Porous Granules Research Articles

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<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<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.

An Electrochemically Surface-modified Porous Granule Developed for Phosphate Removal from Aqueous Solution

Abstract A porous granule was developed from Kanuma clay, corn starch, iron powder, white cement, and calcium oxide for phosphate removal. An electrochemical surface modification (ESM) process was then adopted during the preparation of the porous granule (PG). The results reflect that PG is a more promising adsorbent than other clay mineral materials for phosphate removal from wastewater, and ESM process is approved to be a novel effective surface modification path.

The use of porous titanium granules for treatment of peri-implantitis lesions: preliminary clinical and radiographic results in humans

The aim of the present study is to report on preliminary clinical and radiographic results of using porous titanium granules for treatment of peri-implantitis lesions. A retrospective cohort of 18 implants presenting with peri-implantitis in 16 consecutive patients from two private practices had been evaluated. Treatment included open flap debridement of the lesion, implant surface decontamination using tetracycline, filling of the defect with porous titanium granules and apically positioning of the flaps. Patients' demographics, site and implant characteristics, as well as clinical and radiographic evaluation as baseline and time of follow-up were recorded. Patients' age ranged from 44 to 79 years with a mean of 61.3 ± 9.5 years. Follow-up time after treating peri-impantitis lesions ranged from 6 to 15 months (mean 7.5 ± 3.9). Two out of the 18 implants still presented with bleeding and suppuration at follow-up and thus the treatment was considered as a failure. This resulted in an overall success rate of 88% for the treatment. Mean bone loss prior to treatment was 4.4 ± 2.1 mm and was reduced following treatment to 2.3 ± 2.1 mm. The use of porous titanium granules might be a viable treatment option in cases of peri-implantitis lesions. Further large-scale long-term studies are warranted in order to assess the additional benefit from this treatment option compared to other available alternatives. assiduous.

Compression and breakage behavior of γ-Al2O3 granules

Abstract The material behavior of dominant elastic–plastic, spherical γ-Al2O3-granules at compression until primary breakage has been experimentally studied. For this, the mechanical properties of the granules were determined using recorded force–displacement-curves. The influence of particle size and moisture content on the compression behavior has also been investigated. Additionally, the specific fracture energy distribution and the distribution of the equivalent impact velocity at fracture were derived from the force–displacement-curves. The work provides a basis for understanding the influence on the material behavior at wetting of hygroscopic and highly porous granules.

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.

Porous Titanium Granules and Blood for Bone Regeneration around Dental Implants: Report of Four Cases and Review of the Literature

A regenerative procedure treating a local osseous defect around titanium dental implant using porous titanium granules is described in four patients. Porous titanium granules represent, for maxillofacial surgery, a new alternative in augmenting osseous defects. Its earliest application was in the field of orthopedics for stabilization of tibia plateau fractures and for reoperations in prosthetic fixation of femoral stems. There is emerging scientific evidence regarding titanium for its potential use in the maxillofacial area and porous titanium granules are now commercially available. The scientific background for the osteoconductive use of porous titanium granules is elucidated in this paper and the supporting literature is reviewed.

Effect of Thermal Treatment of the Hydroxyapatite Powders on the Micropore and Microstructure of Porous Biphasic Calcium Phosphate Composite Granules

The effect of thermal treatment of the hydroxyapatite powders on the micropore structure of porous biphasic calcium phosphate (BCP) granules was examined. The porous BCP granules could be attained through mixing and sintering/fracturing thermally treated 60 wt% hydroxyapatite powders and calcined 40 wt% β-tricalcium phosphate powders. The observed Scanning electron microscopy (SEM) morphologies showed that the density of micropores (0.1 - 2.0 μm) including interconnected micropores of the porous BCP granules mixed with hydroxyapatite powders thermally treated at 900°C was significantly improved and the composite particles of porous BCP granules were homogeneously mixed and distributed. This result indicates that the particles of hydroxyapatite powders that have a tendency to agglomerate at a room temperature were well isolated and dispersed through thermal treatment processing before mixing with calcined β-tricalcium phosphate powders. The microstructural characterizations such as phase purity and composition of porous BCP granules were performed and verified by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analysis.

