Kai-Olaf Henkel
University of Rostock
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Featured researches published by Kai-Olaf Henkel.
Clinical Oral Implants Research | 2008
Werner Götz; Thomas Gerber; Barbara Michel; Stefan Lossdörfer; Kai-Olaf Henkel; Friedhelm Heinemann
OBJECTIVES Bone substitute biomaterials may be osteogenic, osteoconductive or osteoinductive. To test for these probable characteristics in a new nanoporous grafting material consisting of nanocrystalline hydroxyapatite embedded in a porous silica gel matrix (NanoBone(s)), applied in humans, we studied biopsies from 12 patients before dental implantation following various orofacial augmentation techniques with healing times of between 3.5 and 12 months. MATERIAL AND METHODS Sections from decalcified specimens were investigated using histology, histochemistry [periodic acid Schiff, alcian blue staining and tartrate-resistant acid phosphatase (TRAP)] and immunohistochemistry, with markers for osteogenesis, bone remodelling, resorption and vessel walls (alkaline phosphatase, bone morphogenetic protein-2, collagen type I, ED1, osteocalcin, osteopontin, runx2 and Von-Willebrand factor). RESULTS Histologically, four specific stages of graft transformation into lamellar bone could be characterized. During early stages of healing, bone matrix proteins were absorbed by NanoBone(s) granules, forming a proteinaceous matrix, which was invaded by small vessels and cells. We assume that the deposition of these molecules promotes early osteogenesis in and around NanoBone(s) and supports the concomitant degradation probably by osteoclast-like cells. TRAP-positive osteoclast-like cells were localized directly on the granular surfaces. Runx2-immunoreactive pre-osteoblasts, which are probably involved in direct osteogenesis forming woven bone that is later transformed into lamellar bone, were attracted. Graft resorption and bone apposition around the graft granules appear concomitantly. CONCLUSIONS We postulate that NanoBone(s) has osteoconductive and biomimetic properties and is integrated into the hosts physiological bone turnover at a very early stage.
European Journal of Trauma and Emergency Surgery | 2006
Thomas Gerber; Gerd Holzhüter; Werner Götz; V. Bienengräber; Kai-Olaf Henkel; Elisabeth Rumpel
Background:The bone substitute NanoBone® consists of nanocrystalline hydroxyapatite embedded in a highly porous matrix of silica gel. It promotes the healing of bone defects and is degraded by osteoclasts during bone remodeling. The present study investigates the interactions of NanoBone® with bone tissue.Methods:Granules of NanoBone® were implanted in defects of critical size in the mandible of minipigs. Samples were taken after 5 and 10 weeks and demineralized. The composition of the implanted granules was analyzed by means of transmission and scanning electron microscopy and EDX. Enzymeand immunohistochemistry was used to investigate organic components of NanoBone® granules that arised after implantation in the host.Results:EDX demonstrated that 5 weeks after implantation the silica gel was degraded and replaced by an organic matrix. Ultrastructurally, the matrix appeared amorphous with only single collagen fibrillae.PAS-staining indicated the presence of carbohydrates. Immunohistochemically, the bone proteins osteopontin, osteocalcin and BMP-2 were found as constituents of the new matrix. Alkalic phosphatase activity was located in osteoblasts and newly formed bone on NanoBone® and focally in particles. Osteoclasts with ruffled borders, sealing zones, and acid phosphatase activity were situated in resorption lacunae at granule surfaces not covered by new bone.Conclusions:In vivo, the silica gel of NanoBone® is replaced by bone matrix glycoproteins with known functions in attraction, adhesion, and differentation of bone cells as osteoblasts and osteoclasts. We assume that the deposition of these molecules supports the early phase of NanoBone® degradation by osteoclasts and promotes the production of new bone tissue.
