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PubMed1999

Short-term effects of mineral particle sizes on cellular degradation activity after implantation of injectable calcium phosphate biomaterials and the consequences for bone substitution.

This in vivo study investigated the influence of two calcium phosphate particle sizes (40-80 microm and 200-500 microm) on the cellular degradation activity associated with the bone substitution process of two injectable bone substitutes (IBS). The tested biomaterials were obtained by associating a biphasic calcium phosphate (BCP) ceramic mineral phase and a 3% aqueous solution of a cellulosic polymer (hydroxypropylmethylcellulose). Both were injected into osseous defects at the distal end of rabbit femurs for 2- and 3-week periods. Quantitative results for tartrate-resistant acid phosphatase (TRAP) cellular activity, new bone formation, and ceramic resorption were studied for statistical purposes. Positive TRAP-stained degradation cells were significantly more numerous for IBS 40-80 than IBS 200-500, regardless of implantation time. BCP degradation was quite marked during the first 2 weeks for IBS 40-80, and bone colonization occurred more extensively for IBS 40-80 than for IBS 200-500. The resorption-bone substitution process occurred earlier and faster for IBS 40-80 than IBS 200-500. Both tested IBS displayed similar biological efficiency, with conserved in vivo bioactivity and bone-filling ability. Differences in calcium phosphate particle sizes influenced cellular degradation activity and ceramic resorption but were compatible with efficient bone substitution.

Acid Phosphatase↗

PubMed2006

Effects of in vitro bone formation on the mechanical properties of a trabeculated hydroxyapatite bone substitute.

This study was designed to test the hypothesis that the mechanical properties of a trabecular bone substitute can be enhanced through in vitro tissue formation. Our specific objectives were to (1) determine the effects of in vitro marrow stromal cell-mediated tissue deposition upon a trabeculated hydroxyapatite scaffold on the strength and toughness of the resulting bone substitute; and (2) identify and characterize regions of newly deposited matrix and mineral. This work provides a basis for future investigations aimed at transforming a brittle hydroxyapatite scaffold into an osteoinductive, biomechanically functional implant through in vitro bone deposition. As hypothesized, the mechanical properties of the trabecular bone substitutes were significantly enhanced by in vitro tissue formation. As a result of cell seeding and a 5 week culture protocol, mean strength increased by 85% (p = 0.008) and energy to fracture increased by 130% (p = 0.003). Accompanying the enhancement of mechanical properties was the deposition of significant amounts of bone matrix and mineral. Fluorescence imaging, scanning electron microscopy, electron probe microanalysis, and nanoindentation confirmed the presence of bonelike mineral with Ca/P ratio, modulus, and hardness similar to that within human and rat trabecular bone tissue. This new mineralization was found to exist within a newly deposited parallel-fibered matrix both encasing and bridging between scaffold trabeculae. Taken as a whole, our results establish the feasibility of the production of an osteoinductive hydroxyapatite-based trabecular bone substitute with mechanical properties enhanced through in vitro bone deposition.

Animals↗

PubMed2005

Osteogenic potential of injectable tissue-engineered bone: a comparison among autogenous bone, bone substitute (Bio-oss), platelet-rich plasma, and tissue-engineered bone with respect to their mechanical properties and histological findings.

Recently, tissue engineering has become available as a regenerative treatment for bone defects. However, the evaluation of its success is limited to histological analysis, and its effects on mechanical hardness remain to be investigated. This study investigated mechanical strength in support of histological findings, specifically for tissue-engineered bone with mesenchymal stem cells (MSCs) and platelet-rich-plasma (PRP). Initially, teeth were extracted, and bone defects on both sides of the mandible were prepared with a trephine bar. The defects were implanted by using the following graft materials: 1) PRP, 2) PRP and dog MSCs (dMSCs), 3) autogenous bone (PCBM), 4) bone substitute (Bio-Oss), and 5) control (defects only). After 2, 4, 8, and 12 weeks of implantation, the defects were histologically assessed to examine their mechanical properties. According to histological observations, the dMSCs/PRP groups had well-formed mature bone compared with the control (defects only), Bio-Oss, and PRP groups. The Vickers hardness test values were 8 (control), 9 (PRP), not detected (Bio-Oss), 11 (PCBM), and 17 (dMSCs/PRP) after 2 weeks. Therefore, tissue-engineered bone can be used for early stage bone regeneration from the viewpoint of histology and mechanical properties.

