If it occurs at all, parasthesia resulting from pressure on or damage to the mental nerve may disappear anytime from several weeks to several months, or never. When contemplating an implant procedure that might accidentally produce such a condition, the prospect should be carefully discussed with the patient. In my experience, most patients are willing to risk the chance in exchange for improved dental function and esthetic appearance. However, the operator's goal is to minimize risks by recognizing the course of the canal and anticipating variations in its structure or direction that might complicate otherwise simple, straightforward implant surgery or implant insertion.

The Mental Foramen

The mental foramen (1) is the opening through which the mental canal (2) releases its neurovascular bundle into the soft tissues to supply the lower lip and chin. The mental canal arises from the mandibular, or inferior dental or inferior alveolar, canal (3) where it bifurcates in the bicuspid region. The mental canal is usually the greater of the two branches. The other branch, the inferior incisal canal (4), continues anteriorly and inferiorly toward the midline within bone as a much less significant anatomical feature. Often by the incisor region the inferior incisal canal is indistinguishable radiographically. Sometimes, however, the incisal canal (5) is as large as the mandibular canal (6) for a very short distance after the bifurcation. This may be confusing radiographically, if the mental canal is not clearly depicted so that the bifurcation of the mandibular canal into two branches is obvious. Even if the inferior incisal canal does appear fat after the bifurcation, it rapidly tapers into the more typically thin size. Also it should be noted that after bifurcation, the branches diverge, with the incisal canal directed inferiorly.

As the mental canal arises from the mandibular canal, it turns outward and slightly backward, terminating as the mental foramen at varying distances from the mandibular canal and from the alveolar crest. When teeth are present, the most common site for the foramen is at or immediately below the apex of the second bicuspid. However, in relation to the second bicuspid — its more common reference point — the foramen may appear mesial (7) or distal (8) to the root, and range in height on the mandibular body from well below (9) the apex of the root to almost half-

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