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PubMed1996

Deformation models and correlation analysis in elastography.

Cross-correlation functions are derived with the purpose of determining how strain inhomogeneities affect the displacement estimates used in ultrasound-based elastography. Variations in the strain profile occur in most imaging situations and are caused by fluctuations in the stress field or elastic modulus of the sample. An analytical framework for developing signal processing strategies in elastography is described, and the limitations of correlation-based methods for measuring displacements in tissuelike media caused by static compression are emphasized. This paper includes (1) an accurate approximation for an inverse coordinate transformation that release pre- and postcompression reflectivity profiles of the media, (2) a derivation of the echo-signal cross-correlation function in media with deterministic or stochastic strain profiles; (3) mathematical and graphical descriptions of the consequences that nonuniformities in the strain profile impose upon the uncertainty of displacement estimation; and (4) a demonstration of the advantages of echo signal conditioning and ultrasonic-pulse shaping to reduce the nonstationary effects that attenuate the cross-correlation peak and reduce the signal-to-noise ration for displacement estimation.

Elasticity↗

PubMed1995

Fatigue behavior of the equine third metacarpus: mechanical property analysis.

This is the first in a series of experiments to study the fatigue properties of equine cannon (third metacarpal) bone specimens from Thoroughbred racehorses. Monotonic and fatigue tests to failure were performed in four-point bending on diaphyseal specimens in a 37 degrees C saline bath to answer three initial questions. (a) Will a linear variable differential transducer yield the same elastic modulus as strain gauges? (b) Will fatigue results depend on whether the periosteal or endosteal side of the beam is in tension? (c) Are there regional variations in the monotonic and fatigue properties of the cannon bone midshaft? Eighteen left-right pairs of specimens from six horses were used. One beam of each pair was fitted with strain gauges. Fatigue tests were conducted on 24 specimens under load control at 2 Hz; an initial range of 0-10,000 microstrain was used so as to produce failure in a reasonable period of time. There were no left-right differences in the fatigue or monotonic properties, and the presence of a gauge had no effect on modulus measured by a linear variable differential transducer. However, gauge-measured moduli were about 1 GPa less than transducer-measured values. Fatigue life was independent of which side of the beam was in tension, and there were significant variations in mechanical properties around the cortex. The lateral region was stiffer than the dorsal region but the latter had a longer fatigue life. The fixed cylindrical supports used in this experiment eventually produced slight wear grooves, causing artifactual stiffening at the end of the load cycle in some specimens. A second experiment using roller supports confirmed the reason for this stiffening. It also showed that fatigue life was shorter when roller supports were used but regional differences were similar.

Analysis of Variance↗

PubMed2002

Displacement sequence and elastic properties of anterior prostate/urethral interface during micturition of spinal cord injured men.

The management of complex micturition problems frequently encountered in patients with spinal cord injury (SCI) may be facilitated by characterization of the elastic properties of the prostate. To this end, we have developed a method of evaluating changes in prostate biomechanics using ultrasound (US) images obtained during routine diagnostic urodynamic evaluations. Ultrasound video sequences of the prostate and urethra during voiding were digitized simultaneously with bladder pressure measurement on 76 patients with spinal cord injury, having a mean age of 47 +/- 16 years. Computer enhancement of the bladder/prostate/urethral interface from sequences of 2-D US images facilitated measurement of midprostatic urethral displacement during micturition. Of 76 patients, 21 were able to initiate voiding. Maximum urethral diameter was 12.0 +/- 1.3 mm, with corresponding maximum voiding pressure of 61.6 +/- 1.9 cmH(2)O. Urethral/prostatic pressure strain elastic modulus (Ep) was 960 +/- 624 N/m(2) and stiffness (beta) calculated as the inverse of compliance was 2.8 +/- 0.1. The diameter of the urethra at P(det50+), during the opening phase, was 0.4 +/- 0.1 mm and, during the closing phase, was 0.7 +/- 0.1 mm. During voiding, the anterior prostate was displaced to a greater extent than the posterior prostate. These observations suggest that distension of the prostate/urethra during micturition is hysteretic and nonuniform and indicates regional differences in compliance within the prostate/urethra interface. These regional differences lend support to the concept that the posterior prostate is implicated in the active process of micturition involving the fibromuscular stroma. Clinical application of this method could include quantification of the biomechanics of micturition consequent to spinal injury, prostatic enlargement, and the impact of targeted evaluation of pharmacological interventions.

