Friedhelm Heinemann

IMMUNOHISTOCHEMICAL CHARACTERIZATION OF NANOCRYSTALLINE HYDROXYAPATITE SILICA GEL (NANOBONE(R)) OSTEOGENESIS: A STUDY ON BIOPSIES FROM HUMAN JAWS

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.

IL-23-producing CD68+ macrophage-like cells predominate within an IL-17-polarized infiltrate in chronic periodontitis lesions

AIM To analyse antigen-presenting cells (APCs), such as dendritic cells (DCs), macrophages (Mo) or B cells depending on the regional site of chronic periodontitis (CP), and to investigate their relation to Th17 cells. MATERIAL AND METHODS Biopsies from oral mucosa as well as the coronal and bottom regions of CP were analysed by immunhistochemistry, immunofluorescence, flow cytometry and real-time PCR. RESULTS A predominance of CD68(+) Mo-like cells and CD20(+) B cells and strong Th17 infiltration was observed in the bottom region of CP lesions, while CD1a(+) DCs were only detected in the coronal regions, where Th17 infiltration was low. Furthermore, CD68(+) Mo-like cells displayed CD163 expression as a typical Mo-marker, but expressed in parallel typical DCs markers, such as CD11c or CD209 and TLR4. Interestingly, Th17-inducing cytokine IL-23p19 was produced by CD68(+) Mo-like cells, but not CD20(+) B cells. Moreover, the stimulation of in vitro generated CD68(+) Mo-like cells by Porphyromonas gingivalis-derived (Pg) lipopolysaccharide resulted in the upregulation of their IL-23p19 mRNA expression, which was inhibited by the blockage of TLR4. CONCLUSIONS In view of these data, a picture emerges that IL-17-producing cells in CP could be in part directed by CD68(+) Mo-like cells, which produce IL-23p19 upon TLR4 activation by Pg.

A preliminary study in osteoinduction by a nano-crystalline hydroxyapatite in the mini pig.

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.

Experimental and histological investigations of the bone using two different Oscillating Osteotomy techniques compared with conventional rotary osteotomy

Over the past decade, coinciding with the appearance of a number of new ultrasonic surgical devices, there has been a marked increase in interest in the use of ultrasound in oral surgery and implantology as alternative osteotomy method. The aim of this study was the comparison of the effect of osteotomies performed using ultrasonic surgery (Piezosurgery(®)), sonic surgery SONICflex(®) and the conventional bur method on the heat generation within the bone underneath the osteotomy and light-microscopy observations of the bone at different cutting positions in porcine mandibular segments. It was found that the average heat generated by SONICflex(®) sonic device was close to that by conventional rotary bur (1.54-2.29°C), whereas Piezosurgery(®) showed a high generated heat up to 18.17°C. Histological investigations of the bone matrix adjacent to the defect radius showed intact osteocytes with all three instruments and similar wide damage diameter at the bottom region. SONICflex(®) showed smooth cutting surfaces with minimal damage in the upper defect zone. Finally, presented results showed that sonic surgery performed with SONICflex(®) is an alternative osteotomy method and can be used as an alternative to the conventional bur method.

Coupling of osteogenesis and angiogenesis in bone substitute healing - a brief overview.

Similar to osteogenesis and bone repair, the healing and osteogenesis of bone substitutes depend on the osteogenesis-angiogenesis interplay which is controlled by different factors, including VEGF or by hypoxia. A brief review of the process of bone substitute angiogenesis is presented and illustrated by our histological and immunohistochemical findings taken from human biopsies after augmentation with a nanocrystalline synthetic bone substitute.

Retrospective evaluation of temporary cemented, tooth and implant supported fixed partial dentures

INTRODUCTION The aim of this study was to examine the clinical performance of this method, and determine which temporary cement was the most appropriate. METHODS Dental fixtures (Tiolox implants GmbH, Germany) were implanted and crown and bridgework applied in a private practice between 1998 and 2003. Copings made of pure gold or titanium were permanently cemented onto the prepared teeth. The bridges were attached with either conventional temporary cements (Zinc oxide/ calcium hydroxide based) or acrylic/urethane cement (IMProv) both to the copings and to the implant abutments. Complications were evaluated by a retrospective review in January 2006. RESULTS A total of 47 patients (response: 81%) with 65 fixed partial dentures could be evaluated. Removal and re-attaching without damage of the dentures was undertaken for the following reasons: for follow-up examinations (n = 31), colour corrections (n = 15), cleaning of the dentures (n = 12), treatment of peri-implantitis (n = 2), repair following ceramic fractures (n = 5), implant failure (n = 1), tooth extractions (n = 2), root canal treatments (n = 2), occlusal corrections (n = 2), or in the case of abutment loosening (n = 4). Accidental detachments with conventional temporary cements occurred more frequently and more rapidly than with IMProv (15% versus 88.7% survival rate after four years). CONCLUSIONS This method for dental implant supported fixed partial dentures is successful and efficient.

