178 Theories and techniques of oral implantology

and mentolabial region. Lew was the first American to make all his implants from impressions taken directly on bone.

Lew's maxillary implant designs also evolved from heavy, bulky early models to lighter ones with more strategically placed struts (Fig. 5-84). A maxillary subperiosteal implant still presents numerous problems, some of which Lew was more efficient in solving than his contemporaries. Because little bone is left in the maxillae after extensive alveolar bone resorption, it is extremely difficult to adapt an implant to the region. Generally there is so little bone in the regions of the various sinuses so that extra support across the hard palate is necessary. Thus the implant tends to be heavy, a problem from the standpoint

of gravity alone. A more extensive exploration of the problems of maxillary subperiosteal implants will be presented in Chapter 12.

Among the first Europeans to expose the bone to make an accurate impression was the Italian Luigi Marziani. He made a master model and set posts in the model. He roughly fashioned a piece of tantalum mesh and slipped it over the posts. Then, using a mallet, he shaped it around the model and burnished it. Finally he put the model, together with its opposing half, into a vise (Fig. 5-85). The finished implant was then placed on the bone (Fig. 5-86).

An interesting single-unit unilateral implant of the early 1950's was that of the American, Roy Bo-

Fig. 5-84. The evolution of Lew's maxillary implant. Again, as the implant design evolved, there was a reduction in the amount of metal. (From Lew, I.: Implant denture, a simplified upper technique using immediate prosthesis, Dent. Dig. 1 [10] : 1952.)