Animals↗

PubMed2006

Novel injectable calcium phosphate/chitosan composites for bone substitute materials.

In this study, a novel injectable bone substitute material was developed which consists of chitosan, citric acid and glucose solution as the liquid phase, and tricalcium phosphate powder as the solid phase. This material was moldable because of its paste consistency after mixing. We used four groups of cement to investigate the mechanical properties and biocompatibility of the new biomaterial in vitro, which were named group A (10% citric acid), B (15% citric acid), C (20% citric acid) and D (25% citric acid). The setting times of the cements were 5-30 min. X-ray diffraction analysis showed that the products were hydroxyapatite (HA) and dicalcium phosphate anhydrous. When the concentration of citric acid was increased, the compressive strength of specimen increased. Through the simulated body fluid test, we observed the material was bioactive. Group D could induce Ca and P ions to deposit the surface group D quickly. These results indicated that the concentration of citric acid in the liquid component affected the mechanical properties and bioactivity of cements. The cell cultivation test showed that the cytocompatibility of the new biomaterial was good. The method for preparing the novel bone substitute material is simple. The starting material is more readily available and cheaper than HA, poly(methyl methacrylate), and so on. The cement could have good prospects for medical application.

Animals↗

PubMedDate not supplied

Tissue reaction and material characteristics of four bone substitutes.

The aim of the present study was to qualitatively and quantitatively compare the tissue reactions around four different bone substitutes used in orthopedic and craniofacial surgery. Cylinders of two bovine bone substitutes (Endobon and Bio-Oss) and two coral-derived bone substitutes (Pro Osteon 500 and Interpore 500 HA/CC) were implanted into 5-mm bur holes in rabbit tibiae. There was no difference in the amount of newly formed bone around the four biomaterials. Interpore 500 HA/CC resorbed completely, whereas the other three biomaterials did not undergo any detectable biodegradation. Bio-Oss was osseointegrated to a higher degree than the other biomaterials. Material characteristics obtained by diffuse reflectance infrared Fourier transform spectrometry analysis and energy-dispersive spectrometry did not explain the differences in biologic behavior.

Animals↗

PubMedDate not supplied

Histologic findings in sinus augmentation with autogenous bone chips versus a bovine bone substitute.

PURPOSE: The aim of this study was to compare a bovine bone substitute (Bio-Oss) to autogenous bone with respect to its value as a material for sinus augmentation. MATERIALS AND METHODS: In 10 beagle dogs 12 months of age, the 3 maxillary premolars were extracted on both sides. Six weeks later, 2 cavities of predefined size were produced in the region of the nasal cavity. The antral window was 25 mm long and had a vertical extension of 7 mm. Two Frialit-2 implants (3 x 8 mm) were placed in each bone defect (n = 20). Every implant was primarily stable because of fixation in native bone. In each maxilla, 1 bone defect was filled with autogenous bone harvested from the mandible and 1 was filled with Bio-Oss (material selected at random). The animals were sacrificed at 90 and 180 days, and histologic specimens were examined and the results subjected to statistical analysis by the Wilcoxon test for paired observations. RESULTS: No healing problems were observed. Histologically, after 90 days the volume of the augmentation showed a reduction of 14.6 +/- 4.4% within the Bio-Oss group and 3.8 +/- 2.5% in the group with autogenous bone. Bone-implant contact of 52.16 +/- 13.15% in the Bio-Oss group and 60.21 +/- 11.46% in the autogenous bone group was observed. At 180 days, the Bio-Oss group showed bony ingrowth of the substitute, whereas in the autogenous group a differentiation from original bone could no longer be made. The volume reduction was 16.5 +/- 8.67% in the Bio-Oss group and 39.8 +/- 16.14% in the autogenous group. Bone-implant contact of 63.43 +/- 19.56% in the Bio-Oss group and 42.22 +/- 12.80% in the autogenous bone group was measured. DISCUSSION AND CONCLUSION: The results indicated that because of the nonresorptive properties of the bone substitute Bio-Oss, regeneration of the defects is achievable. It was demonstrated that the bone substitute seemed to behave as a permanent implant. The volume of the area augmented by autogenous bone decreased over the observation period.