Maxillary Sinus Augmentation with Porous Titanium Granules: A Microcomputed Tomography and Histologic Evaluation of Human Biopsy Specimens

The aim of this study was to assess bone ingrowth into porous titanium granules used for maxillary sinus augmentation. Eighteen biopsy specimens from 17 patients participating in a clinical trial on sinus augmentation using porous titanium granules (PTG) were received in the laboratory. The specimens (trephine cores of 4.5 mm) were obtained 6 months after PTG placement. After being embedded in methacrylate, the samples were scanned in a microcomputed tomography (micro-CT) scanner. Specimens were then cut along the long axis and central slices were ground to 70 μm before staining with hematoxylin and eosin. The micro-CT analysis demonstrated an average bone fill of 19% (standard deviation [SD] 5.8%), whereas the graft material occupied 22.7% (SD 4.7%). The volume of newly formed bone decreased with the distance from the residual bone of the sinus floor. Two-dimensional histomorphometric analysis demonstrated a mean area of new bone of 16.1% (SD 9.4%). The PTG alone occupied 25.9% of the total mean area (SD 6.1%). The newly formed bone consisted mainly of woven bone growing in close contact with the granules and bridging the intergranular space. The remaining area was occupied predominantly by nonmineralized connective tissue. There were no signs of inflammation in any of the biopsy specimens. After 6 months, new bone had formed at a similar rate and quality as has been reported for other well-recognized bone graft substitutes. The new bone formed in close contact with the PTG, suggesting that the material is osteoconductive.

Degradation of Porous Starch Granules and Poly(Butylene Adipate-co-Terephthalate)(PBAT) Blends: Soil Burial and Enzymatic Tests

In order to confirm the feasibility of porous rice starch granules and PBAT blends as biodegradable composites, their degradability were carried out. Enzymatic degradability evaluation showed that α-amylase degradation of starch increased as the starch content in the blend increased. Burial test of the blends for 1-4 months was carried out and the rate of degradation of the PBAT/porous starch blend was confirmed to be slower than those of PBAT/native rice starch blend. Observation of the film blends structure by scanning electron microscope revealed that the starch was dispersed in a PBAT matrix. Furthermore, changes in the film surface after enzyme treatments were observed. The results obtained from the degradability of the porous starch granules and PBAT blends showed that this bio-composite was relatively slow, regarding as controllable degradation material.

The Influence of Physically Doping NaCl with Other Salts on Aerosol and Solion Generation

The paper presents the influence of physically doping NaCl grains with 0.5% KCl, KI, MgCl2 and CaCl2 on the release of negative aerosols/solions in dynamic halochambers. The salts used for doping were chosen according to the current procedures to obtain therapeutic and ambient mediums in aerosols with a negative charge based on NaCl. The aerosols were released by pumping an airflow of 1.8 L/min through a cartridge containing 60g of porous granules, with diameters between 4.0 and 6.6 mm, which were obtained by extruding dispersions of aqueous pasty-damp, saline solutions. We used an optical particle counter and a micro-chamber, divided into 10 equal rooms and with a zigzagged airflow delimited into three areas in each room. The upper side was fitted with several injectors to be coupled to the particle counter. Using this device we studied the aerosol emission dynamics over time, by keeping the temperature and humidity in normal conditions, as in the atmospheric air. Based on the evolution of the saline particles, which were divided into two stable groups in the air, namely gaseous microdispersions and gigantic dispersions, we evaluated their concentrations over time, by keeping the airflow that was pumped into the capsule constant. We thus determined the emission ratio over time and the lifespan of the solions in the three areas, over the halochamber functioning period and after the emission ceased. Aerosol/solion generation involves different sets of laws, based on the nature of the doping salt and the conditions in the environment. Therefore, one may select the doping conditions for the aerosol/solion generation granules and the optimal dynamic halochamber functioning time, for use with preventive, therapeutic, or physical performance enhancing applications.

