Irradiation with 590-nm yellow light-emitting diode light attenuates oxidative stress and modulates UVB-induced change of dermal fibroblasts.

Recently, light-emitting diode (LED)-based devices have emerged as effective and safe tools for the treatment of photoaged skin. However, few studies have been conducted to elucidate the underlying mechanism behind the effect on photoageing of LED light. In this study, we induced photoageing of human dermal fibroblasts (HDFs) with Ultraviolet B (UVB) irradiation and evaluated the ability of 590-nm LED radiation to induce recovery from oxidative stress, restore collagen formation and regulate inflammatory changes. Photoageing was induced in cultured human dermal fibroblasts (HDFs) using UVB irradiation of 50 mJ/cm2 . Then, the photoaged HDFs were irradiated with LED using a custom-built 590-nm LED device which emits light with an intensity of 38 mW/cm2 (irradiated for 900 s with 34.2 J/cm2 of total energy). LED irradiation significantly attenuated UVB-induced reactive oxygen species generation and UVB-induced phosphorylation of JNK, c-Fos and c-Jun. In addition, the procollagen levels were recovered significantly, and MMP-9 levels were significantly suppressed after LED irradiation. The UVB-induced phosphorylation levels of NF-κB and pro-inflammatory enzyme COX-2 also significantly decreased. Our results suggest that 590-nm yellow light irradiation may be an effective and safe anti-oxidative and anti-inflammatory treatment modality for photoaged skin.

Fabrication and evaluation of osteoblastic differentiation of human mesenchymal stem cells on novel CaO-SiO2-P2O5-B2O3 glass-ceramics.

Apatite-wollastonite glass-ceramics have high mechanical strength, and CaO-SiO2 -B2 O3 glass-ceramics showed excellent bioactivity and high biodegradability. A new type of CaO-SiO2 -P2 O5 -B2 O3 system of bioactive glass-ceramics (BGS-7) was fabricated, and the effect and usefulness was evaluated via bioactivity using simulated body fluid and human mesenchymal stem cells (hMSCs). The purpose of this study was to compare BGS-7 and hydroxyapatite (HA) using hMSCs in order to evaluate the bioactivity of BGS-7 and its possibility as a bone graft extender. Alkaline phosphatase (ALP) staining, ALP activity, cell proliferation 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay, Alizarin Red-S (AR-S) staining, calcium levels, the mRNA expression of ALP, osteocalcin, osteopontin, and runt-related transcription factor 2 (runx-2) using reverse-transcription polymerase chain reaction (RT-PCR) and the protein expression of osteocalcin and runx-2 using Western blot were measured by transplanting hMSC onto a tissue culture plate, HA, and BGS-7. The ALP staining and AR-S staining of BGS-7 was greater than that of HA and control. The ALP value of BGS-7 was significantly higher than that of HA and control. The MTS results showed that BGS-7 had a higher value than the groups transplanted onto HA and control on day 15. The calcium level was higher than the control in both HA and BGS-7, and was especially high in BGS-7. There were more mineral products on BGS-7 than on the HA when analyzed by scanning electron microscopy. The mRNA expression of ALP, osteopontin, osteocalcin, and runx-2 were higher on BGS-7 than on HA and the control when analyzed by RT-PCR. The relative gene expression of osteopontin and runx-2 were found to be higher on BGS-7 than on HA and the control by Western blot. Accordingly, it is predicted that BGS-7 would have high biocompatibility and good osteoconductivity, and presents a possibility as a new bone graft extender.

In vivo evaluation of CaO-SiO2-P2O5-B2O3 glass-ceramics coating on Steinman pins.

