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PubMed2006

[Preparation and properties of medical calcium phosphate cement].

The preparation of tetracalcium phosphate (Ca4(PO4)2O, TTCP)was studied. Then calcium phosphate cement (CPC) was prepared. The setting time, pH value, compressive strength, X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis of CPC were studied. The results show that TTCP containing small amount of CaO can be successfully attained heated at 1 500 degrees C for 6 h in vacuum condition. The initial setting time and final setting time of CPC is 4 min and 15 min, respectively. Its compressive strength is 20 MPa after 1-day immersion and 35 MPa after 7-day immersion. The pH value of the solution changes between 6.4 and 8.9. These properties can satisfy the clinical requirements of CPC. The final product of CPC is flake-like or needle-like hydroxyapatite (Ca5(P04)3OH, HA). The continuous network structure of HA appears in the microstructure, this leads to increase the strength of the material. This CPC can be used as bone substitute material.

Bone Cements↗
PubMed1999

Risk assessment of bovine spongiform encephalopathy transmission through bone graft material derived from bovine bone used for dental applications.

BACKGROUND: Several commercial products are currently available for clinical application as bone graft substitutes. These products can be broadly classified into two categories: synthetic and natural. Bovine bone is a popular source for several of the natural bone substitutes. The availability of bovine derived xenogenic bone substitutes has made it possible to avoid traumatic and expensive secondary surgery to obtain autogenous bone once thought essential for effective bone replacement. While autogenous bone still remains the undisputed "gold standard" in bone grafting, the realization that bone requirement in several clinical applications is as effectively met by xenografts has lead to their widespread use. But the convenience of using xenografts is tempered by the possibility of disease transmission from cattle to humans. The recent incidents of bovine spongiform encephalopathies (BSE) in humans have underscored this likelihood. In this paper, we report a risk analysis performed to assess the possibility of such disease transmission from a commercially available bone graft substitute (BGS) that is popularly used in clinical dentistry. METHODS: An extensive review of current literature on the status of risk assessment of BSE transmission was conducted, and two risk assessment models were identified as applicable to the present study. Risk assessment models developed by the German Federal Ministry of Health and by the Pharmaceutical Research and Manufacturers Association of America were applied to BGS. RESULTS: Results from the analyses conducted using both models showed that the risk of disease (BSE) transmission from BGS was negligible and could be attributed to the stringent protocols followed in sourcing and processing of the raw bovine bone used in the commercial product. CONCLUSIONS: Based on the risk analysis, it is evident that the risk of BSE infection from BGS is several orders of magnitude less than that posed by the risk of death related to, lightning, tornadoes, or similar remote events. However, this low risk can only be maintained as long as an effective and active risk management program is implemented in operations that involve processing xenogenic tissue for human use.

Algorithms↗
PubMed2004

Histomorphometry of human sinus floor augmentation using a porous beta-tricalcium phosphate: a prospective study.

Tricalcium phosphate (TCP) has been historically a well-accepted material for bone augmentation. We examined the use of a porous beta-TCP (100%) in a split mouth model for sinus floor augmentation. Five patients were treated bilaterally, receiving 1-2 mm-sized beta-TCP particles (Cerasorb) on one side (test side) and autologous chin bone particles on the other (control) side. Four other patients were treated with a unilateral sinus floor augmentation using 100% beta-TCP (no controls). Biopsies of the augmented sites were taken at 6 months. Histomorphometry measurements were carried out in order to quantify bone augmentation at test and control sides. The average bone volume (BV) formed in the augmented sinus at the control side was 41% (32-56%) and 17% (9-27%) in the test side when all nine patients were included (statistically significant, P=0.04). When only the five bilateral patients were included, mean BV of the test side was 19% (13-27%), which was also significantly different from the control side (P=0.009). Osteoid formation tended to be higher in the test side biopsies (1.3%) than in the controls (0.3%) (marginally significant, P=0.1), indicating ongoing bone formation in the TCP material. The amount of lamellar bone at the test side was less than half the amount in the control side, indicating that remodelling had only recently started in the TCP-augmented side. The resorption surface, however, did not differ significantly between the two sides. These histological results indicate that Cerasorb is an acceptable bone substitute material for augmentation of the maxillary sinus. Due to the osteoconductive, but not osteoinductive properties of this material, the rate of bone formation is somewhat delayed in comparison to autologous bone.

