Microscopic evaluation of bone-implant contact between hydroxyapatite, bioactive glass and tricalcium phosphate implanted in sheep diaphyseal defects

Avaliação histológica e por microscopia eletrônica de varredura da biocerâmica de fosfato de cálcio nano-estruturada micromacro porosa em grânulos em defeito crítico de rádio de coelhos

RESUMO Objetivou-se avaliar, histologicamente e por microscopia eletrônica de varredura (MEV), a evolução de defeitos críticos experimentais em rádio de coelhos preenchidos ou não com biocerâmica fosfocálcica nanoestruturada micromacro porosa em grânulos. Utilizaram-se 70 coelhos, Nova Zelândia, adultos jovens, machos, e realizou-se um defeito crítico nos rádios. Os membros constituíram os grupos: GI, biocerâmica lenta, GII, biocerâmica moderada e GIII, controle negativo. Após cada período experimental, os animais foram sacrificados, e os rádios coletados. As avaliações histológicas foram realizadas aos oito, 15, 30, 45, 60, 90 e 120 dias, e as análises de MEV aos 60, 90 e 120 dias. Histologicamente, observou-se processo de reparação óssea mais adiantado nos grupos GI e GII comparando-se ao GIII. Na MEV, constatou-se maior proporção de osso maduro e presença de ósteons secundários nos GI e GII, sendo mais evidente no GII, confirmando os achados histológicos. As cerâmicas promoveram preenchimento completo do defeito, enquanto no grupo controle houve preenchimento no centro do defeito, permanecendo espaços vazios nas laterais. Conclui-se que o emprego das biocerâmicas de absorção lenta e moderada favorece a regeneração óssea completa em defeitos críticos sendo indicadas como substituto ósseo. A maturação óssea ocorre mais precocemente quando se emprega a cerâmica de absorção moderada.

Evaluation of bone morphogenic proteins in periodontal practice

Forty years ago Marshal R. Urist discovered a substance in bone matrix that had inductive properties for the development of bone and cartilage, until date, at least 20 bone morphogenetic proteins (BMPs) have been identified, some of which have been shown in vitro to stimulate the process of stem cell differentiation into osteoblasts in human and animal models. The purpose of this paper is to give a brief overview of BMPs and to review critically the clinical data currently available on the use of BMPs in various periodontal applications. The literature on BMPs was reviewed. A comprehensive search was designed. The articles were independently screened for eligibility. Articles with authentic controls and proper randomization and pertaining specifically to their role in periodontal applications were included. The available literature was analyzed and compiled. The analysis indicates BMPs to be a promising, as well as an effective novel approach to reconstruct and engineer the periodontal apparatus. Here, we represent several articles, as well as recent texts that make up a special and an in-depth review on the subject. On the basis of the data provided in the studies that were reviewed BMPs provide revolutionary therapies in periodontal practice.

Tissue-engineered bone constructed in a bioreactor for repairing critical-sized bone defects in sheep

PURPOSE

Repair of bone defects, particularly critical-sized bone defects, is a considerable challenge in orthopaedics. Tissue-engineered bones provide an effective approach. However, previous studies mainly focused on the repair of bone defects in small animals. For better clinical application, repairing critical-sized bone defects in large animals must be studied. This study investigated the effect of a tissue-engineered bone for repairing critical-sized bone defect in sheep.

METHODS

A tissue-engineered bone was constructed by culturing bone marrow mesenchymal-stem-cell-derived osteoblast cells seeded in a porous β-tricalcium phosphate ceramic (β-TCP) scaffold in a perfusion bioreactor. A critical-sized bone defect in sheep was repaired with the tissue-engineered bone. At the eighth and 16th week after the implantation of the tissue-engineered bone, X-ray examination and histological analysis were performed to evaluate the defect. The bone defect with only the β-TCP scaffold served as the control.

RESULT

X-ray showed that the bone defect was successfully repaired 16 weeks after implantation of the tissue-engineered bone; histological sections showed that a sufficient volume of new bones formed in β-TCP 16 weeks after implantation. Eight and 16 weeks after implantation, the volume of new bones that formed in the tissue-engineered bone group was more than that in the β-TCP scaffold group (P < 0.05).

CONCLUSION

Tissue-engineered bone improved osteogenesis in vivo and enhanced the ability to repair critical-sized bone defects in large animals.

