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Two essentially different implant-prosthetic
concepts are known for the treatment of edentulous maxillae.
One concept propagates a “concentrated” arrangement of four
to six implants in the premolar and anterior regions with
a fixed cantilever superstructure. An alternative is a “spread-out”
implant arrangement of six implants placed in the tuberosity,
premolar, and anterior regions. The prosthetic rehabilitation
consists of a fixed horseshoe-shaped bar and removable prosthesis.
A cantilever situation is avoided. The biomechanical aspects
of these implant-prosthetic concepts were studied with clinical
strain-gauge measurements and theoretical three-dimensional
analysis using the finite element method. Results revealed
that the distribution of bone stresses is more favorable
with a spread-out implant arrangement than with a concentrated
implant arrangement and cantilever restoration. The resistance
to bending of a superstructure has an influence on bone
stress concentration that should not be ignored. Stresses
are controlled not only by the number or distribution of
implants, but also by the material and design of the superstructure.
( Int J Oral Maxillofac Implants 1995;10:188-198) |
