Porous Hydroxyapatite Granules Research Articles

Synthetic Hydroxyapatite Inhibits Bisphosphonate Toxicity to the Oral Mucosa In Vitro.

Medication-related osteonecrosis of the jaw (MRONJ) is a side effect of bisphosphonate therapy, characterised by exposed necrotic bone. The soft tissues of the oral mucosa no longer provide a protective barrier and MRONJ patients experience pain, infections and difficulties eating. We hypothesised that hydroxyapatite (Ca5(PO4)3(OH)) could reduce bisphosphonate concentrations and protect the oral mucosa by exploiting bisphosphonate’s calcium binding affinity. The effect of zoledronic acid (ZA) and pamidronic acid (PA) on the metabolism of oral fibroblasts, oral keratinocytes and three-dimensional oral mucosa models was investigated and then repeated in the presence of hydroxyapatite granules. Without hydroxyapatite, ZA and PA significantly reduced the metabolic activity of oral cells in a dose-dependent manner. Both drugs reduced epithelial thickness and 30 µM ZA resulted in loss of the epithelium. Hydroxyapatite granules had a protective effect on oral cells, with metabolic activity retained. Oral mucosa models retained their multi-layered epithelium when treated with ZA in the presence of hydroxyapatite granules and metabolic activity was comparable to controls. These results demonstrate hydroxyapatite granules protected oral soft tissues from damage caused by bisphosphonate exposure. Porous hydroxyapatite granules are currently used for socket preservation and this data suggests their potential to prevent MRONJ in at-risk patients.

In vivo evaluations of hydroxyapatites with small and large grain sizes

ABSTRACTThe effect of grain size of hydroxyapatite on its osteoconductivity was newly investigated. The hydroxyapatite discs, which had small (specimen S) and large grain size (specimen L), were prepared through microwave sintering at 1100°C for 6 and 720 min, respectively. The average grain size of specimen S was about 15 times smaller than that of specimen L. The surface energy of specimen S was about 1.6 times higher than that of specimen L under the same surface roughness. For the osteoconductivity test, porous hydroxyapatite granules were prepared using PEG porogen. The osteoconductivity of specimen S was superior to that of specimen L four weeks after implantation in calvarial defects of New Zealand white rabbits. Taken together, it can be concluded that the hydroxyapatite with small grain size had a higher osteoconductivity compared with the hydroxyapatite with large grain size due to its high surface energy.

Fabrication of Porous Hydroxyapatite Granules as an Effective Adsorbent for the Removal of Aqueous Pb(II) Ions

Porous hydroxyapatite (HAp) granules have been successfully fabricated from a HAp powder precursor and polyvinyl alcohol (PVA) additive by a simple sintering process. The composition and microstructures of the HAp were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with an energy dispersive X-ray (EDX) spectrometer. The effects of sintering temperature and PVA/HAp mass ratios on color, water stability, morphology, and chemical composition of HAp are discussed. Optimum conditions for the fabrication of HAp granules were found to be a PVA/HAp mass ratio of 3/20 and a sintering temperature of 600°C for 4 h. Accordingly, the obtained HAp is white in color, is in the granular form with a size of about 2 × 10 mm, and has a specific surface area of 70.6 m2/g. The adsorption of Pb2+ onto the as-prepared HAp granules was carried out in aqueous solution by varying the pH, the adsorbent dose, the initial concentration of Pb2+, and the contact time. The results of adsorption stoichiometry of Pb2+ on the HAp granule adsorbent were fitted to the Langmuir adsorption isotherm model (R2 = 0.99). The adsorption capacity and removal efficiency of the HAp granule adsorbent for Pb2+ under optimal conditions were found to be 7.99 mg/g and 95.92%, respectively. The adsorption process obeyed a pseudo-second-order kinetic model with R2∼1. The porous HAp granules studied in this work showed potential for the removal of Pb2+ from industrial wastewater.

