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Thermomechanics of the shape memory effect in polymers for biomedical applications
Gall, K., C. M. Yakacki, et al. (2005), J Biomed Mater Res A 73(3): 339-48.
Abstract: We examine the shape memory effect in polymer networks intended for biomedical, and specifically cardiovascular, applications. The polymers were synthesized by photopolymerization from a tert-butyl acrylate monomer with a diethyleneglycol diacrylate crosslinker. Three-point flexural tests were used to systematically investigate the thermomechanics of shape storage (predeformation) and shape recovery. The glass transition temperature, T(g), of the polymers was determined to be approximately 65 degrees C. The polymers show 100% strain recovery, at low and high predeformation temperatures, up to maximum strains of approximately 80%. The polymers show a sigmoidal free strain recovery response as a function of increasing temperature at a constant heating rate. Free strain recovery was determined to depend on the temperature during predeformation; lower predeformation temperatures (T < T(g)) decreased the temperature required for free strain recovery. Constrained stress recovery shows a complex evolution as a function of temperature and also depends on the temperature during predeformation. Stress recovery after low-temperature predeformation (T < T(g)) shows a peak in the generated recovery stress, whereas stress recovery after high-temperature predeformation (T > T(g)) is sigmoidal. The isothermal free strain recovery rate was found to increase with increasing temperature or decreasing predeformation temperature. The thermomechanical results are discussed in light of potential biomedical applications, and a prototype device is presented.

Thermosensitive and biodegradable polymeric micelles for paclitaxel delivery
Soga, O., C. F. van Nostrum, et al. (2005), J Control Release 103(2): 341-53.
Abstract: The preparation, release and in vitro cytotoxicity of a novel polymeric micellar formulation of paclitaxel (PTX) were investigated. The micelles consisted of an AB block copolymer of poly(N-(2-hydroxypropyl) methacrylamide lactate) and poly(ethylene glycol) (pHPMAmDL-b-PEG). Taking advantage of the thermosensitivity of pHPMAmDL-b-PEG, the loading was done by simply mixing of a small volume of a concentrated PTX solution in ethanol and an aqueous polymer solution and subsequent heating of the resulting solution above the critical micelle temperature of the polymer. PTX could be almost quantitatively loaded in the micelles up to 2 mg/mL. By dynamic light scattering and cryo-transmission electron microscopy, it was shown that PTX-loaded micelles have a mean size around 60 nm with narrow size distribution. At pH 8.8 and 37 degrees C, PTX-loaded micelles destabilized within 10 h due to the hydrolysis of the lactic acid side group of the pHPMAmDL. Because the hydrolysis of the lactic acid side groups is first order in hydroxyl ion concentration, the micelles were stable for about 200 h at physiological conditions. The presence of serum proteins did not have an adverse effect on the stability of the micelles during at least 15 h. Interestingly, the dissolution kinetics of pHPMAmDL-b-PEG micelles was retarded by incorporation of PTX, indicating a strong interaction between PTX and the pHPMAmDL block. The PTX-loaded micelles showed a release of the incorporated 70% of PTX during 20 h at 37 degrees C and at pH 7.4. PTX-loaded pHPMAmDL-b-PEG micelles showed comparable in vitro cytotoxicity against B16F10 cells compared to the Taxol standard formulation containing Cremophor EL, while pHPMAmDL-b-PEG micelles without PTX were far less toxic than the Cremophor EL vehicle. Confocal laser-scanning microscopy (CLSM) and fluorescence activated cell sorting (FACS) analysis of fluorescently labelled micelles showed that pHPMAmDL-b-PEG micelles were internalized by the B16F10 cells. The present results suggest that pHPMAmDL-b-PEG block copolymer micelles are a promising delivery system for the parenteral administration of PTX.

Thermosensitive and biodegradable polymeric micelles with transient stability
Soga, O., C. F. van Nostrum, et al. (2005), J Control Release 101(1-3): 383-5.

Thermosensitive biodegradable polydepsipeptide
Ohya, Y., M. Toyohara, et al. (2005), Macromol Biosci 5(4): 273-6.
Abstract: A poly(N-isopropylacrylamide) (PNIPAAm)-like biodegradable thermosensitive polydepsipeptide, poly[Glc-Asn(N-isopropyl)], was synthesized by introducing an isopropyl amide group into poly[Glc-Asn]. Poly[Glc-Asn(N-isopropyl)] was degraded in vitro by cleavage of the ester bonds in the main chain in water at room temperature. The non-toxic nature of the polymer and its degradation products, coupled with a cloud point at 29 degrees C in water, make this polymer attractive for biomedical implant applications.