Surface coating using ceramics improves the bone bonding strength of an implant. We questioned whether a new type of glass-ceramics (BGS-7) coating (CaO-SiO2 -P2 O5 -B2 O3 ) would improve the osseointegration of Steinman pins (S-pins) both biomechanically and histomorphometrically. An in vivo study was performed using rabbits by inserting three S-pins into each iliac bone. The pins were 2.2-mm S-pins with a coating of 30-µm-thick BGS-7 and 550-nm-thick hydroxyapatite (HA), as opposed to an S-pin without coating. A tensile strength test and histomorphometrical evaluation was performed. In the 2-week group, the BGS-7 implant showed a significantly higher tensile strength than the S-pin. In the 4- and 8-week groups, the BGS-7 implants had significantly higher tensile strengths than the S-pins and HA implants. The histomorphometrical study revealed that the BGS-7 implant had a significantly higher contact ratio than the S-pin and HA implants in the 4-week group. The biomechanical and histomorphometrical tests showed that the BGS-7 coating had superior bone bonding properties than the groups without the coating from the initial stage of insertion. The BGS-7 coating of an S-pin will enhance the bone bonding strength, and there might also be an advantage in human bone bonding.

Finite element modeling of stress distribution in intervertebral spacers of different surface geometries.

Intervertebral disc spacers using bioactive ceramics have been used to treat degenerative spinal disease. Tooth-shaped spacers are commonly used to prevent migration, but there is a possibility of fracture when inserted or after insertion. Intervertebral disc spacers with either an isosceles triangle-shaped tooth (T1) or a right triangle-shaped tooth (T2) were used as a control group. The design factors for the experimental group were modified to prevent fractures induced by stress concentration, and the surfaces of the spacers were designed as either an isosceles triangle-shaped valley (V1) or a right triangle-shaped valley (V2). Linear analysis using finite element model (FEM) was performed, and Von Mises stress distribution was calculated by applying 1000 N of uniformly distributed load. Samples of the V2 design were made with bioactive glass-ceramics (BGS-7) and evaluated for compressive strength, fatigue degree, and impact strength. Von Mises stress was highest at the first tooth from the posterior side for the control group and at the center for the experimental group. Compared with the control group, the experimental group showed 18.4% and 82.5% reduction (V1 vs. T1 and V2 vs. T2, respectively) in the maximum stress at the bottom of the valleys. The FEM analysis revealed that the V2 design had the most even load distribution. The V2 samples with bioactive glass-ceramics were evaluated for compressive strength, and all six samples were not fractured up to 24 000 N. However, the average impact strength was 19.42 kN, suggesting that momentary force caused damage at a lower load than compression with a steady speed. The BGS-7 intervertebral disc spacer with V2 design was not fractured during the fatigue test at maximum pressure of 8000 N, R ≥10, 5 Hz, and 5 million cycles. These data confirm that the BGS-7 spacer with the V2 design may be clinically applicable. Collectively, the modified surface geometry of the experimental group significantly lowered Von Mises stress values at the bottom of the valleys, and thus the possibility of fracture by compressive load was greatly reduced. Also, impact during insertion was confirmed to cause fracture more easily, as the impact strength was lower than the compressive strength in the experimental group.

Effects of porous beta-tricalcium phosphate-based ceramics used as an E. coli-derived rhBMP-2 carrier for bone regeneration.

Recombinant human bone morphogenetic protein-2 (rhBMP-2) requires carriers for clinical effectiveness. In this study, whether porous beta-tricalcium phosphate (ß-TCP)-based ceramics are ideal carriers for rhBMP-2 was investigated. Hydroxyapatite (HA), ß-TCP, TCP/HA (80 %/20 %), HA with rhBMP-2, TCP with rhBMP-2, and TCP/HA (80 %/20 %) with rhBMP-2 were manufactured by a sponge method with a pore size of 300 µm or more and macro-porosity of 83 %. The alkaline phosphatase (ALP) activity and ALP expression of the cells with 100 % ß-TCP granules were more increased than the those of cells with 100 % HA and TCP/HA (80 %/20 %) at the baseline or when treated with 15 ng/ml of rhBMP-2. In an SD rat calvarial defect model, new bone formation was evidently shown in the TCP 100 %-rhBMP-2 and TCP/HA (80 %/20 %)-rhBMP-2 groups, showing that the most affected area was filled with newly-formed bone, that the percent bone volume and trabecular number were larger when compared to the groups without rhBMP-2 treatment at both 4 and 8 weeks after surgery using micro-CT and histology. Porous TCP-based ceramic granules enhanced the osteoblastic differentiation in the hMSC system when treated with 15 ng/ml of rhBMP-2 and accelerated bone-healing by trabecular number in a rat calvarial defect model. Thus, in this study it was proposed that TCP-based ceramics might be useful carriers of rhBMP-2.