Preparation of spherical porous hydroxyapatite granules as support materials for microorganisms

Preparation of spherical porous hydroxyapatite granules as support materials for microorganisms

Increased Internal Porosity and Surface Area of Hydroxyapatite Accelerates Healing and Compensates for Low Bone Marrow Mesenchymal Stem Cell Concentrations in Critically-Sized Bone Defects

For clinical treatment of skeletal defects, osteoinductive scaffolds must have the ability to conform to the unique geometry of the injury site without sacrificing biologically favorable properties, including porosity. This investigation seeks to combine the osteoinductive properties of porous hydroxyapatite (HA) scaffolds with the beneficial handling characteristics of granules or putties, while evaluating the effects of mesenchymal stem cell (MSC) concentration on the composite grafts’ ability to regenerate bone in vivo. The results demonstrate that porous HA granules regenerate significantly larger volumes of bone compared to non-porous HA. Increased MSC concentrations in autologous bone marrow aspirate (BMA) contributed to greater bone regeneration. This effect was most predominant with non-porous HA. While the extent of bone regeneration using non-porous HA was strongly correlated with MSC concentration of the marrow, porous HA microparticles combined with autologous BMA were successful in faster treatment of critically-sized bone defects and with less dependence on the MSC concentration than non-porous HA.

Spherical porous hydroxyapatite granules containing composites of magnetic and hydroxyapatite nanoparticles for the hyperthermia treatment of bone tumor.

Spherical porous granules of hydroxyapatite (HA) containing magnetic nanoparticles would be suitable for the hyperthermia treatment of bone tumor, because porous HA granules act as a scaffold for bone regeneration, and magnetic nanoparticles generate sufficient heat to kill tumor cells under an alternating magnetic field. Although magnetic nanoparticles are promising heat generators, their small size makes them difficult to support in porous HA ceramics. We prepared micrometer-sized composites of magnetic and HA nanoparticles, and then supported them in porous HA granules composed of rod-like particles. The spherical porous HA granules containing the composites of magnetic and HA nanoparticle were successfully prepared using a hydrothermal process without changing the crystalline phase and heat generation properties of the magnetic nanoparticles. The obtained granules generated sufficient heat for killing tumor cells under an alternating magnetic field (300 Oe at 100 kHz). The obtained granules are expected to be useful for the hyperthermia treatment of bone tumors.

Hydroxyapatite/Collagen Composite Is a Reliable Material for Malar Augmentation

To evaluate the long-term results of cheekbone augmentation using porous hydroxyapatite granules mixed with microfibrillar collagen in a large group of patients. Four hundred thirty patients who underwent zygomatic augmentation and intermaxillary osteotomy were evaluated clinically, radiologically, and histologically. Complications were found in 13 patients (1.56%). There were no relevant radiologic differences in prosthesis volume after 1month (T1) or after 24months (T2) in any patient; there were no clinically relevant differences in 110 patients after 36months. At T1, the prosthesis had a granular structure and the granules had not migrated; at T2, the prosthesis was staunchly adhering to the underlying bone. Over time, the radiopacity of the material increased. Histologic results of 19 biopsy specimens obtained from 8 patients 2years after the procedure showed prominent ossification with low inflammation, confirming new bone formation over time. According to the visual analog scale, the patients were generally satisfied with the aspects that were considered. Hydroxyapatite and collagen composite used during malarplasty produced a successful outcome. Its main drawback is a learning curve that is longer than for more frequently used implantable biomaterials.

Hydroxyapatite-calcium sulfate-hyaluronic acid composite encapsulated with collagenase as bone substitute for alveolar bone regeneration

Periodontitis is a very severe inflammatory condition of the periodontium that progressively damages the soft tissue and destroys the alveolar bone that supports the teeth. The bone loss is naturally irreversible because of limited reparability of the teeth. Advancement in tissue engineering provides an effective regeneration of osseous defects with suitable dental implants or tissue-engineered constructs. This study reports a hydroxyapatite, calcium sulfate hemihydrate and hyaluronic acid laden collagenase (HAP/CS/HA-Col) as a bone substitute for the alveolar bone regeneration. The composite material was mechanically tested and the biocompatibility was evaluated by WST-1 assay. The in vivo bone formation was assessed in rat with alveolar bone defects and the bone augmentation by the HAP/CS/HA-Col composite was confirmed by micro-CT images and histological examination. The mechanical strength of 6.69 MPa with excellent biocompatibility was obtained for the HAP/CS/HA-Col composite. The collagenase release profile had facilitated the acceleration of bone remodeling process and it was confirmed by the findings of micro-CT and H&E staining. The bone defects implanted with HAP/CS/HA composite containing 2 mg/mL type I collagenase have shown improved new bone formation with matured bone morphology in comparison with the HAP/CS/HA composite that lacks the collagenase and the porous hydroxyapatite (p-HAP) granules. The said findings demonstrated that the collagenase inclusion in HAP/CS/HA composite is a feasible approach for the alveolar bone regeneration and the same design can also be applied to other defective tissues.