Thermosensitive N-isopropylacrylamide-N-propylacrylamide-vinyl pyrrolidone terpolymers: synthesis, characterization and preliminary application as embolic agents
Li, X., W. Liu, et al. (2005), Biomaterials 26(34): 7002-11.
Abstract: In this article, thermosensitive N-isopropylacrylamide (NIPAAm)-N-propylacrylamide (NPAAm)-vinyl pyrrolidone (VP) terpolymers (PNINAVP) were prepared by varying feed ratios with free radical copolymerization method. The composition ratios and molecular weights of PNINAVP were examined by NMR and GPC. The thermo-responsive behaviors of copolymer solutions in the absence and with addition of Iohexol, a radiopaque agent, were investigated by differential scanning calorimetry (DSC) and rheometer. The sol-gel transition of the copolymer solutions occurred reversibly within 1 min in response to temperature. Incorporation of Iohexol increased the transition time and transition temperature of PNINAVP solutions; the rheological properties were also influenced. It was observed that at body temperature, PNINAVP and Iohexol could form an integrated bulky hydrogel presumably due to the hydrogen bonding between them, which was favorable for the clinical follow-up and reducing toxic side effects. In vitro embolic model experiment indicated that 5 wt% 16:16:1H PNINAVP solution containing Iohexol displayed a satisfactory embolization effect. This solution was injected into the rete mirabiles (RM) of six swines through a microcatheter. The angiographical results obtained immediately after the operation showed a complete occlusion of the RM, and no recanalization was observed at postoperative month 1. The histological examination demonstrated no acute inflammatory reaction inside the RM and surrounding tissue. This work could provide a beneficial guidance for designing a new temperature-sensitive polymer-based embolic agent.

Thickness measurement of soft tissue biomaterials: a comparison of five methods
Lee, J. M. and S. E. Langdon (1996), J Biomech 29(6): 829-32.
Abstract: Thickness measurement in soft connective tissues is a continuing problem due to the apparent compression of the tissue by micrometer-type gauges. We have compared five methods for the measurement of thickness: (1) a Mitutoyo non-rotating thickness gauge; (2) a custom-built, instrumented thickness gauge which was strain-gauged to measure contact force; (3) a commercial Hall effect probe (Panametrics Magna-Mike); (4) a custom-built electrical resistance probe; and (5) measurement of fresh frozen histological sections under polarized light. Using bovine pericardium as a test material, all the methods examined were adequate to assess sample-to-sample and location-to-location differences in thickness. The resistance gauge gave significantly greater thicknesses than did the other methods, with little or no compression; indeed, extrapolation to zero load of thickness readings from the instrumented gauge yielded identical thickness. Thicknesses measured by frozen sections were indistinguishable from those measured with the non-rotating gauge, the instrumented gauge under 0.5-1.2 g compressive load, or the Hall effect probe. With the correct technique, the simple and inexpensive non-rotating gauge remains a pragmatic choice for thickness measurement in planar soft tissue.

Thin calcium phosphate coatings on titanium by electrochemical deposition in modified simulated body fluid
Peng, P., S. Kumar, et al. (2006), J Biomed Mater Res A 76(2): 347-55.
Abstract: Adherent and optically semitransparent thin calcium phosphate (CaP) films were electrochemically deposited on titanium substrates in a modified simulated body fluid at 37 degrees C. Coatings deposited by using periodic pulsed potentials showed better adhesion and better mechanical properties than coatings deposited with use of a constant potential. Scanning electron microscopy was used to study the morphology of the coatings. The coatings displayed a polydispersed porous structure with pores in the range of a few nanometers to 1 mum. Furthermore, X-ray diffractometry and the O(1s) satellite peaks in X-ray photoelectron spectroscopy indicated that the coatings possessed a similar surface chemistry to that of natural bone minerals. These results were confirmed by inductively coupled plasma optical emission spectrometry, which yielded a Ca:P ratio of 1.65, close to that of hydroxyapatite. Contact mode atomic force microscopy (AFM) showed the average thickness of the coatings was in the order of 200 nm. Root-mean-square (RMS) roughness values, also derived by AFM, were shown to be much higher on the titanium-CaP surfaces in comparison with untreated titanium substrates, with RMS values of about 300 and 110 nm, respectively. Cell culture experiments showed that the CaP surfaces are nontoxic to MG63 osteoblastic cells in vitro and were able to support cell growth for up to 4 days, outperforming the untreated titanium surface in a direct comparison. These easily prepared coatings show promise for hard-tissue biomaterials. (c) 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2006.

