Abdalmalik O. Ghandourah,Mohd. B. Badaoud,Anmar Dahlawi,Abdullah Alghamdi,Faisal Alhazmi,Shahinaz N. Sembawa,Abrar K. Demyati
A radiographic analysis of the location of the mental foramen
Panorama,OPG,Mental foramen
Background Accurate knowledge and identification of anatomical landmarks on radiographic imaging are essential when preparing for any invasive procedure. The mental foramen has been the subject of many publications because of its significance as the origin point of the mental nerve and its proximity to the lower premolar area. The aim of this study was to assess the horizontal location of the mental foramen (MF) in the samples collected from the Faculty of Dental Medicine at Umm Al-Qura University, Mecca, Saudi Arabia. This included comparing genders, ages, and bilateral symmetry. In addition, the study aimed to assess inter-rater reliability in locating the mental foramen on a digital panoramic radiograph (OPG). Methods A total of 334 digital panoramic radiographs were chosen for retrospective analysis from a total of 2,199 images taken from the Umm Al-Qura University, Faculty of Dental Medicine, teaching hospital database. The locations were scored independently by four examiners. The area was divided into six zones, determined by drawing straight lines along the long axis of the premolars and contact areas. A scoring index of 1–6 was utilized to describe the location in relation to the premolars. Analysis was carried out using chi-square and descriptive statistics. The inter-rater reliability was calculated using Fleiss’ Kappa to determine observer agreement. Results The ages of the patients ranged from 13 to 76 years, with a mean of 29.66. There was no significant difference related to gender, but there was a significant difference related to age. The most frequent location was zone 4, 47.6% on the left side and 51.5% on the right, followed by zone 5, 18.6% on the left side and 16.2% on the right, and zone 3, 15.3% on both the right and the left side. The location was symmetrical in 64.7% of the cases and asymmetrical in 35.3%. The inter-rater reliability among the examiners was fair. Conclusions The findings of this study indicate that the MF’s location was more closely related to the mandibular second premolar than the first premolar. Furthermore, bilateral symmetry was found in 65% of the sample. There was no statistical significance observed in differences between the genders. Both newly graduated and experienced dentists could identify the location of the MF from the radiograph using the MF’s location in relation to the six zones.
A radiographic analysis of the location of the mental foramen

Accurate knowledge and identification of anatomical landmarks on radiographic imaging are essential when preparing for any invasive procedure. The mental foramen has been the subject of many publications because of its significance as the origin point of the mental nerve and its proximity to the lower premolar area. The aim of this study was to assess the horizontal location of the mental foramen (MF) in the samples collected from the Faculty of Dental Medicine at Umm Al-Qura University, Mecca, Saudi Arabia. This included comparing genders, ages, and bilateral symmetry. In addition, the study aimed to assess inter-rater reliability in locating the mental foramen on a digital panoramic radiograph (OPG).

A total of 334 digital panoramic radiographs were chosen for retrospective analysis from a total of 2,199 images taken from the Umm Al-Qura University, Faculty of Dental Medicine, teaching hospital database. The locations were scored independently by four examiners. The area was divided into six zones, determined by drawing straight lines along the long axis of the premolars and contact areas. A scoring index of 1–6 was utilized to describe the location in relation to the premolars. Analysis was carried out using chi-square and descriptive statistics. The inter-rater reliability was calculated using Fleiss’ Kappa to determine observer agreement.

The ages of the patients ranged from 13 to 76 years, with a mean of 29.66. There was no significant difference related to gender, but there was a significant difference related to age. The most frequent location was zone 4, 47.6% on the left side and 51.5% on the right, followed by zone 5, 18.6% on the left side and 16.2% on the right, and zone 3, 15.3% on both the right and the left side. The location was symmetrical in 64.7% of the cases and asymmetrical in 35.3%. The inter-rater reliability among the examiners was fair.

The findings of this study indicate that the MF’s location was more closely related to the mandibular second premolar than the first premolar. Furthermore, bilateral symmetry was found in 65% of the sample. There was no statistical significance observed in differences between the genders. Both newly graduated and experienced dentists could identify the location of the MF from the radiograph using the MF’s location in relation to the six zones.

