A precise knowledge about the position of the mandibular foramen is indispensable to attain a successful inferior alveolar nerve block. The data obtained from dry mandibles and radiographs have shown that the position of mandibular foramen is highly variable. [10, 13, 16]
In the current study, each half of the mandibles collected from sixteen cadavers were examined for the position of mandibular foramen in relation to the gonion, base of the mandible and mandibular notch. The position of the mandibular foramen in relation to the occlusal plane was also noted.
In the present study, in 87.5% of the samples, the mandibular foramen was at the level of the occlusal surface of the third molar. In 6.25% of the samples, it was approximately 9.51 mm above the occlusal surface of the third molar. In 6.25% of the samples, it was 8.19 mm below the occlusal surface of the third molar. Afadhali et al., advocated that the mandibular foramen could be located immediately above the occlusal plane of mandibular first molar and second premolar.[17] Augier M et al., and Basmajian et al., described the mandibular foramen slightly above the level of the occlusal plane [18, 19] whereas Thangavelu et al., demonstrated it at or below the level of the occlusal plane.[20]
In the previous studies, the mandibular foramen was described in relation to the ramus of the mandible and gonion angle. In a study conducted by Nicholson et al., the mandibular foramen was located predominantly at the centre of the ramus of the mandible.[11] In another study, the mandibular foramen was located slightly above the middle of the mandibular ramus.[21]Ennes JP et al., tried to explore the relation between the gonion angle and the distance between the mandibular foramen and the base of the mandible and concluded that the distance from the mandibular foramen to the base of the mandible was inversely related to the gonion angle.[12] (Table 3)
In the current study, the mandibular foramen was described in relation to the angle of the mandible. In addition, the angle formed by the mandibular foramen with the base of the mandible has been explored. The mandibular foramen was located 21 ± 3.33 mm superior to the gonion at an angle of 980±50 with the base of the mandible (Table 1).
In this study, we also studied the relationship between the mandibular foramen and mandibular notch. Mandibular foramen was located 20.13 ± 3.1 mm inferior to the lowest point of
the mandibular notch (Table 1). This is consistent with the findings of Oguz et al., who observed that the shortest distance between the mandibular foramen and the mandibular notch was 22.27 mm. [22]
In the present study, no significant statistical difference was observed in the position of the mandibular foramen between the right and left sides (Table 2). This is consistent with the findings of Tsai HH [23] and Braga et al.,[24] indicating bilateral symmetry of the mandibular foramen.
Accessory Mandibular Foramen:
Presence of accessory mandibular foramen could lead to ineffective inferior alveolar nerve block.[21] In the present study, accessory mandibular foramen was observed in 9.37% of the samples (Fig. 4). In all 9.37% of the samples, they are seen inferior to the mandibular foramen. In a study done in Brazilian population, accessory mandibular foramina were observed below the mandibular foramen in 22.07% of the mandibles and above the mandibular foramen in 25.22% of the population.[25]
Table 3
Topography of the mandibular foramen
Sl. No | Authors | Landmarks | Location of the mandibular foramen |
1. | Thangavelu et al., (2012) | Occlusal plane | At or below the occlusal plane |
2. | Nicholson (1985) | Ramus of the mandible | Centre of the ramus of the mandible |
3. | Mbajiorgu (2000) | Ramus of the mandible | 2.5 mm behind the midpoint of width of the ramus; 3 mm superior to the midpoint of the height of the ramus |
4. | Padmavathi et al., (2014) | Ramus of the mandible | 0.9 mm behind the midpoint of width of the ramus; 1.4 mm superior to the midpoint of the height of the ramus |
5. | Lavanyaet al., (2011) | Mandibular notch | 20 mm below the centre of the mandibular notch |
6. | Current study | Mandibular notch, gonion | 20.13 mm inferior to the mandibular notch; 21 mm superior to the gonion at an angle of 980 with the base of the mandible |