Mandibular canal, foramina of the mandible and their variations: part II: the clinical relevance of the preoperative radiographic evaluation and report of five cases

Abstract

Aims In part I of the article, a detailed description of the anatomical variations of the mandibular canal and the foramina of the mandible was given. The aim of part II is to discuss the clinical relevance of the anatomical variations. Materials and methods A literature review was carried out, and five cases of mandibular canal variations are reported. Results Anatomical variations of the mandibular canal and foramina of the mandible are reported in bibliography. Bifid and double mandibular canals have been firstly reported in 1973. Since then, the anatomical variations of the mandibular canal have been described by case reports, cadaveric and retrospective radiological studies. It has been proved that the inferior alveolar nerve gives communication fibers to other nerves and extraosseous branches, before entering the mandibular canal, whereas even if it enters the mandible, it branches during its course into the canal. Also, the supplementary innervation of mandibular teeth and periodontal tissues by the long buccal and mylohyoid nerves has been suggested. Several authors also reported the existence of retromolar foramen and supplementary buccal and lingual foramina and their important role either in vascularisation or innervation. Conclusions The neurovascular contents of the mandibular canals and foramina gain more importance in oral surgery and implantology because these components are vulnerable to damage during implant placement and sagittal split osteotomy surgery, and complications may occur during the surgery (i.e. unsuspected bleeding, nerve injury). Also, clinicians should be aware of accessory foramina or canals of the mandible in understanding failed inferior alveolar nerve block.

The clinical anatomy of accessory mandibular canal in dentistry

“…Correr et al () demonstrated that when third molars were present, half of their cases showed an intimate relationship, and almost one third a close relationship, between the roots of the third molar and the bifurcation of the mandibular canal. However, as described by Eliades et al (), nerve branching does not necessarily cause local anesthetic or postoperative problems. Their case involved a supplementary canal that coursed towards the periapical lesion of a third molar, with the tooth successfully removed.…”

“…He described how CT helped him to avoid iatrogenic injury to a bifurcated branch that had not been detected using panoramic radiography. Similarly, Eliades et al (2016) reported reducing the length of an implant from 11.5 to 10 mm because of a bifid canal detected by preoperative CT. In endodontics, Concepcion andRankow (2000) andvon Arx, Hanni, Sendi, Buser, andBornstein (2011) reported an accessory mental foramen and nerve during periapical surgery on a mandibular second premolar.…”

“…Accessory canals have two major clinical implications if they are not detected preoperatively, namely potential failure to achieve complete local anesthesia, and iatrogenic surgical injury to the neurovascular bundles. For the latter complication, unexpected intra-operative hemorrhage or postoperative paresthesia in the area innvervated can complicate surgery (Azaz & Lustmann, 1973;Eliades, Papadeli, & Tsirlis, 2016).…”

“…Correr et al (2013) demonstrated that when third molars were present, half of their cases showed an intimate relationship, and almost one third a close relationship, between the roots of the third molar and the bifurcation of the mandibular canal. However, as described by Eliades et al (2016) (Iwanaga et al, 2018). Mizbah et al (2012) adopted a different surgical approach when a bifurcation was observed.…”

The clinical significance of the retromolar canal and foramen in dentistry

“…For the latter complication, unexpected intraoperative hemorrhage or postoperative paresthesia in the area innvervated can complicate surgical procedures (Azaz & Lustmann, 1973; Eliades, Papadeli, & Tsirlis, 2016). The retromolar region is an important donor site for autogenous bone block (Khoury & Hanser, 2015; Nkenke et al, 2002; Yildirim, Spiekermann, Handt, & Edelhoff, 2001).…”