S. Petter Lyngstadaas

In vivo expression of osteogenic markers and bone mineral density at the surface of fluoride-modified titanium implants.

The aim of the present study was to investigate the biological mechanisms of the functional attachment of fluoride-modified titanium implants to cortical bone by studying the association of the pull-out test results with gene expression of osteoblast (runx2, osteocalcin, collagen-I and IGF-I), osteoclast (TRAP, H(+)-ATPase and calcitonin receptor) and inflammation (TNF-alpha, IL-6 and IL-10) markers from peri-implant bone tissue using real-time RT-PCR, following a 4- and 8-week healing period. After implant detachment, wound fluid from the implant site was collected for LDH and ALP activity analysis. A new method to study volumetric bone mineral density (vBMD) of sub-implant cortical bone was developed using micro-computed tomography. Our results show lower LDH activity and TRAP mRNA levels in fluoride implants after 4 weeks of healing, yet no differences were found either on the pull-out force or expression of bone formation marker genes. After 8 weeks of healing, both pull-out, vBMD and osteocalcin, runx2 and collage type I gene expression were higher in fluoride implants. In conclusion, fluoride-modified implants seem to modulate both inflammation and bone resorption/formation events at the bone-implant interface, suggesting that these biological effects are an intrinsic part of the clinical performance of this surface.

Bio-Implant Interface : Improving Biomaterials and Tissue Reactions

The progression of dentistry beyond restorative care to include regenerative therapy has been promoted by successes involving tooth root replacement using endosseous dental implants. This success of commercially pure (c.p.) titanium endosseous implants in support of dental prostheses is now well documented. There is growing consensus that uncoated, threaded c.p. titanium implants can provide survival rates greater than 95% when used to support anterior single tooth restorations1 or mandibular prostheses supported by four to five parasymphyseal implants.2 Clinical successes notwithstanding, we confront the absence of significant data to guide future efforts to apply endosseous implant use in the more challenging environments of low density bone and high stress situations such as single implant replacements for molar teeth.SUCCESS AND FAILURE FOR BONE-IMPLANT ATTACHMENTS: AN EVIDENCE-BASED APPROACH The Role of Implant Surface Properties on the Clinical Outcome of Osseointegrated Oral Implant Therapy, M. Esposito, H.V. Worhington, P. Coulthard, A. Wennerberg, P. Thomsen CAN THE IMPLANT MACRO DESIGN AND MICRO TEXTURING IMPROVE BONE RESPONSE? Toward an Optimized Dental Implant Design, S. Hansson Implant Surface Design for Development and Maintenance of Osseointegration, R. Pilliar Bone Response to Surface Roughness Measurement and Results, Experiment and Clinical Studies, A. Wennerberg, T. Albrektsson From Microroughness to Resorbable Bioactive Coatings, S. Szmukler-Moncler, P. Zeggel, D. Perrin, J-P Bernard, H-G Neumann CELL AND TISSUE REACTIONS TO BIOMATERIALS Improving the Bio-Implant Interface by Controlling Cell Behavior Using Surface Topography, D. Brunette, A. Khakbaznejad, M. Takekawa, M. Shimonishi, H. Murakami, M. Wieland, B. Chehroudi, J. Glass-Brudzinski, M. Textor Osteoblast Response to Pure Titanium and Titanium Alloy, M. Paine, J.C. Wong Biomedical Implant Surface Topography and its Effects on Osteoblast Differentiation in vitro, C. Stanford, G. Schneider, H. Perinpanayagam, J.C. Keller, R. Midura Cellular Interactions at Commercially Pure Titanium Implants, L.F. Cooper A Selection of Oral Implant Materials Based on Experimental Studies, P. Thomsen, C.B. Johansson Possibilities to Improving Implants and Regenerating Dentoalveolar Tissues by Tissue Engineering Using Stem Cells and Growth Factors, I. Thesleff, M. Tummers Critical Issues in Endosseous Peri-Implant Wound Healing, J.E. Davies, J.Y. Park THE EXTRACELLULAR MATRIX BIOLOGY AND BIOMINERALIZATION IN BONE FORMATION AND IMPLANT INTEGRATION Initiation and Modulation of Crystal Growth in the Skeletal Tissues: Role of the Extracellular Matrix, C. Robinson, R.C. Shore, S.R. Wood, S.J. Brookes, D. Alistair Smith, J. Kirkham Use of a Matrix Scaffold for Tissue Engineering and Bone Regeneration, M. Bartold, Y. Xiao Inducing Bone Growth Using Extracellular Matrix Proteins, S.P. Lyngstadaas, J.E. Ellingsen, A. Spahr, I. Slaby SURFACE CHEMISTRY, BIOCHEMISTRY, AND MOLECULES: HOW DO THEY INTERACT WITH BIOLOGICAL ENVIRONMENT? How Surfaces Interact with the Biological Environment, P. Tengvall Osteocapacities of Calcium Phosphate Ceramics, J. Jansen, P.J. Rugge, E. van der Wal, A.M. Vredenberg, J.G.C. Wolke Increasing Biocompatibility by Chemical Modification of Titanium Surfaces, J.E. Ellingsen, S.P. Lyngstadaas Use of Molecular Assembly Techniques for Tailoring Chemical Properties of Smooth and Rough Titanium Surfaces, M. Textor, S. Tosatti, M Wieland, D.M. Brunette DEVELOPMENT AND APPLICATION OF SCIENTIFIC DATA: REGULATORY AND COMMERCIAL ASPECTS Development and Application of Scientific Data: Do Industry and Academia Have Different Scientific Perspectives? B. Delin Medical Devices--Regulatory Perspectives and Aspects of Regulatory Risk Management, S. Gestrelius, A. Hensten-Pettersen INVENTIVE FORWARD LOOKS-WHERE DO WE GO FROM HERE? Self-Assembling and Bimimetic Biomaterials, S. Stupp, E. Beniash, J.D. Hartgerink, E.D. Sone The Inert-Bioactivity Conundrum, D.F. Williams Enhancing the Process of Discovery and Innovation for Optimal Host Response at the Implant Surfaces, M.L. Snead

