Porous Hydroxyapatite Block Research Articles

Effects of fluoride on in vitro hydroxyapatite demineralisation analysed by 19F MAS-NMR

IntroductionFluoride plays a major role in inhibiting enamel dissolution and promoting fluorapatite formation. Porous hydroxyapatite (HAP) discs can be used as an enamel analogue in artificial demineralisation/remineralisation studies.MethodThe aim of the study was to monitor the fluoride-mineral phases formed on HAP surfaces as a function of fluoride concentration ([F−]) under demineralising conditions, using 19F magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy, and compare the results with a previous study using an enamel substrate. Porous HAP blocks were immersed in demineralisation solutions (0.1 M acetic acid, pH 4.0) with increasing [F−] (0–1450 ppm).ResultsAt below 50 ppm [F−], 19F MAS-NMR showed fluoride-substituted apatite formation; above 50 ppm [F−], calcium fluoride (CaF2) was formed in increasing proportions. These results mirrored those of previous similar studies with an enamel substrate. Further increases in fluoride caused no further measurable reduction in demineralisation but increased the proportion of CaF2 formed. The total calcium concentration [Ca] and total phosphorus [P] concentrations in the solution were measured by inductively coupled plasma atomic emission spectroscopy. At high fluoride concentrations, the solution total [P] increased, and the molar Ca:P ratios decreased to values consistent with the formation of CaF2. However, Ca:P ratios found at low [F−] were higher than those in the previous enamel study and consistent with the formation of a partially fluoridated apatite.ConclusionsUnder demineralising conditions, CaF2 formed on HAP at an [F−] of 50 ppm and above, whereas fluoridated apatite formed at an [F−] below 50 ppm. The results were consistent with those obtained when an enamel substrate was used.

Is There a Difference in Postsurgical Complications between Alloplastic and Allogeneic Bone Grafting following Le Fort I Osteotomy?

Statement of the problemWidening, advancing, and/or inferiorly repositioning the maxilla during Le Fort I osteotomy provides challenges to the surgeon secondary to interpositional bony gaps created across the osteotomy. Although several studies investigate the use of autogenous and non-autogenous bone graft materials to help overcome such challenges, there is a scarcity in the literature regarding the use of allogeneic bone as a bone graft substitute. The aim of the present study is to evaluate differences in postsurgical complications following use of allogeneic and alloplastic bone graft substitutes during Le Fort I osteotomy. Materials and methodsThis retrospective study involved analysis of electronic medial records of all patients who underwent Le Fort I osteotomy with internal rigid fixation and grafting over an 8-year period. A total of 233 records were reviewed, and subjects grafted with exclusively autogenous bone graft, grafted with multiple bone substitute types, or with less than 6 months follow-up were excluded. The study sample included 97 patients who were divided into 2 groups based on the bone graft material used; Group 1: porous block hydroxyapatite (PBHA); and Group 2: allogeneic iliac tricortical bone. Incidence of graft dehiscence, surgical site infection, and non-union was recorded for each group. Method of data analysisA Chi-square test of independence was performed to examine the relation between bone graft substitute and incidence of postsurgical complications. A P-value of less than .05 was considered statistically significant. ResultsThe patients’ mean age at surgery in Group 1 was 20 years and in Group 2 was 29 years. Average follow-up in each group was 9 months. The overall incidence of postsurgical complications was 9.97%, and 11.76% in Group 1 and 7.94% in Group 2. There were no statistically significant differences in postsurgical complications between Group 1 and Group 2 . Patients younger than 37 years of age had fewer postsurgical complications (5.56%) when compared to those over the age of 37 years (20.00%) (P < .05). Patients with concomitant mandibular orthognathic surgery had lower graft healing complication incidence (6.98%) as compared to isolated Le Fort I osteotomy patients (27.27%) (P < .05). ConclusionBoth bone graft materials have comparable graft-related complication rates in Le Fort I osteotomies. Incidence of complications is lesser in younger patients and those undergoing concomitant mandibular orthognathic surgery. The need for autogenous bone grafting in maxillary surgery could be questioned based on the results of this study.

