Imaging of accessory mental foramen before implant therapy

Selin Aykol; Fikriye Orduyilmaz; Mustafa Gumusok; Nurdan Ozmeric; Meryem Toraman Alkurt

doi:10.4103/2321-3841.170626

CASE REPORT

Year : 2015 | Volume : 3 | Issue : 3 | Page : 105-107

Imaging of accessory mental foramen before implant therapy

Selin Aykol¹, Fikriye Orduyilmaz¹, Mustafa Gumusok², Nurdan Ozmeric¹, Meryem Toraman Alkurt²
¹ Department of Periodontology, Faculty of Dentistry, Gazi University, Ankara, Turkey
² Department of Dentomaxillofacial Radiology, Faculty of Dentistry, Gazi University, Ankara, Turkey

Date of Web Publication

27-Nov-2015

Correspondence Address:
Prof. Nurdan Ozmeric
Department of Periodontology, Faculty of Dentistry, Gazi University, Ankara
Turkey

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/2321-3841.170626

Abstract

It is critical to determine the location and variation of mental foramen (MF) during the implant treatment. Multiple numbers of MF can be seen in the mandible, and they are called as accessory MF (AMF). Detecting the anatomic variations including AMFs with radiological examinations before surgical applications are important to prevent neurovascular complications. Cone-beam computed tomography (CBCT) is a beneficial method to determine the anatomical structures such as MF and its anatomical variations. The aim of this case report was to present the diagnosis of AMF localized at the left side of the mandible of a 44-year-old woman patient who was applied for implant therapy. Treatment planning and postoperative evaluation were performed with CBCT.

Keywords: Accessory mental foramen, cone-beam computed tomography, implant

How to cite this article:
Aykol S, Orduyilmaz F, Gumusok M, Ozmeric N, Alkurt MT. Imaging of accessory mental foramen before implant therapy. J Oral Maxillofac Radiol 2015;3:105-7

How to cite this URL:
Aykol S, Orduyilmaz F, Gumusok M, Ozmeric N, Alkurt MT. Imaging of accessory mental foramen before implant therapy. J Oral Maxillofac Radiol [serial online] 2015 [cited 2023 Mar 29];3:105-7. Available from: https://www.joomr.org/text.asp?2015/3/3/105/170626

Introduction

The mental nerve is a terminal branch of the inferior alveolar nerve. It emerges from mental foramen (MF), divides into three branches beneath the anguli oris muscle and provides for the innervation of the skin and mucous membrane of the lower lip and chin, and vestibular gum of the mandibular incisors. ^[1],[2] MF is generally localized under the second premolar or between two premolars. ^[2] Multiple MFs can rarely be seen in the mandible. In such situations, one of them is considered as MF, and the others as accessory mental foramen (AMF) which can be presented as a result of branching of MF. ^[3] Detecting the anatomic variations including AMFs with radiological examinations before surgical applications are important to prevent neurovascular complications. ^[4],[5] Cone-beam computed tomography (CBCT) is a beneficial method that provides three-dimensional (3D) imaging with low ionized radiation for imaging AMFs. ^[6]

Case Report

A 44-year-old female patient with no systemic diseases applied for implant therapy. CBCT was used to diagnose the height and thickness of the edentulous alveolar bone. CBCT images were acquired with ProMax 3D ^® (Planmeca, Helsinki, Finland) with exposure settings of 90 kVp, 12 mA, and 13.8 s. A thickness of radiographic slices was 1 mm. After the examination of CBCT images, AMF was observed at the left side of the mandible, superior to MF. AMF's relation with canalis mandibularis was determined at cross-sectional and coronal section images [Figure 1] and [Figure 2].

