Osseointegration of two types of titanium cylinders with geometric or trabecular microarchitecture: A nanotomographic and histomorphometric study.

Porous biomaterials promote osseointegration. We have prepared porous titanium cylinders by additive manufacturing from titanium beads. Two types of morphology were tested: cylinders with geometric pores or mimicking trabecular microarchitecture. Cylinders were decontaminated and cleaned by HF/HNO3 to remove unmelted balls. Surgical implantation in ewes was performed under general anesthesia and the animals were housed for 90 and 270days. The femoral condyles were collected and analyzed by nanoCT, embedded in pMMA and analyzed by histomorphometry. No significant difference was found in terms of bone volume or bone/titanium interface between the two types of cylinders. There was no evolution over time except for the mineralization rates which decreased, reflecting the effect of the aging of the animals. The influence of the pores (geometrical or "natural") did not influence osseointegration. HF/HNO3 etching treatments are effective on the outermost surfaces but do not seem to reach the central cavities of the samples. Finally, osseointegration seems to occur only in the few millimeters around the periphery of the implants and does not extend in the center. This is explained by the absence of stress transmission within the very rigid metal cylinders, preventing bone modeling and remodeling.

Bone lesions in systemic mastocytosis: Bone histomorphometry and histopathological mechanisms.

Osteoporosis is considered the most frequent skeletal manifestation of systemic mastocytosis (SM). We performed a retrospective analysis of sixty patients (37 males and 23 females) who underwent a bone biopsy in the assessment of SM or in the assessment of unexplained bone fragility. Thirty-three had simultaneously a bone marrow biopsy with a Jamshidi's needle; this sample was used for immunohistochemical analysis (tryptase, c-KIT. CD20, VCAM-1). Bone biopsy was realized in 42 cases in the assessment of SM to provide histologic proof of the disease and in 18 cases in the assessment of unexplained bone fragility and surprisingly revealed a SM. An increased bone turnover was observed in patients with SM with elevated eroded surfaces, osteoclast number and bone formation rate. In addition to nodules of mast cells (MC), a high number of MC was directly apposed on the trabeculae, affixed on the osteoblasts or the lining cells. The VCAM-1 adhesion protein recognizing α4ß7 and α4ß1 integrins may be a candidate to explain this particular adherence. One third of the bone marrow biopsies did not exhibit MC nodules or MC infiltration and led to a false negative diagnosis for SM. SM can be discovered in the assessment of fracture or osteoporosis. Transiliac bone biopsy allows for the diagnosis of the disease more accurately than bone marrow biopsy; it also provides a histomorphometric analysis of bone remodeling.

Skull fractures in forensic putrefied/skeletonised cases: The challenge of estimating the post-traumatic interval.

The objective of our study was to assess the reliability of the estimation of posttraumatic survival time (PTST) in forensic cases based on microCT and histology of putrefied/dry bone samples with comparison of initial macroscopic fracture classification performed during autopsy. Macroscopic morphological patterns of bone fracture are routinely used in forensic pathology and anthropology to distinguish between antemortem, perimortem and postmortem injuries. Based on macroscopic and microscopic analysis of six craniofacial fractures, our study results illustrate the need to complete macroscopical findings and initial fracture classification with microscopic analysis to avoid any inaccuracy. MicroCT has become a powerful technique to identify early bone healing signs but histology remains the gold standard to estimate the PTST and determine vital fracture based on hemorrhage marker. Raman microspectroscopy can identify a blood clot in the fracture line.

Hyaluronic Acid Stimulates Osseointegration of ß-TCP in Young and Old Ewes.