Adult↗
PubMed1998

Transmission FT-IR microspectroscopy of mineral phases in calcified tissues.

Fourier-transform infrared microspectroscopy (FT-IRM) was used to study bone mineralization processes in an in vivo model and in enamel in osteogenesis imperfecta. Finally, the ability of FT-IRM to map new bone formed in implanted macroporous calcium phosphate biomaterial from sections was reported for the first time. FT-IRM allowed the correlation of the microstructure of bone formation in the in vivo model with modifications in carbonate and phosphate environments of the mineral phases during maturation. FR-IRM analysis on enamel sections revealed changes in the mineral environment of carbonate and phosphate ions and probably in the size of enamel crystals. These modifications contributed to the fragility of enamel in osteogenesis imperfecta. The infrared functional group imaging of a part of implanted biomaterial and the bone ingrowth provided the visualization of chemical modifications occurring in biomaterial implants at 20 microns spatial resolution. The use of FT-IRM, in conjunction with appropriate sampling methods and data analysis should provide further insight into the molecular structure of mineral phases of calcified tissues and help to elucidate mineralization processes, skeletal disorders and properties of the biomaterials used as bone substitute.

Animals↗
PubMed1976

[Continuity resection in tumors of the tube bones, indication and technique].

The continuity resection of benign, semimalignant and malignant tumours above all of the long bones as well as defect bridging of bone substance with bone autograft is a serious ordeal for the patient, a technically difficult procedure with the possibility of various complications. Therefore the indication should be limited specifically. The technique of bridging plastics requires on adequate bone substitute of sufficient stability. Seven typical cases are represented and discussed.

Adolescent↗
PubMed1993

A ferric calcium phosphorous oxide (FECAP) ceramic for rebuilding bone.

A ferric-calcium-phosphorous oxide ceramic (FECAP) was fabricated for repairing traumatized bone. Seventy-two Sprague-Dawley rats were distributed into three groups: non-operated controls, sham-operated, and FECAP implanted animals. A 4 mm hole was drilled into the diaphysial ridge communicating with the medullary canal in the femurs of sham-operated and experimental animals. In the experimental animals, the hole was packed with 0.25 g of FECAP ceramic particles. Eight animals from each group were sacrificed at 15, 30, and 45 days. Morphological examination and analysis of blood data, body weights, and organ:body weight ratios indicated that FECAP ceramics can be used as non toxic bone substitutes.

Animals↗
PubMedDate not supplied

Free-standing nanogold membranes as supports for the growth of calcium phosphate crystals.

Current strategies for bone tissue regeneration focus on the development of implantable matrices that mimic biological tissues. Inorganic composites are of special interest for bone substitute applications. It is necessary to create an artificial three-dimensional scaffold-like porous material with certain geometrical structure to induce bone growth. We report here the growth of calcium phosphate crystals on free-standing carboxylic acid functionalized gold nanoparticle membranes. The gold nanoparticle membrane is synthesized by the spontaneous reduction of aqueous chloroaurate ions by a diamine molecule at a liquid-liquid interface. This membrane is robust and malleable, and most importantly, the gold nanoparticles in the membrane may be functionalized with suitable ligands. In this study, the amino acids aspartic acid and cysteine together with an aromatic bifunctional molecule, anthranilic acid, were used to modify the surface of the gold nanoparticles in the membrane. The free carboxylic acid groups on the gold nanoparticles further to functionalization with these molecules were then used to bind Ca(2+) ions and reacted with phosphate ions to yield calcium phosphate. The nature of the nanogold surface modifier directed the formation of either crystalline hydroxyapatite or amorphous calcium phosphate. The nanogold membrane thus suggests potential biomedical application as biocompatible implants and grafts.

Aspartic Acid↗
PubMed1992

New developments and advances in dental implantology.