Alveolar Ridge Augmentation↗

PubMed1998

[Pyrost, a spongious, mineral bone substitute. Experimental bases and 13-year clinical experience in over 1000 cases].

In different animal investigations Pyrost demonstrated osteoconductive and osteostimulative effects. In ectopic tissues and especially in conditions of low osteogenetic potency, the combination of Pyrost and autogenic bone marrow effects bone formation. In a clinical prospective study, Pyrost was implanted in 1117 cases in the following indications: Donor site defects after bone transplantation, bone defects after tumor resection, revision of THA, acetabuloplasty, fracture treatment, pseudarthrosis and lengthening osteotomy, spondylodesis. In 87.3% the regeneration of the bone defects was complete, in 8% a partial regeneration was found. Excessive bone formation took place in 2.7%, insufficient regeneration in 2.0% in cases of instability or infection. According to the clinical results Pyrost is a suitable bone substitute in small bone defects and it is a valuable completion to the autogenic bone graft in large defects. In disadvantageous bone bed Pyrost has to be augmented with bone marrow and in large segmental defects the combination with autogenic bone grafts is recommendable. Presupposition for the application of bone substitutes like Pyrost in large defects is a sufficient primary stability of the bone bed. The application in infected tissue is not favorable.

Animals↗

PubMed2004

Histomorphometric evaluation of bone regeneration using allogeneic and alloplastic bone substitutes.

PURPOSE: The purpose of this investigation was to assess bone regeneration in critical sized defects in the rabbit calvarium using allogeneic and alloplastic bone substitutes. MATERIALS AND METHODS: Thirty New Zealand White rabbits were divided into 3 groups of 10 animals each. Bilateral 15 mm x 17 mm calvarial defects were made in the parietal bones of each animal. Group 1 had demineralized bone matrix (DBM) gel placed in one defect, while the other defect was left unfilled and served as the control. Group 2 had one defect filled with calcium hydroxide (CaOH)-treated DBM gel and the other defect filled with DBM gel. Group 3, the calcium-phosphate cement group, had Norian CRS (Norian Corp, Cupertino, CA) placed on one side and Bone Source (Howmedica Leibinger, Dallas, TX) placed on the contralateral side. Five animals in each group were killed at 6 and 12 weeks. Data analysis included qualitative assessment of the calvarial specimens and radiographic evaluation. Histomorphometric analysis was used to quantify the amount of new bone within the defects. RESULTS: Histomorphometric analysis showed that DBM gel-treated defects had significantly more new bone at 12 weeks compared with all other groups. There was no significant difference between defects filled with CaOH-treated DBM gel and those filled with DBM gel at 12 weeks. In group 3, Norian CRS- and Bone Source-treated defects were not statistically different from the unfilled controls. CONCLUSION: DBM gel was an effective allogeneic bone substitute that showed reliable osseous healing of critical size defects in the rabbit calvarium. The addition of CaOH to DBM gel did not significantly improve the bone regenerative capacity of the DBM gel. Both Norian CRS and Bone Source did not promote bone regeneration in this animal model.

Animals↗

PubMed2004

Transforming growth factor (TGF)-beta1 releasing tricalcium phosphate/chitosan microgranules as bone substitutes.