Cross-linked hyaluronic acid (HyAR) increases the local concentration of growth factors. We compared ß-TCP osseointegration in old and young ewes with/without HyAR addition. A blind tunnel was drilled on the medial femoral condyle of each knee in nine young and nine old ewes and was filled with ß-TCP, ß-TCP + HyAR or left unfilled. Double labeling with calcein allowed histodynamic analysis. Ewes were sacrificed at 84 days and the knees were harvested. MicroCT provided histomorphometric parameters: trabecular bone volume, residual volume of biomaterial. Histodynamic parameters were: mineralization rate, mineralized surfaces, bone formation rate. A non-parametric ANOVA and post hoc test analyzed differences between subgroups. Osseointegration of ß-TCP was similar in the aged/young grafted groups. Trabecular bone volume was significantly increased versus ungrafted animals (p < 0.001). There were no significant difference for bone volume, residual volume of biomaterial and histodynamic parameters when a single parameter was considered but additional effects of ß-TCP and HyAR were evidenced by 3D analysis. Addition of HyAR to ß-TCP does not significantly increase bone volume but tends to increase histodynamic parameters. However, considering the reduction of osteoblastic activity in aged animals, ß-TCP, and HyAR boosts osteoblastic activity. HyAR leads to an equivalent response between young and old animals.

In vivo erosion of orthopedic screws prepared from nacre (mother of pearl).

BACKGROUND: Biodegradable biomaterials have been proposed to prepare orthopedic devices. Nacre is a natural aragonitic material made of calcium carbonate and is bioerodible. WORKING HYPOTHESIS: We postulated that nacre is biodegradable without provoking bone erosion and favors bone apposition. MATERIAL AND METHODS: We prepared orthopedic screws from nacre of the giant oyster Pinctada maxima. Threaded screws (3.5mm diameter) were implanted in 6 ewes in the upper tibial metaphysis (3 to 4 screws per animal). Their trajectory was transcortical and intramedullary to the opposite cortex. Animals were kept for 3months (n=2) and 6 months (n=4). They did not develop local inflammation. Before euthanasia, they received a double calcein labeling. Bone samples were analyzed by X-ray nanotomography and histology after embedding in poly(methyl methacrylate). The fractal dimension of the screw profiles (measured by the box-counting method) was used to quantify surface erosion. RESULTS: 3D nanotomography showed a gradual erosion of the threads, which was confirmed by a decreased fractal dimension. Histologically, multinucleated cells (non-osteoclastic appearance) were visible at the surface of the screws. No ruffled border was seen in these cells but they had extensions creeping in the organic matter between the aragonite tablets. Bone apposition was noted in the transcortical path of the screws with limited osteoconduction at the endosteum. Mineralization rate was increased in these zones composed of woven bone in contact with the nacre. DISCUSSION AND CONCLUSION: Screws prepared from nacre have the advantage of an in vivo resorbability by macrophage-derived cells and an osteoconductive apposition in contact with the material without triggering a local inflammatory reaction.

Does milling one-piece titanium dental implants induce osteocyte and osteoclast changes?

One-piece dental implants avoid adverse effects sometimes associated with the traditional implant-abutment interface and may provide a suitable alternative to two-piece implants; however, one-piece implants often need in situ milling, which may exacerbate cell apoptosis from excessive heat at the bone-implant interface and induce secondary crestal bone loss. Twelve implants were placed in the metaphyses of two sheep under general anesthesia. Six implants were milled with a diamond bur while the other six implants remained intact. Animals were euthanized after four days, and bone blocks were harvested. Bone samples were studied without decalcification. Osteocytes were stained with Hoechst 33342 and osteoclasts by the TRAcP reaction. Both cell types, in the cortical and trabecular bone around the implant's cervical region, were counted utilizing morphometric methods. Values were compared to areas at a distance from the cervical region. No difference was observed between milled and unmilled implants, which suggested that the amount of generated heat did not provoke osteocyte loss or induce osteoclastogenesis. Intraoral abutment preparations did not increase cellular apoptosis at the bone-implant interface after four days in the ovine model.

Measurement by vertical scanning profilometry of resorption volume and lacunae depth caused by osteoclasts on dentine slices.