Adult↗

PubMed2004

Mechanical and biological properties of hydroxyapatite reinforced with 40 vol. % titanium particles for use as hard tissue replacement.

Hydroxyapatite (HA)-based composite reinforced with 40 vol. % Ti particles was fabricated by the optimal technical condition of hot pressing technique. The mechanical and biological properties of the composite were studied by mechanical and in vivo methods. The experimental results show that HA and Ti phases are the predominant phases of the composite with partially decomposition of HA phase into alpha-Ca3(PO4)2 and Ca4O(PO4)2. Comparing with HA-20 vol. % Ti composite manufactured under the same conditions, HA-40 vol. % Ti composite with similar elastic modulus (79.3 GPa) and Vicker's hardness (2.94GPa) has a higher bending strength (92.1 MPa). Moreover, fracture toughness of HA-40 vol. % Ti composite with crack bridging as the chief toughening mechanisms can reach 2.692 MPa m(-1) , which can meet the basic toughness demand of the replaced hard tissues for heavy load-bearing applications. Work of fracture of HA-40 vol. % Ti composite is 91.2J m2, which is 22.9 times that of pure HA ceramic and even 2.4 times that of Al2O3 bioceramic. The results of in vivo studies show HA-40 vol. % Ti composite has excellent biocompatibility and could integrate with bone. In the early stage after the implantation of the samples, the osteointegration ability of the composite is better than that of pure titanium.

Animals↗

PubMed2004

Susceptibility of deciduous and permanent enamel to dietary acid-induced erosion studied with atomic force microscopy nanoindentation.

The initial stages of dental enamel demineralization by dietary acids are of particular clinical relevance. Some authors have reported a difference in the susceptibility of deciduous and permanent enamel to erosion, although other studies could not confirm these findings. The aim of the present study was therefore to investigate whether there are differences in the susceptibility of deciduous and permanent enamel to dietary acid induced erosion (demineralization). Nanoindentation combined with atomic force microscopy was used to investigate the erosive effect of four different drinks (cola, lemonade, juice drink, and water) on enamel at early stages in vitro. Surface nanohardness and reduced elastic modulus were obtained for the soft drink-treated enamel samples as a function of the exposure time. The results obtained showed that the four drinks had widely differing erosive effects due to their diverse compositions. Water did not show statistically significant changes in nanomechanical properties for all exposure times compared with untreated enamel. Exposure of enamel to cola, lemonade and the juice drink led to a statistically significant surface softening of the enamel with cola and the lemonade having a much stronger softening effect than the juice drink. For longer exposure times enamel softening increased for cola and lemonade and stayed unchanged for the juice drink. Deciduous enamel was not found to be more susceptible to erosion than permanent enamel under the conditions of the present study.

Acids↗

PubMed1999

Characterization of the mechanical and ultrastructural properties of heat-treated cortical bone for use as a bone substitute.

Heat-treated bovine cortical bone has been proposed as an alternative to bone grafts and synthetic bone substitutes because it may combine the advantages of allografts (high stiffness and strength) and synthetic materials (abundant supply, reduced risk of rejection and disease transfer). Its mechanical properties and ultrastructure, however, are not well characterized. To address this, we compared the compressive (n = 20, bovine bone) and tensile (n = 26, bovine bone) mechanical properties and the ultrastructure (n = 12, human bone) of intact versus 350 degrees C heat-treated cortical bone. The 350 degrees C heat-treated bone had a mean +/- SD elastic modulus similar to the intact bone for both compression (16.3 +/- 2.2 GPa, pooled; p = 0.68) and tension (16.3 +/- 3.7 GPa, pooled; p = 0.95). It also maintained 63% of the intact strength in compression but only 9% in tension (p < 0.001). Infrared scans and X-ray diffraction patterns showed no differences between the 350 degrees C heat-treated and intact bone but large differences between ashed (700 degrees C) and intact bone. Similarly, heat-treated bone previously has been shown to be biocompatible and osteoconductive. We conclude, therefore, that 350 degrees C heat-treated cortical bone may be an excellent load-bearing bone substitute provided that it is loaded in compression only in vivo and is shown by future work to have acceptable fatigue properties.

