

In men, this measurement was 10.84 mm (SD 6.584) while in women it was 9.91 mm (SD 5.827) [Table 4 and Figure 2].

Table 4.

Comparison of mean and s.d. for measurement and number of foramen

Gender	n	Mean	Std. deviation
Males
Measurement	67	10.84	6.584
Number of foramen	67	1.28	0.813
Females
Measurement	37	9.91	5.827
Number of foramen	37	1.27	0.804

Figure 2.

Cross sectional CBCT image showing the parameters calculated

DISCUSSION

This research set out to assess how common lingual foramen are among people from the Northeast of India. The lingual foramen is mentioned in textbooks, although it is not considered clinically significant. Recent years have seen an increase in the number of implants placed in the anterior mandible, and with that has come to a rise in the number of reports detailing serious bleeding complications following implant surgery.[6,7] The increased risk of interforaminal hemorrhage cannot be ruled out. These considerations guided us in designing this study. Additionally, there was a dearth of similar research involving the Northeast Indian population.

Our study’s 77.9% visibility rate for foramen was consistent with previous studies by Makis et al. (81%), Jacobs et al. (82%), Bernardi et al. (75%), and Santos et al. (97.3%).[2,5,8,9]

Studies on dry skulls have shown an incidence rate of 85–90%, thus our findings are inconsistent with that.[4,10] This has been shown by many groups (Mc Donnel et al. 1994, Liang et al. 2007).

Limitations in the radiographic examination process, the degree of certication of the foramen opening, and image deterioration play a role in this anatomic variation. Osteoporotic alterations occur more commonly in females, which might account for the difference in the proportion of incidence between males and females.

In agreement with the research by Santos et al. in 2020 (99.5% in females and 99% in males), we found that the proportion of visible foramen was slightly higher in females (i.e. 78.4%) than in males (i.e. 77.7%).[9]

Fifty percent of people were found to have two lingual foramina after an examination (superior and inferior). Liang et al. (2007) reported a 22% incidence; Kawai et al. (2007) claimed an 84% occurrence; and Moshfeghi et al. (2021) reported a 21.5% occurrence. All of these figures differ significantly from the current data. The study’s focus on specific racial groups likely explains these striking discrepancies.[10-12]

Through our measurements, we aimed to provide a median value for the maximum implant depth that is appropriate for usage in the midline. Males had a mean of 10.84 and a much higher SD of 6.584 than females, who averaged 9.91 and had a much more manageable SD of 5.827. Because of such a large difference in the values obtained, it was not possible for us to postulate on a range of lengths of implants that could be safely used in this region.

These findings were consistent with those of a 2017 research conducted by Aoun et al., which found that the average distance between the lingual canal and the crest of the alveolar ridge was greater in men than in women.[13] However, these findings diverge from the work of Shekhi et al. (2012) and Arun K. (2017), which found that females were more likely to be affected than men.[14,15] Reasons for this include a smaller female sample size and the anatomical differences between the male and female mandible.

When we compared the lingual canals of the Northeast Indian population to those of other populations, we observed that the number of lingual canals and their anatomical markers vary.[16,17] Therefore, CBCT imaging will be necessary to demonstrate the anatomical variance of the lingual canal to minimize post-operative difficulties in the anterior mandible area.[18,19]

We propose more research with a bigger sample size to verify our findings in the Northeast Indian community since ours is a rather small study.

CONCLUSION

Given the prevalence of lingual foramina in these cases, Maxillofacial radiologists may play an undeniably crucial role in preventing complications during surgeries involving the mandibular midline, such as the removal of friendly spines in edentulous patients, genioplasty techniques, and oral embed arrangement.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.