CHAPTER 8 Single tooth implants

A great many presenting patients require only a single tooth implant, and it is very tempting to try to insert one without preparing neighboring teeth as supports. Experience has proved, however, that a single tooth implant unsupported by any other teeth is rarely successful. The reasons are basically physiologic and mechanical.

As a site is prepared for the implant, tissues are injured and destroyed. Damage to bone occurs not only to that portion directly in contact with the burs but also to the area around the site. This is a result of the structure of bony tissue. Bone is composed of haversian systems, and each system is a matrix containing interconnected living cells. If a peripheral cell is destroyed by drilling, the effect will usually spread throughout the linked cells. Thus as cells a few cells away from the wound die, resorption occurs over a wider area than that suffering the original injury. This means that no matter how carefully the site has been prepared, bone directly in contact with and up to several cells away from the implant has been destroyed and must heal in order to stabilize the implant. For this reason alone, an implant that is tight immediately after insertion could become loose as the bone around it resorbs during the healing process.

Good healing around an unstabilized implant is difficult, if not impossible. Normally, if the implant has been correctly inserted, the following will occur. Soft tissues proliferate. Collagenous tissue forms around the implant from the periosteum. Epithelial tissues start to grow downward from the oral cavity. The bone resorbs and begins to be replaced by new bone, which heals toward the implant and is separated from it only by the collagenous tissue.

During this time the tissues are in a great state of flux, with the amount and character of the tissue extremely susceptible to stimuli. If the implant is not relatively immobile, it will inflict continual trauma,

more than the normal limits that can be tolerated by healing bone. The bone will fail to mature and the site will become filled with epithelial tissues. If the implant is very loose from the beginning and is left unsplinted, the normal movements of the tongue, cheeks, and lips against the implant will further loosen it, and the epithelial tissue, which proliferates faster, will invaginate down to the implant's base and cause its expulsion. If the implant is partially loose and continually aggravated, the collagenous tissue will be loose, poorly differentiated, and too thick to effectively restore tension on the neighboring bone. This bone will then resorb because of hypofunction, and more soft tissues—usually epithelial—will invade the site until the implant fails.

Relative immobility is clearly desirable for an implant. If an implant is protected from movements of the tongue, cheeks, and lips, the site can heal normally and secure the implant. The collagenous tissue will form a narrow band of dense, fibrous tissue, providing a false periodontal membrane. Fibers extending from the membrane into neighboring bone will pull on it, restoring the tension needed to help mature the bone. The healthy maturing bone and the false periodontal membrane will limit epithelial invagination to about 2 1/2 to 3 mm., which is the depth of a healthy gingival sulcus or cuff. With the implant in functional use and exerting normal pressure on the site, the site will heal naturally and effectively. This, however, can only occur if the implant has the proper architectural design, so that the tissues nearest to it can tenaciously attach to and through it.

The following cases represent some of the many single tooth implantations done by Linkow. The first cases clearly indicate that no matter how carefully an implant is inserted, it should be stabilized. The implants used were post or pin type implants.

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