Quantification of bone mass gain in response to the application of biphasic bioceramics and platelet concentrate in critical-size bone defects

Biphasic bioceramics have been widely indicated for bone reconstruction; however, the real gain in bone mass due to the presence of such biomaterials has not been established yet nor the advantages of its association with platelet concentrate. This study aims at quantifying the volume of bone matrix, osteoblasts, osteocytes, blood vessels and adipose tissue after the application of a biphasic bioceramics composed of 65% hydroxyapatite and 35% beta-tricalcium phosphate. Critical-size bone defects were produced in rabbit femora and reconstructed with bioceramics only, with bioceramics combined with platelet concentrate, with platelet concentrate alone, and with no treatment (blood clot). The quantitative evaluation was performed on histological sections using histomorphometry. Our data provide original evidence that consolidates the indication of bioceramics for clinical bone loss reconstruction. The application of biphasic bioceramics alone led to major bone mass gain and was followed by its association with platelet concentrate. On the other hand, platelet concentrate can contribute to the augmentation and maintenance of the adipose tissue, representing a new field for future applications in plastic surgery.

Drug/device combinations for local drug therapies and infection prophylaxis

Combination devices-those comprising drug releasing components together with functional prosthetic implants-represent a versatile, emerging clinical technology promising to provide functional improvements to implant devices in several classes. Landmark antimicrobial catheters and the drug-eluting stent have heralded the entrance, and significantly, routes to FDA approval, for these devices into clinical practice. This review describes recent strategies creating implantable combination devices. Most prominent are new combination devices representing current orthopedic and cardiovascular implants with new added capabilities from on-board or directly associated drug delivery systems are now under development. Wound coverings and implantable sensors will also benefit from this combination enhancement. Infection mitigation, a common problem with implantable devices, is a current primary focus. On-going progress in cell-based therapeutics, progenitor cell exploitation, growth factor delivery and advanced formulation strategies will provide a more general and versatile basis for advanced combination device strategies. These seek to improve tissue-device integration and functional tissue regeneration. Future combination devices might best be completely re-designed de novo to deliver multiple bioactive agents over several spatial and temporal scales to enhance prosthetic device function, instead of the current 'add-on' approach to existing implant device designs never originally intending to function in tandem with drug delivery systems.

Nanoporous delivery system to treat osteomyelitis and regenerate bone: Gentamicin release kinetics and bactericidal effect

Conventional treatment of osteomyelitis involves the repeated surgical removal of dead bone tissue coupled with repeated irrigation of the wound and prolonged systemic administration of antibiotics. Therapy of bone infections could easily last the rest of the patient's life because of the poor accessibility of the infection site by common systemically administered antibiotics. The objective of the present study is to develop a novel bone bioactive resorbable nanocomposite that can serve as a delivery system for antibiotics. We synthesized three different samples of porous bioactive resorbable silica-calcium phosphate nanocomposite (C3S1, C1S1, and C1S3) that has the ability to provide a sustained release of effective dose of gentamicin for 28 days. Porosity measurements showed that the average pore diameter of C3S1, C1S1, and C1S3 samples is 44.8, 54.4, and 70.9 nm, respectively. Moreover, the silica-rich composite (C1S3) is characterized by a significantly higher surface area (155.8 m(2)/g) than the silica-poor samples (C3S1) (42.9 m(2)/g). For all samples, the release profile study showed initial burst release followed by a sustained release of gentamicin. The released gentamicin has a strong inhibitory effect on Staphylococcus aureus bacteria. In addition FTIR analysis showed the formation of a biological apatite layer on the material surface after 24 h of immersion in simulated body fluid. Results of the study suggest that the silica-calcium phosphate nanocomposite can serve as a delivery vehicle for gentamicin to treat osteomyelitis and regenerate bone.

HA/TCP compounding of a porous CaP biomaterial improves bone formation and scaffold degradation—A long-term histological study

In the present study, two biphasic calcium phosphate biomaterials (BCP) with HA/TCP ratios of 50/50 and 30/70 were obtained from a pure HA biomaterial. The biomaterials which showed the same three-dimensional geometry were implanted into corticocancellous costal defects of sheep. In the specimens of all three biomaterials, abundant bone formation, mineral dissolution from the biomaterial scaffolds, and active cellular resorption of the scaffolds was present after 6 and 12 months. Backscattered electron microscopy showed bone invasion into the pores of the scaffolds and micromechanical interlocking at the bone/biomaterial interface without intervening soft tissue. The pattern of bone formation and scaffold resorption was different for cortical and cancellous bone. No time-based effect, however, was observed. Overall, the BCP biomaterials had formed significantly more bone than the HA biomaterial. Also, scaffold resorption, which was followed by a replacement with newly formed bone, was significantly higher in the BCP biomaterials. Although no significant differences were observed between both BCP biomaterials, the present study had confirmed the assumption that HA/TCP compounding was suitable to improve bone formation and scaffold resorption in the investigated biomaterials and at the same time maintain the osteoconductive properties of the scaffolds.