A Novel Ultra-porous Titanium Dioxide Ceramic with Excellent Biocompatibility:

The current study compares biocompatibility, cell growth and morphology, pore diameter distribution, and interconnectivity of a novel titanium dioxide (TiO2) bone graft substitute granules with three different commercially available bone graft granules Natix®, Straumann® BoneCeramic, and Bio-Oss®. Human primary mesenchymal stem cells were cultured on the bone graft substitutes and cell viability and proliferation were evaluated after 1 and 3 days. The microstructural properties of the bone graft substitutes were evaluated by scanning electron microscopy, micro-computed tomography analysis, and mechanical testing. The cell viability and proliferation, porosity, interconnectivity, open pore size, and surface area-to-volume ratio of TiO2 granules were significantly higher than commercial bone granules (Bio-Oss® and Straumann ® BoneCeramic).

Crown morphology, enamel distribution, and enamel structure in mouse molars

Biomolecular research and genetic manipulations have stressed the importance of thorough knowledge of normal organ morphology. Mouse molar teeth are convenient models for studying basic interactions in organ development and morphogenesis. The aim of the present study was to provide basic information on their morphology.

Bone formation in TiO2 bone scaffolds in extraction sockets of minipigs

The osteoconductive capacity of TiO(2) scaffolds was investigated by analysing the bone ingrowth into the scaffold structure following their placement into surgically modified extraction sockets in Gottingen minipigs. Non-critical size defects were used in order to ensure sufficient bone regeneration for the evaluation of bone ingrowth to the porous scaffold structure, and sham sites were used as positive control. Microcomputed tomographic analysis revealed 73.6±11.1% of the available scaffold pore space to be occupied by newly formed bone tissue, and the volumetric bone mineral density of the regenerated bone was comparable to that of the native cortical bone. Furthermore, histological evidence of vascularization and the presence of bone lamellae surrounding some of the blood vessels were also observed within the inner regions of the scaffold, indicating that the highly interconnected pore structure of the TiO(2) scaffolds supports unobstructed formation of viable bone tissue within the entire scaffold structure. In addition, bone tissue was found to be in direct contact with 50.0±21.5% of the TiO(2) struts, demonstrating the good biocompatibility and osteoconductivity of the scaffold material.

Adaptor protein complex 2–mediated, clathrin-dependent endocytosis, and related gene activities, are a prominent feature during maturation stage amelogenesis

Molecular events defining enamel matrix removal during amelogenesis are poorly understood. Early reports have suggested that adaptor proteins (AP) participate in ameloblast‐mediated endocytosis. Enamel formation involves the secretory and maturation stages, with an increase in resorptive function during the latter. Here, using real‐time PCR, we show that the expression of clathrin and adaptor protein subunits are upregulated in maturation stage rodent enamel organ cells. AP complex 2 (AP‐2) is the most upregulated of the four distinct adaptor protein complexes. Immunolocalization confirms the presence of AP‐2 and clathrin in ameloblasts, with strongest reactivity at the apical pole. These data suggest that the resorptive functions of enamel cells involve AP‐2 mediated, clathrin‐dependent endocytosis, thus implying the likelihood of specific membrane‐bound receptor(s) of enamel matrix protein debris. The mRNA expression of other endocytosis‐related gene products is also upregulated during maturation including: lysosomal‐associated membrane protein 1 (Lamp1); cluster of differentiation 63 and 68 (Cd63 and Cd68); ATPase, H+ transporting, lysosomal V0 subunit D2 (Atp6v0d2); ATPase, H+ transporting, lysosomal V1 subunit B2 (Atp6v1b2); chloride channel, voltage‐sensitive 7 (Clcn7); and cathepsin K (Ctsk). Immunohistologic data confirms the expression of a number of these proteins in maturation stage ameloblasts. The enamel of Cd63‐null mice was also examined. Despite increased mRNA and protein expression in the enamel organ during maturation, the enamel of Cd63‐null mice appeared normal. This may suggest inherent functional redundancies between Cd63 and related gene products, such as Lamp1 and Cd68. Ameloblast‐like LS8 cells treated with the enamel matrix protein complex Emdogain showed upregulation of AP‐2 and clathrin subunits, further supporting the existence of a membrane‐bound receptor‐regulated pathway for the endocytosis of enamel matrix proteins. These data together define an endocytotic pathway likely used by ameloblasts to remove the enamel matrix during enamel maturation.