Bone Induction in Porous HAp Block Modified by Partial Dissolution-Precipitation Technique with Supersonic Treatment in Rat Scalp

Microcracks and trabecular fractures can be observed in physiological bone. Biomimetic hydroxyapatite (HAp) scaffolds have been strongly needed in bone regenerative medicine. We have been developing the combination method of the partial dissolution-precipitation techniques involving the stirring-supersonic treatment in 1.7×10-2 N HNO3 solution containing Ca2＋and PO43- ions to improve the surface and the bulk of commercially available synthetic HAp block (82.5% in porosity, 50-300µm in macropore). The modified HAp was named as a partially dissolved and precipitated HAp (PDP-HAp). The aims of this study are to characterize the PDP-HAp and to observe cell response for the ceramics in rat scalp tissue. The PDP-HAp exhibited the macropore sizes of 50-200µm, the porosities of 85-90%, and the specific surface areas of 1.0-2.0 m2･g-1, with many micro-cracks. Twenty rats were divided into 2 groups. At 9 months, bone induction occurred inside the many pores in the PDP-HAp group, while bone and cartilage were not found in the HAp group. We believe that osteoinduction by the PDP-HAp is different from the process of BMP-loaded HAp-induced bone formation. The PDP-HAp might be applied as potential ceramics with osteoinductive properity and excellent biocompatibility in difficult bone regenerative cases.

Application of porous hydroxyapatite blocks for maxillofacial deformities

Background In maxillofacial fields, concave deformity often requires hard tissue augmentation. Various types of materials are used for facial augmentation: Hydroxyapatite is the most ideal material because of its remarkable biocompatibility and ability to maintain the desired form for a long period. This article describes a simple surgical procedure to augment facial concavity with porous hydroxyapatite block (pHA-B) and its clinical applications and potential complications.

Vertical Ridge Augmentation of the Atrophic Posterior Mandible With Custom-Made, Computer-Aided Design/Computer-Aided Manufacturing Porous Hydroxyapatite Scaffolds

The present study describes a new protocol for the manufacturing of custom-made hydroxyapatite scaffolds using computer-aided design/computer-aided manufacturing (CAD/CAM), to augment posterior mandibular bone and minimize surgery when severe atrophy is present. Computed tomographic images of an atrophic posterior mandible were acquired and modified into a 3-dimensional (3D) reconstruction model. This model was transferred as a stereolithographic file to a CAD program, where virtual 3D reconstructions of the alveolar ridge were performed, drawing 2 anatomically shaped, custom-made scaffolds. Computer-aided-manufacturing software generated a set of tool-paths for manufacture on a computer-numerical-control milling machine into the exact shape of the 3D projects. Clinically sized, anatomically shaped scaffolds were generated from commercially available porous hydroxyapatite blocks. The custom-made scaffolds well matched the shape of the bone defects and could be easily implanted during surgery. This matching of the shape helped to reduce the time for the operation and contributed to the good healing of the defects. At the 6-month recall, a newly formed and well-integrated bone was observed, completely filling the mandibular posterior defects, and implants were placed, with good primary stability. At the 1-year follow-up examination, the implant-supported restorations showed a good functional and esthetic integration. Although this is an interim report, this study demonstrates that anatomically shaped custom-made scaffolds can be fabricated by combining computed tomographic scans and CAD/CAM techniques. Further studies are needed to confirm these results.

