Anatomy of Mandibular Vital Structures. Part II: Mandibular Incisive Canal, Mental Foramen and Associated Neurovascular Bundles in Relation with Dental Implantology

Abstract

Objectives: The purpose of the present study was to review the literature of how to identify the mental foramen, mandibular incisive canal and associated neurovascular bundles during implant surgery and how to detect and avoid the damage of these vital structures during implant therapy.

Material and methods: Literature was selected through a search of PubMed, Embase and Cochrane electronic databases. The keywords used for search were mandibular incisive canal, mental foramen, mental nerve, anterior mental loop. The search was restricted to English language articles, published from 1979 to November 2009. Additionally, a manual search in the major anatomy, dental implant, and periodontal journals and books was performed.

Results: In total, 47 literature sources were obtained and reviewed. The morphology and variations of the mandibular incisive canal, mental foramen and associated neurovascular bundles were presented as two entities. It suggested that clinicians should carefully assess these vital structures to avoid nerve/artery damage.

Conclusions: The mandibular incisive canal, mental foramen and associated neurovascular bundles exist in different locations and possess many variations. Individual, gender, age, race, assessing technique used and degree of edentulous alveolar bone atrophy largely influence these variations. It suggests that the clinicians should carefully identify these anatomical landmarks, by analyzing all influencing factors, prior to their implant surgical operation.

Keywords: chin; cross-sectional anatomy; dental implants.; inferior alveolar nerve; mandible; radiography.

Figure 1

Anatomical variations and position of mandibular incisive canal (MIC). Colours: blue = MIC, red = mental canal (the anterior opening of the mandibular canal) yellow = mandibular canal. 1 = distance from the inferior border of the mandible to the canal (7.2 to 10.2 mm); 2 = MIC has complete, partial, or no bony cortical borders; 3 = MIC is terminating apically to the lateral incisor and sometimes apically to the central incisor (approximate length 7 mm); 4 = distance to the buccal plate (approximate distance 2.4 mm); 5 = tooth apex-canal distance (in dentate subjects) (approximate distance 5.3 mm); 6 = MIC diameter (0.48 to 6.6 mm).

Figure 2

Panoramic radiograph showing mandibular incisive canal (arrow).

Figure 3

Anatomical variations of the mental foramen (MF) position in the horizontal plane in relation to the roots of teeth. Colours: blue = MIC, red = mental canal (the anterior opening of the mandibular canal) yellow = mandibular canal. 1 = distance from MF to midline of the mandible (approximate distance 28 mm); 2 = distance from MF to the inferior border of the mandible (14 to 15 mm); 3 = possible MF location zone in the horizontal plane in relation to the roots of teeth; 4 = the shape of MF can be round or oval, the diameter is 1.68 to 3.5 mm; 5 = prevalence location of MF in the horizontal plane for Caucasian population; 6 = prevalence location of MF in the horizontal plane for Mongoloids and African people.

Figure 4

The appearance of the mental foramen on panoramic radiographs: classification by Yosue and Brooks [18]. A = continuous; B = separated; C = diffuse; D = unidentified type.

Figure 5

Panoramic radiographs showing variations of the mental foramen (MF) position in the vertical plane in relation to premolars apex: classification by Fishel et al. [24]. A = the MF situated coronal to the apex; B = the MF situated at the apex; C = the MF situated apical to the apex.

Figure 6

Emergence patterns of the mental canal and mental foramen opening. Colours: blue = MIC, red = mental canal (the anterior opening of the mandibular canal) yellow = mandibular canal. A = superiorly, B = posterosuperiorly; C = labially; D = mesially (anteriorly); E = posteriorly.

Figure 7

The anterior loop (AL) of the mental nerve: length variations from the most anterior loop point to mental foramen. Colours: blue = MIC, red = mental canal (the anterior opening of the mandibular canal) yellow = mandibular canal. 1 = length of the AL (0.00 to 10 mm).

Figure 8

Panoramic radiograph showing extension of the mental nerve beyond the mental foramen boundary as an intraosseous anterior loop (arrows).