Causes of implant failure 621

Fig. 14-27. The bone around the mesial pin now revealed the true picture.

edentulous spans or in totally edentulous jaws should be stabilized by a thin metal plate set directly over the bone, wherever possible.

Using the old operative method, each and every triplant exhibits what in a natural tooth would be considered to be a trifurcation involvement concerning the fibromucosal tissue lying between the bony alveolar crest and the tissue-bearing surface of the acrylic core. As the fibromucosa moves during normal activities of the jaw, it tugs on the emerging triplant pins. As a result, they move and cause bone resorption (Fig. 14-28).

Triplants may be stabilized in such a way as to eliminate potential soft tissue trifurcation involvement. This can be done by incising and retracting the tissue over the site and by driving the pin implants directly through a thin metal plate adapted over the bone. The pins are then fused together right over the plate (Fig. 14-29) . The incised tissues are sutured around the protruding acrylic core.

In addition to the thin metal plate fitted over the bone with each triplant, a template should be placed over the fibromucosal tissue to act as a stress-distributing bar. Together, these should complement one another and resolve the movement problems that encourage bone resorption (Fig. 14-30).

When a triplant is anticipated in an edentulous area between natural teeth, neither the plate nor a template is necessary if the implant is secured to the teeth on either side with a fixed splint.

In long edentulous spans or in the totally edentulous jaw, the addition of a fourth pin making the triplant actually a quadraplant   has been found helpful. The problem here is that all the legs should diverge. If this is difficult with a triplant, it is even harder with a quadraplant.

Improper acrylic fusion of triplant pins. Unless the acrylic used to fuse the triplant pins together is brushed on layer by layer, air bubbles may be

Fig. 14-28. Three serial radiographs show the steady bone resorption around a mandibular triplant.

Fig. 14-29. A, The acrylic core was built over a thin metal plate adapted to the bone. The core included the triplant pins, which were driven through the plate. B, In a completely edentulous maxilla, placing pin implants directly through the fibromucosal tissue and into the bone without the use of a metal rigid template could easily lead to failure.

A