and proper force distribution patterns can it be expected to stimulate the bone. The properly designed implant that is placed correctly into the bone can maintain the alveolar bone height and width through stimulation. This stimulation can be attained in at least two ways.

After the implant is inserted and some of the bone resorbs around its periphery as it did with the various metal screw type implants, it is replaced by fibrous connective tissue, mostly collagenous in nature. Since the tissue was already attached to the alveolar bone directly surrounding the implant, the innermost surfaces of the tissue would tenaciously bind around the threads and grow through the openings of the implant if the design exhibited these characteristics. Thus all occlusal forces brought to bear on the implant posts would be transmitted to areas of tension to the deeper portions of the implant via the pulling action of the fibers against the surrounding alveolar bone to which they are attached. These fibers pulling on the surrounding alveolar bone seemed to be all that was necessary to create a state of osteogenesis. It formed a mechanical suspensory type of ligament. Again, however, I must emphasize the fact that this only happened when the screw was correct and the widest portion of the screw which included all of the threads as well as the opened vents was buried well beyond the crestal bone. When these threads were too close to the crest, a V-shaped resorption of the surrounding crestal bone would occur since the pressure was greatest at the alveolar crest. Every movement of the implant laterally would cause excessive pressure at the crest since the wide threads were immediately contacting the bone in this area. Epithelial tissue would then replace the bone and prevent the more elastic fibrous tissue from adapting to that portion of the screw and finally the screw implant would loosen.

In the same manner when the open vents were placed too superficially to the crest, epithelial tissue would rapidly invaginate into them causing ultimate failure.

The tripodial pins failed for other reasons—mainly because the fibrous tissue that replaced the bone that resorbed around the pins could not tenaciously bind to them. Thus, the minute movements of the pins during mastication and swallowing became more excessive, since they slipped through the surrounding membrane cuffs. The membranes unfortunately could not be stretched and could not pull on the surrounding alveolar bone. The end result, as most qualified implantologists know, was an excessive amount of bone resorption camouflaged, how-ever, by the thick buccal and palatal cortical bone flanking the medullary area.

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