Journal of Cranio-maxillofacial Surgery | 1999
Silke C. Mueller; Kai-Olaf Henkel; Joachim Neumann; Eva Maria Hehl; Karsten K.H. Gundlach; Bernd Drewelow
Although clindamycin is recommended for prophylactic use in oral and maxillofacial surgery, there is little data available regarding its ability to provide sufficient tissue concentrations at the operative site. We investigated tissue samples from 31 patients, who had to undergo oral and maxillofacial surgery and who received at least one dose of 600 mg clindamycin i.v. preoperatively, to determine clindamycin tissue concentrations in muscle, oral mucosa, fatty tissue, skin and bone between 15 min and 8 h after administration. After homogenization, clindamycin concentration was determined by bioassay. It was demonstrated that clindamycin concentrations above the MIC90 of those pathogens most likely to cause contamination were reached in all kinds of tissues investigated. Already 15 min after administration, tissue concentrations above the MIC90 were reached and were still detectable in the last samples taken between 4 and 8 h after the last clindamycin administration. From the pharmacokinetic point of view, clindamycin is suitable for perioperative prophylaxis during oral and maxillofacial surgery providing sufficient tissue concentrations with no intraoperative additional dosage necessary unless procedures exceed 4 h duration.
Folia Histochemica Et Cytobiologica | 2011
Werner GÜtz; Solvig Lenz; Christoph Reichert; Kai-Olaf Henkel; Volker Bienengrä ber; Laura Pernicka; Karsten K.H. Gundlach; Tomasz Gredes; Thomas Gerber; Tomasz Gedrange; Friedhelm Heinemann
To test the probable osteoinductive properties of NanoBone, a new highly non-sintered porous nano-crystalline hydroxylapatite bone substitute embedded into a silica gel matrix, granules were implanted subcutaneously and intramuscularly into the back region of 18 mini pigs. After periods of 5 and 10 weeks as well as 4 and 8 months, implantation sites were investigated using histological and histomorphometric procedures. Signs of early osteogenesis could already be detected after 5 weeks. The later periods were characterized by increasing membranous osteogenesis in and around the granules leading to the formation of bone-like structures showing periosteal and tendon-like structures with bone marrow and focal chondrogenesis. Bone formation was better in the subcutaneous than in the intramuscular implantation sites. This ectopic osteogenesis is discussed with regard to the nanoporosity and microporosity of the material, physico-chemical interactions at its surface, the differentiation of osteoblasts, the role of angiogenesis and the probable involvement of growth factors. The results of this preliminary study indicate that this biomaterial has osteoinductive potential and induces the formation of bone structures, mainly in subcutaneous adipose tissue in the pig.
Journal of Sol-Gel Science and Technology | 2003
Th. Gerber; T. Traykova; Kai-Olaf Henkel; V. Bienengraeber
A novel bioceramic derived via sol gel method was developed and very good resorption properties in long term period of implantation were established.Calcium phosphate materials are bioactive, osteoconductive materials used as guides for bone regeneration. An identical sequence of events apparently occurred at the contact of the ceramics when implanted in vivo. Two kinds of calcium phosphate ceramics have been produced in a form of threads with 1 mm in diameter: hydroxyapatite SiO2-containing ceramic and hydroxyapatite—β-tricalcium phosphate SiO2-containing ceramic. Above mentioned calcium phosphate ceramic established an interconnecting macroporous structure, which is responsible for growth of bone and for replacement of ceramic by bone. Three ranges of pores were designed.Viscosity measurements were made to control the point of gelation and production phase of transplant material.In vivo experiments were carried out for 5 weeks and 8 months. The results after the short period of examination have shown the early stage of bone formation and material dissolution. Within 6 months nearly 100% of implanted ceramic was resorpted and new bone around place of intervention was formed.
Journal of Sol-Gel Science and Technology | 2000
Th. Gerber; G. Holzhüter; B. Knoblich; P. Dörfling; V. Bienengräber; Kai-Olaf Henkel
A novel porous material produced via sol gel process is disclosed which is osteoinductive and biodegradable. Due to the fact that high temperatures are avoided during the production process, the degree of crystallinity is very low and the packing of the crystallites is relatively loose. These are important parameters for the biodegradation properties.Nanoporous silica gel is contained to the support of strength. The low degree of crystallinity and the high degree of porosity (50–70%, pores in the range of few microns) make the material resorbable. A second type of pores designed in the range of few millimetres supports the bone ingrowth.An in vitro formation of bone tissue is shown when the material is exposed to tissue culture medium and inoculated with human osteoblastic cells. Animal tests show the formation of new bone tissue and first steps of biodegradation.