Aged↗

PubMed2000

Sliding mechanics of coated composite wires and the development of an engineering model for binding.

A tribological (friction and wear) study, which was designed to simulate clinical sliding mechanics, was conducted as part of an effort to determine the suitability of poly(chloro-p-xylylene) coatings for composite orthodontic archwires. Prototype composite wires, having stiffnesses similar to those of current initial and intermediate alignment wires, were tested against stainless steel and ceramic brackets in the passive and active configurations (with and without angulation). Kinetic coefficient of friction values, which were determined to quantify sliding resistances as functions of the normal forces of ligation, had a mean that was 72% greater than uncoated wire couples at 0.43. To improve analysis of the active configuration, a mathematical model was developed that related bracket angulation, bracket width, interbracket distance, wire geometry, and wire elastic modulus to sliding resistance. From this model, kinetic coefficients of binding were determined to quantify sliding resistances as functions of the normal forces of binding. The mean binding coefficient was the same as that of uncoated wire couples at 0.42. Although penetrations through the coating were observed on many specimens, the glass-fiber reinforcement within the composite wires was undamaged for all conditions tested. This finding implies that the risk of glass fiber release during clinical use would be eliminated by the coating. In addition, the frictional and binding coefficients were still within the limits outlined by conventional orthodontic wire-bracket couples. Consequently, the coatings were regarded as an improvement to the clinical acceptability of composite orthodontic archwires.

Aluminum Oxide↗

PubMed2006

Transient elastography: a valid alternative to biopsy in patients with chronic liver disease.

BACKGROUND: Transient elastography is a novel and non-invasive technique for the evaluation of fibrosis in chronic liver disease. Few studies that exist value the efficacy of transient elastography, mainly in hepatitis C virus-infected patients. AIM: To evaluate the effectiveness, objectivity, reproducibility and safety of this technique. METHODS: We included 103 consecutive patients who underwent a liver biopsy in the last 48 months with a wide spectrum of chronic liver diseases. Median stiffness value (expressed as kilopascals - kPa) was kept as representative of the liver elastic modulus. All biopsy specimens were analysed by the same pathologist according to the METAVIR scoring system. RESULTS: Median value of stiffness in patients with mild or moderate fibrosis (FI and FII), and severe fibrosis or cirrhosis (FIII and FIV) was of 7, 4 +/- 5 and 16, 4 +/- 10 kPa, respectively, with a significant difference between them (P < 0.05). The areas under the receiver operating characteristic curves showed the optimal liver stiffness cut-off values for each group. CONCLUSIONS: We found a positive correlation between the liver stiffness found by transient elastography and fibrosis stage on biopsy in all patients, independently of the liver disease aetiology. Transient elastography is an easy, quick to perform and safe non-invasive procedure, reliable for assessing liver fibrosis.

Biopsy↗

PubMed2002

Stress and strain distribution behavior in the bone due to the effect of cancellous bone, dental implant material and the bone height.

The stress and strain distribution in the bone surrounding a dental implant have been analyzed using the finite element and optimization techniques. The effect of removing cancellous bone completely or not was investigated. Two models were used, the first model without cancellous bone and the second with it. The elastic modulus of the implant material and the length of the implant neck or the height of bone surrounding the implant were used as design variables in the two models. In the first model a higher level of stress in the cortical bone surrounding the neck of the implant was found. While in the second model, it was found surrounding the tip of the implant. The result indicates that the stress concentration factor in the bone of the first model is reduced by 30% compared to the initial design. However, when the implant was surrounded by sleeve of cancellous bone (second model) the stress concentration is reduced by 16% for cortical bone and 15% for cancellous bone. This reduction help to reduce fatigue failure and bone resorption.

Coated Materials, Biocompatible↗

PubMed2005

An in vitro study of cryopreserved and fresh human arteries: a comparison with ePTFE prostheses and human arteries studied non-invasively in vivo.