Anatomical structures have been a point of interest in many studies, thanks to their influence on surgical approaches. The mental nerve is a branch of the inferior alveolar nerve, which supplies sensory innervation to the lower lip, buccal vestibule, and gingiva (Chkoura and El Wady, 2013). The mental foramen (MF) is vital to the dentist when planning a surgical or endodontic intervention in the premolar region to avoid post-surgical complications such as pain, paresthesia, or numbness (Alhassani & AlGhamdi, 2010). The MF appears on radiographs as a single oval radiolucent spot in the premolar region on both sides (Neves et al., 2010). However, the MF is usually difficult to locate, owing to the lack of a definitive anatomical feature that could be used as a guide and the inability to palpate it clinically (Phillips et al., 1990). Many methods have been tried to precisely determine the position of the MF before different surgical procedures (Aminoshariae et al., 2014). These methods include direct visualization during surgery, dissection of cadavers, panoramic and peri-apical radiographs, computed tomography (CT), cone-beam computed tomography (CBCT), and magnetic resonance imaging (MRI) (Aminoshariae et al., 2014). Most methods have disadvantages of cost, traumatic surgical site, radiation, and unavoidable magnification or distortion (Aminoshariae et al., 2014). Several studies evaluating various radiographic techniques for determining the location of the MF have found that digital panoramic radiographs were fairly accurate (Peker et al., 2009, Yosue and Brooks, 1989). Panoramic radiographs are easy and economical to obtain for interpretation (Serhal et al., 2002). In addition, digital software can enhance the quality of panoramic radiographs (Halwani & Muteq, 2017). The clinical importance of determining the anatomical position of the MF is to avoid injury of the mental nerve in local anesthesia administration, treatment of parasymphyseal area fracture, orthognathic surgery, implant placement, and complete denture in the mandible, especially in a severe resorbed edentulous ridge (Mohammad et al., 2016). MF location varies among different genders, ages, and ethnic groups (Mahabob et al., 2021). Regarding age, it is known that, with the eruption of permanent premolars, aging, and subsequent bone resorption, the MF location may change (AlOtaibi et al., 2022, Lim et al., 2015). A study done in Egypt in 2017 by Shaaban and El-Shall compared the horizontal position of MF in different age groups, showing that there was a significant difference in distance between the midline and the MF between children and adults. Regarding ethnicity, the same ethnic population may share the same parameters for the MF features, including position and the presence of an anterior loop (AlOtaibi et al., 2022, Mishra et al., 2021). Among the Saudi population, published data revealed the position of the MF to be in close proximity to the second premolars (Alam et al., 2018, Aldosimani et al., 2019, Mashyakhy et al., 2021, Srivastava, 2021). A study by Abed et al. (2016) in the western region of Saudi Arabia, though not specifying the ethnicity of the population, showed that the MF was most commonly located between the first and second premolars, the second most common location being under the apex of the second premolar(Abed et al., 2016). Previous studies utilized different classifications to describe the location of the MF, the majority identifying zones and describing the location as being under the apices and between the mandibular premolars (Abed et al., 2016, Al-Mahalawy et al., 2017, Halwani and Muteq, 2017). In the present study, we opted to bisect the region between the mandibular premolars and forgo the description used in previous studies. The aim of this study was to assess the horizontal location of the MF in the samples collected from the Faculty of Dental Medicine at Umm Al-Qura University. This included comparing genders, ages, and bilateral symmetry. In addition, we aimed to assess inter-rater reliability in locating the MF on a digital panoramic radiograph (OPG).

This study was conducted with the approval of the Umm Al-Qura University institutional review board (HAPO-02-k-012–2022-12–896). A retrospective analysis of digital panoramic radiographs (OPG) scans collected from the database of four teaching hospitals between 2020 and 2021 was conducted to determine the location of the MF. The radiographs were collected by four dentists in their internship year. Prior to the analysis, 10 radiographs were chosen from the included sample for calibration by examiners and then discarded from the study. The examiners were instructed by a consultant in oral and maxillofacial surgery, who explained the zones and the recording process. The calibration was carried out individually, and the complete analysis of the sample was carried out over a period of one week. Inclusion criteria: Clear OPG with high quality and good visibility of anatomic structures of patients attending the dental teaching hospital at Umm Al-Qura University, of both genders, age 13 and above, with permanent canine to first molar, present bilaterally, and visible MF bilaterally on OPG radiographs. Exclusion criteria: Malformations, malocclusion, bony lesions, endodontic treatment, orthodontic appliance, history of orthognathic surgery or orthodontic treatment, crowns or bridges, missing teeth, mixed dentition, history of mandibular fracture involving the parasymphyseal region, dental implants in the anterior or premolar areas, artifacts. Additionally, images with unclear or absent MF on one or both sides were excluded.

All radiographs were taken by a GENDEX® OPG scanner (GXDP-700TM, Hatfield, USA) by an experienced radiograph technician. Imaging was carried out with the following settings: 70 kV, 16 s, and 71 mGy.cm2. All radiographs were analyzed independently by four examiners with the same level of experience in their internship year. A scoring index was devised for the antero-posterior position of the MF with respect to the teeth of the lower jaw (Table 1). The area was divided into six zones to describe the location of the MF by drawing parallel lines, segmenting the area between the canine and the first molar bilaterally (Fig. 1). In a case where the line drawn to separate a zone intersected with the MF, the score was attributed to the zone that had the larger part of the radiolucency.