PURPOSE: Tricalcium phosphate (TCP)/chitosan composite microgranules were developed as bone substitutes and tissue engineering scaffolds with the aim of obtaining a high bone forming efficacy. The microgranules have the ability to fill various types of defect sites with closer packing. In addition, the transforming growth factor-beta 1 (TGF-beta1) was added to the microgranules in order to improve bone-healing efficacy. METHODS: TCP/chitosan microgranules were fabricated by dropping a TCP suspended chitosan solution into a NaOH/ethanol solution. TGF-beta1 was incorporated into the TCP/chitosan microgranules by soaking the microgranules into the TGF-beta1 solution. Scanning electron microscopy (SEM) observations as well as experiments examining the release of TGF-beta1 from chitosan and TCP/chitosan microgranules were performed. SEM was used to examine the cell morphologies on the microgranules, and the extent of cell proliferation was evaluated using a dimethyl-thiazol tetrazolium bromide (MTT) assay. The differentiated cell function was assessed by measuring the alkaline phosphatase activity as well as performing an osteocalcin assay. RESULTS: The size of the prepared microgranules was 350-500 microm and TCP powders were observed on the surface of the microgranules. TGF-beta1 was released from the TCP/chitosan microgranules at a therapeutic concentration for 4 weeks. The proliferation of osteoblasts on the TGF-beta1 loaded microgranules was the highest among the microgranules. SEM indicated that the seeded osteoblastic cells were firmly attached to the microgranules and proliferated in a multilayer fashion. The ALPase activity and osteocalcin content of all the samples increased during the culture period. CONCLUSIONS: These results suggest that the TCP/chitosan microgranules are potential bone substitutes with a drug releasing capacity and a osteoblastic cells culture scaffold.

3T3 Cells↗

PubMed1999

Calcium sulfate- and calcium phosphate-based bone substitutes. Mimicry of the mineral phase of bone.

Calcium sulfate and calcium phosphate have provided the orthopedic surgeon a viable alternative to autogenous bone grafting as either an osteoconductive bone void filler or a bone graft extender. These materials mimic the mineral phase of bone and are resorbed at a rate similar to the rate of bone formation. Thus, they are able to provide some structural support and prevent ingrowth of fibrous tissue while facilitating creeping substitution by the host bone.

Biocompatible Materials↗

PubMed2004

Theoretical model to determine the effects of geometrical factors on the resorption of calcium phosphate bone substitutes.

A theoretical approach was used to determine the effect of geometrical factors on the resorption rate of calcium phosphate bone substitutes that are either dense, microporous, and/or contain spherical macropores. Two cases were considered: (a) macroporous blocks that can be invaded by resorbing cells either directly because the structure is fully open-porous, or indirectly after some resorption of the macropores walls and/or interconnections. (b) Microporous or dense blocks/granules that cannot be invaded by resorbing cells, i.e. can only be resorbed from the outside to the inside, layer by layer. The theoretical approach was based on five assumptions: (i) the pores are spherical; (ii) the pores are ordered according to a face-centered cubic packing; (iii) the resorption is surface-controlled; (iv) the resorption is only possible if the surface can be accessed by blood vessels of 50 microm in diameter; and (v) the resorption time of a given amount of calcium phosphate is proportional to the net amount of material. Based on these assumptions, the calculations showed that the resorption time of a macroporous block could be minimized at a specific pore radius. This pore radius depended (i) on the size of the bone substitute and (ii) on the interpore distance. Typical radii were in the range of 100-400 microm. These values are similar to the numerous pore size optima mentioned in the scientific literature. For microporous or dense blocks/granules, the model suggested that a relatively small radius should be preferred. Such a radius leads to an optimum combination of a high surface area favorizing resorption and the presence of large intergranular gaps favorizing blood vessel ingrowth. In that case, the optimum of granule radius is around 100-200 microm. Finally, a very good agreement was found between the predictions of the model and experimental data, i.e. the model explained in all but two cases the results with an accuracy superior to 80%. In conclusion, the model appears to be a useful tool to better understand in vivo results, and possibly better define the geometry and distribution of the pores as well as the size of a bone substitute.

Absorbable Implants↗

PubMed1999

Structure-function relationships for coralline hydroxyapatite bone substitute.

