Position And Symmetry Of Mental Foramen In Orthopantomogram (OPG) - A Retrospective Observational Study

Keywords

Mental Foramen; Position; Symmetry; Orthopantomogram.

Introduction

Mental foramen is a small round/oval structure present in the body of the mandible [30, 28] It is a small foramen situated in the anterolateral aspect of the body of the mandible [7]. It opens in a posterior direction and the mental nerve and vessels supplying sensation to the lower lip and the labial mucosa traverses via the mental foramen [8]. The foramen is contained entirely within the buccal cortical plate of bone [34].

Studying the position and morphological variations of mental foramen is important because it is a critical and distinctive landmark for localising the neuromuscular bundle passing through it. Human jaws have shrunk from its large ape size to a smaller one with evolution. Therefore, the third molars are most often impacted which may lead to various complications. Oral squamous cell carcinoma (OSCC) is the major form of oral cancer and the sixth common malignancy in the world. Due to habits like areca nut chewing there is a high chance of oral squamous cell carcinoma formation. mdm-2 participates in the autoregulation of p53 function [13, 17, 24, 25, 27, 32, 33]. The accurate identification of the mental foramen is important for both diagnostic and clinical procedures [3, 14, 35]. The knowledge of the position of the mental foramen is very important while administering local anaesthesia. Anaesthesia of these nerve could be effective only if the dental practitioners adequately locate the mental foramen. [17, 31, 36]. Lack of knowledge regarding the correct position of mental foramen leads to repeated failure during injections and operation procedures [5, 12, 21, 22].

The knowledge of the mental foramen also plays an important role in endodontic procedure, especially those involving the premolars, fractures related to the parasymphysis region of the mandible, mandibular implant placement and construction of complete denture in the mandible [15-17].

Invasion of squamous cell carcinoma to the mandible can progress through the residual alveolar occlusal ridge [9, 29]. The radiographic appearance of the mental foramen could also lead to misdiagnosis of a radiolucent lesion such as osteolytic lesions in oral squamous cell carcinoma radiographically [1, 4, 11]. Also in addition to it there is a considerable variation in the shape, position of mental foramen. Literature evidence also supports the fact about presence of accessory foramen or complete absence in few cases. The aim of the current study is to analyse the position and symmetry of mental foramen in orthopantomogram (OPG).

Materials and Methods

This is a University hospital based retrospective clinical study, carried out at Private Dental Institution, Chennai. Ethical Approval was obtained from the Institutional Review Board.

Study setting: This study involves the analysis of orthopantomogram (OPGs) that were taken over a period of one year, from June 2019 to March 2020. A total of 500 OPGs were collected and assessed for age, gender, position of mental foramen (right and left) and symmetry of mental foramen. Collected data was tabulated in the excel sheet. Cross verified by two examiners. Incomplete dental records were excluded from the study. Randomization was done to minimise sampling bias.

Parameters Evaluated:

● Good quality OPG with respect to angulation and contrast.
● Presence of all mandibular teeth in both quadrant 3 and quadrant 4.
● Radiographs in which the mandibular teeth were absent, presence of caries, RCT or various restoration were eliminated due to associated periapical radiolucency.

The position of the mental foramen on the OPGs were classified as:

Position 1: position of mental foramen anterior to the first premolar Position 2: location of MF along the long axis of first premolar Position 3: MF situated between the first and second premolar Position 4: MF in line with the second premolar Position 5: between the second premolar and the first molar Position 6: MF in line with first molar.

Statistical Analysis

The data was imported and transcribed in the statistical analyses package for social sciences version 20 (SPSS) IBM corporation. Independent variables include and gender. Descriptive analyses were applied and frequencies were found for variables. The relationship between dependent and independent variables was determined using Pearson correlation with P value < 0.05 was considered statically significant.

Results And Discussion

A total of 500 patient’s OPGs were evaluated in this study. Of the 500 patient’s OPGs, 205 were males (41%) and 295 (59%) were females (figure 1). From the present study the relative order of frequency of position of mental foramen on the right side was 48.20% (figure 2). Similarly the prevalence of mental foramen on the left side was 52.00% (figure 3).