Hemostatic Effect and Mechanism of Epidermal Growth Factor-Hemostatic Powder after Endoscopic Submucosal Dissection in a Porcine Model.

Background/Aims: Among several methods used to prevent endoscopic submucosal dissection (ESD) bleeding, the recently developed hemostatic powder (HP) has few technical limitations and is relatively easy-to-use. This study aimed to analyze the hemostatic effects and mechanisms of two HPs using a porcine upper gastrointestinal hemorrhage model. Methods: We evaluated HPs (Endospray and epidermal growth factor [EGF]-endospray) for adhesion, waterproofing ability, permeability, and absorption in vitro. ESD was performed to induce bleeding ulcers in the porcine stomachs. In a total of three pigs, three bleeding ulcers per animal were generated. Hemostasis and rebleeding were evaluated endoscopically. After 72 hours, the animals were sacrificed, and histologically analyzed. Results: The water absorption of HPs was over 20 times the initial value within 30 minutes. The gelated HPs completely blocked water penetration into the applied site within 5 minutes and strongly adhered to the Petri-dish surface for up to 6 hours. The initial hemostasis rates within 5 minutes were 33.3%, 100.0%, and 66.7%, and the rebleeding rates at 6 to 72 hours after HP application were 33.3%, 16.7%, and 33.3% (control, Endospray, and EGF-endospray groups, respectively). Histological analysis revealed the thickness of the regenerated mucosa (522.1, 514.5, and 680.3 µm) and the submucosal layer (1,510.3, 2,848.2, and 3,062.3 µm) and the number of newly formed blood vessels (15.3, 17.9, and 20.5) in the control, Endospray, and EGF-endospray groups, respectively. Conclusions: The endoscopic HPs demonstrated the ability to elicit effective initial hemostasis and the histological ulcer-healing effect of EGF in an animal model of hemorrhagic gastric ulcers.

Bioactive ceramic coating of cancellous screws improves the osseointegration in the cancellous bone.

BACKGROUND: A number of methods for coating implants with bioactive ceramics have been reported to improve osseointegration in bone, but the effects of bioactive ceramic coatings on the osseointegration of cancellous screws are not known. Accordingly, biomechanical and histomorphometric analyses of the bone-screw interface of uncoated cancellous screws and cancellous screws coated with four different bioactive ceramics were performed. METHODS: After coating titanium alloy cancellous screws with calcium pyrophosphate (CPP), CaO-SiO(2)-B(2)O(3) glass-ceramics (CSG), apatite-wollastonite 1:3 glass-ceramics (W3G), and CaO-SiO(2)-P(2)O(5)-B(2)O(3) glass-ceramics (BGS-7) using an enameling method, the coated and the uncoated screws were inserted into the proximal tibia and distal femur metaphysis of seven male mongrel dogs. The torque values of the screws were measured at the time of insertion and at removal after 8 weeks. The bone-screw contact ratio was analyzed by histomorphometry. RESULTS: There was no significant difference in the insertion torque between the uncoated and coated screws. The torque values of the CPP and BGS-7 groups measured at removal after 8 weeks were significantly higher than those of the uncoated group. Moreover, the values of the CPP and BGS-7 groups were significantly higher than the insertion torques. The fraction of bone-screw interface measured from the undecalcified histological slide showed that the CPP, W3G, and BGS-7 groups had significantly higher torque values in the cortical bone area than the uncoated group, and the CPP and BGS-7 groups had significantly higher torque values in the cancellous bone area than the uncoated group. CONCLUSIONS: In conclusion, a cancellous screw coated with CPP and BGS-7 ceramic bonds directly to cancellous bone to improve the bone-implant osseointegration. This may broaden the indications for cancellous screws by clarifying their contribution to improving osseointegration, even in the cancellous bone area.

Simple large-scale synthesis of hydroxyapatite nanoparticles: in situ observation of crystallization process.

