The MF is a channel-like opening that is narrow at the base and wide at the top through which the mental nerve exits the mental canal (Phillips et al. 1990). It is important to be aware of the position of the MF during clinical procedures such as elevation of mucoperiosteal flaps, local anesthesia injection, and any bone surgery being performed in the vicinity of the MF. During surgical procedures close to the MF such as the placement of endo-osseous implants, root end surgery, surgical removal of impacted teeth, cysts, and tumors, the operator must avoid injuring the neurovascular bundle exiting through the MF. Although it has been recommended that a safe distance of 2 mm should be kept between endo-osseous implants and the MF, some studies have reported altered sensation in the area supplied by the mental nerve following their placement (Bartling et al. 1999; Wismeijer et al. 1997; Walton 2000).
The part of inferior alveolar nerve (IAN) presents anterior to the MF, before leaving the canal is known as the anterior loop (AL) of the IAN (Apostolakis and Brown 2012). Prevalence and location of the AL is also important during different surgical procedures, especially during placing dental implants in fully edentulous patients. A study comparing the dissection of the AL anatomically and CBCT scans of cadaver specimens showed almost near equal measurements, from which the authors concluded that CBCT is considered reliable in determining the extent of the AL (Uchida et al. 2009).
The exact location of MF is important for both diagnostic and clinical purposes.
As for diagnosis, MF can be mistaken for a pathology near the apices of the premolar teeth. From a clinical aspect, knowing precisely the exact location of the nerve and presence/absence of AL is paramount to prevent any nerve injury with its postoperative sequala (Ngeow and Yuzawati 2003). It was previously stated that the MF most common position is below the apex of second premolar (Fabian 2007) or between the apices of first and second premolar (Al Jasser and Nwoku 1998). The MF position is influenced by ethnic background, gender, age, tooth loss, and subsequent ridge resorption (Igbigbi and Lebona 2005). Literature shows that the length of AL may vary among different groups of the population (Apostolakis and Brown 2012; Chen et al. 2013; Lu et al. 2015).
Injury to the mental nerve can cause sensory disturbance in the lower lip, skin, and surrounding mucosa (Greenstein and Tarnow 2006; Ritter et al. 2012), and temporary or permanent neurosensory following surgical placement of endo-osseous implants have been reported (Bartling et al. 1999; Walton 2000).
To accurately locate the MF and AL, various techniques have been suggested. This includes manual detection, direct inspection during surgery, panoramic or periapical radiographs, magnetic resonance imaging (MRI), computed tomography (CT), and cone beam computed tomography (CBCT). Most of these methods have limitations such as cost, excess radiation, and magnification (Aminoshariae et al. 2014).
High-resolution CBCT is considered one of the most promising and precise techniques present that can accurately determine the position of MF and presence of AL (Vujanovic-Eskenazi et al. 2015).
To the knowledge of the authors, no previous study has mentioned the location of MF and prevalence of AL among Egyptians using CBCT; hence, the present study was done to determine the position of MF and its relationship to neighboring teeth and prevalence of AL in the Egyptian population using CBCT.