The resorption pit assay is classically used to evaluate osteoclast activity on bone or dentine slices that can be eroded by these cells. Two different types of cells were generated from peripheral blood mononuclear cells cultured in the presence of M-CSF + sRANKL or with M-CSF + LPS. At the end of the culture period (21 days), cells were discarded and the dentine slices stained with toluidine blue and examined with an NT9100 Wyco vertical scanning profilometer. The images of the dentine surface were corrected for tilt and the eroded volume was calculated on the whole images. The depth of the eroded pits was determined. The data files were used to reconstruct the surface of the slices by standardizing the ground level to compare both conditions. Osteoclasts generated with M-CSF + sRANKL were capable of resorbing a more important volume than those generated with M-CSF + LPS. In addition, the formers were able to resorb the dentine matrix more deeply. Data provided by the microscope were used to reconstruct three-dimensional images of the dentine slices with pseudo colours varying with the depth of erosion. Vertical scanning profilometry, a technique used to measure the roughness of polished or etched surfaces in metallurgic industry, can be used to accurately measure the eroded volume and the mean erosion depth done by osteoclasts in the resorption pit assay.

Osteopontin is histochemically detected by the AgNOR acid-silver staining.

Silver nitrate staining of decalcified bone sections is known to reveal osteocyte canaliculi and cement lines. Nucleolar Organising Regions (NOR) are part of the nucleolus, containing argyrophilic proteins (nucleoclin/C23, nucleophosmin/B23) that can be identified by silver staining at low pH. The aim of this study was to clarify the mechanism explaining why AgNOR staining also reveals osteocyte canaliculi. Human bone and kidney sections were processed for silver staining at light and electron microscopy with a modified method used to identify AgNOR. Sections were processed in parallel for immunohistochemistry with an antibody direct against osteopontin. Protein extraction was done in the renal cortex and decalcified bone and the proteins were separated by western blotting. Purified hOPN was also used as a control. Proteins were electro-transferred on polyvinylidene difluoride membranes and stained for AgNOR proteins. In bone, Ag staining identified AgNOR in cell nuclei, as well as in osteocyte canaliculi, cement and resting lines. In the distal convoluted tubules of the kidney, silver deposits were also observed in cytoplasmic granules on the apical side of the cells. Immunolocalization of osteopontin closely matched with all these locations in bone and kidney. Ag staining of membranes at low pH revealed bands for NOR proteins and 56 KDa (kidney), 60KDa (purified hOPN) and 75 KDa (bone) bands that corresponded to osteopontin. NOR proteins and osteopontin are proteins containing aspartic acid rich regions that can bind Ag. Staining protocols using silver nitrate at low pH can identify these proteins on histological sections or membranes.

Osteopontin is an argentophilic protein in the bone matrix and in cells of kidney convoluted tubules.

Nucleolar organising regions (NOR) are part of the nucleolus, containing argyrophilic proteins (nucleoclin/C23, nucleophosmin/B23). They are identified by silver staining at low pH. The method also reveals osteocyte canaliculi and cement lines and granules in the cytoplasm of kidney cells in locations that mimic osteopontin distribution. Human bone and kidney sections, benign and lymphomatous pleural effusions were processed for silver staining to identify AgNOR. Sections were processed in parallel for immunohistochemistry with an antibody direct against osteopontin. In pleural effusions, AgNORs were found increased in the nuclei of lymphoma cells. In bone, Ag staining identified AgNOR in cell nuclei, as well as in osteocyte canaliculi, cement and resting lines. In the distal convoluted tubules of the kidney, silver deposits were also observed in cytoplasmic granules on the apical side of the cells. Immunolocalization of osteopontin closely matched with all these locations in bone and kidney. NOR proteins and osteopontin are proteins containing aspartic acid rich repeats that can bind Ag. Staining protocols using silver nitrate at low pH can identify these proteins on histological sections. AgNOR is a useful histochemical method to identify osteopontin in bone sections.

Polymethylmethacrylate (PMMA) as an embedding medium preserving tissues and foreign materials encroaching in endovascular devices.