A simple non invasive computerized method for the assessment of bone repair within osteoconductive porous bioceramic grafts

Single energy X-ray imaging, due to its low cost and flexibility, is one of the most used and common technique to assess bone state and bone remodeling over time. Standardized X-ray images are needed to compare sets of radiographs for semi-quantitative analyses of tissue remodeling. However, useful mathematical modeling for the analysis of high level radiographic images are not easily available. In order to propose a useful evaluation tool to a wide clinical scenario, we present an innovative calibration algorithm for a semi-quantitative analysis of non-standardized digitized X-ray images. For calibration on a unique standardization scale, three time invariant regions (ROI) of radiographs were selected and analyzed. The accuracy of the normalization method for X-ray films was successfully validated by using an aluminum step wedge for routine X-ray exposures as tool to standardize serial radiographs (Pearson correlation test: R(2) = 0.96). This method was applied to investigate the progression of the new bone deposition within ceramic scaffolds used as osteoconductive substitute in large bone defects taking advantage of a large animal model. This innovative image-processing algorithm allowed the identification and semi-quantification of the bone matrix deposited within the implant. The osteo-integration at the bone-implant interface was also investigated. A progressively increasing bone tissue deposition within the porous bioceramic implant and a progressive osteo-integration was observed during the 12 months of the trial.

Alcohol Intake and Osseointegration Around Implants: A Histometric and Scanning Electron Microscopy Study

Alveolar wound healing can be modified by local and systemic factors. The aim of this study was to evaluate the possible effect of alcoholic beverage administration (sugarcane brandy) on reparative bone formation around hydroxyapatite/tricalcium phosphate implants inside the alveolar socket. Male Wistar rats had their upper right incisors extracted and the bioceramic granules implanted in the alveoli. The animals received increasing concentrations of brandy until 30 degrees Gay-Lussac was achieved starting 30 days before dental extraction and maintained for periods varying from 1 hour to 6 weeks, until sacrifice. Blood alcohol concentration analysis was performed as well as histological and histometric analysis through light and scanning electron microscopy to examine the relation between alveolar healing components, including new bone trabeculae, and the implants. Blood alcohol concentration was significantly higher in treated animals compared with controls. A significant delay in reparative bone formation was detected in the alveolus of alcoholic rats by a histometric differential point counting method, whereas the presence of the bioceramic in the alveolar socket improved alveolar wound healing in alcohol-treated rats. It is suggested that the osteoconductive properties of this bioceramic accelerated alveolar wound healing in alcoholic rats.

Early dissolution of a morsellised impacted silicate-free bioactive glass in metaphyseal defects

The purpose of this study was to evaluate the biological properties of idealized, morsellised impacted Corglaes, a soluble silicate-free glass. Twenty-two sheep underwent implantation of pellets in six metaphyseal defects in both rear limbs. Particle size distribution of all aggregates (except the autograft) approached the ideal logarithmic grading line and all implants were impacted to a standard compactive effort. Treatment groups consisted of (1) empty defect (negative control), (2) autograft (positive control), (3) allograft (clinical control), (4) allograft idealized with Corglaes, (5) 50/50 allograft/Corglaes and (6) Corglaes. Defects were sealed with polymethylmethacrylate. Healing of the defects was evaluated at 7 weeks (n=6) and 14 weeks (n=16) with computed tomography, histology, and histomorphometry. Remnants of Corglaes were found within one of the defects 7 weeks after implantation. Defects filled with mixtures containing 50% or 100% Corglaes were less dense, contained less bone and more fibrous tissue than defects with allograft, autograft, or allograft idealized with Corglaes. Allograft idealized with Corglaes may be considered for impaction grafting in revision hip arthroplasty, as well as local delivery of antibiotics. However, further studies and potential revision of the agent are required before mixtures containing concentrations of Corglaes equal to or higher than 50% can be recommended.

Push-out testing and histological evaluation of glass reinforced hydroxyapatite composites implanted in the tibia of rabbits

In vitro and in vivo bioactivity studies were performed to assess the biocompatibility of CaO-P2O5 glass-reinforced hydroxyapatite (GR-HA) composites. The ability to form an apatite layer by soaking in simulated body fluid (SBF) was examined and surfaces were characterized using FTIR reflection and thin-film X-ray diffraction analyses. Qualitative histology, histomorphometric measurements, and push-out testing were performed in a rabbit model for characterizing bone/implant bonding. Under the in vitro conditions using SBF, an apatite layer could not be formed on GR-HA composites within 8 weeks. Results of push-out testing showed bonding between the composites and bone, ranging from 130-145 N after 2 weeks of implantation. After the longest implantation period, 16 weeks, the GR-HA composite prepared with the higher content of CaO-P2O5 glass showed the highest bonding force, 606 +/- 45 N, compared to 459 +/- 30 N for sintered HA. Development of immature bone and modifications in the turnover of a more mature bone on the surface of GR-HA composites were similar to those on sintered HA.