Thin film electron probe-electron microscope microanalysis techniques in biomaterials studies
Ansell, G. S. and G. Judd (1969), Trans N Y Acad Sci 31(6): 637-47.

Thiolation of chitosan. Attachment of proteins via thioether formation
Masuko, T., A. Minami, et al. (2005), Biomacromolecules 6(2): 880-4.
Abstract: Chitosan has a variety of biological functions through conjugating of other compounds to their amino and hydroxyl groups. To further expand applicability of chitosan, we have modified the amino group of chitosan with 2-iminothiolane to bestow thiol groups and obtained about 20% yield, which is equivalent to 913 microequiv SH/g chitosan or 457 nequiv SH/nmol chitosan. Bovine serum albumin (BSA) was reacted with N-(epsilon-maleimidocaproyloxy)sulfosuccinimide ester (sulfo-EMCS), and maleimide-modified BSA (MalN-BSA) was obtained. The yield of sulfo-EMCS addition was 12.8-36.8 mol MalN/mol BSA. When the chitosan-SH was reacted with MalN-BSA via thioether, 97.8% of the maleimide group was reacted, and 37.2% of the SH group was consumed. The remaining SH group was quenched by bromoacetamide. This is the first report of covalent conjugation of a protein to chitosan. Our method should find many applications in developing new chitosan-based biomedical materials containing other components such as growth factors and cell adhesion molecules, known to be crucial to cells. Our thiolated chitosan will facilitate conjugation of such biomedical components to provide new types of materials for tissue engineering.

Third-body wear testing of a highly cross-linked acetabular liner: the effect of large femoral head size in the presence of particulate poly(methyl-methacrylate) debris
Bragdon, C. R., M. Jasty, et al. (2005), J Arthroplasty 20(3): 379-85.
Abstract: The hip simulator wear performance of an electron beam cross-linked and subsequently melted ultrahigh molecular weight polyethylene against femoral heads of 28-, 38-, and 46-mm diameter in the presence of poly(methyl-methacrylate) particulate debris was contrasted with that of conventional polyethylene against a 46-mm diameter head. Over 5 million cycles of testing, the average wear rate of the conventional polyethylene liners was 29.3 +/- 3.0 mg per million cycles. All highly cross-linked components exhibited marked reduction in wear, with the highest wear measuring 0.74 +/- 0.85 mg per million cycles. This study, using a clinically relevant third-body material, showed the electron beam cross-linked material to be far more resistant to this third-body wear than conventional ultrahigh molecular weight polyethylene, even when very large diameter femoral heads were used.

Thirty-day incidence and six-month clinical outcome of thrombotic stent occlusion after bare-metal, sirolimus, or paclitaxel stent implantation
Ong, A. T., A. Hoye, et al. (2005), J Am Coll Cardiol 45(6): 947-53.
Abstract: OBJECTIVES: We sought to determine the real-world incidence of angiographically confirmed and possible stent thrombosis (ST) in an unrestricted population during the first 30 days after bare-metal stent (BMS), sirolimus-eluting stent (SES), and paclitaxel-eluting stent (PES) implantation. BACKGROUND: Current data on ST in drug-eluting stents (DES) have come from randomized trials with strict entry criteria, which limits their generalizability to daily practice. METHODS: The study population comprised three sequential cohorts of 506 consecutive patients with BMS, 1,017 consecutive patients with SES, and 989 consecutive patients treated with PES. RESULTS: In the first 30 days after stent implantation, 6 BMS (1.2%, 95% confidence interval [CI] 0.5% to 2.6%; p = 0.9), 10 SES (1.0%, 95% CI 0.5% to 1.8%), and 10 PES (1.0%, 95% CI 0.6% to 1.9%) patients developed angiographically proven ST. Multiple potential risk factors were identified in most patients with ST. Bifurcation stenting in the setting of acute myocardial infarction was an independent risk factor for angiographic ST in the entire population (odds ratio [OR] 12.9, 95% CI 4.7 to 35.8, p < 0.001). In patients with DES who had angiographic ST, 30-day mortality was 15%, whereas another 60% suffered a nonfatal myocardial infarction; no further deaths occurred during six months of follow-up. Including possible cases, 7 BMS (1.4%, 95% CI 0.7% to 2.8%), 15 SES (1.5%, 95% CI 0.9% to 2.4%), and 16 PES (1.6%, 95% CI 1.0% to 2.6%) patients had ST. CONCLUSIONS: The unrestricted use of SES or PES is associated with ST rates in the range expected for BMS. Stent thrombosis was associated with a high morbidity and mortality. Bifurcation stenting, when performed in patients with acute myocardial infarction, was associated with an increased risk of ST.

