Four cement applications were tested in this investigation. Two dicalcium phosphate dihydrate (DCPD-
brushite) hydraulic cements, an apatite hydraulic fiber loaded cement, and a calcium sulfate cement
(Plaster of Paris) were implanted in epiphyseal and metaphyseal cylindrical bone defects in sheep. The
in vivo
study was performed to assess the biocompatibility and bone remodeling of four cement formu-
lations. After time periods of 2, 4, and 6 months, the cement samples were clinically and histologically
evaluated. Histomorphometrically, the amount of new bone formation, fibrous tissue, and bone marrow
and the area of remaining cement were measured. In all specimens, no signs of inflammation were
detectable either macroscopically or microscopically. Cements differed mainly in their resorption time.
Calcium sulfate was already completely resorbed at 2 months and showed a variable amount of new bone
formation and/or fibrous tissue in the original drill hole over all time periods. The two DCPD cements in
contrast were degraded to a large amount at 6 months, whereas the apatite was almost unchanged over
all time periods.