From the present study, in males and females, the most common site of mental foramen (right) is between the first and second premolar (49.27% & 47.67 respectively) i.e position -3 (figure 4).

Negative correlation was found between gender and position of mental foramen with P value = 0.7 >0.005 statistically not significant.

The most common position mental foramen(left) in the present study in males and females were between first and second premolar (53.6% & 50.85% respectively) i.e position -3 (figure 5). Similar results were in seen in previous literature done by [26] (same evidence-57%), [10] (same evidence-63%), [20] (same evidence- 40-50%),. This variation is mostly seen due to morphological variation seen in mandibles among different gender, ethnicities and races. Negative correlation was found between gender and position of mental foramen with P value = 0.2 >0.05 statistically not significant.

The mental foramen was asymmetrical in 28% of males and 33.40 % in females (figure 6) which is consistent with literature by [3]51.3%, [6] 51.1%. On contract some previous literature shows most of the individuals have symmetrical mental foramen as in [2]. This variation is mostly seen due to morphological variation seen in the mandible among different gender, ethnicities and races.

The knowledge of mental foramen also plays an important role in various dental treatments and clinical procedure [1, 23]. Limitations of the present study is small sample size and single centered study.

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Figure 1:

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Figure 1. Bar graph representing the correlation between the most commonly preferred by both the gender. X axis represents the most commonly preferred antibiotics and Y axis represents the number of patients.Among the male patients,2 9.41% of the dentists preferred amoxicillin, 5.88% of them preferred amoxi clav. Among all the females 52.94% of the dentists preferred amoxicillin,5.88% of the dentists preferred amoxi clav and 5.88% of the dentists preferred Clindamycin. On chi square analysis test results showed p value 0.692. (> 0.05). Hence there was no significant association between gender and antibiotics.

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Figure 2:

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Figure 2. Bar chart representing the frequency association of most commonly preferred antibiotics by dentist post extractions. X axis represents the most preferred antibiotics and Y axis represents the number of respondents. Orange colour represents the dentists who prescribed amoxicillin, Green colour represents the number of dentists who prefer amoxi clav and blue colour represents the number of dentists who prefer clindamycin. 82.4% of the participants prescribe amoxicillin, 11.76% of the dentists prefer amoxi clav and 5.89% of the dentists prefer clindamycin. Amoxicillin is mostly preferred antibiotics by most of the dentists.

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Figure 3:

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Figure 3. Bar chart representing the frequency distribution of duration of antibiotic course prescribed by dentists. X axis represents the duration of antibiotic course and Y axis represents the number of dentists. 47.06% of dentists prescribe antibiotics for less than three days ( orange) and 52.94% of the dentists prescribe it for 3-5 days( Green). Majority of the dentists prescribed antibiotics for a period of 3-5 days.

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Figure 4:

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Figure 4. Bar graph representing the frequency distribution of dentists’ opinion on prescription of antibiotics prior extractions. X axis represents the opinion of dentists and Y axis represents the number of dentists. 47.06% of the dentists accept antibiotic prescription before extraction is helpful for reducing pain and anxiety ( Orange) whereas 52.94% of the dentists do not agree with it ( Green ). Majority of the dentists do not accept antibiotics before extraction is necessary.

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Figure 5:

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Figure 5. Bar graph representing the frequency distribution of most important factor for choosing a drug. X axis represents the factors for choosing a drug and Y axis represents the number of dentists. 70.59% of the dentists prescribe antibiotics based on symptoms (orange) and 29.41% of the dentists prescribed antibiotics based on guidelines (Green). Majority of the dentists prescribe antibiotics based on patients‘ symptoms.

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Figure 6:

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Figure 6. Bar chart representing the frequency distribution of dentists ‘ opinion on importance of medical history before starting any surgical procedure. X axis represents the opinion of dentists and Y axis represents the number of dentists. Every dentist accepted that the medical history of a patient is an important consideration before starting any surgical procedure (orange).

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Conclusion

Variation in the position and symmetry of mental foramen is mostly seen due to morphological variation seen in the mandible among different gender, ethnicities and races. Bearing in mind the limits of the study , the most common site of mental foramen in both right and left is in between the first and second premolar , with most being asymmetrical.

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