The surgical options in arterial reconstruction are: the use of autologous arteries; autologous veins; or expanded polytetrafluoroethylene (ePTFE) grafts. However, the development of intimal hyperplasia when using veins or ePTFE grafts has been associated with graft failure. Since autologous arteries are not always available, the use of cryopreserved arteries has to be considered. The aims of this study were: (a) to compare the viscoelastic properties of stored cryopreserved arteries and fresh arteries by in vitro analysis; and (b) to compare the viscoelastic properties of arteries measured non-invasively in normotensive patients, with fresh arteries, cryopreserved arteries, and ePTFE segments. The viscoelastic studies were performed in normotensive patients using stress-strain analysis with non-invasive measurement of pressure and diameter in the common carotid artery, and in vitro measurements of pressure and diameter in arteries and prostheses. The in vitro studies showed that the elastic modulus (E), viscous modulus (eta), Stiffness Index (SI), Peterson modulus (Ep), and the pulse wave velocity (PWV) values for human cryopreserved carotid arteries were similar to the values obtained non-invasively in normotensive subjects (P>0.05) and to human fresh vessels (P>0.05). In vitro, the SI, Ep, PWV, and E values of ePTFE were significantly higher than the observed values in subjects and with fresh and cryopreserved arteries (P<0.05); on the other hand the ePTFE eta values were the lowest (P<0.05). We concluded that cryopreserved arteries have similar viscoelastic properties to those obtained in vivo in the arteries of normotensive subjects and in vitro in fresh arteries. Consequently, we conclude that the cryopreservation procedure does not modify the mechanical properties of the arterial wall.

Arteries↗

PubMed1983

The retention mechanics of LTI carbon, carbon-coated aluminum oxide, and uncoated aluminum oxide dental implants.

The in vitro mechanical behavior of identical geometry LTI carbon, carbon-coated aluminum oxide, and uncoated aluminum oxide blade-type dental implants has been evaluated using rosette type strain gauges and a LVDT system. The implants served as a distal abutment for a three-unit fixed prosthesis and functioned for a period of 2 years in female baboons. The comparison of the LTI carbon implants to the carbon-coated aluminum oxide implants allowed for a study of the effect of implant elastic modulus on the mechanical behavior, while the comparison of the carbon-coated and uncoated aluminum oxide implants allowed for a study of the effect of chemical composition at the tissue-implant interface. The results of the mechanical testing indicate that the implant displacement response of the LTI carbon implants was greater than that of the carbon-coated and uncoated aluminum oxide implants. Little difference in displacement response was observed for the carbon-coated and uncoated aluminum oxide implants. No clear trend in the strain response of the buccal mandibular bone was observed for the three implant systems. The greatest differences in strain response, however, was observed between the uncoated aluminum oxide implants and the LTI carbon and carbon-coated aluminum oxide implants.

Aluminum Oxide↗

PubMed1992

An analytical and numerical study of the stability of bone remodelling theories: dependence on microstructural stimulus.

The origin of unstable bone remodelling simulations using strain-energy-based remodelling rules was studied mathematically in order to assess whether the unstable behavior was due to the mathematical rules proposed to characterize the processes, or to the numerical approximations used to exercise the mathematical predictions. A condition which is necessary for the stability of a strain-energy-based remodelling theory was derived analytically using the calculus of variation. The analytical result was derived using a simple elastic model which consists of a long beam loaded by an axial force and a bending moment. This loading situation mimics the coupling between local density and global density distributions seen in vivo. A condition necessary for a stable remodelling scheme is arrived at, but the conditions necessary to guarantee a stable remodelling scheme are not. In this remodelling scheme, the elastic modulus is proportional to volumetric density raised to an exponent n, and the microstructural stimulus is taken as the strain energy density divided by volumetric density raised to an exponent m. In order for a remodelling scheme to be stable in this loading situation, m must be greater than n. Finite-difference time-stepping is used to verify the predictions of the analytical study. These numerical studies appear to confirm the analytical studies. Physiologic interpretation of the behavior found with n greater than m indicates that this type of unstable behavior is unlikely to be observed in vivo. Since numerical approximations are not made in deriving this stability condition, we conclude that the mathematical rules proposed to characterize bone remodelling based on strain energy density should meet this condition to be relevant to physiologic bone remodelling.

Bone Density↗

PubMedDate not supplied

Biomechanics of soft tissues.