Problems of displacement, poor healing, degradation of the polymers and corrosion of the metallic frame in endovascular devices still require in-depth investigations. As the tissues and the foreign materials are in close contact, it is of paramount importance to efficiently investigate the interfaces between them. Inclusion in polymethymethacrylate (PMMA) permits us to obtain thin slides and preserve the capacity to perform the appropriate stainings. An AneuRx prosthesis was harvested in bloc with the surrounding tissues at the autopsy of a patient 25 months post deployment in a 5.7 cm diameter AAA and sectioned in the direction of the blood flow in two halves. A cross-section of the encapsulated distal segment together with the surrounding aneuryshmal sac was embedded in polymethylmethacrylate (PMMA). Further to complete polymerization, slices of the specimen were cut on a precision banding saw under coolant. They were affixed onto methacrylate slides with a UV cured adhesive. Binding and polishing were done on a numeric grinder and slices 25 to 30 microm in thickness were stained with toluidine blue prior to observation in light microscopy. Additional slices were prepared for scanning electron microscopy and X-ray energy dispersive spectrometry for determination of the elemental composition of the Nitinol stent. The aortic wall did not demonstrate complete integrity along with its circumference. Some areas of rupture were noted. The content of the sac was heavily shrunk and was mostly acellular. The walls of the device were very well encapsulated. The PMMA embedding permitted the polyester wall, the Nitinol wire and the collagen to keep in close contact. Scanning electron microscopy involved backscattered electrons and confirmed the corrosion the Nitinol wire at the boundary with living tissues. Based upon the results obtained, we believe that PMMA embedding is the most appropriate method to process endovascular devices for histological and material investigation. Needless to say, that paraffin embedding would have not been feasible for such a big size specimen involving different materials.

The in vivo calcification capacity of a copolymer, based on methacryloyloxyethyl phosphate, does not favor osteoconduction.

Polymers can be interesting alternatives to bone grafts; they must present suitable mechanical and osteoconductive properties. Biomimetic properties may be a key factor for the recognition by bone cells. Methacryloyloxyethyl phosphate (MOEP) was found to enhance hydroxyapatite deposition. The copolymer containing MOEP and 1-vinyl-2-pyrrolidinone (50-50%) binds large amounts of calcium. Particles of the copolymer were used to fill large cranial bone defects in the rat. After a 12-week healing period, the animals were euthanized and the skulls examined by X-ray, histology, and electron microscopy (EM). The high phosphate content of the polymer conferred a marked calcium-binding capacity, and the particles were heavily calcified. They were embedded in a light fibrous stroma containing numerous capillaries and multinucleated giant cells. The osteoconductive properties were poor: only few trabeculae developed centripetally from the margins of the defects. There was no bone bonding and no osteoblast on the surface of the calcified material. Backscattered EM revealed that the degree of calcification was homogeneous in all particles. Calcium-phosphorus calcospherites were never observed. The material appeared to trap calcium but to impair nucleation because only small hydroxyapatite tablets were occasionally observed. Polyphosphated materials do not represent a suitable source of potentially usable bone substitutes.

[Study of two types of dental implants for immediate loading (expansion implants and locking pin implants) in the Beagle dog]. / Etude de deux types d'implants dentaires pour la mise en charge immediate (implants à expansion et à clavettes) chez le chien Beagle.

Titanium implants have become a treatment of choice for total or partially edentulous patients. The method, however, requires a double surgical time and the placement of the dental prosthesis after a healing phase of 3 to 6 months during which the patients have a toothless mandible with the top of the implants emerging at the gengiva. Immediate loading of standard implants is responsible for micromotions which induce implant failure. New designs of implants would allow an immediate anchoring in the bone, would prevent the shearing forces and would precociously authorize the setting of the prosthesis. We made an experimental study in the Beagle dog. After partial tooth removal, two types of implants were placed (expansion implants and locking pin implants). After 2 weeks, the implants were covered with a gold-palladium prosthesis and left in place during 12 weeks. After sacrifice, a study by resonance frequency (ISQ) and histomorphometry was done. The two types of implants were covered by the same quantity with bone (volume and interface) without interposition of fibrous tissue. The locking pin implants were associated with an increase in the ISQ parameter of stability, higher than that of the expansion implants. The locking pin implant, tested in the dog which has a chewing function close to man, appears interesting for the immediate loading with dental prosthesis.