To improve the understanding of the functional requirements of trabecular bone substitutes, the structure-function relationships of coralline hydroxyapatite were determined and compared to those of trabecular bone from a variety of anatomic sites. Mechanical properties and permeability of cylindrical coralline hydroxyapatite specimens were measured and related to various morphological parameters that were obtained from analysis of high-resolution (20 microm) computer reconstructions of each specimen. Results indicated the average (+/-SD) Young's modulus (2900 +/- 1290 MPa, n = 20) and permeability (0.50 +/- 0.19 x 10(-9) m2, n = 21) of the coralline hydroxyapatite were within the range of values exhibited by high density trabecular bone; ultimate stress (5.87 +/- 1.92 MPa, n = 13), while in the range of mid-density trabecular bone, was low considering its high volume fraction (31.3 +/- 1.9%, n = 49); and ultimate strain (0.22 +/- 0.03%, n = 13) was much lower than that of trabecular bone from any anatomic site. The only correlation found between mechanical and morphological parameters was between Young's modulus and "fabric" (a scalar measure of architecture that combined the degree of microstructural anisotropy with orientation). These results provide insight into the in vivo performance of this implant, as well as the biomechanical requirements for successful trabecular bone substitutes in general.

Animals↗

PubMed1989

[Self-setting apatite cement. 6. Possibility as bone substitute].

Self-setting apatite cement was investigated to evaluate its use as a possible bone substitute in the rat femur. The implant sites were recovered at intervals up 12 weeks postoperatively and investigated by the use of x-ray diffraction, contact microradiography, light and electron microscopy. By x-ray diffraction analysis, the cement placed for at least one day in the medullary canal of rats was found to be completely converted to a set phase of hydroxyapatite resembling the main inorganic phase of bone. In any specimens prepared at 1, 4, 12 weeks after implantation, no appreciable foreign body response was observed in the tissue around the set cement. At four weeks after implantation the set cement was in tight contact with the newly formed bone which appeared to involve osteocytes in lacunae and osteoblastic cells on its surface. At twelve weeks after implantation, the newly formed bone tended to grow into the interior of the set cement. With scanning electron microscopy, the newly formed bone was found to be directly deposited on the set cement. The newly formed bone consisted of fine needle-like crystals. These results strongly suggest that this cement is well tolerated by bone tissue and osteogenesis when used as a bone substitute. The advantage of the present material as a promising bone substitute is that it can be filled in surgical or traumatic bone defect as a slurry or paste.

Animals↗

PubMed1993

Ionomer-based bone substitute in otologic surgery.

During post-set hardening the self-curing bone substitute Ionocem develops a solid bond with the adjacent bony tissue, leaving no empty spaces. The fully matured material can be fixed to bone with freshly mixed cement or it may be used as a blank, e.g. an ossicular implant (Ionos ossicle). After insertion of 945 alloplastic middle ear prostheses over a period of 4.5 years, the take-rate was 94%. In some patients revision surgery became necessary, in 50% of cases because of prosthesis dislocation. A granular version of the cement (Ionogran) was implanted in 46 ears for obliteration of mastoid cavities and showed complete mucosal overgrowth within a maximal period of 3 months. Posterior canal wall reconstruction with the self-curing bone substitute was done in 74 patients, with revisions required in 12 cases because of persistent epithelial deficits in the external ear canal or epitympanic retraction. Overall results showed that the ionomer-based cement was a useful substitute for bone in reconstructive otologic surgery.

Animals↗

PubMed1998

Biphasic calcium phosphate concept applied to artificial bone, implant coating and injectable bone substitute.

The development of calcium phosphate ceramics and other related biomaterials for bone graft involved a better control of the process of biomaterials resorption and bone substitution. The bioactive concept was developed for biphasic calcium phosphate ceramics (BCP). An optimum balance of the more stable phase of HA and more soluble TCP was obtained for controlling gradual dissolution in the body, seeding new bone formation as it releases calcium and phosphate ions into the biological medium. The bone/material interface and the events occurring in the development of this dynamic interface such as cellular response, biodegradation or bioresorption of the materials and their transformation to carbonate hydroxyapatite (CHA) were described. These processes were observed in both bulk samples, implant coating and injectable bone substitute (IBS).

