76 Theories and techniques of oral implantology

but rarely tension. This leads to gradual resorption of the bone, resulting from both excessive pressure and disuse.

The loss of bone in a triplant site is very difficult to distinguish in x-rays, because a triplant pin usually occupies a very narrow amount of bone whose true internal structure is camouflaged by its overlying cortical plates. Because a prime site for triplant pins is the bone flanking the maxillary sinus, few trabeculae are distinct anyway because the sinus itself acts as a stress distributor.

"Pseudoperiod on tal ligament"

The connective tissue that forms around an implant plays a vital role in the outcome of the intervention. Its width and fiber orientation determine the nature and direction of functional stimulation on bone. In a successful post type or blade implant, the connective tissue membrane so closely resembles a periodontal ligament in form and function that it is called a false or pseudoperiodontal ligament by implantologists.

With a stable implant that moves very little in its site, the connective tissue is thin. It encapsulates any irregularity in the implant, following the de-sign configurations. In a post type implant design, there must be enough room for sufficient connective tissue accompanied by blood vessels and nerves to grow through. This is why the width and spacing of the spirals in a Formiggini-Chercheve type implant is so important and tvhy the vent is a successful design feature.

As the maturing connective tissue is stimulated by pressure, its fibers form bundles that become oriented along the directions of stress. This is similar to the orientation of the fiber bundles in a natural periodontal ligament, except that the fiber

Fig. 3-35. The fiber bundles of a "false" or pseudoperiodontal ligament are deflected around the metallic spirals (S) of a spiral-post type implant. The more complex the implant design, the more irregularly oriented the bundles.

bundles in this membrane tend to be more irregularly arranged.

The connective tissue follows the shape of the implant. It winds in and around the spirals and through the vents. Although it directly contacts the metal implant, the ends of the fiber bundles do not penetrate it as Sharpey's fibers. The fiber bundles are deflected around the design variations and may be redirected back toward the bone in any direction (Fig. 3-35). This lack of distinct groups of specifically oriented fibers, which resembles the situation around the apex of a natural tooth, seems to have

Fig. 3-37. A pseudoperiodontal membrane cannot form around a triplant pin. Because the tissue is not closely involved with the pin, it does not create the tension on bone necessary for its stimulation.