Non-connected versus interconnected macroporosity in poly(2-hydroxyethyl methacrylate) polymers. An X-ray microtomographic and histomorphometric study.

Poly(2-hydroxyethyl methacrylate) (pHEMA) has potentially broad biomedical applications: it is biocompatible and has a hardness comparable to bone when bulk polymerized. Porous biomaterials allow bone integration to be increased, especially when the pores are interconnected. In this study, three types of porogens (sugar fibers, sucrose crystals, and urea beads) have been used to prepare macroporous pHEMA. The pore volume and interconnectivity parameters of the porosity were measured by X-ray microtomography and image analysis. Sucrose crystals, having a high volumetric mass, gave large pores that were located on the block sides. Urea beads and sugar fibers provided pores with the same star volume (2.65 +/- 0.46 mm3 and 2.48 +/- 0.52 mm3, respectively) but which differed in interconnectivity index, fractal dimension, and Euler-Poincarés number. Urea beads caused non-connected porosity, while sugar fibers created a dense labyrinth within the polymer. Interconnectivity was proved by carrying out surface treatment of the pHEMA (carboxymethylation in water), followed by von Kossà staining, which detected the carboxylic groups. Carboxymethylated surfaces were observed on the sides of the blocks and on the opened or interconnected pores. The disconnected pores were unstained. Macroporous polymers can be prepared with water-soluble porogens. X-ray microtomography appears a useful tool to measure porosity and interconnectedness.

Enhanced bone integration of implants with increased surface roughness: a long term study in the sheep.

OBJECTIVES: This study evaluated the quality and the remodeling of bone around commercially pure titanium implants after 3, 6, 12 and 18 month implantation periods in the sheep. METHODS: Twelve animals were implanted in the cortico-trabecular areas of both femurs. Each femur received four implants with a rough surface (type 1) in the right femur and four with a smooth surface (type 2) in the left one. Bone blocks containing the implants were studied by histomorphometry on undecalcified specimens. The amount of bone around implants was measured (bone volume, fractional woven bone volume, bone thickness, contact interface) together with osteoblastic activity (mineral apposition rates, bone formation rates) and resorption activity (eroded surfaces). RESULTS: No significant differences could be observed for the two types of implants between 3 and 6 months. At 12 and 18 months, bone volume and contact interface were still increasing and there was always a tendency for type 1 implants to be associated with higher values. On the contrary, mineral apposition rate, bone formation rates and eroded surfaces decreased in the referent area in contact with the implant; this phenomenon of 'return to the normal' was more evident with type 1 implants. The remodeling process appears to increase bone quality and bone-titanium interface around implants in long term periods. CONCLUSIONS: The net bone quantity necessary to immobilize implants is obtained rapidly but the adapting process to mechanical strength can lead to a small but persistent increase in bone volume around implants. Although the differences between type 1 and type 2 implants were often small or statistically insignificant, the rougher type 1 implants seemed to be associated with stronger bone response.

Effects of negatively charged groups (carboxymethyl) on the calcification of poly(2-hydroxyethyl methacrylate).