Maxillary Ridge Augmentation with Custom-Made CAD/CAM Scaffolds. A 1-Year Prospective Study on 10 Patients

Several procedures have been proposed to achieve maxillary ridge augmentation. These require bone replacement materials to be manually cut, shaped, and formed at the time of implantation, resulting in an expensive and time-consuming process. In the present study, we describe a technique for the design and fabrication of custom-made scaffolds for maxillary ridge augmentation, using three-dimensional computerized tomography (3D CT) and computer-aided design/computer-aided manufacturing (CAD/CAM). CT images of the atrophic maxillary ridge of 10 patients were acquired and modified into 3D reconstruction models. These models were transferred as stereolithographic files to a CAD program, where a virtual 3D reconstruction of the alveolar ridge was generated, producing anatomically shaped, custom-made scaffolds. CAM software generated a set of tool-paths for manufacture by a computer-numerical-control milling machine into the exact shape of the reconstruction, starting from porous hydroxyapatite blocks. The custom-made scaffolds were of satisfactory size, shape, and appearance; they matched the defect area, suited the surgeon's requirements, and were easily implanted during surgery. This helped reduce the time for surgery and contributed to the good healing of the defects.

An in vitro scanning microradiography study of the reduction in hydroxyapatite demineralization rate by statherin‐like peptides as a function of increasing N‐terminal length

Enamel demineralization is slowed by salivary proteins that inhibit calcium hydroxyapatite (HA) demineralization. Statherin (StN43), a 43-residue phosphorylated salivary protein with primary sequence similarities to osteopontin and caseins, binds calcium and HA. The aim of this study was to identify the minimum length of the functional domain of the statherin molecule required for cariostatic function by measuring the efficacy of peptides of progressively shorter length (i.e. containing only the N-terminal 21 (StN21), 15 (StN15), 10 (StN10), or 5 (StN5) residues) to reduce HA demineralization rates (RD(HA) ). Porous HA blocks were used as enamel analogues, and were exposed to 0.1 M acetic acid at pH 4 for 120 h, rinsed, and treated with StN21, StN15, StN10, or StN5 peptides (1.88 × 10(-5) M) for 24 h, then demineralized for a further 120 h. The RD(HA) was measured, before and after peptide treatment, using scanning microradiography. Hydroxyapatite blocks treated with StN21 and StN15 demonstrated a 50-60% reduction in the RD(HA) . However, no reduction in the RD(HA) was observed following treatment with either StN10, StN5, or buffer only. The mechanism by which statherin-like peptides reduce RD(HA) may be associated with their binding to HA surfaces. Comparisons with previously published binding energies of statherin to HA also suggest that statherin-like peptides containing 15 N-terminal residues or more, are required for binding, suggesting a link between binding and demineralization reduction.

Effects of low-intensity pulsed ultrasound stimulation on porous hydroxyapatite blocks for posterolateral fusion of lumbar spine in rabbits

The effects of porous hydroxyapatite blocks (PHABs) and an adjunct low-intensity pulsed ultrasound stimulation (LIPUS) on the fusion rate in a rabbit spinal posterolateral fusion (PLF) model were evaluated. Twenty rabbits underwent PLF with autograft and PHABs were randomly assigned to two groups: treated group with 20 min LIPUS daily and untreated control group for 4 weeks until euthanasia. The fused motion segments were subjected to manual palpation, gross observation, and radiographic investigation before histomorphologic and scanning electron microscopic analyses. Statistical differences between the LIPUS group and the control group are found in the fusion rate, bone density gray scale, trabecular bone formation, osteoblast-like cells, chondrocytes and positive expression of BMP-2 and TGF-β1 in the junction zone (significance level p<0.05). The results suggest that LIPUS can increase fusion rates and accelerate bone in-growth into PHAB. Hence, PHAB and LIPUS may be used together to increase fusion rates in a rabbit spinal fusion model with a promising extension to human application.