The noble synthesis method for hydroxyapatite (HAp) nanoparticles was exploited using a fairly simple reaction of Ca(OH)(2) and H(3)PO(4), which does not generate residual harmful anions and consequently does not need an additional washing process. HAp nanoparticles were found to yield from dicalcium phosphate dehydrate (DCPD) as the only intermediate phase, which was monitored by in situ observation study using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), (1)H and (31)P magic-angle spinning (MAS) NMR. Furthermore, we found that the phase evolution of HAp was preceded by heteronucleation of HAp onto the DCPD surface. The combination of scanning electron microscopy (SEM) and inductively coupled plasma atomic emission spectroscopy (ICP-ES) analysis gave more information on the HAp crystallization process, which was found to be retarded by the residual Ca(OH)(2) and slow diffusion process of Ca ions into the interface between HAp and DCPD. These results demonstrate that the synthesis of pure HAp nanoparticles with high throughput can be achieved by controlling the residual Ca(OH)(2) and diffusion process of Ca ions.

A 90-day intravenous administration toxicity study of CaO-SiO2-P2O5-B2O3 glass-ceramics (BGS-7) in rat.

CaO-SiO(2)-P(2)O(5)-B(2)O(3) glass ceramics directly bond to bone and have potential use as a bone substitute material. The present study evaluated the toxicity from subchronic intravenous administration of CaO-SiO(2)-P(2)O(5)-B(2)O(3) glass ceramics to male and female Sprague-Dawley rats. The rats were divided into four groups, each consisting of 10 male and 10 female rats, and administered different amounts of CaO-SiO(2)-P(2)O(5)-B(2)O(3) glass ceramics (aqueous extract 5, 2.5, and 1.25 mL/kg body weight/day and saline) 7 days per week for 90 consecutive days. During the experiment, no deaths were observed in any groups, and there were no remarkable changes in clinical signs, body weight, food and water intake, hematological and serum biochemical parameters, organ weight, and histopathological findings between the control and treated groups. The results show no adverse toxic effects of CaO-SiO(2)-P(2)O(5)-B(2)O(3) glass ceramics (aqueous extract 5 mL/kg body weight/day) to rats of either sex.

Acute transverse myelitis following scrub typhus: A case report and review of the literature.

Context: Scrub typhus is an acute febrile disease caused by Orientia tsutsugamushi. The disease can usually involve the lungs, heart, liver, spleen and brain through hematogenous dissemination. However, very rarely, acute transverse myelitis in the spinal cord develops from scrub typhus. We present a case of acute transverse myelitis following scrub typhus with a review of the literature. Findings: A 66-year-old male visited a hospital for general myalgia, mild headache, and fever in October. He was noted to have thick, black papule skin on his abdomen, which was highly suggestive of scrub typhus. To confirm the diagnosis, O. tsutsugamushi antibody titers were examined and detected highly in serum by an indirect fluorescence antibody assay. Doxycycline, the standard treatment for scrub typhus, was administered. However, after seven days of treatment, he rapidly developed weakness in the right leg, paresthesia in both lower limbs, and voiding difficulty. Spinal magnetic resonance imaging (MRI) revealed lesions with high signal intensity involving the spinal cord at the thoracolumbar junction. Paraparesis gradually improved following steroid pulse therapy for five days. At one-year follow-up, he could walk without cane. Conclusions:Orientia tsutsugamushi causes scrub typhus, which can affect not only the brain, but also the spinal cord. Although acute transverse myelitis develops rarely from scrub typhus, this should be considered as differential diagnosis in patients of fever with neurological deficit in endemic areas.

A 90-day subchronic toxicity study of beta-calcium pyrophosphate in rat.

beta-calcium pyrophosphate has been used as a bone-graft extender. The present study evaluated the toxicity from the subchronic administration of beta-calcium pyrophosphate to male and female Sprague-Dawley rats. Animals were divided into two groups consisting of 10 male and 10 female rats each and fed beta-calcium pyrophosphate extract (30 mg/kg body weight/day) and saline, 7 days per week for 90 consecutive days. During the experiment, no deaths were observed in any groups, and there were no remarkable changes in clinical signs, body weight, food and water consumption, hematological and serum biochemical parameters, organ weight, and histopathological findings between the control and treated groups. The results show no adverse toxic effects of beta-calcium pyrophosphate extract (30 mg/kg body weight/day) for rats of either sex.

Clinical Outcomes and Prognostic Factors in Patients With Myelopathy Caused by Thoracic Ossification of the Ligamentum Flavum.