Three-dimensional aqueous-derived biomaterial scaffolds from silk fibroin
Kim, U. J., J. Park, et al. (2005), Biomaterials 26(15): 2775-85.
Abstract: A new all-aqueous process is described to form three-dimensional porous silk fibroin matrices with control of structural and morphological features. The result of this process are scaffolds with controllable porosity and pore sizes that fully degrade in the presence of proteases, unlike prior methods to generate silk-based biomaterials that required the use of organic solvent treatments to impart control of structure and stability in aqueous environments, with low rates of proteolytic hydrolysis. A mechanism is proposed for this novel process that imparts physical stability via hydrophobic interactions. Adjusting the concentration of silk fibroin in water, and the particle size of granular NaCl used in the process, leads to the control of morphological and functional properties of the scaffolds. The aqueous-derived scaffolds had highly homogeneous and interconnected pores with pore sizes ranging from 470 to 940 microm, depending on the mode of preparation. The scaffolds had porosities >90% and compressive strength and modulus up to 320 +/- 10 and 3330 +/- 500 KPa, respectively, when formed from 10% aqueous solutions of fibroin. The scaffolds fully degraded upon exposure to protease during 21 days, unlike the scaffolds prepared from organic solvent processing. These new silk-based three-dimensional matrices provide useful properties as biomaterial matrices due to the all-aqueous mode of preparation, control of pore size, connectivity of pores, degradability and useful mechanical features. Importantly, this process offers an entirely new window of materials properties when compared with traditional silk fibroin-based materials.

Three-dimensional co-culture models to study prostate cancer growth, progression, and metastasis to bone
Wang, R., J. Xu, et al. (2005), Semin Cancer Biol 15(5): 353-64.
Abstract: Cancer-stromal interaction results in the co-evolution of both the cancer cells and the surrounding host stromal cells. As a consequence of this interaction, cancer cells acquire increased malignant potential and stromal cells become more inductive. In this review we suggest that cancer-stromal interaction can best be investigated by three-dimensional (3D) co-culture models with the results validated by clinical specimens. We showed that 3D culture promoted bone formation in vitro, and explored for the first time, with the help of the astronauts of the Space Shuttle Columbia, the co-culture of human prostate cancer and bone cells to further understand the interactions between these cells. Continued exploration of cancer growth under 3D conditions will rapidly lead to new discoveries and ultimately to improvements in the treatment of men with hormonal refractory prostate cancer.

Three-dimensional composites manufactured with human mesenchymal cambial layer precursor cells as an alternative for sinus floor augmentation: an in vitro study
Turhani, D., E. Watzinger, et al. (2005), Clin Oral Implants Res 16(4): 417-24.
Abstract: Bone tissue engineering is a promising approach for treatment of defective and lost bone in the maxillofacial region. Creating functional tissue for load bearing bone reconstruction using biocompatible and biodegradable scaffolds seeded with living cells is of crucial importance. The aim of our study was to compare the effects of poly-lactic-co-glycolic acid (PLGA) and hydroxyapatite (HA) ceramic granulae on growth, differentiation, mineralization and gene expression of mandibular mesenchymal cambial layer precursor cells (MCLPCs) cultured onto tissue engineered three-dimensional (3-D) composites in vitro. These 3-D composites were cultivated in a rotating cultivation system under osteogenic differentiation conditions for a maximum period of 21 days. After 6 and 21 days, histological examination was performed; scanning electron microscopy (SEM), alkaline phosphatase (ALP) activity and levels of DNA were investigated. Expression of bone-specific genes osteocalcin, osteonectin, osteopontin, ALP, core binding factor alpha 1 and collagen type I were investigated by using a reverse transcription-polymerase chain reaction (RT-PCR) method. After 6 and 21 days of incubation an initiation of mineralization and the presence of newly formed bone at the surface of the composites were shown after evaluation of ALP activity, DNA content, SEM and histological staining. Expression of bone-specific genes confirmed the bone-like character of these composites and different effects of PLGA or HA granulae on the osteogenic differentiation of human MCLPCs in vitro. The results of this study support the concept that substrate signals significantly influence MCLPCs growth, differentiation, mineralization and gene expression in vitro, and that the use of these cells in the manufacturing of 3-D cell/HA composites is a promising approach for load bearing bone reconstruction in the maxillofacial region in vivo.

