The implant site 77

little adverse effect on the bone. It receives its stimulation anyway. Although the stress must pass over a longer distance, it is still passed onto bone. Naturally the thinner the connective tissue, the shorter the distance to be traversed by the fiber bundles and the more efficiently the connective tissue functions as a false periodontal ligament.

Because of the blade's design, its site is much narrower than the site created for a post type implant, and many of the fiber bundles involved with it extend more or less horizontally through the vents from the buccal to the lingual faces of the bone (Fig. 3-36). This regularity of orientation more closely resembles the fiber bundle pattern of a natural periodontal ligament than does that of the connective tissues involved with any other implant design.

When the connective tissue is intimately involved with an implant, movements of the implant will affect the fiber bundles so that they will restore and maintain functional stimulation on the surrounding bone. Close adaptation of the connective tissue to variations in an implant's design is thus an essential ingredient for the health of the implant site. Unfortunately, this is not the situation around pin implants.

A pin implant, which is usually smooth-surfaced, never becomes involved with its adjacent connective tissue. Even if the pin is notched, the variations are not sufficient to invite connective tissue involvement. Thus the connective tissues do not move with the implant. When a pin moves, it only compresses the tissues it contacts (Fig. 3-37) . Movement of this type is not beneficial to either connective tissues or bone, and it is certainly not conducive to the apposition of new bone along the wall of the implant site. Also, connective tissue is known to mature into a dense, closely knit tissue upon regular directional stimulation. Continued traumatic compression does not provide this kind of stimulation. As a result of compressive forces and lack of tension, the connective tissues around a pin tend to be disorganized and thicken as the unstimulated bone resorbs away from the site.

This tendency can be counteracted to some degree by reducing the amount of movement. For this reason the legs of a triplant must be placed as far apart as possible to brace one another, and it is advisable to reflect the tissues and join the pin heads directing over the bone. The more soft tissues intervening between the bone and the head of the triplant, the less efficiency the implant has as a tripod.

Other essential motion-reducing methods are immediate splinting to nearby teeth or using a template in long edentulous spans. These methods will be discussed extensively later in the book.

If the pins do not form a truly three-dimensional triplant (or, in some cases, a quadraplant), movement of the individual pins is facilitated. This means that the bone around each pin resorbs from lack of stimulation aggravated by trauma, the connective tissue thickens, and the implant can be easily slipped out of its site. It is held neither by tightly bound connective tissues nor by the growth of a shelf of bone over the implant or spicules of bone through the implant itself.

Despite the drawbacks of the pins, Linkow does not mean to imply that this type of implant is not extremely useful in certain situations. Correctly stabilized, a triplant or a quadraplant provides a very effective brace in posterior edentulous situations when another type of implant would be contraindicated because of local anatomic problems.

Epithelial attachment

The root of a natural tooth is protected against bacterial invasion and the infiltration of food decay products by a tight band of epithelial tissue organically anchored to the tooth. Naturally an organic attachment is not possible with a metallic implant, but there is considerable histologic evidence that the epithelial cuff that forms around the protruding abutment post of a post type implant, a blade-vent, or a subperiosteal implant in all other respects closely resembles that around a natural tooth.

The epithelial cuff around an implant contains fiber bundles that form rings around the abutment post. These rings are numerous, closely knit, and tight. Thus by its fiber orientation and its turgor, the epithelial attachment constitutes a very effective harrier against the spread of inflammation to the underlying tissues of the implant site. (It is interesting to note here that it was originally believed that the epithelial cuff around a natural tooth was held there by its fiber orientation and turgor only. The organic bond was discovered much later.)

The gingival sulcus of an implant site is usually not much deeper than that of a tooth in good occlusion. In a properly inserted implant in good occlusion it shows no more inflammation than is normal.

The epithelial attachment around a triplant pin or a failing post or blade type endosseous implant is slack and disorganized. It provides little protection