As with any other form of oral surgery, the danger of post-operative infection must be considered after an implantation procedure. Blood-borne infections can lead to serious complications, including cavernous sinus thrombosis. In the vast majority of cases, simple prophylactic measures are adequate.

Blood from anterior maxillary implant sites, together with that from the upper lip and ala of the nose, usually enter the facial vein (1) via the labial veins (2). The blood then flows upward to the inner canthus of the eye, where it enters the angular (3) and nasofrontal veins and then the superior opthalmic veins (4). If infection is present in an anterior implant site, it may be reflected by a puffiness or discoloration of the eye due to the infection's effect on the opthalmic veins. From the eye region, the blood passes through the superior orbital fissure and enters the cavernous sinus (5) . This, in turn, is drained almost entirely by the internal jugular vein (6).

Posteriorly, blood from the upper posterior dental arch and the maxillary pneumatic sinus may drain through a network (7) of small, twisting, venous by-passes into the cavernous sinus. This "direct" route can spread infection in a slow, retrograde manner, with its worst feature being no obvious symptoms until the cavernous sinus is infected.

Blood from the posterior portions of the maxilla can also drain via the posterior facial and internal maxillary veins or pass into the anterior drainage route.

Because of the serious consequences of infection, it is necessary to stress that unfortunate but possible sequela of oral surgery or an infected dental or implant site. However, the presence of a correctly inserted, stable implant has proven repeatedly as harm-less as a healthy tooth. A loose implant can provoke infection, and for this reason should be removed if it cannot be stabilized. Normally, minor antibiotic treatment is adequate for most postoperative situations to prevent infection.

Lymph

The lymphatic system is clinically significant because of its role in fighting infection. Lymph, a pale fluid consisting chiefly of blood plasma and white blood cells, circulates in thin-walled tubes that follow, as a rule, the veins. The lymph vessels conduct the

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