Three-dimensional culture and differentiation of human osteogenic cells in an injectable hydroxypropylmethylcellulose hydrogel
Trojani, C., P. Weiss, et al. (2005), Biomaterials 26(27): 5509-17.
Abstract: The present work evaluates a newly developed silated hydroxypropylmethylcellulose (Si-HPMC)-based hydrogel as a scaffold for 3D culture of osteogenic cells. The pH variation at room temperature catalyzes the reticulation and self-hardening of the viscous polymer solution into a gelatine state. We designed reticulation time, final consistency and pH in order to obtain an easy handling matrice, suitable for in vitro culture and in vivo injection. Three human osteogenic cell lines and normal human osteogenic (HOST) cells were cultured in 3D inside this Si-HPMC hydrogel. We show here that osteosarcoma cells proliferate as clonogenic spheroids and that HOST colonies survive for at least 3 weeks. Mineralization assay and gene expression analysis of osteoblastic markers and cytokines, indicate that all the cells cultured in 3D into this hydrogel, exhibited a more mature differentiation status than cells cultured in monolayer on plastic. This study demonstrates that this Si-HPMC hydrogel is well suited to support osteoblastic survival, proliferation and differentiation when used as a new scaffold for 3D culture and represents also a potential basis for an innovative bone repair material.

Three-dimensional distribution of the collagen fibers in the submucosa of the swine terminal ileum
Prado, I. M., L. J. Di Dio, et al. (2005), Ital J Anat Embryol 110(2 Suppl 1): 77-86.
Abstract: Collagen has an important role in controlling mechanical function and physiopathology of intestinal wall. Swine small intestine may be used as biomaterial source for tissue repairing. Changes of collagen arrangement and three-dimensional (3D) distribution may be related to the dissimilar biomechanical proprieties showed by different intestine tracts. 3D spatial distribution of collagen bundles of swine submucosal terminal ileum (SSTI) was studied by a correlated analysis of light (LM) and scanning electron microscopy (SEM) of NaOH macerated samples. Bundles of collagen fibers were greatly represented in the submucosa at the mesenteric border and also extended along the longitudinal folds beneath mucosa layer. Polarized LM of picrosirius stained samples evidenced yellow and red fibers (type I collagen), and green fibers (type III collagen). Silver-impregnated sections showed predominant brown-stained fibers and, in a smaller amount, black-stained ones. By SEM submucosal collagen, isolated by NaOH maceration, appeared arranged in wide bundles forming a complicated 3-D network. The bundles presented a sinuous course, opened and closed repeatedly forming meshes fashioned in a regular net. These observations originally demonstrated that 3-D distribution of SSTI collagen is different from that observed in other gut segments and species. The arrangement of SSTI collagen fibers that we observed seems to be morphofunctionally adjusted to provide appropriate resistance to mechanical forces and to assure compliance to deformations induced by intestinal wall motion. The studies for selection of optimal intestinal patches for surgical replacement should take into consideration the basic morphological evaluation of parietal collagen 3D distribution.

Three-dimensional extracellular matrix textured biomaterials
Goodman, S. L., P. A. Sims, et al. (1996), Biomaterials 17(21): 2087-95.
Abstract: Clinical and experimental investigations have reported that manufactured surface topographies have significant effects on cell adhesion and tissue integration. However, essentially all previously examined topographies bear little relation to cell adhesion substrates found in biological tissues. In vivo, many cells are adherent to extracellular matrices (ECM), which have an extremely complex 3-D topography in the micrometre to nanometre range. In addition, many studies indicate that micro- and nano-scale mechanical stresses generated by cell-matrix adhesion have significant effects on cellular phenotypic behaviour. In this report we describe methodology for the fabrication of topographic replicas of the subendothelial ECM topography with a biomedical polyurethane. Using three-dimensional high resolution scanning electron microscopy, accurate replication of subendothelial ECM topography from the macroscopic to the macromolecular scale is demonstrated. Bovine aortic endothelial cells cultured on the ECM replicas spread more rapidly and had a three-dimensional appearance and spread areas at confluence which appeared more like endothelial cells in native arteries, compared with cells cultured on untextured control surfaces. Since the fabrication process may be used with many different types of materials, including polymers of synthetic and biological origin, these biomimetic ECM-textured surfaces may find both research and clinical applications.