Bioinformatic analysis and molecular modelling of human ameloblastin suggest a two-domain intrinsically unstructured calcium-binding protein

Ameloblastin (AMBN) was originally believed to be an enamel-specific extracellular matrix glycoprotein secreted by ameloblasts. Recently, AMBN expression was also detected in developing mesenchymal dental hard tissues, in trauma-induced reparative dentin, and during early craniofacial bone formation. The function and structure of AMBN still remain ambiguous, and there are no known proteins with similar primary sequences. We therefore performed a bio-informatic analysis of AMBN to model ab initio the three-dimensional structure of the molecule. The results suggest that AMBN is a two-domain, intrinsically unstructured protein (IUP). The analysis did not reveal any regions with structural similarity to known receptor-ligand systems, and did not identify any higher-order structures similar to functional regions in other known sequences. The AMBN model predicts 11 defined regions exposed on the surface, internalizing the rest of the molecule including a human-specific insert. Molecular dynamics analysis identified one specific and several non-specific calcium-binding regions, mostly at the C-terminal part of the molecule. The model is supported by previous observations that AMBN is a bipolar calcium-binding molecule and hints at a possible role in protein-protein interactions. The model provides information useful for further studies on the function of AMBN.

Rosuvastatin Promotes Osteoblast Differentiation and Regulates SLCO1A1 Transporter Gene Expression in MC3T3-E1 Cells

Rosuvastatin (RSV) is a synthetic statin with favourable pharmacologic properties including minimal metabolism, hepatic selectivity and enhanced inhibition of HMG-CoA reductase. An induction of osteoblast differentiation has been reported in vitro with lipophilic statins but not with RSV, which, like pravastatin, is relatively hydrophilic compared with other statins. To mediate its action, an active transport mechanism via solute carrier (SLC) transporters from the SLC16, SLC21/SLCO and SLC22 gene family - specifically Slc16a1, Slco1a1, Slco2b1 and Slc22a8 - may be present to allow effective entry in osteoblastic cells. In this study, we demonstrate that RSV induced osteoblast differentiation, as measured by increased BMP-2 gene expression and secretion, and ALP activity in MC3T3-E1 osteoblast cells, without significantly affecting cell proliferation within the concentration range of 0.001-10 µM. Low concentrations of RSV (0.001-0.01 µM) were protective against cell death whereas higher concentrations (10-100 µM) showed cytotoxicity. Moreover, MC3T3-E1 osteoblasts expressed high levels of Slco1a1 and Slc16a1 mRNA and low levels of Slco2b1 and Slc22a8 mRNA, when compared with kidney and liver tissues from mice. Slco1a1 gene expression increased 12-fold during osteoblast differentiation and was further regulated after RSV treatment. In conclusion, as for other statins, RSV promotes osteoblast differentiation, and also, demonstrated for the first time, regulates the expression of Slco1a1, which may constitute the transport system for RSV across the cell membrane in mature osteoblasts.

Enhanced Osteoblast Differentiation on Scaffolds Coated with TiO2 Compared to SiO2 and CaP Coatings

The aim was to compare the protein release from normal human osteoblasts (NHO) cultured on scaffolds with similar morphology but different coatings. Different ceramic coatings; TiO2, SiO2 and calcium phosphate (CaP); Ca9HPO4(PO4)5OH, were applied to porous TiO2 scaffolds prepared by polymer sponge replication. NHO were cultured on scaffolds in triplicates. The concentration of cytokines and Ca2+, and alkaline phosphatase (ALP) activity in the cell media was quantified. The secretion of osteopontin, osteoprotegerin, vascular endothelial growth factor and interleukin-6 was higher from NHO on TiO2 compared to SiO2 and CaP. The secretion from cells on the three scaffolds was, however, either similar or lower than the control cells cultured on plastic. The Ca2+ concentration was higher in cell media on CaP the first week, and no difference in ALP activity was observed. TiO2 coating induced a higher secretion of factors indicating enhanced osteoblast differentiation as compared to CaP and SiO2.

Hydrogen content in titanium and a titanium–zirconium alloy after acid etching

Dental implant alloys made from titanium and zirconium are known for their high mechanical strength, fracture toughness and corrosion resistance in comparison with commercially pure titanium. The aim of the study was to investigate possible differences in the surface chemistry and/or surface topography of titanium and titanium-zirconium surfaces after sand blasting and acid etching. The two surfaces were compared by X-ray photoelectron spectroscopy, secondary ion mass spectroscopy, scanning electron microscopy and profilometry. The 1.9 times greater surface hydrogen concentration of titanium zirconium compared to titanium was found to be the major difference between the two materials. Zirconium appeared to enhance hydride formation on titanium alloys when etched in acid. Surface topography revealed significant differences on the micro and nanoscale. Surface roughness was increased significantly (p<0.01) on the titanium-zirconium alloy. High-resolution images showed nanostructures only present on titanium zirconium.