The effect of an alginate carrier on bone formation in a hydroxyapatite scaffold.

This study investigated the osteoconductive properties of a porous hydroxyapatite (HA) scaffold manufactured using a novel technique similar to the bread-making process, alone and in combination with an alginate polysaccharide fiber gel (HA/APFG putty) and autologous bone marrow aspirate (BMA). The hypothesis was that the HA/APFG putty would be as osteoconductive as granular HA and that the presence of BMA would further enhance bone formation in an ovine femoral condyle critical defect model. Thirty-six defects were created and either (1) porous HA granules, (2) HA/APFG putty, or (3) HA/APFG putty + BMA were implanted. After retrieval at 6 and 12 weeks, image analysis techniques were used to quantify bone apposition rates, new bone area, bone-HA scaffold contact, and implant resorption. At 6 weeks postsurgery, significantly lower bone apposition rates were observed in the HA/APFG putty group when compared to the HA (p = 0.014) and HA/APFG putty + BMA (p = 0.014) groups. At 12 weeks, significantly increased amounts of new bone formation were measured within the HA scaffold (33.56 ± 3.53%) when compared to both the HA/APFG putty (16.69 ± 2.7%; p = 0.043) and the defects containing HA/APFG putty + BMA (19.31 ± 3.8%; p = 0.043). The use of an APFG gel as a carrier for injectable CaP bone substitute materials delayed bone formation in this model compared to HA granules alone which enhanced bone formation especially within the interconnected smaller pores. Our results also showed that the addition of autologous BMA did not further enhance its osteoconductive properties. Further study is required to optimize the degradation rate of this APFG binding agent before using as a directly injectable material for repair of bone defect. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1328-1335, 2016.

Stem cell engineered bone with calcium-phosphate coated porous titanium scaffold or silicon hydroxyapatite granules for revision total joint arthroplasty

Aseptic loosening in total joint replacements (TJRs) is mainly caused by osteolysis which leads to a reduction of the bone stock necessary for implant fixation in revision TJRs. Our aim was to develop bone tissue-engineered constructs based on scaffolds of clinical relevance in revision TJRs to reconstitute the bone stock at revision operations by using a perfusion bioreactor system (PBRS). The hypothesis was that a PBRS will enhance mesenchymal stem cells (MSCs) proliferation and osteogenic differentiation and will provide an even distribution of MSCs throughout the scaffolds when compared to static cultures. A PBRS was designed and implemented. Scaffolds, silicon substituted hydroxyapatite granules and calcium-phosphate coated porous TiAl6V4 cylinders, were seeded with MSCs and cultured either in static conditions or in the PBRS at 0.75 mL/min. Statistically significant increased cell proliferation and alkaline phosphatase activity was found in samples cultured in the PBRS. Histology revealed a more even cell distribution in the perfused constructs. SEM showed that cells arranged in sheets. Long cytoplasmic processes attached the cells to the scaffolds. We conclude that a novel tissue engineering approach to address the issue of poor bone stock at revision operations is feasible by using a PBRS.

The efficacy of porous hydroxyapatite granule as a carrier of E.coli-derived recombinant human bone morphogenetic protein-2

Porous hydroxyapatite (HA) has great osteoconductivity, which allows it to be used as a bone graft extender. Porous HA enables bone formation by binding with recombinant human bone morphogenetic protein-2 (rhBMP-2). This research is to assess the capability of porous HA granules as a carrier of E.coli-derived rhBMP-2 (E.BMP-2). We compared the release of E.BMP-2 from porous HA of both block and granular forms for 120 min by using an ELISA. Using alkaline phosphatase (ALP) activity assay of human mesenchymal stem cells (hMSC), and the rat abdominal ectopic bone formation model, we also examined the osteogenic capacity of granular HA containing E.BMP-2. The result has shown that the rate of E.BMP-2 released from porous HA for 120 min indicated 42% of HA granules and 27.9% of HA block; the amount of HA granules was larger than HA block. At each set time interval of 10 min, 20 min, 40 min, 80 min, and 120 min, the amount of E.BMP-2 released from HA granules were significantly higher than those from HA block. The ALP activity on the third day of porous HA granules treated with 100 μg E.BMP-2 was significantly higher than that of pure HA granules. In addition, in the rat in vivo model, bony tissue was confirmed in the all of the cases in the E.BMP-HA group but not in the pure HA group, according to the micro-CT and the histology 8 weeks after the surgery. Moreover, in contrast to the pure HA group, the E.BMPHA group showed a higher level of bone volume, percent bone volume, structure model index, trabecular thickness, and trabecular number in the micro-CT scan. In conclusion, porous HA granules can be bound with E.BMP-2 and can properly release E.BMP-2, so that it can increase the osteoblastic differentiation of hMSC and induce the ectopic bone formation, consequently qualifying as a carrier of E.BMP-2.