Development and in vitro assays of porous calcium polyphosphate granules

Abstract Porous calcium polyphosphate granules (CPPGs) for hard tissue regeneration were developed using amorphous calcium phosphate (CaP) glass particles. The glass particles were synthesised using a conventional glass melting technique, and the CPPGs were fabricated by a cement hardening process consisting of an acid–base reaction and a condensation reaction, which was developed in our previous studies. The pore sizes of the CPPGs were controlled using polymeric pore generators (porogens) of various sizes. The glass particles and CPPGs were analysed using X-ray diffractometry and Fourier transform infrared spectroscopy. The porosity of the CPPGs increased from 33.327% to 48.706% as the size of the porogens was decreased. To evaluate the cellular response to the developed porous CPPGs, cell proliferation and differentiation tests were performed, and an analysis of the relationship between the porosity and bioactivity was carried out. The results showed that both pore size and porosity influenced the osteogenic differentiation as well as the cell proliferation. This was due to the calcium ion release rate, which increased as the porosity increased and affected cellular behaviour. In conclusion, the porous CPPGs fabricated using amorphous CaP glass particles were shown to have potential as excellent bone graft materials.

Expression of an engineered granule-boundEscherichia coliglycogen branching enzyme in potato results in severe morphological changes in starch granules

The Escherichia coli glycogen branching enzyme (GLGB) was fused to either the C- or N-terminus of a starch-binding domain (SBD) and expressed in two potato genetic backgrounds: the amylose-free mutant (amf) and an amylose-containing line (Kardal). Regardless of background or construct used, a large amount of GLGB/SBD fusion protein was accumulated inside the starch granules, however, without an increase in branching. The presence of GLGB/SBD fusion proteins resulted in altered morphology of the starch granules in both genetic backgrounds. In the amf genetic background, the starch granules showed both amalgamated granules and porous starch granules, whereas in Kardal background, the starch granules showed an irregular rough surface. The altered starch granules in both amf and Kardal backgrounds were visible from the initial stage of potato tuber development. High-throughput transcriptomic analysis showed that expression of GLGB/SBD fusion protein in potato tubers did not affect the expression level of most genes directly involved in the starch biosynthesis except for the up-regulation of a beta-amylase gene in Kardal background. The beta-amylase protein could be responsible for the degradation of the extra branches potentially introduced by GLGB.

Sorption of Inorganic Substances on the Porous Latvian Clay Ceramic

Devonian clay of Liepa deposit (district of Cesis) and Quaternary clay of Laza deposit (district of Aizpute) was investigated. Pellets were fired at four different temperatures of 700, 800, 900, and 1050 °C. Porosity and surface area of pellets was determined by mercury porosimetry. The pH values after water immersion of fired pellets was determined with a pHmeter. The sorption ability of molecular substance (iodine) and ionic substances (ammonia and dichromate) were determined by titrimetric methods. The best sorption ability was found for iodine molecules. The entire amount of iodine in the water suspension was absorbed in two weeks, and the sorption ability reached 12.5 mg/g for samples fired at 700 and 800 °C temperature for the Liepa clay and 13.0 mg/g for the Laza clay. The sorption ability of these clay pellets for ammonia was lower and amounted to 3.0 and 2.5 mg/g, respectively. The sorption ability for dichromate ion was even less - only 0.6 mg/g for pellets of both clays. The investigated fired porous clay granules exhibited distinct sorption properties towards water-soluble ionic and molecular substances, which depended more on the firing temperature of granules and less on the source of clay.

Osseointegration of dental implants in extraction sockets preserved with porous titanium granules – an experimental study

