Implant histology 117

and were made larger and fewer in number. This appears to support the evidence from metallic implant studies that open spirals should always be buried away from the alveolar crest.

A low-power section of an implant with a hole fairly close to the apex shows a distinct bony bridge (Fig. 4-74). The bridge, under higher power, is seen to be composed of new bone surrounded by a periodontal membrane, all in a healthy state (Fig. 4-75). A slightly higher power view of the same section illustrates freedom from inflammatory or other unfavorable reactions (Fig. 4-76). The inferior border of the previous figures, upon greater magnification, shows a distinct line of osteoblasts (Fig. 4-77).

Fig. 4-72. The most obvious difference between a metallic and a crystalline implant was the presence or absence of a connective tissue membrane. In this photomicrograph of a bone section around a crystalline implant site (X), there is no fibrous tissue membrane. (Courtesy K. R. Blakey, Howard University.)

Fig. 4-73. Implant replicas of animal teeth with holes to encourage bony bridging. (Courtesy M. Hodosh.)

Fig. 4-74. The bony bridge that grew through the hole in the implant appears well defined under low power (arrow). (Courtesy M. Hodosh.)