Background: Many different surgical techniques have been developed to remove
open mastoid cavities. In addition to autologous materials, alloplastic substances
have been used. A very slow absorption of these materials and extrusion reactions
have been reported. We investigated a newly developed, highly porous bone grafting
material to eliminate open mastoid cavities, in an animal model. To characterise
the transformation process, the early tissue reactions were studied in relation
to the matrix transformation of the bone material.
Material and methods: NanoBone (NB), a highly porous bone grafting material
based on calcium phosphate and silica, was filled into the open bullae
from 20 guinea pigs. The bullae were examined histologically. Energy dispersive
X-ray spectroscopy (EDX) was used to investigate the change in the elemental
composition at different sampling times. The surface topography of the
sections was examined by electron microscopy.
Results: After 1 week, periodic acid-Schiffs (PAS) staining demonstrated accumulation
of glycogen and proteins, particularly in the border area of the NB particles.
After 2 weeks, the particles were evenly coloured after PAS staining. EDX analysis
showed a rapid absorption of the silica in the bone grafting material.
Conclusions: NanoBone showed a rapid matrix change after implantation in the
bullae of guinea pigs. The absorption of the silica matrix and replacement by PAS-positive substances like glycoproteins and mucopolysaccharides seems to play
a decisive role in the degradation processes of NB. This is associated with the good
osteoinductive properties of the material