The Cleft Palate-Craniofacial Journal | 1998
Kai-Olaf Henkel; Karsten K.H. Gundlach; Basam Saka
OBJECTIVE This study was conducted to ascertain the frequency of surgeries typically required to adequately repair a cleft lip. MATERIAL All operations performed on patients with clefts of the lip (alveolus and palate) from 1968 to 1990 in the Rostock Cleft Center were evaluated. METHODS Procedures were classified as primary labioplasties versus secondary revisions. Patients were also classified according to cleft type, the anatomical segment revised, and the reason for lip revision. Two indices were calculated. The revision index related the number of revisions to the number of primary labioplasties. The index of indication related the number of patients with revisions to the number of primary labioplasties. RESULTS During the period of study, 712 primary labioplasties and 771 secondary revisions were performed. The overall revision index was 1.10. The index of indication varied from 0.28 for unilateral complete clefts of the lip to 0.67 for bilateral complete clefts of the lip. Revision of the lip was the most common secondary procedure, followed by nostril and columella revision, and revision of the oral vestibule. CONCLUSIONS The incidence of secondary surgery of the repaired cleft lip (index of indication) of about 35% is similar to previously reported data. However, the incidence varies with cleft type and is required more often with bilateral complete clefts of the lip.
Mund-, Kiefer- Und Gesichtschirurgie | 2002
Kai-Olaf Henkel; Th. Gerber; P. Dörfling; J. Härtel; L. Jonas; K. Gundlach; V. Bienengräber
Fragestellung. Ist es möglich, Critical-size-Defekte durch die artifizielle Stimulation von Osteokonduktion und Osteogenese zur knöchernen Ausheilung zu bringen, sodass spätere Knochentransplantate nicht mehr notwendig werden? Material und Methode. Der knöcherne Durchbau von definierten Critical-size-Defekten im Bereich des vorderen Unterkieferkörpers wurde bei 24 adulten Minischweinen klinisch, histologisch und im Rasterelektronenmikroskop analysiert. Die Defekte wurden mit einer im innovativen Sol-Gel-Verfahren hergestellten Biokeramik, bestehend aus 60% Hydroxylapatit (HA) und 40% β-Trikalziumphosphat (βTCP), allein bzw. kombiniert mit autologen kultivierten Osteoblasten aufgefüllt. In einer Kontrollgruppe wurden die Defekte nur mit Periost gedeckt. Das Beobachtungsintervall betrug 5 Wochen. Dabei wurde die Rolle des Periosts, der Biokeramik und der autolog transplantierten Osteoblasten untersucht. Ergebnisse. Die Biokeramik zeigte eine der Knochenneubildung angepasste Biodegradation und führte mit 72,3% im Vergleich zur Kontrollgruppe (59,3%) zu einer ausgeprägteren Reossifikation der Defekte. Die Defektauffüllung mit autologen, durch Kultivierung vermehrten Osteoblasten in Kombination mit dieser Biokeramik führte zu keiner weiteren Steigerung des Knochendurchbaus. Schlussfolgerung. Die in vivo getestete hochporöse Biokeramik, die sich durch ein lockeres Kristallgefüge auszeichnet, ist als ein geeignetes Knochenersatzmaterial einzuschätzen, welches auch als Matrix für osteoinduktive Substanzen, wie z. B. BMP (bone morphogenic protein), dienen könnte. Question. Does artificial stimulation of osteoconduction and osteogenesis lead to improved bone formation in defects of critical size? Material and methods. Full-thickness, critical-sized defects in the anterior mandible were created in 24 adult mini-pigs. These defects were treated with a new kind of bioactive ceramic (60% hydroxylapatite and 40% β-tricalcium phosphate), applied as a unique sol gel [9]. The bioceramic was tested alone and in combination with autologous osteoblasts. In a control group, periosteum was the only bone-producing source. After 5 weeks, the animals were sacrificed and the defects analyzed clinically, histologically, and by X-ray examination. The effects of periosteum, bioceramics, and osteoblasts were investigated in particular. Results. The new bioceramic was degraded at the same speed as new bone was laid down. The rate of newly formed bone was highest in the bioceramic group at 72.3% (control group with periosteal covering only 59.3%). Additional transplantation of autologous osteoblasts did not result in faster bone production. Conclusion. It seems that this bioactive ceramic is successful as a bone replacement material and will be suitable as a carrier for osteoinductive substances such as bone morphogenetic proteins.