Progress in laboratory investigation of the biologic basis of osseointegration coupled with an extensive world-wide clinical experience have created a better understanding of implant and tissue integration and has allowed expanded clinical applications. Techniques are now available to provide alloplastic tooth replacements that are biomechanically stable and predictable and provide adequate masticatory, phonetic, and esthetic function approximating that of the normal dentition. Computed tomography is now used to assist the surgeon in determining available recipient bone sites and to determine the exact three-dimensional positioning of endosseous implants in the jaw bone. Surgical management of bone volume deficiencies, utilizing grafting techniques with bone and bone substitutes and guided tissue regeneration with membrane barriers, have given previously rejected patients an opportunity to benefit from osseointegrated implants. Congenital and acquired bone defects may now be managed and reconstructed with techniques that include dental implant surgery. Osteoinductive and osteoconductive substances are now available to assist in accelerating healing and present great promise for future applications.

Alveolar Ridge Augmentation↗
PubMed2004

In vitro response of osteoblast-like and odontoblast-like cells to unsubstituted and substituted apatites.

Different types of calcium phosphate compounds [calcium-deficient apatite (CDA); beta-tricalcium phosphate (beta-TCP); biphasic calcium phosphate (BCP)] are commercially available for medical and dental applications as bone substitute materials. Most of the reported in vitro studies on cell-material interactions have used osteoblast-like cells. The purpose of this study was to investigate the in vitro response of osteoblast-like (MC3T3-E1) and odontoblast-like (MDPC23) cells on unsubstituted (HA) and substituted (F-substituted) apatites. MC3T3-E1 and MDPC23 were cultured in alpha-modified medium containing 10% fetal bovine serum, ascorbic acid (50 microg/mL) and beta-glycerophosphate (2 mM). The cells were seeded on pellets made from HA, and FAp (with low, medium, and high F concentrations). Cell morphology was observed after 7 and 14 days using scanning electron microscopy (SEM). Cell attachment and differentiation were determined from the DNA content, alkaline phosphatase (ALP) activity, and total collagen content. Pellet surface composition was characterized by using Fourier Transform infrared spectroscopy. MC3T3-E1 and MDPC23 cells on HA were normal in shape and in fusion but not on FAp. Results of this study showed that the pattern of cell proliferation of osteoblast-like cells was different from that of the odontoblast-like cells. This study suggests that cell morphology, fusion, and proliferation on biomaterial surfaces depend on cell type (osteoblast-like vs odontoblast-like cell) and biomaterial composition (unsubstituted vs substituted F-apatites).

Alkaline Phosphatase↗
PubMed2006

Bone-bonding ability of a hydroxyapatite coated zirconia-alumina nanocomposite with a microporous surface.

Using a combination of hydroxyapatite (HA) coating and microporous surface treatment, bone-bonding ability was given to composites of ceria-stabilized tetragonal zirconia and alumina (CZA), which possesses excellent mechanical and wear properties and phase stability. Four types of CZA plates (2 x 10 x 15 mm3) were prepared for this study, which were CZA with a polished surface (group 1), a microporous surface prepared by hydrofluoric acid and heat treatment (group 2), a microporous surface with a submicron HA coating prepared by alternately soaking the plate from group 2 in aqueous CaCl2/HCl and Na2HPO4 solutions (group 3), and a microporous surface with a 4-microm HA coating prepared by the biomimetic method, where the plates from group 3 were soaked in simulated body fluid (group 4). Plates were implanted into rabbit tibia, and after 4, 8, and 16 weeks, tensile testing and histological examination of the bone-implant interface were conducted. At 4 weeks, group 4 had superior bone-bonding ability compared with other implants, which was maintained at the later postimplantation times. This HA-coated CZA with a microporous surface has the possibility of clinical use as a bearing material in cementless joint prostheses or as a load-bearing bone substitute.

Aluminum Oxide↗
PubMed2000

Biomaterial developments for bone tissue engineering.