Short Term Culture of Human Mesenchymal Stem Cells with Commercial Osteoconductive Carriers Provides Unique Insights into Biocompatibility.

For spinal fusions and the treatment of non-union fractures, biological substrates, scaffolds, or carriers often are applied as a graft to support regeneration of bone. The selection of an appropriate material critically influences cellular function and, ultimately, patient outcomes. Human bone marrow mesenchymal stem cells (BMSCs) are regarded as a critical component of bone healing. However, the interactions of BMSCs and commercial bone matrices are poorly reported. BMSCs were cultured with several commercially available bone substrates (allograft, demineralized bone matrix (DBM), collagen, and various forms of calcium phosphates) for 48 h to understand their response to graft materials during surgical preparation and the first days following implantation (cell retention, gene expression, pH). At 30 and 60 min, bone chips and inorganic substrates supported significantly more cell retention than other materials, while collagen-containing materials became soluble and lost their structure. At 48 h, cells bound to β-tricalcium phosphate-hydroxyapatite (βTCP-HA) and porous hydroxyapatite (HA) granules exhibited osteogenic gene expression statistically similar to bone chips. Through 24 h, the DBM strip and βTCP-collagen became mildly acidic (pH 7.1–7.3), while the DBM poloxamer-putties demonstrated acidity (pH < 5) and the bioglass-containing carrier became basic (pH > 10). The dissolution of DBM and collagen led to a loss of cells, while excessive pH changes potentially diminish cell viability and metabolism. Extracts from DBM-poloxamers induced osteogenic gene expression at 48 h. This study highlights the role that biochemical and structural properties of biomaterials play in cellular function, potentially enhancing or diminishing the efficacy of the overall therapy.

Avaliação morfológica da capacidade osteocondutora da hidroxiapatita implantada na calota craniana de camundongos diabéticos

Introduction: Diabetes mellitus is a worldwide public health problem that, if not treated adequately, can cause various diseases, including loss of bone mineral density as a characteristic manifestation of osteoporosis. In this condition, bone is more vulnerable to pathological fractures that can be treated by conventional clinical methods. However, depending on the severity and quantity of bone loss, implantation of biomaterial grafts such as hydroxyapatite is necessary. Clinical studies have demonstrated the biocompatibility and osteoconductive capacity of this material. Objectives: To evaluate the osteogenic capacity of hydroxyapatite implanted into bone defects experimentally induced in the skull of diabetic NOD mice. Methods: Fifteen NOD mice were divided into three groups: control (non-diabetic), spontaneously diabetic, and spontaneously diabetic receiving insulin replacement applied subcutaneously into the dorsum. Defects were created experimentally in the skull with a surgical bur and filled with porous hydroxyapatite granules. The animals were sacrificed 4 weeks after surgery and samples were obtained for analysis. Stereology was used to quantify the volume of newly formed bone in the recipient area according to the principle of Delesse. Data were analyzed by ANOVA followed by the Tukey test (p&lt;0.05). Results: Radiology showed good radiopacity of the hydroxyapatite. However, radiolucent spots were seen between the hydroxyapatite granules in the diabetic groups, indicating infiltration of connective tissue. Microscopy showed projection of newly formed bone from the margin of the bone defect toward the implant, a finding indicating good bone-implant interaction. The volume of newly formed bone was 46% in the control group and was significantly higher (p&lt;0.05) than that observed in the diabetic group (14%) and diabetic group receiving insulin (17%). Thus, in the diabetic groups the recipient area contained a larger amount of connective tissue as demonstrated by radiology. In all groups, the defect was filled with partially mature (cortical arrangement) and partially immature bone (trabecular morphology and disorganized osteocytes). Conclusion: Osteogenesis guided by the properties of hydroxyapatite may even occur in bone suffering from the effects of diabetes, but the volume of newly formed is lower and the process is slower.