Fabrication of porous blocks of calcium phosphate through hydrothermal processing under glycine coexistence

Porous hydroxyapatite (HA) and beta-tricalcium phosphate (β-TCP) blocks are well known biomaterials employed as bone substitutes. Control of the porosity and morphology of these ceramics are important in governing their biological properties upon implantation. One synthetic method, hydrothermal processing, produces porous ceramics with distinct morphologies. In the present study, porous calcium phosphate blocks with unique structures were produced from compacted powder mixtures of alpha-tricalcium phosphate (α-TCP) and glycine (Gly) treated by exposure to water vapor at 120, 160, and 200°C for 5 h. Hydrothermal treatment at 200°C for 5 h of mixtures of Gly/α-TCP with mass ratios of 50/50 and 67/33 could give the porous materials of single phase HA. The obtained porous HA blocks had micrometer-sized pores due to the entanglement of rod-shaped particles, and large-sized pores of over 100 µm in diameter derived from Gly. After the heating at 900°C for 3 h in air, HA was converted to β-TCP with almost same microstructure in comparison with that of pre-heating one. The present methods provided insight into the production of porous blocks composed of rod-shaped calcium phosphate particles with both submicron-sized pores and large-sized pores of about 100 µm in size.

Two-stage revision surgery for hip prosthesis infection using antibiotic-loaded porous hydroxyapatite blocks

Infection of a hip prosthesis is one of the most severe complications encountered in orthopedic practice. Two-stage reconstruction using an antibiotic-impregnated cement spacer has become a popular procedure for the treatment of this condition. However, there are some disadvantages with the use of antibiotic-loaded cement, including low biocompatibility, a very low release ratio, and the possibility of thermal damage to the antibiotic. We have developed an effective drug delivery system for osteomyelitis in which porous hydroxyapatite (HA) blocks are loaded with an antibiotic by the vacuum method. We report here a modification of this delivery system applied for the first stage of two-stage reconstruction surgery against infected hip prosthesis. Eight consecutive patients who developed hip prosthesis infection underwent two-stage revision total hip arthroplasty (THA) using antibiotic-loaded porous HA blocks prepared by the vacuum method. Thorough debridement and insertion of antibiotic-loaded HA blocks was performed in the first stage, followed by conversion to THA after eradication of infection in the second stage. The mean interval between the stages was 16.8 weeks. There were no complications related to the use of the antibiotic-loaded HA blocks. The patients were followed up for an average of 49 months with no evidence of recurrent infection. The mean Japanese Orthopedic Association hip score improved from 45.1 before surgery to 79.6 at the latest follow-up. This simple approach utilizing antibiotic-impregnated HA blocks prepared by the vacuum method is considered to be effective for treatment of hip prosthesis infection.

Maxillo-mandibular counter-clockwise rotation and mandibular advancement with TMJ Concepts® total joint prostheses

The purpose of this study was to evaluate soft tissue response to maxillo-mandibular counter-clockwise rotation, with TMJ reconstruction and mandibular advancement using TMJ Concepts total joint prostheses, and maxillary osteotomies in 44 females. All patients were operated at Baylor University Medical Center, Dallas TX, USA, by one surgeon (Wolford). Eighteen patients had genioplasties with either porous block hydroxyapatite or hard tissue replacement implants (Group 2) 26 had no genioplasty (Group 1). Surgically, the maxilla moved forward and upward by counter-clockwise maxillo-mandibular rotation with greater horizontal movement in Group 2. Vertically, both groups showed diversity of maxillo-mandibular mean movement. Group 1 showed a consistent 1: 0.97 ratio of hard to soft tissue advancement at pogonion; Group 2 results were less consistent, with ratios between 1: 0.84 and 1: 1.02. Horizontal changes in upper lip morphology after maxillary advancement/impaction, VY closure, and alar base cinch sutures showed greater movement in both groups, than observed in hard tissue. Counter-clockwise rotation of the maxillo-mandibular complex using TMJ Concepts total joint prostheses resulted in similar soft tissue response as previously reported for traditional maxillo-mandibular advancement without counter-clockwise rotation of the occlusal plane. The association of chin implants, in the present sample, showed higher variability of soft tissue response.