This study investigated osseointegration of dental implants inserted in healed extraction sockets preserved with porous titanium granules (PTG). Three adult female minipigs (Gøttingen minipig; Ellegaard A/S, Dalmose, Denmark) had the mandibular teeth P2, P3 and P4 extracted. The extraction sockets were preserved with metallic PTG (Tigran PTG; Tigran Technologies AB, Malmö, Sweden) n = 12, heat oxidized white porous titanium granules (WPTG) (Tigran PTG White) n = 12 or left empty (sham) n = 6. All sites were covered with collagen membranes (Bio-Gide; Geistlich Pharma, Wolhausen, Switzerland) and allowed 11 weeks of healing before implants (Straumann Bone Level; Straumann, Basel, Switzerland) were inserted. The temperature was measured during preparation of the osteotomies. Resonance frequency analysis (RFA, Osstell; Osstell AB, Gothenburg, Sweden) was performed at implant insertion and at termination. After 6 weeks of submerged implant healing, the pigs were euthanized and jaw segments were excised for microCT and histological analyses. In the temperature and RFA analyses no significant differences were recorded between the test groups. The microCT analysis demonstrated an average bone volume of 61.7% for the PTG group compared to 50.3% for the WPTG group (P = 0.03) and 57.1% for the sham group. Histomorphometry demonstrated an average bone-to-implant contact of 68.2% for the PTG group compared to 36.6% for the WPTG group and 60.9% for the sham group (n.s). Eight out of ten implants demonstrated apical osseous defects in the WPTG group, but similar defects were observed in all groups. PTG preserved extraction sockets demonstrate a similar outcome as the sham control group for all analyses suggesting that this material potentially can be used for extraction socket preservation prior to implant installment. Apical osseous defects were however observed in all groups including the sham group, and a single cause could not be determined.

Hydrolysis of native and cross‐linked corn, tapioca, and sweet potato starches at sub‐gelatinization temperature using a mixture of amylolytic enzymes

AbstractThe objectives of this research were to investigate the capability of a new hydrolyzing enzyme to hydrolyze native and cross‐linked starches in the granular state and to examine the influence of cross‐linking on hydrolysis. Corn, tapioca, and sweet potato starches were chemically modified by cross‐linking with 1% epichlorohydrin. The native and cross‐linked starches were subjected to hydrolysis using a new commercial enzyme, STARGEN™ 001 (a blend of α‐amylase and glucoamylase), at 35°C for 24 h, and the physicochemical properties of the starches were determined at different time points. After hydrolysis, the dextrose equivalent (DE) values of corn and tapioca starch decreased significantly after being cross‐linked (from 52.5 to 48.8% and from 35.7 to 27.9%, respectively). However, the sweet potato starch underwent a minimal reduction in DE value (from 27.3 to 26.8%). Scanning electron micrographs revealed that all cross‐linked starches had less porous granules compared to native starches after being hydrolyzed. Enzymatic erosion occurred mainly on the surface of starch granules, and the pores deepened into the interior part of the granules. The swelling power and solubility of all three cross‐linked starch decreased significantly after hydrolysis. Cross‐linking had a greater effect on pasting properties but little influence on the gelatinization properties of starch. The pasting temperature of cross‐linked tapioca starch was undetectable due to high degree of cross‐linking (92.4%). This study showed that cross‐linking had a considerable impact on the hydrolysis of corn and tapioca starch in particular by reducing the swelling power and solubility of its granules.

Intraoperative engineering of osteogenic grafts combining freshly harvested, human adipose-derived cells and physiological doses of bone morphogenetic protein-2

Engineered osteogenic constructs for bone repair typically involve complex and costly processes for cell expansion. Adipose tissue includes mesenchymal precursors in large amounts, in principle allowing for an intraoperative production of osteogenic grafts and their immediate implantation. However, stromal vascular fraction (SVF) cells from adipose tissue were reported to require a molecular trigger to differentiate into functional osteoblasts. The present study tested whether physiological doses of recombinant human BMP-2 (rhBMP-2) could induce freshly harvested human SVF cells to generate ectopic bone tissue. Enzymatically dissociated SVF cells from 7 healthy donors (1 x 10(6) or 4 x 10(6)) were immediately embedded in a fibrin gel with or without 250 ng rhBMP-2, mixed with porous silicated calcium-phosphate granules (Actifuse(®), Apatech) (final construct size: 0.1 cm(3)) and implanted ectopically for eight weeks in nude mice. In the presence of rhBMP-2, SVF cells not only supported but directly contributed to the formation of bone ossicles, which were not observed in control cell-free, rhBMP-2 loaded implants. In vitro analysis indicated that rhBMP-2 did not involve an increase in the percentage of SVF cells recruited to the osteogenic lineage, but rather induced a stimulation of the osteoblastic differentiation of the committed progenitors. These findings confirm the feasibility of generating fully osteogenic grafts using an easily accessible autologous cell source and low amounts of rhBMP-2, in a timing compatible with an intraoperative schedule. The study warrants further investigation at an orthotopic site of implantation, where the delivery of rhBMP-2 could be bypassed thanks to the properties of the local milieu.