Effects of chronic passive smoking on the regeneration of rat femoral defects filled with hydroxyapatite and stimulated by laser therapy

Defects associated with bone mass loss are frequently treated by autogenous bone grafting. However, synthetic biomaterials such as calcium phosphate ceramics can substitute autologous grafts as long as they are biocompatible with bone tissue. In addition, low-level laser therapy (LLLT) is used to enhance bone regeneration by stimulating the local microcirculation and increasing the synthesis of collagen by bone cells. However, bone health is fundamental for osseointegration of the graft and bone repair. In this respect, excessive tobacco consumption can compromise expected outcomes because of its deleterious effects on bone metabolism that predispose to the development of osteoporosis. The objective of this study was to evaluate the regeneration of bone defects implanted with biomaterial and stimulated by LLLT in rats submitted to passive cigarette smoking. Porous hydroxyapatite granules were implanted into critical-size defects induced experimentally in the distal epiphysis of the right femur of 20 female Wistar rats submitted to passive smoking for 8 months in a smoking box. The defect site was irradiated with a gallium-arsenide laser at an intensity of 5.0J/cm2. The animals were divided into four groups: control (non-smoking) rates submitted (G2) or not (G1) to laser irradiation, and smoking rats submitted (G4) or not (G3) to laser irradiation. The animals were sacrificed 8 weeks after biomaterial implantation. The right femurs were removed for photodocumentation, radiographed, and processed for routine histology. The results showed good radiopacity of the implant site and of the hydroxyapatite granules. Histologically, formation of new trabecular bone was observed adjacent to the hydroxyapatite granules in G1 and G2. In G3 and G4, the granules were surrounded mainly by connective tissue. In conclusion, passive smoking compromised bone neoformation in the defects and the LLLT protocol was not adequate to stimulate local osteogenesis.

Synthesis of nanosized porous hydroxyapatite granules in hydrogel by electrophoresis

Nanosized porous hydroxyapatite (HA) granules are expected to be useful as DNA and drug carriers for cells. We attempted to synthesize nanosized HA granules in an agarose gel by electrophoresis of calcium and phosphate ions. Wells were prepared on an agarose gel, and a CaCl2 solution was placed in the wells on the positive side and a Na2HPO4 solution was placed in the wells on the negative side. After a potential was applied, white precipitates appeared in the gel. The precipitates were calcium-deficient HA granules of approximately 300–600nm in diameter. These granules were composed of fiber-like particles and had a porous structure. The diameters of the granules were decreased by an increase in the gel concentration. Hence, we successfully synthesized nanosized porous HA granules to be used as DNA and drug carriers.

A Long Term Histological Analysis of Effect of Interposed Hydroxyapatite between Bone and Bone Cement in THA and TKA

The standard cementing technique for total hip and knee arthroplasty (THA, TKA) was modified by interposing osteoconductive porous polycrystalline hydroxyapatite (HA) granules at the cement-bone interface to augment cement-bone bonding. Twenty-one specimens from the acetabulum and two specimens from the femur containing well-fixed bone-cement interface were retrieved five months to twenty-two years after THA and TKA with an interface bioactive bone cement technique. Histological findings were evaluated in terms of the retrieved sites, the interval between index operation and revision, patient age at retrieval and bone pathology. Dense bone ingrowth was observed in all specimens retrieved from the superior wall of the acetabulum. Cancellous bone ingrowth was observed in specimens retrieved from the infero-medial wall of the acetabulum. Connective tissue interposition and osteolysis were observed at the sites where hydroxyapatite granules were absent. Findings of bone ingrowth for the HA interposed retrievals were similar regardless of the interval between index operation and revision, patient age at retrieval, and bone pathology. Longer survivability of the bone-cement bonding was attributed more to the interposed HA granules. In spite of various degrees of aging, postmenopausal osteoporosis, and pathological bone condition the histological findings were not affected by the bone pathology. There was long-term direct contact between the bone and hydroxyapatite granules. Thus, the interface bioactive bone cement technique can ensure longevity of bone-cement bonding even after the onset of osteoporosis and for pathological bone conditions.

Characterisation and photocatalytic activity of structure-controlled spherical granules of an anatase/hydroxyapatite composite

Materials that can purify the environments are desirable. Anatase (TiO 2) has received attention because it is stable and can decompose organic substances because of its photocatalytic activity. To make use of anatase effectively, we deposited nano-sized anatase particles on porous hydroxyapatite (HA) ceramics composed of rod-shaped particles. Spherical porous HA granules composed of rod-shaped HA particles were prepared using a hydrothermal process. The granules were soaked in a solution containing a water-soluble titanium complex and then hydrothermally treated. Nano-sized anatase particles were deposited on each rod-shaped HA particle. The anatase/HA granules composed of rod-shaped HA particles showed higher photocatalytic activity than those composed of globular HA particles. The granules are expected to be useful as an environment-purifying material with high manageability and photocatalytic activity.