Biomechanical finite element analysis of small diameter and short dental implant.

Abstract Short and mini dental implants have been widely used as treatment alternatives in certain selected clinical situations. However, a profound scientific analysis of the mechanical and biomechanical impact of the reduced length and diameter of these implant geometries has not been published until now. Using finite element analysis, a series of different experimentally designed short and mini implants have been analysed with regard to their load transfer to the alveolar bone and have been compared to respective standard commercial implants. Mini implants have been inserted in an idealised bone bed representing the anterior mandibular jaw region and loaded with a force of 150 N. An immediate loading condition was assumed and analysed using the contact analysis option of the FE package MSC.Marc/Mentat. Short implants were inserted in an idealised posterior bone segment and loaded in osseointegrated state with forces of 300 N. Clearly increased bone loading was observed for the short and mini dental implants compared with standard implants, clearly exceeding the physiological limit of 100 MPa. The determined biomechanical characteristics could explain the slightly increased failure rate of short and mini dental implants.

Biomechanical finite element analysis of small diameter and short dental implants: extensive study of commercial implants.

Abstract In recent years, mini and short dental implants have become increasingly popular as treatment alternatives for patients in whom the bone is unsuitable for a standard implant. As yet, no detailed scientific analysis of the mechanical and biomechanical impact of the reduced diameter and length of these implants has been published. We analysed 21 commercially available implants (13 mini, eight short) with respect to material behaviour and load transfer to the alveolar bone, using finite element (FE) analysis. Following μCT scanning and geometry reconstruction, FE models of mini implants and short implants were inserted into idealised bone segments. Mini implants were analysed in the anterior mandibular jaw region at a force of 150 N under immediate loading, using a contact analysis in the FE software package Marc Mentat 2007. Short implants were inserted in posterior bone segments and analysed in the osseointegrated state at an occlusal force of 300 N. Von Mises stresses (up to 1150 MPa) in mini implants partly exceeded the ultimate strength. Implant diameter and geometry had a pronounced effect on stresses in the cortical plate (up to 266 MPa). Strains in spongy bone and stresses in cortical bone around short implants were markedly increased compared to those in standard implants. An increased risk of bone damage or implant failure may be assumed in critical clinical situations.

Bone stability around dental implants: Treatment related factors.

The bone bed around dental implants is influenced by implant and augmentation materials, as well as the insertion technique used. The primary influencing factors include the dental implant design, augmentation technique, treatment protocol, and surgical procedure. In addition to these treatment-related factors, in the literature, local and systemic factors have been found to be related to the bone stability around implants. Bone is a dynamic organ that optimises itself depending on the loading condition above it. Bone achieves this optimisation through the remodelling process. Several studies have confirmed the importance of the implant design and direction of the applied force on the implant system. Equally dispersed strains and stresses in the physiological range should be achieved to ensure the success of an implant treatment. If a patient wishes to accelerate the treatment time, different protocols can be chosen. However, each one must consider the amount and quality of the available local bone. Immediate implantation is only successful if the primary stability of the implant can be provided from residual bone in the socket after tooth extraction. Immediate loading demands high primary stability and, sometimes, the distribution of mastication forces by splinting or even by inserting additional implants to ensure their success. Augmentation materials with various properties have been developed in recent years. In particular, resorption time and stableness affect the usefulness in different situations. Hence, treatment protocols can optimise the time for simultaneous implant placements or optimise the follow-up time for implant placement.

Maxillary sinus floor augmentation using a nano-crystalline hydroxyapatite silica gel: Case series and 3-month preliminary histological results

The aim of this case series is to histologically examine a new hydroxyapatite in sinus lift procedure after 3 months. Ten 2-stage sinus lifts were performed in 10 healthy patients having initial bone height of 1-2mm and bone width of 5mm, asking for a fixed implant-supported rehabilitation. After graft material augmentation, a rough-surfaced mini-implant was inserted to maintain stability of the sinus widow. A bioptical core containing a mini-implant was retrieved 3 months after maxillary sinus augmentation with NanoBone(®) and processed for undecalcified histology. From the histomorphometric analysis, NanoBone(®) residuals accounted for the 38.26% ± 8.07% of the bioptical volume, marrow spaces for the 29.23% ± 5.18% and bone for the 32.51% ± 4.96% (new bone: 20.64% ± 2.96%, native bone: 11.87% ± 3.27%). Well-mineralized regenerated bone with lamellar parallel-fibred structure and Haversian systems surrounded the residual NanoBone(®) particles. The measured bone-to-implant contact amounted to 26.02% ± 5.46%. No connective tissue was observed at the implant boundary surface. In conclusion, the tested material showed good histological outcomes also 3 months after surgery. In such critical conditions, the use of a rough-surfaced mini-implant showed BIC values supposed to be effective also in case of functional loading. Although longer follow-up and a wider patient size are needed, these preliminary results encourage further research on this biomaterial for implant load also under early stage and critical conditions.