Nonstoichiometric hydroxyapatite-anionic collagen composite as support for the double sustained release of gentamicin and norfloxacin/ciprofloxacin

This work studied the sustained release of ciprofloxacin or norfloxacin and gentamicin from nonstoichiometric hydroxyapatite (nHA) and anionic collagen composite. Within the first 24 and 48 h, the total antibiotic supply was significantly higher than the minimal inhibitory concentration required for the majority of the gram-negative bacteria. Although gentamicin was completely released from the matrix after 48 h by a normal diffusion mechanism, ciprofloxacin or norfloxacin release was characterized by a 2-phase release mechanism due to binding to nHA by complexation with calcium ion. Under the conditions studied, most of the norfloxacin or ciprofloxacin only will be disposable due to bioresorption or dissociation of the complexes. In conclusion, due to its biocompatibility nHA-anionic collagen composite may be a convenient support for the double sustained release of the antibiotics gentamicin and ciprofloxacin/norfloxacin for the control of bone infection while promoting bone tissue growth.

Reconstruction of calcaneal skeletal defects caused by trauma

Since 1976, we have treated displaced intra-articular fractures of the calcaneus by open reduction through a lateral approach, temporary percutaneous fixation, and bone grafting. We assessed the results after a mean follow-up time of 98.9 (SD = 53) months in 30 patients with 35 fractures. In this report we review, clinically and radiologically, 35 fractures in 30 patients (five bilateral). Autografts was used in five cases (five patients) with an average follow-up of 145 months (SD = 43.7). Allografts were used in 19 cases (16 patients) with an average follow-up of 124 months (SD = 31.2), and hydroxyapatite was used in 11 cases (nine patients) with an average follow-up of 34 months (SD = 12.9). Clinical assessment was based on the Creighton-Nebraska Health Foundation scoring system and radiological measurements made from a lateral view. Seventy-seven percent of the patients had excellent or good clinical results and none had a poor result. Open reduction restored the "crucial angle" and the height of the calcaneus. The tuber joint angle described by Böhler was above 20 degrees in all the cases. There were no significant differences among the three groups of patients with regard to degree of residual pain, walking activities, range of subtalar movement, ability to return to their original jobs, hindfoot swelling, or change in footwear.

The controlled release of antibiotic by hydroxyapatite: anionic collagen composites

Major problems with the treatment of osteomyelitis are associated with poor antibiotic distribution at the site of infection due to limited blood circulation to the skeletal tissue. Improved treatment procedures have been used in drug delivery systems that include bioceramics and natural and synthetic polymers. This work reports the development of anionic collagen:hydroxyapatite composite paste for sustained antibiotic release. Antibiotic release by the composite was characterized by two steps. In the first, 15.0+/-4.9% was released in the first 5 h (n = 53) by a normal Fick diffusion mechanism. In the second step, only 16.8+/-2.2% was released after 7 days. In conclusion, hydroxyapatite:anionic collagen composite can be an efficient support for sustained antibiotic release in the treatment of osteomyelitis because most of the antibiotic release may be associated with composite bioresorption, thus permitting antibiotic release throughout the healing process. Hydroxyapatite:anionic collagen paste showed good biocompatibility associated with bone tissue growth with material still being observed after 60 days from the time of implants.

Long-term results of hydroxyapatite-fibrin glue implantation in plastic and reconstructive craniofacial surgery

The bone tissue formed in orthotopic or heterotopic implants of granular, porous hydroxyapatite and fibrin glue was examined several (2 1/2-8) years after implantation. The results showed distinct ossification in all cases and the functional situation and external appearance were also satisfactory. The reconstituted spongy and compact bone underwent a remodelling process similar to that of normal bone. Most of the hydroxyapatite granules were embedded in the bone tissue; a few were very close to the fibrillar connective tissue of the intertrabecular spaces and were either covered by osteoid-like collagenous borders or were in contact with osteoclast-like giant cells. Even if the results refer only to a few patients, and were obtained from a cross-sectional study, they allow the conclusion to be reached that the implantation of porous hydroxyapatite and fibrin glue leads to the formation of long-lasting bone whose hardness is equal to, or greater than, that of normal bone.