Poly(2-hydroxyethyl methacrylate) (pHEMA) has potentially wide biomedical applications: it is biocompatible, allows immobilization of cells or bioactive molecules and has a hardness comparable to bone. We previously reported that immobilization of alkaline phosphatase (AlkP) in pHEMA can initiate mineralization in a manner that mimics the calcification of cartilage and woven bone. Because numerous proteins known to initiate mineralization possess acidic species, we have modified the neutral electrical surface of pHEMA by carboxymethylation (CM). We have studied the effects of these negative groups on the calcification process in vitro. Calibrated pellets of pHEMA were prepared and carboxymethylated by soaking with 0.5 M bromoacetic acid in 2 M NaOH. Pellets of pHEMA, pHEMA-AlkP and pHEMA-CM were incubated during 5, 10 and 15 days in two types of body fluid: normal (1X) and 1.5X concentration of ions. Nodules of hydroxyapatite developed on pHEMA-AlkP and pHEMA-CM but not on pHEMA. Hydroxyapatite crystals were dissolved in HCl allowing calcium to be dosed. CM significantly increased the amount of deposited Ca by 1.8 folds in the 1X fluid and 15.8 folds in the 1.5X fluid. The presence of AlkP considerably increased the amount of deposited Ca: 25.9 folds in 1X and 23.3 in 1.5X. ROS 17/2.8 osteoblast-like cells were seeded on the materials and examined by confocal microscopy after phalloidin staining. Cells grown on pHEMA alone appeared round, while cells grown on the crystals deposited on the pHEMA-CM or pHEMA-AlkP were flattened. The presence of AlkP favours the mineralization process more than the existence of surface negative groups on the polymer. Cells preferentially adhere to the polymer when hydroxyapatite crystals were developed.

The early remodeling phases around titanium implants: a histomorphometric assessment of bone quality in a 3- and 6-month study in sheep.

The purpose of this study was to evaluate the quality of the bone matrix around commercially pure titanium implants at 3 and 6 months postplacement in sheep. Implants were placed in the corticotrabecular areas of both femurs in 6 animals. Each animal received 4 Euroteknika implants in the right femur and 4 Nobel Biocare implants in the left femur. Bone blocks containing the implants were studied undecalcified after being embedded in methylmethacrylate. Sections were stained with toluidine blue and basic fuchsin. The amount of bone around the implants, the contact interface between the implant and bone, and the mineral apposition rates were measured. The fractional amount of woven bone could be quantified because of its high glycosaminoglycan content. No differences could be observed between the 2 types of implants. Total bone volume did not increase around both types of implants between 3 and 6 months, indicating that ankylosis was rapidly achieved. In contrast, in the area in contact with the implant, the bone-titanium interface drastically increased and the mineral apposition rate decreased. The fractional volume of woven bone around implants was considerably reduced after 6 months. Bone quality around implants was improved at 6 months (volume of woven bone near zero), and true osteonic structures were observed in close contact with titanium. The remodeling process appeared to improve bone quality and increase the bone-titanium interface around implants, while the net bone quantity necessary to immobilize implants was achieved rapidly and remained unchanged.

Shape and orientation of osteoblast-like cells (Saos-2) are influenced by collagen fibers in xenogenic bone biomaterial.

The surface topography of a substratum has been shown to influence the growth and morphology of cells in culture. In this study, human osteoblast-like cells (Saos-2) were cultured on two types of xenogenic biomaterials obtained from bovine bone. Both biomaterials were similar in architectural organization and surface topography, but they differed in matrix components. The first one was characterized by preservation of the mineralized collagen matrix, and the second by complete deproteinization which only preserved the mineral phase. Cells cultured at the surface of both biomaterials were observed using scanning electron microscopy. The beta 1-integrin subunit, known to bind cell and collagen, is the major integrin of the osteoblast. It was localized using immunogold in transmission electron microscopy. At the surface of the collagen-containing matrix, cells exhibited an elongated shape and oriented axis parallel to the underlying collagen bundles. The beta 1-integrin subunit was localized at the outer surface of cells, in close association with collagen and at the contact points between cells and biomaterials. In contrast, at the surface of the single mineral matrix, cells were round shaped with random disposition. Gold particles were found around the cells with no specific relation to the biomaterial. These results strongly suggest that the chemical nature of the surface of a bone biomaterial directly influences adhesion process, shape, and spatial organization of cultured osteoblastic cells.

[Type I collagen in xenogenic bone material regulates attachment and spreading of osteoblasts over the beta1 integrin subunit]. / Typ-I-Kollagen im xenogenen Knochenmaterial reguliert Anbindung und Verbreitung von Osteoblasten über die beta 1-Integrin-Untereinheit.