The development of bone tissue engineering is directly related to changes in materials technology. While the inclusion of materials requirements is standard in the design process of engineered bone substitutes, it is also critical to incorporate clinical requirements in order to engineer a clinically relevant device. This review presents the clinical need for bone tissue-engineered alternatives to the present materials used in bone grafting techniques, a status report on clinically available bone tissue-engineering devices, and recent advances in biomaterials research. The discussion of ongoing research includes the current state of osseoactive factors and the delivery of these factors using bioceramics and absorbable biopolymers. Suggestions are also presented as to the desirable design features that would make an engineered device clinically effective.

Biocompatible Materials↗
PubMed1994

Bone differentiation in porous hydroxyapatite in baboons is regulated by the geometry of the substratum: implications for reconstructive craniofacial surgery.

Previous studies have shown the morphogenesis of bone in a porous hydroxyapatite substratum when implanted intramuscularly in baboons. This hydroxyapatite-induced osteogenesis model was used to study the effect of geometry and pore size of the substratum on bone differentiation. Two distinct geometric configurations of porous hydroxyapatite of different pore size were obtained after hydrothermal conversion of the calcium carbonate exoskeleton of corals (genera Porites and Goniopora). Substrata were blocks of hydroxyapatite in rod configuration of 200- and 500-microns pore size and granular hydroxyapatite (400 to 620 microns in diameter) of 200- and 500-microns pore size. A total of 64 granular hydroxyapatite implants and 32 hydroxyapatite rods were implanted intramuscularly in 8 subadult male baboons (Papio ursinus). Specimens were harvested on days 60 and 90 and subjected to histologic and histomorphometric analysis. With the exception of an island of bone that formed in two implants of granular hydroxyapatite of 500-microns pore size, bone differentiation occurred only in blocks of hydroxyapatite in rod configuration of either pore size at both observation periods. The lack of bone formation in the granular hydroxyapatite indicates the critical role of geometry of the substratum in bone differentiation. These results in primates may have implications for the appropriate selection of porous bone substitutes for reconstructive craniofacial surgery in humans.

Animals↗
PubMed2005

[Vertical distraction osteogenesis of the alveolar process for implant treatment].

The rehabilitation of the chewing function of a patient is ultimately dependent on the quality and volume of the available jawbone. The vertical augmentation of the jawbone is often a challenge for the implanting dentist. Various methods, from transplanting autogenous bone through to the employment of bone substitute materials have been described and often controversially discussed. Vertical distraction offers an alternative to the pre-implantological augmentation of the vertically reduced bone. A technique which shows certain advantages over conventional augmentative methods.

Adolescent↗
PubMed2004

Biological and biophysical principles in extracorporal bone tissue engineering. Part II.

The aim of this review is to characterise the biological and biophysical background of in vitro bone tissue engineering. The paper focuses on basic principles in extracorporal engineering of bone-like tissues, considering parameters such as scaffold design, tissue construction, bioreactors, and cell stimulation in vivo and in vitro. Scaffolds have a key function concerning cellular invasion and bone formation. The intra-architectural scaffold geometry, as well as the scaffold material, play an important role in the process of bone regeneration. Various types of bioreactors have been tested for their utility in bone substitute fabrication that is clinically effective and reproducible. Sophisticated bioreactor systems are those that mimic the three-dimensional morphology and the mechanical situation of bones. Mechanical stimulation as well as other biophysical stimuli appear to be critical factors for proliferation and differentiation of bone cells and for bone mineral and structure formation. Furthermore an enhancement of bone regeneration by application of chemical stimulation factors is discussed.

Animals↗
PubMedDate not supplied

Correlation between hydroxyapatite osseointegration and Young's Modulus.