OBJECTIVE: The objective of this study was to investigate the surgical outcomes and prognostic factors for thoracic ossification of the ligamentum flavum (OLF) after decompressive laminectomy, focusing on the quantitative signal intensity ratio (SIR) of preoperative magnetic resonance imaging (MRI) and its prognostic significance. METHODS: We retrospectively reviewed 24 patients who previously underwent total laminectomy to remove OLF from 2010 to 2015. MRI and computed tomography were performed to detect OLF. The SIR between the regions of interest of high signal intensity lesions and the normal cord at the T1-2 disc levels was calculated. We divided patients into 2 groups based on the extent of the modified Japanese Orthopaedic Association (JOA) recovery rate (RR): good (RR ≥ 50%) and poor (RR < 50%). RESULTS: The mean preoperative and postoperative modified JOA scores for thoracic myelopathy were 6.67 ± 1.73 and 8.63 ± 1.81, respectively (p < 0.001). The preoperative JOA score (7.5 vs. 5.83, p = 0.028), postoperative JOA score (9.83 vs. 7.42, p = 0.000), and SIR (1.16 vs. 1.41, p = 0.009) were significantly different between the good and poor RR groups. A higher preoperative JOA score and lower SIR were associated with a good RR according to the JOA criteria. CONCLUSION: The clinical outcomes for thoracic OLF after decompressive laminectomy were favorable. A higher RR was correlated with a lower SIR and higher preoperative modified JOA score. Therefore, a relatively low SIR on MRI and a relatively high preoperative JOA score could be positive prognostic indicators for the JOA RR in patients with thoracic OLF.

Dural Penetration of Cavernous Hemangioma on Skull: Uncommon Clinical Presentation.

BACKGROUND: Cavernous hemangioma (CH) of the bone is a rare, benign neoplasm found usually in the vertebral body. This tumor rarely develops in the calvaria, with predilection to occur in the frontal and temporoparietal bones. CASE DESCRIPTION: A 56-year-old man with a right frontal palpable mass was admitted to our hospital. Magnetic resonance imaging (MRI) revealed a large extra-axial tumor in the right frontal bone. Intraoperatively, the bony mass involved the multilayers composed of extracranium-skull-dura-intradura-cortex. Pathologic examination revealed a typical calvarial CH penetrating dura mater. CONCLUSIONS: This is the second reported case of calvarial CH with complete erosion of the dural plane and extension into subdural space. Although surgical resection is generally safe and easy, the possibility of dural invasion should be kept in mind for safe resection of calvarial CH, especially overlying the eloquent brain area.

A rapamycin derivative, biolimus, preferentially activates autophagy in vascular smooth muscle cells.

Although rapamycin is a well-known conformational inhibitor of mTORC1, it is now widely used for treating arterial restenosis. Various rapamycin analogues (rapalogue) have been made for applying to drug-eluting stents. Here we show that two major rapalogues, everolimus and biolimus, exert a differential effect on the mTORC1-mediated signaling pathways in vascular smooth muscle cells. In balloon-injured carotid arteries, both rapalogues strongly inhibit neointimal hyperplasia. Signaling pathway analyses reveal that everolimus exert cytotoxicity by increasing cellular reactive oxygen species and consequently reduce energy metabolism. By contrast, biolimus confers a preferential induction of autophagy by more strongly activating major autophagy regulator, ULK1, in vascular smooth muscle cells than everolimus does. As a consequence, the implantation of biolimus-eluting stent reduces endothelial loss, which in turn reduces inflammation, in porcine coronary arteries. Thus, this study reveals that a chemical derivatization can cause a change among mTORC1-dependent signaling pathways in vascular smooth muscle cells, thereby enabling to elicit a differential efficacy on arterial restenosis.

Recurred Intracranial Meningioma: A Retrospective Analysis for Treatment Outcome and Prognostic Factor.