In VivoMaturation of Scaffold-free Engineered Articular Cartilage on Hydroxyapatite

Tissue engineering is a promising approach, not only for cartilage, but also for osteochondral repair. Recent studies have demonstrated that scaffold-free cartilaginous tissue can be engineered using the alginate-recovered-chondrocyte (ARC) method. This method has also been applied to form osteochondral tissue using bovine articular chondrocytes and coralline hydroxyapatite (HA). The purpose of this study was to test whether osteochondral tissue, fabricated in vitro using the ARC method combined with a block of HA, would undergo maturation in vivo using a subcutaneous model in immunodeficient mice. Articular chondrocytes were isolated from the cartilage of New Zealand white rabbits and cultured in alginate beads. The cells with their associated matrix were recovered by dissolving the alginate beads with a sodium citrate buffer, resuspended in media and seeded onto a porous HA block. After 4 weeks of culture, some samples were analyzed, and others were implanted into subcutaneous pockets in nude mice. The analysis involved removing the cartilage portion of the de novo-formed ARC-HA graft and performing biochemical and histological examinations. Some samples were subjected to nondecalcified histology. Histological and immunohistochemical analyses of cartilaginous tissue were performed at 0, 2, 4, and 8 weeks after implantation. Biochemical characteristics were examined at 0, 4, and 8 weeks. The size and shape of the implanted ARC osteochondral tissue changed with time. The histological and immunohistochemical examination of the tissue revealed that it contained a cartilage-like matrix that stained strongly with Toluidine blue and for collagen type II. The proteoglycan (PG) content had increased significantly at 4 weeks from baseline. However, by 8 weeks, the PG content had decreased from 4 weeks. The results presented here represent a possible approach to form a tissue-engineered osteochondral implant. Further studies are needed to improve biomechanical properties of the osteochondral implant to be suitable for surgical transplantation.

Biocompatibility Evaluation of Porous Si-Containing Hydroxyapatite Derived from Coral

A porous silicon-containing hydroxyapatite has been prepared using natural coral as a calcium source to obtain a biomaterial having an improved biocompatibility. From the XRD analysis, it was confirmed that the single-phase hydroxyapatite containing silicon has formed without revealing the presence of extra phases related to silicon dioxide or other calcium phosphate species. Silicon content is ranged from 0.5wt% to 1wt% by weight. The porous silicon-containing hydroxyapatite blocks were inserted into the 5mm diameter of drill holes made through the lateral femoral condyles of New Zealand white rabbits. The new bony formation did not begin after 1 week. At 3 week, bony ongrowth to the inserted porous silicon-containing hydroxyapatite block could be found, and the new bone surrounded the inserted block entirely after 24weeks. Based on in-vivo test, Si-containing porous hydroxyapatite derived from coral possesses high biodegradability and can be considered a useful material for bone implants.

Sterilization using Antibiotic-impregnated Porous Hydroxyapatite Block for Osteomyelitis of Rib and Sternum: A Case Report

A 79-year-old woman was referred to our department with osteomyelitis of the first rib and sternum. She had previously undergone left radical mastectomy for breast cancer and partial resection of the left clavicle. Pus had been observed on the medial side of the residual clavicle. After debridement, an antibiotic-loaded porous hydroxyapatite block was placed to sterilize the wound. Although the wound was dehiscent, no positive results were obtained for bacterial culture. Because the patient's ipsilateral pectoralis major muscle had been removed during radical mastectomy, the wound was closed using sternocleidomastoid muscle and skin flaps. No evidence of wound dehiscence was apparent after 5 years. Antibiotic impregnated block placement may prove useful when local sterilization is required.

Tailor-made tricalcium phosphate bone implant directly fabricated by a three-dimensional ink-jet printer