Study of the osteoconductive capacity of hydroxyapatite implanted into the femur of ovariectomized rats

Osteoporosis is a global public health that affects postmenopausal women due to the deficiency of estrogen, a hormone that plays an important role in the microarchitecture of bone tissue. Osteoporosis predisposes to pathological bone fracture that can be repaired by conventional methods. However, depending on the severity and quantity of bone loss, the use of autogenous grafts or biomaterials such as hydroxyapatite might be necessary. The latter has received increasing attention in the medical field because of its good biological properties such as osteoconductivity and biocompatibility with bone tissue. The objective of this study was to evaluate using histologic and radiographic analyses, the osteogenic capacity of hydroxyapatite implanted into the femur of rats with ovariectomy-induced osteoporosis. Eighteen rats were divided into three groups with six animals in each: group nonovariectomized, bilaterally ovariectomized not receiving estrogen replacement therapy, and bilaterally ovariectomized submitted to estrogen replacement therapy. Defects were created experimentally in the distal epiphysis of the femur with a surgical drill and filled with porous hydroxyapatite granules. The animals were sacrificed 8 weeks after surgery. The volume of newly formed bone in the implant area was quantified by morphometrical methods. The results were analyzed by ANOVA followed by the Tukey test (P < 0.05). The hydroxyapatite granules showed good radiopacity. Histological analysis revealed less quantity of newly formed bone in the ovariectomized group not submitted to hormone replacement therapy. In conclusion, bone neoformation can be expected even in bones compromised by estrogen deficiency, but the quantity and velocity of bone formation are lower.

Synthesis of spherical hydroxyapatite granules with interconnected pore channels using camphene emulsion

The aim of this study was to fabricate porous spherical hydroxyapatite (HA) granules with interconnected pore channels for use as a bone graft substitute. Various weights of camphene porogen were mixed with nano-sized HA powder (camphene/HA = 0, 10, 30, 50, 70, and 90% w/w) and 10% gelatin aqueous solution then added to the mixture. The water-in-oil emulsion method was employed to obtain spherical-shaped granules, of which those 1000-2000 μm in diameter were selectively classified using a standard sieve set. Thermogravimetric analysis and X-ray diffraction were used to determine optimal sintering conditions. The sintered granules were characterized using field emission-scanning electron microscopy (FE-SEM), microcomputed tomography, and porosimetry. The pore size and porosity of spherical HA granules increased with the addition of camphene. Granules with a HA/camphene ratio of 90% (HG90) demonstrated macropores (>50 μm) with interconnected pore channels (porosity: 58.49%). In addition, FE-SEM examination of HG90 coated with polycaprolactone showed that the granule may hold promise as a drug delivery carrier. We concluded that these HG90 granules merit consideration as a bone graft substitute or drug delivery carrier in bone tissue engineering.

Comparative evaluation of bone regeneration using spherical and irregularly shaped granules of interconnected porous hydroxylapatite. A beagle dog study

Bone regeneration stimulated by two different shapes of interconnected porous calcium hydroxyapatite (IP-CHA) granules was evaluated in the mandibles of 3 beagle dogs. Deferent shapes of IP-CHA were used, spherical (spherical shaped IP-CHA granules) and irregular shapes (irregularly shaped IP-CHA granules). Two bone sockets (3mm in diameter and 5mm in depth) were prepared in the right edentulous mandible of each animal where right premolars had been extracted and sites healed for 3 months. The two types of IP-CHA were filled into the sockets to stimulate bone regeneration. New bone formation was evaluated histologically at 4, 8 and 12 weeks after filling. At 4 weeks, little bone formation was apparent in any of the bony sockets. At 8 weeks, newly formed bone was detected between the granules but not in the pores. In contrast, at 12 weeks, bone formation was clearly observed not only between the granules but also inside the granule pores. Comparing the two sites at 8 and 12 weeks, more bone formation was detected in sites receiving irregularly shaped IP-CHA than in sites receiving spherical IP-CHA. These results indicate that use of irregularly shaped IP-CHA may enhance bone regeneration. The results of this preliminary study suggest that irregularly shaped IP-CHA granules may have more possible usefulness than spherically shaped granules as a scaffold for bone regeneration.