Key Engineering Materials | 2005
Kai-Olaf Henkel; V. Bienengräber; Solvig Lenz; Th. Gerber
In clinical practice arises an increasing need for bone substitute materials. The main inorganic part of bone is the hydroxyapatite (HA). A new hydroxyapatite formula was created by a sol-gel-process at low temperature level [4]. The aim of this investigation was to test the biodegradation and the induction of bone formation by this new material and to compare these versus conventional fabricated HA and ß-TCP. 30 one-year-old Goettingen minipigs were divided into five groups. Critical size defect (>5 m3) in the mandible was treated differently in all 5 groups:-group I- filling with pure HA, which was fabricated by sol-gel-technique, group II- control, only gelatinous material was given, group III- conventional ß-TCP [Cerasorb®], in group IV- conventional HA [Endobone®] and in group V [Targobone®], a non denatureted bovine collagen matrix was used. Macroscopical and microscopical investigations of the former defects were made eight months postoperatively. The bone formation was superior in the sol-gel-HA-group (group I) in comparison with the control groups (group II) and the conventional fabricated ceramics groups (III and IV). In the sol-gel-HA group, the biodegradation of this new biomaterial was considered to very good with a resorption rate of more than 98%; eight months postoperatively. In this group complete bone formation was seen in former defects. In the control group, only an incomplete bone formation with 48.4% of the defect area was noted. This difference was significant (p<0,001). A less bone formation was also observed in group III and IV with 57.6% and 56.9%. The bovine non-denaturated collagen matrix (group V) leads to only 20% of new formed bone. The new calcium phosphate formula made by a sol-gel method seems to be superior and suitable for filling bone defects.
Journal of Biomedical Materials Research Part B | 2011
Mark Kirchhoff; Solvig Lenz; Kai-Olaf Henkel; Bernhard Frerich; Gerd Holzhüter; Sven Radefeldt; Thomas Gerber
The purpose of this study was to evaluate biomaterial degradation and new bone formation after implantation of a nanostructured hydroxyapatite (HA) grafting block. Furthermore, physical characteristics of the biomaterial were measured. The biomaterial consists of nanostructured HA embedded in a porous matrix of silica (SiO(2) ) gel. The blocks with two different contents of silica (group A: 24 wt % and group B: 39 wt %) were fixed with titanium screws at the lateral aspect of the mandible of minipigs (n = 5). The specific surface areas of both blocks were measured using Brunauer-Emmett-Teller (BET) equation and mercury intrusion. In all animals, the wound healing was uneventful. After 5 weeks, the biomaterial percentage was 51.5% ± 12.1% for group A and 33.2% ± 5.9% for group B (p = 0.017). New bone formation accounted to 7.6% ± 6.0% for group A and 15.3% ± 8.3% for group B (p = 0.126) after 5 weeks. After 10 weeks, further resorption of the biomaterial led to percentages of 30.6% ± 10.0% for group A and 12.1% ± 6.7% for group B (p = 0.000). After 10 weeks, new bone formations were measured to be 34.1% ± 10.8% in group A and 39.9% ± 13.5% in group B (p = 0.383). The rate of degradation of the biomaterial is controlled by the composition of the material. A higher content of silica gel matrix leads to faster degradation of the biomaterial. The formation of new bone failed to show a significant difference between both groups.