Rapid prototyping (RP) is a molding technique that builds a three-dimensional (3D) model from computer-aided design (CAD) data. We fabricated new tailor-made bone implants (TIs) from alpha-tricalcium phosphate powder using an RP ink-jet printer based on computed tomography (CT) data, and evaluated their safety and efficacy. CT data of the skulls of seven beagle dogs were obtained and converted to CAD data, and bone defects were virtually made in the skull bilaterally. TIs were designed to fit the defects and were fabricated using the 3D ink-jet printer with six horizontal cylindrical holes running through the implants, designed for possible facilitation of vascular invasion and bone regeneration. As a control, hydroxyapatite implants (HIs) were cut manually from porous hydroxyapatite blocks. Then, craniectomy was performed to create real skull defects, and TIs and HIs were implanted. After implantation, CT was performed regularly, and the animals were euthanized at 24 weeks. No major side effects were observed. CT analysis showed narrowing of the cylindrical holes; bony bridging between the implants and the temporal bone was observed only for TIs. Histological analysis revealed substantial new bone formation inside the cylindrical holes in the TIs, while mainly connective tissues invaded the porous structures in HIs. Bone marrow was observed only in TIs. Osteoclasts were seen to resorb regenerated bone from inside the cylindrical holes and to invade and probably resorb the TIs. These data suggest that TIs are a safe and effective bone substitute, possessing osteoconductivity comparable with that of HIs.

Preparation and Characterization of Porous Hydroxyapatite Block Using a HHP Method

Porous hydroxyapatite has been prepared using a hydrothermal hot pressing method from calcium carbonate as a starting material. SEM result shows porous hydroxyapatite block is formed of three dimensionally inter-connected pores of 100-400µm in size, similar to human cancellous bone. At the ~ 70% porosity, the compressive strength was about 4MPa, which is similar to that of the commercially available porous hydroxyapatite derived from natural coral.

MCM-41 /PCL Coated Hydroxyapatite and its Application to Drug Delivery System

Porous hydroxyapatite coated with MCM-41/PCL has been utilized as the matrix for controlled drug delivery. SEM result shows porous hydroxyapatite block is formed of three dimensionally inter-connected pores of 250 –300 *m in size, similar to human cancellous bone. TEM observation confirms the pore size of MCM-41 scatters about 50 Å. Ibuprofen was loaded into the pores of MCM-41 and hybridized with polycaprolactone to coat on the surface of hydroxyapatite block and controlled release profiles were studied by soaking the samples in a simulated body fluid using a UV-VIS spectrophotometer.

Comparison between porous hydroxyapatite block and iliac autograft for single-level anterior cervical spinal fusion

Comparison between porous hydroxyapatite block and iliac autograft for single-level anterior cervical spinal fusion

Surface modification of a porous hydroxyapatite to promote bonded polymer coatings.

Porous hydroxyapatite (Hap) blocks were sintered at several temperatures and methyl methacrylate (MMA) grafted onto the surface in a 2-step heterogeneous system as a model example for surface modification. First, sintered porous Hap was modified with 2-methacryloyloxyethylene isocyanate (MOI) monomer in anhydrous dimethyl sulfoxide using di-n-butyltin (IV) dilaurate as a catalyst and hydroquinone as an inhibitor. Amount of the introduction of MOI monomer on porous Hap was 1.62 wt % at sintered temperature 800 degrees C, 0.68 wt % at it of 1000 degrees C, and 0.59 wt % at it of 1200 degrees C. Scanning electron microscopy (SEM) showed that porous Hap pore size and shape before and after MOI treatment were unchanged. Second, graft polymerization with MMA through the vinyl bond on porous Hap was conducted using alpha,alpha'-azobis isobutyronitrile (AIBN) as an initiator. Amount of Grafted PMMA on the MOI modified porous Hap was 2.84 wt % at sintered temperature of 800 degrees C, 6.97 wt % at it of 1000 degrees C, and 6.27 wt % at it of 1200 degrees C. MOI-modified and PMMA-grafted porous Hap were characterized using Fourier transform infrared (FT-IR) spectroscopy. The compressive strength of sintered porous Hap with grafted PMMA increased about 2.7-6.7 times compared to intact porous Hap. This 2-step surface modification on porous Hap is widely applicable to graft polymerization with vinyl polymer and conjugation with a protein or an oligopeptide, such as growth factor or an adhesion molecule, to improve Hap mechanical properties and functionality.

Treatment of osteomyelitis with antibiotic-loaded porous hydroxyapatite blocks

Treatment of osteomyelitis with antibiotic-loaded porous hydroxyapatite blocks