Biomedical Engineering Reference
In-Depth Information
6 weeks after implantation. In this minipig model there was also indication of extensive bioac-
tivity 6 weeks after the placement of the nanomaterial with osseous deposition and extensive
contact of osteoblasts with the material that appeared to act as a scaffold. There was also indica-
tion of resorption with polynucleated cells in close contact to the material's surface.
Vascularization at the implant site was also histologically identified from the 6 week time period
onward
[14]
. Based on the handling characteristics as well as the chemical properties of this
nanosized HA material, it was concluded in this study that despite the fact that full resorption
did not occur even after 12 months postoperatively, Ostim
s
is suited for minimally invasive
applications into defect sites that are stable or that need to be surgically augmented
[14]
.
Although there are several reports of successful osseointegration with the use of nano-HA pro-
ductssuchasOstim
s
and nanOss
s
, it is still difficult to ascertain if these nanoproducts yield
significantly more optimal bone remodeling properties than the conventional materials without
nanosized properties. For example, a study by Huber et al.
[17]
designed to evaluate the Ostim
s
paste and a solid HA ceramic, Cerabone
s
, for treatment of critical size bone defects in rabbits
found only slightly more significant increases in bone ingrowth with Ostim
s
in comparison to
Cerabone
s
and reported similarly excellent results for Ostim
s
andagroupinwhicha
Cerabone
s
core was surrounded by the Ostim
s
paste. No doubt, however, that different osseous
defect models might produce relatively different results depending upon such parameters as the
size, shape, and location of the defect and so care must be taken in the interpretation of results
from various animal models that might not truly represent the clinical conditions in which the
grafts are intended to be used.
There have been recent published reports of two randomized controlled clinical studies
designed to assess the efficacy of Ostim
s
after open flap debridement (OFD) on healing of intra-
bony periodontal defects
[18,19]
. The results of these studies have indicated statistically signifi-
cantly higher clinical improvements following OFD and subsequent defect fill with the nano paste
compared to OFD alone
[18,19]
. However, since these studies did not provide histological data, it
has been difficult to definitively assess the effect of the nanomaterial on bone regeneration in the
treated individuals. In a very recent study
[20]
,theOstim
s
material was further evaluated, both
clinically and histologically, in six patients, each of them displaying very advanced intrabony
defects around teeth scheduled for extraction due to advanced chronic periodontitis and further
prosthodontics considerations. Seven months following surgery, there was a significant reduction
in probing pocket depth and clinical attachment level gain similar to other studies with the
material. However, histological analysis of the surrounding hard and soft tissue around the teeth
extracted after end of the regeneration period revealed a healing predominantly characterized by
epithelial down growth with only limited formation of new cementum (NC) and bone regeneration
in three of the six biopsies (
Figure 19.4
).
There was resorption of the nano-HA in four out of the six biopsies with a few remnants of the
graft particles (either surrounded by newly formed mineralized tissue or encapsulated in connective
tissue) in two biopsies. On the basis of these results and with the recognition that the teeth selected
for this study displayed very advanced destruction of the periodontal supporting apparatus and pos-
sible limited regenerative potential, the investigators in this study concluded that this nanomaterial
has only limited potential for periodontal healing of intrabony defects
[20]
. Therefore, clinical out-
comes obtained following surgery with OFD and the nano-HA may not always be indicative of
actual periodontal regeneration.
