Accessory mental foramina and nerves: Application to periodontal, periapical, and implant surgery

Abstract

Recent studies investigating accessory mental foramina using developments in diagnostic imaging have primarily defined the morphology of the foramina; however, few studies have described the structures passing through them. Additional clinical knowledge of the foramina is therefore required for preoperative diagnosis prior to surgery, including implant, periodontal and periapical surgery. In this study, we investigated the accessory mental foramina and the associated nerves and arteries in donated cadaveric mandibles using anatomical and radiological observation methods. We examined 63 mandibles with overlying soft tissue by cone-beam computed tomography and noted the existence of the accessory mental foramina. Mandibles with accessory mental foramina were subsequently analyzed. Additionally, the neurovascular bundles passing through these foramina were dissected using anatomical methods.The incidence of accessory mental foramina was 14.3%. The larger foramina tended to be located anteriorly or superiorly and proximal to the mental foramen, while the smaller foramina tended to be located posterosuperiorly and distal to the mental foramen. The mental foramen ipsilateral to the accessory mental foramen was smaller than the one contralateral to it. The comparatively distant and large accessory mental foramen included an artery.This study elucidated the relationship between accessory mental foramina and the associated nerves and arteries. We believe that the results will contribute to the clinical dentistry field.

Undetected Small Accessory Mental Foramina Using Cone-Beam Computed Tomography

“…In addition, oral surgeons and oral radiologists are familiar with interpreting CT images of the mandible, while many general dentists are not. Most previous reports regarding AMF have been authored by oral surgeons, radiologists, or anatomists [2, 13, 18]. These studies have analyzed AMFs in both cross-sectional and 3D reconstructed images, but not in surface rendered images, which many general dentists use for developing treatment plans.…”

“…In our previous study [2], 20 AMF on nine adult cadaveric mandibles were examined with CBCT (GALILEOSR, Sirona, Germany) (image acquisition parameters: 85 kV, 6 mA). Axial images were transmitted in the digital imaging and communication in medicine (DICOM) format, and two-dimensional images of the body of the mandible were reconstructed using the OsiriX DICOM viewer (Pixmeo, Geneva, Switzerland) [12].…”

“…The area of each foramen was calculated using the following formula: elliptical area = π x (long axis)/2 x (short axis)/2. The lengths of the long and short axes, as calculated from the CBCT images, were assumed to represent the physical values as no difference in length was previously observed when comparing the two methods [2]. …”

“…During the development of a treatment plan, especially for implant surgery, many dentists work from volume and surface-rendered images after verifying the position of the mental foramen on the cross-sectional images. In our previous study, we found that the detection of AMF was dependent on the image type [2]. These foramina could not be identified on some imaging modalities such as surface-rendered images.…”

“…The incidence of AMF ranges from 2.0% [1] to 14.3% [2]. Dentists and oral surgeons have found AMF during oral procedures including implant surgeries [3], periapical surgeries [4-5], trauma surgeries [6-7], and neurectomies [8-9].…”