80 research outputs found
The in vitro viability and growth of fibroblasts cultured in the presence of different bone grafting materials (NanoBone® and Straumann Bone Ceramic®)
Different clinical applications, including dentistry, are making increasing demands
on bone grafting material. In the present study we have analysed the viability,
proliferation and growth characteristics of fibroblasts cultured in vitro together
with two different bone grafting materials, NanoBone® and Straumann Bone
Ceramic®, over a period of 24 and 28 days respectively. Viability was measured
at least every 72 hours by using the alamarBlue assay, a test that measures
quantitatively cell proliferation and viability but does not require cell fixation or
extraction. After one week of culture fibroblast viability was as high as in controls
for both grafting materials and remained high (> 90%) for the duration of
the experiment. Cell growth was evaluated microscopically. Scanning electron
microscopy revealed a dense fibroblast growth at the surface of both bone grafting
materials after three weeks of in vitro culture. Generally, our in vitro analyses
contribute to further insights into cell - scaffold interactions
The biodegradation of hydroxyapatite bone graft substitutes in vivo
Hydroxyapatite (HA) ceramics are widely used for bone reconstruction. They are
osteoconductive and serve as structural scaffolds for the deposition of new bone.
Generally, scaffold materials should be degradable as they affect the mechanical
properties of the reconstructed bone negatively. Degradation by osteoclasts
during the bone remodelling process is desirable but often does not take place.
In the current study we analysed by light microscopy the degradation of two
granular HA implants in critically sized defects in the mandibula of Goettingen
mini-pigs five weeks after implantation. Bio-Oss® consists of sintered bovine
bone and NanoBone® is a synthetic HA produced in a sol-gel process in the
presence of SiO2. We found that both biomaterials were degraded by osteoclasts
with ruffled borders and acid phosphatase activity. The osteoclasts created
resorption lacunae and resorptive trails and contained mineral particles. Frequently,
resorption surfaces were in direct contact with bone formative surfaces
on one granule. Granules, especially of NanoBone®, were also covered by osteoclasts
if located in vascularised connective tissue distant from bone tissue.
However, this usually occurred without the creation of resorption lacunae. The
former defect margins consisted of newly formed bone often without remnants
of bone substitutes. Our results show that the degradation of both biomaterials
corresponds to the natural bone degradation processes and suggest the possibility
of complete resorption during bone remodelling
The survival and proliferation of fibroblasts on orthodontic miniscrews with different surface treatment: an in vitro study
It is of fundamental importance for prosthodontic and orthodontic applications
that there is a short osseointegration time of dental implants without inflammation
of the surrounding tissue. In addition to the chemical properties of the
implant material, the surface morphology is an equally critical parameter. The
objective of this work was to study the effect of two simple surface treatments
on the survival and proliferation of fibroblasts.
Three groups of orthodontic miniscrews (Mondeal®) were used. One group was
given an airflow (EMS, Schweiz) treatment, the second was sand-blasted in the
area of the threading and a third group served as a control. After preparation
sterilised screws were cultured in vitro with fibroblasts (L-929). The metabolic
cell activity on the implant surface was determined after 24, 48 and 120 hours
using the alamarBlue assay and a count of DAPI labelled fibroblasts was performed
with a fluorescence microscope.
After 24 hours, but not at 48 hours and 120 hours, the metabolic activity of the
fibroblasts was slightly decreased for the airflow screw group. Generally, no
significant difference was found regarding metabolic activity and proliferation
of fibroblasts within the different groups
Bone functions and the requirements for bone grafts and substitutes in the orofacial region
Bone is the largest calcium storage, has distinctive plasticity and adaptability and
is part of the supporting tissue. An adequate composition is thus necessary. The
bone matrix consists of organic and anorganic structures. Osteoblasts, osteoclasts
and osteocytes are responsible for bone formation, resorption and metabolism.
The periosteum, endosteum and bone tissue are a functional unit and provide
protection, nutrition and growth. Bone is subject to continuous remodelling
Wound management after the application of bone grafting substitutes in the orofacial region
Surgical dressing after the application of bone grafting material depends on the
type and size of the defect. A complete and tension-free wound closure has
proved to be successful. In this context the infection problem needs special
attention. Bone graft substitutes with an adequate surface structure, porosity
and chemical properties, in combination with sufficient blood circulation, hold
osteoconductive potential. They serve as a guide rail for the osteoblast-induced
formation of new bone tissue, which at best may lead to complete replacement
of the grafting material
Critical considerations on the diagnostic appraisal, adaptation and remodelling of bone graft substitutes
The diagnostic assessment of skeletal defects has a long-standing tradition. As
a result of the development of new bone grafting materials, the demands on
diagnostic assessment have also increased. The mode and quality of diagnostic
appraisal are crucial to further clinical use and outcome prediction. Alongside
traditional clinical and biological techniques, molecular biological methods have
gained a broad scope of application and will be used even more frequently in
the future
Spintronics: Fundamentals and applications
Spintronics, or spin electronics, involves the study of active control and
manipulation of spin degrees of freedom in solid-state systems. This article
reviews the current status of this subject, including both recent advances and
well-established results. The primary focus is on the basic physical principles
underlying the generation of carrier spin polarization, spin dynamics, and
spin-polarized transport in semiconductors and metals. Spin transport differs
from charge transport in that spin is a nonconserved quantity in solids due to
spin-orbit and hyperfine coupling. The authors discuss in detail spin
decoherence mechanisms in metals and semiconductors. Various theories of spin
injection and spin-polarized transport are applied to hybrid structures
relevant to spin-based devices and fundamental studies of materials properties.
Experimental work is reviewed with the emphasis on projected applications, in
which external electric and magnetic fields and illumination by light will be
used to control spin and charge dynamics to create new functionalities not
feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes
from the published versio
Spin dynamics in semiconductors
This article reviews the current status of spin dynamics in semiconductors
which has achieved a lot of progress in the past years due to the fast growing
field of semiconductor spintronics. The primary focus is the theoretical and
experimental developments of spin relaxation and dephasing in both spin
precession in time domain and spin diffusion and transport in spacial domain. A
fully microscopic many-body investigation on spin dynamics based on the kinetic
spin Bloch equation approach is reviewed comprehensively.Comment: a review article with 193 pages and 1103 references. To be published
in Physics Reports
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