muscle, the inferior alveolar artery directly branches off the maxillary artery. However, if the main artery follows a deep course, it produces a branch which winds around the lower border of the lateral pterygoid muscle (8) and bifurcates into the posterior deep temporal artery and the inferior alveolar artery.

Almost at its point of origin" the inferior alveolar artery turns almost vertically downward, usually closely following the lingual surface of the ramus. It enters the ramus at the mandibular fora-men, and moves inferiorly and anteriorly together with the mandibular nerve within the mandibular canal. Just before entering the canal, the inferior alveolar artery produces the mylohyoid artery (9), which accompanies the mylohyoid nerve to the mylohyoid muscle, where it anastomoses with branches of the sub-mental artery.

Two phases of implant surgery might threaten the inferior alveolar artery and one of its branches, the mental artery. When retracting the mucoperiosteal tissues to expose the ridge in the region of the mental foramen, great care must be taken not to perforate or tear the mental artery as it leaves the body of the mandible. A scalpel should never be used here. The subperiosteal elevator, used to push the periosteum and its overlying tissues away from the bone, should not be directed down at the neurovascular bundle but rather worked around it. As the instrument is worked toward the bundle, a semilunar circle will appear. This is the superior margin of the foramen. Because the neurovascular bundle is ensheathed by loose connective tissue, the mucoperiosteal tissues should slip along the vessels away from the bone, leaving the bundle safely intact.

Impression-taking can also damage the mental artery and its accompanying vessels as the operator tries to remove a set impression without checking to see if the impression material has crept under the neurovascular bundle. Pulling the artery in such a situation can bruise or tear it.

The more obvious danger to the inferior alveolar artery is drilling in the bone above the mandibular canal to create a seat for an endosteal bladevent. The sweep of the canal within bone must always be determined radiographically, and distances between the superior limit of the canal and the alveolar crest care-fully noted. The mental foramen area may be confusing because of differences in the divergencies of the mandibular, incisive, and mental canals.

When the mandibular canal appears to closely approach the

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