Figure 1: Accessory mental foramen located on cone-beam computed tomography cross-sectional image in the upper part of the mental foramen by arrow (a), accessory mental foramen progresses as intraosseous canal after starting on mandibular surface (b), the anastomosis of canalis mandibularis and intraosseous canal (c)

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Figure 2: Three-dimensional image of accessory mental foramen (a), accessory mental foramen on cone-beam computed tomography coronal image (b), the anastomosis of canalis mandibularis and accessory mental foramen (c)

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Anatomic variations should be considered during the planning of dental implant placement to prevent neurovascular bundle damage. The area of mandibular second left premolar was measured about 8.25 mm in height and 5.34 mm in width. The area of mandibular first left molar was measured about 12.03 mm in height and 4.02 mm in width to place dental implants. Regarding to the measurements, for area of mandibular second left premolar 4.1-8 mm, for mandibular first left molar 4.1-10 mm, (Institut Straumann AG, CH-4002 Basel, Switzerland) regular neck Sand Blasted Large Grid Acid-Etched implants were applied. Considering that, it was hard to diagnose the MF, AMF, and intraosseous relationships with conventional methods such as intraoral and panoramic radiography, postoperative CBCT images were obtained. On the CBCT cross-sectional image of the related area, no relation was detected between implants and neurovascular canals [Figure 3].

Figure 3: No relation was detected between implants and neurovascular canals on the cone- beam computed tomography cross-sectional image

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During 1 year of postoperative follow-up, no neurosensory disturbance was observed.

Discussion

The location of inferior alveolar nerve or mental nerve should be detected to prevent neurosensory disturbances and hemorrhage at the anterior side of the mandible. If the presence of AMF (part of MF region), is missed, complications such as hemorrhage, paralysis, and paresthesia may occur after the surgical procedures in mental and cheek regions. ^[7],[8] In this patient, before implant surgery AMF was detected during radiographic examination, so shorter implant was planned to use to avoid nerve damage. Knowledge of anatomic structures and localizations plays an important role for a successful surgery.

Buccal foramina with no connection with mandibular canal are called nutrient foramina. AMFs are buccal foramina that have connection with the mandibular canal. ^[6] It has been reported that AMFs are commonly located at inferior region to MFs, with smaller sizes as compared to the MFs. ^[3] In our patient, AMF located at premolar area superior to MF. The measurement of MF and AMF were 3, 69 and 1, 13 mm in diameter, respectively. This measurement performed on cross-sectional images for each foramen.

AMFs were showed in several studies. ^{[6],[7],[8],[9],[10]} It was mentioned that incidence of AMF is 2-10%. ^[11] Furthermore, the prevalence of AMF has been reported to range from 6.3% to 6.5% in a Turkish population. ^[9],[10]

The panoramic radiography, which is popular in dental practice, is an inexpensive, quick, easy, and low dose diagnostic tool. ^[12] However, offering only two-dimensional (2D) images, inability to measure the bone width, distortions in the horizontal plane, and magnifications in the vertical plane are the limitations of this method. In addition, the accuracy of the image depends largely on the experience of the technician; accurate positioning of the patient is also important. ^[13]

CBCT is a more effective tool for presurgical 2D assessment of the neurovascular structures (such as MF and its variations), than panoramic radiography. ^[6] CBCT is specifically designed for 3D imaging of the maxillofacial region. CBCT has better resolution with lower dose radiation than CT. Clinicians can have an opinion about anatomical volume acquisition with CBCT. ^[14] Implants position and anatomical structures can be checked with CBCT analysis. It gives exact linear measurements with isotropic pixels, and metallic artifacts are significantly reduced. It is commended tool in implantology due to its 2D and 3D reconstruction possibilities. CBCT is considered to be a gold standard for dental and maxillofacial imaging. ^[15]

Conclusion

Detecting the variations of MF is important to avoid complications such as paresthesia and hemorrhage before implant surgery although AMF is a rare anatomical variation of MF. Therefore, 3D imaging with CBCT is essential to determine the anatomical structures anatomical variations. Radiographic examination particularly 3D images can be useful and help the clinicians for the treatment and surgical plan.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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