Implant histology 133

the implantation procedure, it begins to resorb. Al-most simultaneously, connective tissue begins to form around the implant. Because this tissue is soft and not well organized, the implant becomes looser than it was just after its insertion. However, as the connective tissue matures into a highly organized tissue with a high fiber content, it begins to stabilize the implant. As soon as the bone around the implant matures, the implant reaches a point of "stable mobility."

Whereas the periodontal membrane around a natural tooth is approximately 0.1 to 0.2 mm. thick, being slightly thicker at the apex, the false periodontal membrane around an implant tends to be some-what thicker. According to George Greene, Jr., the pseudoperiodontal membrane around a well-placed endosseous implant in proper occlusion is from about 0.4 to 0.5 mm. thick. If an implant is set into bone loosely or improperly, this membrane will become thicker, preventing bone from regenerating close to the implant. The resultant mobility will eventually cause the implant to fail. The fibrous connective tissue between alveolar bone and implant must be thin enough to give stability, yet strong enough to withstand the kind of mobility necessary for bone stimulation.

Although even a successful post type implant is never as immobile as a healthy normal tooth, it attains sufficient rigidity to function properly. This has been repeatedly shown radiographically and in several instances under the microscope. This does not apply to blade implants, since they are often tighter than natural teeth.

This, of course, does not imply that implants function in exactly the same manner as do natural teeth. However, radiographic and some histologic evidence suggests that if an implant is properly inserted and occluded, it can simulate the functions of natural teeth.

Epithelial tissue

The soft tissues around an implant abutment post have been clearly demonstrated to be firm in texture and healthy in color. Tissue biopsies taken from the area around an abutment post revealed a low-grade type of inflammation in the region of the gingival sulcus or cuff. This inflammation, however, is not greater than the inflammation found in the gingival sulci of natural teeth. It could have resulted from poor dental hygiene, the usual local irritants, or poorly constructed restorations.

The collagenous tissue below the gingival sulcus was free from epithelial rests, except in those areas where the implants were originally placed loosely. In successful implants, very few inflammatory cells have been observed below the gingival cuff. However, it should be remembered that as natural teeth are subject to periodontal disease, so are dental implants.