Mechanical Debridement of a Peri‐Implant Osseous Defect With a Novel Titanium Brush and Reconstruction With Porous Titanium Granules: A Case Report With Reentry Surgery

Introduction: The scientific evidence for one specific treatment strategy for peri‐implant osseous defects is scarce. It will be important to develop methods for efficient decontamination of ailing implants and for reconstruction of lost peri‐implant osseous attachment. Access for instrumentation of narrow peri‐implant defects is difficult, and to the best of our knowledge, this case report describes, for the first time, the use of a novel titanium brush for mechanical debridement of the implant surface and the defect. Histologic evidence that porous titanium granules (PTGs) support reosseointegration has recently been reported.Case Presentation: A healthy female patient had two implants placed for prosthetic rehabilitation of teeth #21 and #23. In conjunction with second‐stage surgery, a buccal osseous defect was disclosed at the most anterior implant. The narrow and deep defect was debrided with a novel titanium brush, chemically decontaminated with 3% H2O2, and filled with PTGs. In conjunction with second‐stage surgery, after 6 months of submerged healing, the peri‐implant defect was almost completely healed, with only a 3 mm osseous defect remaining at the coronal part of the implant. The PTG bone replacement graft appeared completely integrated in new bone, with no signs of loose particles. At clinical and radiographic examinations, 24 months after surgical treatment, no signs of inflammation or reoccurring bone loss were seen.Conclusion: To the best of our knowledge, this case report demonstrates, for the first time, that debridement with a titanium brush, 3% H2O2, and reconstruction with PTGs is a potential treatment modality of narrow peri‐implant osseous defects.

Evaluation of formation process of spherical porous biphasic calcium phosphate (BCP) granules by slurry dripping method

In this study, we investigated the formation behavior of spherical porous biphasic calcium phosphate (BCP) granules, in which PCL was both the binder and fugitive pore former. The formation of porous granules was based on the immiscibility of PCL slurry containing BCP powder and distilled water. The porosity was controlled by controlling the volume fraction of PCL. In addition, the effect of the composition on the rheological properties and consequently the droplet formation mechanism was examined. After drying and sintering, the resulting BCP granules had a porous structure, which could promote stronger cell in-growth behavior. The method developed in this study can be utilized to successfully fabricate granules with controlled porosity and size.

Production and Characterization of Porous Starch Granule and Poly(butylene adipate-co-terephthalate) Blend as a Bio-Composite

To improve the miscibility of native rice starch granules and poly(butylene adipate-co-terephthalate)(PBAT), rice starch was hydrolyzed by a mixture of α-amylase and amyloglucosidase. The obtained porous rice granular starch was then mechanically blended with PBAT by single screw extruder. Many pits and holes on the surface of starch granules were observed by scanning electron microscopy (SEM). The rough surface of the rice starch granules improved the compatibility of the polymers in the blends, which consequently increased the tensile strength and the elongation at break. In addition, SEM also revealed that the porous granules were homogeneously distributed in the polymer matrix with no appearance of gaps.

Performance of double-layer biofilter packed with coal fly ash ceramic granules in treating highly polluted river water

To improve trickling filters’ denitrification efficiency, a biofilter with a trickling upper layer and a submerged lower layer was developed and applied in treating highly polluted river water. It was packed with porous coal fly ash ceramic granules. Its start-up characteristics, influence of hydraulic loading rates (HLR), carbon/nitrogen (C/N) ratio and filter depth on pollutants removal were investigated. The results indicated this biofilter was started quickly in 16days with river sediment as inoculum. Alternating nitrification and denitrification were achieved when water flowed downwards. COD and nitrogen were mainly removed in the upper layer and the lower layer, respectively. With HLR of 4.0–5.0m3/(m2d), chemical oxygen demand (COD), ammonium (NH4+–N) and total nitrogen (TN) in the effluent were below 50, 5 and 15mg/L, respectively. This biofilter removed more than 80% of COD, 85% of NH4+–N and 60% of TN with C/N ratios ranging from 6 to 10.