Abstract
The aim of this study was to evaluate the effects of both
dense hydroxyapatite and ß tricalcium phosphate on mandibular bone,
in an attempt to offer guidelines for their use. The importance of
these guidelines is that although both of these bioceramics have
been used in clinical studies there are no established guidelines
to indicate which clinical situation is best served by either dense
hydroxyapatite or ß tricalcium phosphate. This is evidenced by the
fact that many materials have been used as dental implants and that
many shapes and forms of implants have been used in an attempt
either to stabilise dentures or to restore facial form.
In vitro and in vivo investigations are included in this
study. The in vivo investigation, on 231 male Sprague-Dawley rats
contained controlled studies on weakened and unweakened mandibular
bone; cryosurgery was used to weaken bone in this investigation as
previous studies demonstrated significant reduction in bone
strength after cryosurgery. The in vivo studies were assessed in
two ways; first, mechanical assessments of fracture strengh were
determined by three-point bending tests. Second, histological
examination of mandibular bone was performed in parallel to the
mechanical evaluation, in an attempt to interpret fracture test
results from histological findings.
The investigations in this thesis indicated, for the first
time, that both materials result in significant increased fracture
strength of mandibular bone. The histological findings indicated
that these increases in fracture strength were biologically
significant.
The results presented in this thesis suggest that both
materials are biocompatible and that g tricalcium phosphate is more
ideally used in unweakened bone whereas dense hydroxyapatite, gives
its optimal effect on weakened bone, although it gives more rapid
early increases in strength than does g tricalcium phosphate. It
is suggested that those biomaterials may be of benefit in those
clinical situations where surgery on mandibular bone may render it
prone to fracture