Bone Substitutes↗

PubMed2000

Use of alpha-tricalcium phosphate (TCP) as powders and as an aqueous dispersion to modify processing, microstructure, and mechanical properties of polymethylmethacrylate (PMMA) bone cements and to produce bone-substitute compounds.

Addition of tricalcium phosphate (alpha-TCP) powders as an aqueous dispersion to a polymethylmethacrylate (PMMA) bone cement is shown to produce a class of composites that due to their microstructure and mechanical properties may be suitable for application as bone substitutes. The PMMA forms a solid cellular matrix with open cells about 100 micrometer in size and incorporating TCP clusters. The TCP aggregates inside the cells form a porous network, with average mesopore diameters of about 0.1 micrometer, that is accessible from the outer surface. If TCP is added to PMMA in the form of dried powders, the composites are not applicable as bone substitutes. The dynamic elastic modulus (DEM) and compressive and tensile strengths were measured and discussed for both classes of composites. The mechanical properties of the bone-substitute composites, although lower than the other class of composites, are still competitive with those properties of a porous ceramic matrix of hydroxyapatite and with those of natural bones.

Bone Cements↗

PubMed2002

Effect of ball milling on the processing of bone substitutes with calcium phosphate powders.

Decreasing the microscale morphology of synthetic bone substitutes is of primary importance in order to enhance the morphology of the surface of the material, which is directly in contact with osteoconductive cells when it is implanted in bone. The aim of this study was to investigate the influence of ball milling of slurries on the microscale morphology of hydroxyapatite and tricalcium phosphate bone substitutes and the influence on their processing. Ball milling appeared to be a successful method in order to raise the sintering reactivity of the powders, that is, to decrease the sintering temperature and microstructural morphology of the material. However, it was demonstrated that ball milling had a great influence on dispersion, which became very difficult under long milling times because of dissolution of the calcium phosphate powders. Due to dissolution, ionic species were generated in the slurry and interfered with the dispersing agent. Moreover a reprecipitation process occurred simultaneously, and large particles of the most stable phase (HAP) formed. The presence of such large particles generated stress gradients and cracks in the material during the sintering stage.

Biocompatible Materials↗

PubMed2006

Superior effect of MD05, beta-tricalcium phosphate coated with recombinant human growth/differentiation factor-5, compared to conventional bone substitutes in the rat calvarial defect model.

BACKGROUND: MD05 consists of beta-tricalcium phosphate (beta-TCP) coated with recombinant human growth/differentiation factor-5 (rhGDF-5) and is under evaluation as an osteoinductive and osteoconductive bone graft material for use in dental and maxillofacial applications. The objective of this study was to compare the bone regenerative properties of MD05 with those of conventional commercially available bone substitutes. METHODS: Full-thickness, 6-mm diameter, calvarial critical-size defects (two per animal) were created in adult Sprague-Dawley rats. Groups of rats were implanted with the following: 1) MD05; 2) bovine bone mineral; 3) bovine bone mineral with collagen; 4) bovine bone mineral with synthetic peptide, 5) beta-TCP (from two different manufacturers); or 6) no filling material (sham controls). Blinded macroscopic analysis, histopathologic analysis, and histomorphometric analysis were carried out 6 weeks after implantation. RESULTS: New bone formation assessed histomorphometrically was about five times greater with MD05 than with the other bone substitutes tested, and bone repair was well advanced in MD05-filled defects after 6 weeks. The extent of fibrous tissue and residual implant were significantly lower in the MD05 group. In contrast to the other materials, the use of MD05 was associated with the complete osseous bridging of the defect and with the presence of normal bone marrow. The osteoinductive effect of rhGDF-5 was apparent from the more pronounced bone ingrowth observed with MD05 compared to the beta-TCP carrier alone. All implants showed good biocompatibility. CONCLUSION: MD05 achieved superior bone regeneration compared to conventional materials and is a promising new bone substitute for dental and maxillofacial applications.

Animals↗