BACKGROUND: In this study, we aimed to compare repeated resection and radiation treatment, such as Gamma knife radiosurgery (GKRS) or conventional radiotherapy (RT), and investigate the factors influencing treatment outcome, including overall survival (OS), progression-free survival (PFS), and complication rates. METHODS: We retrospectively reviewed 67 cases of recurred intracranial meningiomas (repeated resection: 36 cases, radiation treatment: 31 cases) with 56 months of the median follow-up duration (range, 13-294 months). RESULTS: The incidence of death rate was 29.9% over follow-up period after treatment for recurred meningiomas (20/67). As independent predictable factors for OS, benign pathology [hazard ratio (HR) 0.132, 95% confidence interval (CI) 0.048-0.362, p<0.001] and tumor size <3 cm (HR 0.167, 95% CI 0.061-0.452, p<0.001) were significantly associated with a longer OS. The incidence of progression rate was 23.9% (16/67). Only treatment modality was important for PFS as an independent predictable factor (GKRS/RT vs. open resection; HR 0.117, 95% CI 0.027-0.518, p<0.005). The complication rate was 14.9% in our study (10/67). Larger tumor size (≥3 cm, HR 0.060, 95% CI 0.007-0.509, p=0.010) was significant as an independent prognostic factor for development of complications. Although treatment modality was not included for multivariate analysis, it should be considered as a predictable factor for complications (p=0.001 in univariate analysis). CONCLUSION: The role of repeated resection is questionable for recurred intracranial meningiomas, considering high progression and complication rates. Frequent and regular imaging follow-up is required to detect recurred tumor sized as small as possible, and radiation treatment can be a preferred treatment.

In vivo study of novel biodegradable and osteoconductive CaO-SiO2-B2O3 glass-ceramics.

To evaluate the possibility of novel CaO-SiO2-B2O3 glass-ceramics (CS10B) as a new bone replacement material, we compared the biodegradation and osteoconduction properties of CS10B, hydroxyapatite (HA), and tricalcium phosphate (TCP). Porous CS10B implants were prepared by the polymer sponge method. L5-6 single-level posterolateral spinal fusions were performed on 30 New Zealand white male rabbits. The animals were divided into three groups by implant material: CS10B, HA, and TCP. Radiographs were performed every 2 weeks. All animals were euthanized 12 weeks after surgery. The ratio of the area occupied by the ceramics by final and initial radiographs was calculated using radiomorphometric analysis. Uniaxial tensile strength was determined from seven cases in each group. The ratio of the area occupied by HA (88.7%+/-16.1%) was significantly higher than the others (p<0.005), and the ratio of the area occupied by CS10B (28.2%+/-9.3%) was significantly lower than those of HA and TCP (37%+/-9.6%, p<0.05). The mean values of the tensile strengths of the CS10B (182.7+/-19.9 N) and HA (191.4+/-33.5 N) were significantly higher (p<0.05) than that of TCP (141.1+/-28.2 N). CS10B had a fusion mass tensile strength similar to that of HA. Histological analysis confirmed that CS10B was well incorporated into the fusion mass. These findings suggest that CS10B is a possible bone replacement material.

Biomechanical and histomorphometric study on the bone-screw interface of bioactive ceramic-coated titanium screws.

The purpose of this study was to compare the osseointegration of 4 different kinds of bioactive ceramic-coated screws with uncoated screws by biomechanical and histomorphometric analysis. Calcium pyrophosphate (CPP), apatite-wollastonite 1:3 glass ceramic (W3G), apatite-wollastonite 1:1 glass ceramic (WAG) and bioactive CaO-SiO2-B2O3 glass ceramic (CSG) coatings were prepared and coated by the dipping method. Coated and uncoated titanium screws were inserted into the tibia of 18 adult mongrel male dogs for 2, 4, and 8 weeks. The insertion torques, radiographs, undecalcified histology, histomorphometric analysis, and extraction torques were evaluated. No difference of insertion torque was found among the five screw types. At 2 and 4 weeks after implantation, the extraction torque of ceramic-coated screws was significantly higher than that of uncoated screws (p < or = 0.0001). At 8 weeks, the extraction torques of CPP-, W3G-, and WAG-coated screws were significantly higher than those of CSG-coated and uncoated screws (p<0.0001). At 2, 4, and 8 weeks, the extraction torques of 4 different ceramic-coated screws were significantly higher than the corresponding insertion torque. Strong fixation was observed even at 2 weeks in the CPP-, W3G- and WAG-coated screws. The bone-screw contacts of the 4 different coated screws at 2 and 4 weeks were statistically higher than that of the uncoated screws, and the bone-screw contacts of the CPP-, W3G- and WAG-coated screws at 8 weeks were also statistically higher than that of the uncoated screws. The fixation strength was increased by the presence of osteoconductive coating materials, such as CPP, W3G, and WAG, which enabled to achieve higher fixation strength even as early as 2-8 weeks after the insertion.