Xenogenic bone biomaterials have been proposed as an alternative to autografts or allografts in human bone restoring or in complement of prosthetic surgery. When appropriate treatments were applied, immunological, inflammatory, bacteriological or virological adverse responses can be prevented. However, these treatments may interact with type I collagen, the major component of the organic bone matrix. Type I collagen can bind osteoblasts via specific cell surface receptors, the integrins. In this work, two different xenogenic biomaterials were studied. Both biomaterials have a bovine bone origin. They displayed similar architectural organization with connected plates and rods and similar surface topography and roughness. They differed by the presence or not of collagen type I. The first one was characterized by preservation of the type I collagen matrix associated with spindle-shaped hydroxypatite crystals and the second was solely composed by heat-modified apatite crystals. Osteoblast-like cells (Saos-2) were cultured on both biomaterials and examined in scanning and transmission electron microscopy after 7 and 14 days. Both biomaterials were cytocompatible as demonstrated by good ultrastructural cell preservation. (1) At the surface of the collagen containing biomaterial, cells were elongated in shape and oriented according to the trabecular architecture and to the superficial collagen network. After 14 days of culture, cells were confluent and the biomaterial surface was hidden by the cell sheet. The beta 1 integrin subunit was detected by immunogold in transmission electron microscopy in close relationship with the superficial collagen fibres of the biomaterial and with the outer cell surface. When cultures were carried out in presence of anti beta 1 integrin subunit, cells were packed and piled up with lack of specific orientation. (2) At the surface of the deproteinized biomaterial, cells were globular without specific disposition and often partially attached to the surface. After 14 days of culture, large areas of the biomaterial surface remained uncovered. Anti beta 1 subunits conjugated with gold particles were detected around the cells but with no specific association with the deproteinized biomaterial. These results strongly suggest that presence of type I collagen fibres in the matrix of a bone biomaterial is of major interest to determine cell attachment, spreading and orientation via interaction between type I collagen and beta 1 integrin subunit of osteoblasts.

Evolution of the bone-titanium interface on implants coated/noncoated with xenogeneic bone particles: quantitative microscopic analysis.

Titanium cylinders having a sandblasted surface were implanted in holes drilled in the internal condyles of rabbit femurs. The right side received a titanium implant coated with xenogeneic bone particles and the left side received a titanium cylinder alone and was used as control. The femoral extremities were removed at 1, 2, and 3 months postsurgery and embedded undecalcified in methacrylic resins. Sections were studied by quantitative analysis and the interface contact between bone and titanium was measured at two microscopic magnifications due to the fractal dimension of this parameter. In addition the amount of bone volume in a given referent volume provided automatically by the image analyzer was obtained. No differences could be evidenced between the two series of implants, supporting the view that xenogeneic particles were ineffective in improving the attachment of bone to the implant. The bone-to-implant interface measured at the low magnification reflected the anchorage of the implant. In both series a progressive increase upon time of the bone-to-implant interface at the highest microscopic magnification evidenced the importance of late remodeling changes responsible for bone bonding and the fractal characteristics of this interface, related to surface quality of the implant responsible for stress transfer.

[Electron microscopic study of a macroporous calcium phosphate ceramic implanted in an osseous site]. / Etude en microscopie électronique d'une céramique phosphocalcique macroporeuse implantée en site osseux.

Cellular and tissular responses to intraosseous graft of a macroporous calcium phosphate ceramic was studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Twelve specimens were implanted in 6 rabbits (tibiae), taken at day 14 after implantation and processed either for TEM (6 samples) or SEM (6 samples). As early as day 14 after implantation osteogenesis so that resorption of the newly formed bone and of the biomaterial, were observed at the surface of the ceramic, inside the macropores. Osteoblasts were clearly visible and well differentiated with abundant rough endoplasmic reticulum and large Golgi zone. The resorption processes were associated with 2 types of multinucleated cells. Based on ultrastructural observations (cellular characteristics and measurement of the microporosity) it appears that incompletely differentiated osteoclast was the major cell responsible of the biodegradation of the ceramic. These results suggest that the cellular events occurring at the surface of a macroporous calcium phosphate ceramic are similar to that observed in physiological bone remodelings.