From the standpoint of hard tissue response to implant materials, calcium phosphate is probably the most compatible of materials known. During the last few years, much attention has been paid to hydroxyapatite and beta-tricalcium phosphate as potential biomaterials for a bone substitute. Good implantation of biomaterials in the skeleton is evidenced by an ability to reach full integration of the non-living implant with living bone. The aim of this study is to correlate hydroxyapatite osseointegration with Young's Modulus. Cylinders (5-6 mm in diameter) of these ceramics were packed into holes made in the femur diaphysis of a mature sheep. At 2, 4, 8, 12, 16, 20, 28, 36 and 48 weeks after the operation, samples of the bone/implant interface were embedded in polymethylmethacrylate. We used the PIXE method (Particles Induced X-rays Emission) to measure the distribution of mineral elements (Ca, P, Sr, Zn, Mn and Fe) at the bone/implant interface. At 4, 8, 12, 16, 20, 28, 36 and 48 weeks after implantation we studied Young's Modulus on a biopsy of the ceramic. Young's Modulus increased with time after implantation and is linked with biomaterials integration into cortical bone.

Animals↗
PubMed2001

Evaluation of the effect of three calcium phosphate powders on osteoblast cells.

The aim of the present study was to assess the effect of three calcium phosphate powders entering in the composition of bone substitute materials on osteoblast-cells activity. These powders were hydroxyapatite (HA) widely used as a biomaterial, nanocrystalline carbonate apatite (C A) very close to bone mineral crystals, and an experimental one: calcium phosphate cement-1 (CPC-1) composed of an amorphous Ca-P phase and brushite. The powders were physico-chemically characterized. The very reactive CPC-1 powder became transformed in cell culture medium: recrystallization of amorphous precursors and hydrolysis of brushite into poorly crystalline apatite occurred. Osteoblast-cells activity was evaluated: for low level of calcium phosphates (>100 microg/ml) CPC-1 enhanced proliferation and, to a lesser degree, differentiation on alkaline phosphatase activity. For 100 microg/ml of powders we observed a great alteration of biological activity of the osteoblasts: evaluation of proliferation indicated an inhibition for all samples, and a decrease of two differentiation markers: alkaline phosphatase activity and osteocalcin release were noticed, suggesting a down regulation due to the presence of large amount of mineral powder.

Journal Article↗
PubMed2002

Space radiation protection: comparison of effective dose to bone marrow dose equivalent.

In many instances, bone marrow dose equivalents averaged over the entire body have been used as a surrogate for whole-body dose equivalents in space radiation protection studies. However, career radiation limits for space missions are expressed as effective doses. This study compares calculations of effective doses to average bone marrow dose equivalents for several large solar particle events (SPEs) and annual galactic cosmic ray (GCR) spectra, in order to examine the suitability of substituting bone marrow dose equivalents for effective doses. Organ dose equivalents are computed for all radiosensitive organs listed in NCRP Report 116 using the BRYNTRN and HZETRN space radiation transport codes and the Computerized Anatomical Man (CAM) model. These organ dose equivalents are then weighted with the appropriate tissue weighting factors to obtain effective doses. Various thicknesses of aluminum shielding, which are representative of nominal spacecraft and SPE storm shelter configurations, are used in the analyses. For all SPE configurations, the average bone marrow dose equivalent is considerably less than the calculated effective dose. For comparisons of the GCR, there is less than a ten percent difference between the two methods. In all cases, the gonads made up the largest percentage of the effective dose.

Bone Marrow↗
PubMed1993

Bone-grafting materials in implant dentistry.

There are three classes of bone-grafting materials based upon the mode of action. Autogenous bone is an organic material and forms bone by osteogenesis, osteoinduction, and osteoconduction. Allografts such as demineralized freeze-dried bone are osteoinductive and osteoconductive and may be cortical and/or trabecular in nature. Alloplasts such as hydroxyapatite and tricalcium phosphate may be synthetic or natural, vary in size, and are only osteoconductive. They can be divided into three types based upon the porosity of the product and include dense, macroporous, and microporous materials. In addition, alloplastic materials may be crystalline or amorphous. These materials have different properties and therefore indications. The use of the three classes of materials in diverse combinations depends upon the size and topography of the bony defect. Small defects or defects with four walls of host bone can be repaired with alloplasts alone or allografts in combination with alloplasts. The loss of three or more bony walls mandates the addition of autogenous bone to the graft or the use of a small pore membrane. The larger the defect, the more autogenous bone is required. The different indications of bone substitutes are discussed as to their specific applications in implant dentistry.

Alveolar Bone Loss↗