An improvement in sintering property of beta-tricalcium phosphate by addition of calcium pyrophosphate.

The sintering behavior of calcium pyrophosphate (CPP, Ca2P2O7)-doped beta-tricalcium phosphate [TCP, Ca3(PO4)2], prepared by solid state reaction, was investigated in-situ, using dilatometry. Pure beta-TCP undergoes phase transition to alpha-TCP at about 1200 degrees C; hence pure beta-TCP ceramics should be sintered bclow 1200 degrees C. Pure beta-TCP sintered body can achieve a relative density of only 86% when sintered at 1150 degrees C. However, the addition of CPP in the range of 0.5-3 wt% delays phasc transition of beta-TCP and enables sintering of beta-TCP at 1200 degrees C without a phase transformation to alpha-TCP. Due to this effect of CPP added to TCP, CPP-doped beta-TCP ceramics with relative density over 95% could be obtained when sintered at 1200 degrees C for 2 h.

Magnesia-doped HA/beta-TCP ceramics and evaluation of their biocompatibility.

The sintering behavior, mechanical properties and biocompatibility of magnesia (MgO)-doped HA/TCP biphasic ceramics were studied. Pure HA/TCP ceramics showed poor sinterability due to the phase transformation of beta- to alpha-TCP. MgO-doped HA/TCP ceramics showed high density without any phase transformation of beta-TCP up to 1300 degrees C, for MgO dopants incorporated into the beta-TCP preferably and increased thermal stability of beta-TCP. However, the addition of MgO higher than a critical content, suppressed grain growth of HA/TCP ceramics and lowered sinterability. The optimum amount of MgO doping was 1 wt%, which lead 99% relative density and higher mechanical properties than HA or beta-TCP ceramics. From in vitro test and in vivo test, 1 wt% MgO-doped HA/TCP ceramics showed a good biocompatibility without cytotoxicity. After implantation under the muscle of rabbits, beta-TCP phase was dissolved from the surface and a biological apatite covered the surface. These results proved that MgO addition increased drastically the sintering and mechanical properties of HA/beta-TCP ceramics without altering the biological safety and biocompatibility of the original composite.

Novel bioactive and biodegradable glass ceramics with high mechanical strength in the CaO--SiO2--B2O3 system.

Novel bioactive and biodegradable glass ceramics with high mechanical strength in the (50-x/2)CaO. SiO(2)--xB(2)O(3) (4.2 < or = x < or = 17.2) system were investigated. The systems consisted of three phases: monoclinic wollastonite, calcium metaborate, and amorphous borosilicate matrix. The glass ceramics containing 4.2 mol% and 8.4 mol% B(2)O(3) showed high bulk density and a dense microstructure. Mechanical strengths of the glass ceramics were higher than those of other bioactive ceramics: high compressive strength (2813 MPa), bending strength of 212 MPa, and fracture toughness of 3.12 MPa. m(1/2). The glass-ceramic formed apatite layer on their surface in the simulated body fluid and showed significant biodegradation. The degree of apatite formation in the glass ceramics depended on the calcium metaborate content and borosilicate glassy matrix. Additional calcium metaborate and borosilicate glassy matrix increased the apatite formation rate on the surface. It might be likely that calcium metaborate causes supersaturation of Ca ions, for its high solubility in SBF and the water-reactive borosilicate glassy matrix formed Sibond;OH groups on the surface to provide nucleation sites for apatite formation. Also, through in vitro test for the biocompatibility of the CaO--SiO(2)--B(2)O(3) glass ceramics, no cytotoxicity of the glass ceramics were found. The results on bioactivity and noncytotoxicity indicated that glass ceramics in the (50-x/2)CaO. SiO(2)--xB(2)O(3) (4.2 < or = x < or = 17.2) system could be useful as a biodegradable bone replacement material.