An anatomical radiographic evaluation of the posterior portion of the mandible in relation to autologous bone harvest procedures

Assessment of the configuration of the mandibular canal using cone beam computed tomography

BACKGROUND

During dental implants placement and bone augmentation procedures, it is important to determine the presence and location of mandibular canal anatomical variation in order to avoid injuries to inferior alveolar bundle. This study aimed to describe the prevalence and configuration of mandibular canal branching in the posterior region of the mandible using cone beam computed tomography (CBCT).

METHODS

The interpretation of the images was conducted according to the presence, classification and location of the mandibular canal. Horizontal and vertical distances from mandibular canal in the ramus region to the molar region was recorded. CBCT images of 751 patients, 486 women (64.7%) and 265 men (35.3%), with a mean age of 54.57 (±13.23; 14-93) years, were interpreted by one calibrated examiner.

RESULTS

Out of 1502 hemi-mandibles images, mandibular canal variations were observed in 130 (8.6%). Sixty-four (49.2%) mandibular canal variations were identified on the right side and 66 (50.8%) on the left side. The mean distances between superior cortical of the mandibular canal and the base of mandible, buccal cortical of mandibular canal and buccal cortical bone, and superior cortical of mandibular canal and alveolar ridge were 12.16 mm (±2.68), 4.17 mm (±1.30), and 12.97mm (±4.01), respectively. Type I mandibular canal variation was the most frequent (68; 52.2%), followed by type III (34; 26.1%).

CONCLUSIONS

Prevalence of mandibular canal variations was 8.6%, type I was the most common and its direction showed proximity with lingual surface in the second molar region.

Clinical Anatomy and Significance of the Retromolar Foramina and Their Canals: A Literature Review

The retromolar foramina (RMF) and the retromolar canal (RMC) are anatomic variants in the mandible located distally to the last molar. The retromolar nerve, which runs through the RMC, is a type 1 bifidity of the mandibular canal. The investigations of the RMF and RMC have been performed by dry mandible studies, the panoramic radiograph (PAN), computed tomography (CT), and the cone beam computed tomography (CBCT) studies. The CBCT has been shown to be the superior method for visualizing the RMF and RMC. There is wide variation in the frequency, location, diameter, and distance of the canal in different individuals. Overall, there is no significant difference in the frequency of the canal in the mandible between sexes or sides of the mandible. The peak incidence of the RMF may occur in adolescence. The RMC is significant due to the neurovascular bundle which runs through it. Injury to this neurovascular bundle during surgical procedures, such as third molar extraction, implant placement, or split sagittal osteotomy, may lead to paresthesia, excessive bleeding, or traumatic neuroma. The presence of RMC may also lead to insufficient anesthesia in the mandible which may be overcome with alternative anesthetic techniques.

Prevention of neurological injuries during mandibular third molar surgery: technical notes

Surgery to the mandibular third molar is common, and injuries to the inferior alveolar nerve and the lingual nerve are well-recognized complications of this procedure. The aim of these technical notes is to describe operative measures for reducing neurological complications during mandibular third molar surgery. The following procedure should be used to prevent damage to the inferior alveolar nerve: a well-designed mucoperiosteal flap, to obtain appropriate access to the surgical area; a conservative ostectomy on the distal and distal-lingual side; tooth sectioning, to facilitate its removal by decreasing the retention zones; tooth dislocation in the path of withdrawal imposed by the curvature of the root apex; and careful socket debridement, when the roots of the extracted tooth are in intimate contact with the mandibular canal. To prevent injury to the lingual nerve, it is important (I) to assess the integrity of the mandibular inner cortex and exclude the presence of fenestration, which could cause the dislocation of the tooth or its fragment into the sublingual or submandibular space; (II) to avoid inappropriate or excessive dislocation proceedings, in order to prevent lingual cortex fracture; (III) to perform horizontal mesial-distal crown sectioning of the lingually inclined tooth; (IV) to protect the lingual flap with a retractor showing the cortical ridge; and (V) to pass the suture not too apically and from the inner side in a buccal-lingual direction in the retromolar area.