Three-dimensional FDTD simulation of biomaterial exposure to electromagnetic nanopulses
Simicevic, N. (2005), Phys Med Biol 50(21): 5041-53.
Abstract: Ultra-wideband (UWB) electromagnetic pulses of nanosecond duration, or nanopulses, have recently been approved by the Federal Communications Commission for a number of different applications. They are also being explored for applications in biotechnology and medicine. The simulation of the propagation of a nanopulse through biological matter, previously performed using a two-dimensional finite-difference time-domain (FDTD) method, has been extended here into a full three-dimensional computation. To account for the UWB frequency range, the geometrical resolution of the exposed sample was 0.25 mm and the dielectric properties of biological matter were accurately described in terms of the Debye model. The results obtained from the three-dimensional computation support the previously obtained results: the electromagnetic field inside a biological tissue depends on the incident pulse rise time and width, with increased importance of the rise time as the conductivity increases; no thermal effects are possible for the low pulse repetition rates, supported by recent experiments. New results show that the dielectric sample exposed to nanopulses behaves as a dielectric resonator. For a sample in a cuvette, we obtained the dominant resonant frequency and the Q-factor of the resonator.

Three-dimensional growth of differentiating MC3T3-E1 pre-osteoblasts on porous titanium scaffolds
St-Pierre, J. P., M. Gauthier, et al. (2005), Biomaterials 26(35): 7319-28.
Abstract: The present work assesses the potential of three-dimensional porous titanium scaffolds produced by a novel powder metallurgy process for applications in bone engineering through in vitro experimentation. Mouse MC3T3-E1 pre-osteoblasts were used to investigate the proliferation (DNA content), differentiation (alkaline phosphatase activity and osteocalcin release) and mineralisation (calcium content) processes of cells on titanium scaffolds with average pore sizes ranging from 336 to 557 microm, using mirror-polished titanium as reference material. Scanning electron microscopy was employed to qualitatively corroborate the results. Cells proliferate on all materials before reaching a plateau at day 9, with proliferation rates being significantly higher on foams (ranging from 123 to 163 percent per day) than on the reference material (80% per day). Alkaline phosphatase activity is also significantly elevated on porous scaffolds following the proliferation stage. However, cells on polished titanium exhibit greater osteocalcin release toward the end of the differentiation process, resulting in earlier mineralisation of the extracellular matrix. Nevertheless, the calcium content is similar on all materials at the end of the experimental period. Average pore size of the porous structures does not have a major effect on cells as determined by the various analyses, affecting only the proliferation stage. Thus, the microstructured titanium scaffolds direct the behaviour of pre-osteoblasts toward a mature state capable of mineralising the extracellular matrix.

Three-dimensional micro-computed tomographic evaluation of periodontal regeneration: a human report of intrabony defects treated with Bio-Oss collagen
Nevins, M. L., M. Camelo, et al. (2005), Int J Periodontics Restorative Dent 25(4): 365-73.
Abstract: This study utilized three-dimensional micro-computed tomography (micro-CT) to evaluate the regenerative response to Bio-Oss Collagen when used alone or in combination with a Bio-Gide bilayer collagen membrane for the treatment of four intrabony defects (5 to 7 mm) around single-rooted teeth. The micro-CT observations are compared to the clinical, radiographic, and histologic results, which have been previously reported. After reflecting a full-thickness flap, thorough degranulation and root planing were accomplished. Bio-Oss Collagen was then used to fill the defects, and in two cases a Bio-Gide membrane was placed over the filled defect. Radiographs, clinical probing depths, and attachment levels were obtained before treatment and immediately preceding en bloc resection of teeth and surrounding tissues 9 months later. A mean pocket depth reduction of 5.75 mm and mean clinical attachment level gain of 5.25 mm were recorded. The histologic evaluation demonstrated the formation of a complete new attachment apparatus with new cementum, periodontal ligament, and alveolar bone at the level of and coronal to the calculus reference notch. Micro-CT evaluation confirmed the histologic results and demonstrated the absence of ankylosis or root resorption for all specimens. This human histologic study demonstrated that Bio-Oss Collagen has the capacity to facilitate regeneration of the periodontal attachment apparatus when placed in intrabony defects. Micro-CT observations confirmed the histologic results and enhanced the three-dimensional understanding of periodontal wound healing. The results indicate that micro-CT may be useful for three-dimensional evaluation of periodontal regenerative procedures.

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Last Modified: 8 February 2006