Sample size calculation was done using the Epitools calculator (Sergeant, 2018) with a 95% confidence level and a 5% margin of error; the significance level was set at P 0.05. Data were entered and analyzed using the Statistical Package for the Social Sciences (SPSS®) software version 28 (IBM®, Chicago, USA) employing chi-square and descriptive statistics. The inter-rater reliability was calculated using Fleiss’ Kappa to determine observer agreement.

Altogether, 2,199 images were reviewed, only 334 of which met the inclusion criteria and were included in the sample. The study included 157 males and 177 females. The ages of the patients ranged from 13 to 76 years, with a mean of 29.66. There was no significant difference in terms of gender. The chi-square test recorded a significant difference in the left side of the mandible related to age (P = 0.026). However, there was no significant difference on the right side (P = 0.32). The most frequent location was zone 4, 47.6% on the left side and 51.5% on the right. The second most common location was zone 5, 18.6% on the left side and 16.2% on the right side. In zone 3, there were 15.3% on both sides (Fig. 2). The location was symmetrical in 64.7% of the cases and asymmetrical in 35.3% (Fig. 3). Fair inter-rater agreement was observed (K = 0.3, 95% CI [0.24–0.35]).

Variations in anatomical structures are to be expected. The complete absence of the MF or the presence of accessory pathways and variation in the typical oval shape have been reported in the literature (Aljarbou et al., 2021, Neves et al., 2010, Voljevica et al., 2015). Although the appearance of the MF mesial to the first premolar or distal to the second premolar is uncommon, it was recorded in this study and by others (al Jasser & Nwoku, 1998). To represent the MF location more accurately, this study increased the segmentation of the area. Previous publications have placed the most common positions between the premolars (Abed et al., 2016, al Jasser and Nwoku, 1998, Bosykh et al., 2019, Dos Santos Oliveira et al., 2018, Halwani and Muteq, 2017, Rosa et al., 2013, von Arx et al., 2013) or in line with the second premolar (Al-Mahalawy et al., 2017, Alrahabi and Zafar, 2018, Han et al., 2016, Muinelo-Lorenzo et al., 2015, Safaee et al., 2016); this is in line with our findings, which place the MF just mesial to the second premolar in almost half of the study group (49.5%). However, the second most common location in our study was zone 5, which is distal to the second premolar. This contrasts with most studies mentioned and can be attributed to differences in the employed classification. In a CBCT radiographic study done at Jouf College of Dentistry, Saudi Arabia, by Srivastava (2021), which compared the MF on the right and left side for different age groups with different dentition status, a statistically significant difference between the groups was found. This is similar to our finding of a statistically significant difference on the left side linking with MF and age. However, this finding contradicted that of Mashyakhy et al. (2021), who conducted a retrospective CBCT study to evaluate the features of the MF and found no significant difference between the right and left symmetry (Mashyakhy et al., 2021). Several studies reported that the most common vertical position was below the apices of mandibular premolar roots; with increasing age, the frequency of more inferior positioning increased (Al-Khateeb et al., 2007, Alrahabi and Zafar, 2018). Moreover, previous studies described asymmetry of the superior–inferior position in 14% of cases (Al-Khateeb et al., 2007, Alrahabi and Zafar, 2018). It has been reported that ethnicity affects the location of the MF. However, the difference was confined to the most common positions, namely between the premolars or in line with the second premolar (Santini & Alayan, 2012). This study was limited by the small sample size owing to the restricted inclusion criteria. Additionally, although digital OPGs are reasonably accurate, they are limited by superimposition, distortion, and magnification (Weiss & Read-Fuller, 2019), making it challenging or impossible to identify the mental path with the anterior loop. Moreover, the fair agreement between the examiners shows the difficulty of pinpointing the MF location. Therefore, it may be advantageous for future studies to analyze cone-beam CT images instead and increase the sample size.

The findings of this study indicate that the MF’s location is more closely related to the mandibular second premolar than the first premolar. Furthermore, bilateral symmetry was found in 65% of the sample. There was no statistical significance observed between the genders. Both newly graduated and experienced dentists can identify the location of the MF from the radiograph by using the MF’s location in relation to the six zones.

Abdalmalik O. Ghandourah: Conceptualization, Project administration, Methodology, Supervision, Writing – original draft. Mohd. B. Badaoud: Project administration. Anmar Dahlawi: Project administration. Abdullah Alghamdi: Project administration. Faisal Alhazmi: Project administration. Shahinaz N. Sembawa: Formal analysis, Supervision. Abrar K. Demyati: Writing – review & editing.

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.