Recent developments in Computer-Integrated and Robot-Aided Surgery (in particular, the emergence of automatic surgical tools and robots (as well as advances in Virtual Reality techniques, call for closer examination of the mechanical properties of very soft tissues (such as brain, liver, kidney, etc.). Moreover, internal organs are very susceptible to trauma. In order to protect them properly against car crash and other impact consequences we need to be able to predict the organ deformation. Such prediction can be achieved by proper mathematical modelling followed by a computer simulation. The ultimate goal of our research into the biomechanics of these tissues is development of corresponding, realistic mathematical models. This paper contains experimental results of in vitro, uniaxial, unconfined compression of swine brain tissue obtained by the author in Mechanical Engineering Laboratory, Japan, and discusses liver and kidney in vivo compression experiments conducted in Highway Safety Research Institute and the Medical Centre of The University of Michigan. The stress-strain curves for investigated tissues are concave upward for all compression rates containing no linear portion from which a meaningful elastic modulus might be determined. The tissue response stiffened as the loading speed increased, indicating a strong stress (strain rate dependence. As the step in the direction towards realistic computer simulation of injuries and surgical procedures, this paper presents two mathematical representations of brain, liver and kidney tissue stiffness. Biphasic and single-phase models are discussed. The biphasic model is shown to be inappropriate due to its inability to account for strong stress-strain relationship. Agreement between the proposed single-phase models and experiment is good for compression levels reaching 30% and for loading velocities varying over five orders of magnitude. Presented mathematical models can find applications in computer and robot assisted surgery, e.g. the realistic simulation of surgical procedures (including virtual reality), control systems of surgical robots, and non-rigid registration, as well as ergonomic design for injury prevention.

Animals↗

PubMed2001

Local anaesthetic block copolymer system undergoing phase transition on dilution with water.

The possibility of formulating a local anaesthetic system displaying in situ gelation on dilution with water, as well as its dependence on concentration of active ingredients and pH was investigated. For this purpose Lutrol F68, water, a eutectic mixture of lidocaine and prilocaine and Akoline MCM were mixed in different ratios and investigated using crossed polarisers, small-angle X-ray diffraction, rheology, conductivity and NMR self-diffusion measurements. In particular, an isotropic phase of low viscosity turning into a high viscous hexagonal phase upon dilution with water was found. The increase in viscosity is only weakly dependent on temperature in the temperature range of 20-37 degrees C. The rheology and in vitro drug release of these systems were studied and the elastic modulus was found to be fairly independent of concentration of active ingredients and pH in the investigated region. The in vitro release of lidocaine and prilocaine was found to increase with increasing concentration of the active ingredients and with decreasing pH, the latter as a consequence of the pH-dependent ionisation of these substances. The behaviour of the system is promising from a pharmaceutical point of view, since the isotropic low-viscous phase can be injected into, e.g. a periodontal pocket where the presence of saliva will cause a temporal transition into a rigid hexagonal phase thus making the formulation stay at the application site. At even higher water content, either as a result of longer application time or rinsing with water, the hexagonal phase is effectively dissolved through transformation to a water-rich micellar phase.

Anesthetics, Local↗

PubMed1997

Analysis of strain gage method for measurement of post-gel shrinkage in resin composites.

OBJECTIVE: The objective of this study was to refine a strain gage method for measuring polymerization contraction of resin composites and to isolate the net post-gel contraction by identifying factors contributing to the measured strains. The hypothesis to be tested was that carefully controlled strain gage measurements of composite polymerization could isolate post-gel contraction events. METHODS: Composite was placed on a biaxial strain gage and light-cured. This method enabled real-time registration of the progress of shrinkage strain, corresponding to elastic modulus development. Strain from the two axes of the strain gage were averaged and plotted as a function of time. A representative curve was calculated from the mean of ten measurements. The following factors influencing the total contraction measurement were evaluated: thermal expansion of the gage, thermal expansion of the composite due to the exothermic reaction and exposure to the curing light, and adhesion of the composite to the gage. These parameters were measured so that the net deformation of the composite during polymerization could be calculated. RESULTS: Parametric studies of pre-cured and photointiator-free materials confirmed the hypothesis that strain gages measure post-gel contraction. Thermal artifacts were measured and subtracted from the total strain output. SIGNIFICANCE: Strain gages are suitable for measuring the clinically significant phase of composite polymerization contraction.

Adhesiveness↗

PubMed2001

The relationship between abdominal aortic aneurysm distensibility and serum markers of elastin and collagen metabolism.

BACKGROUND: abdominal aortic aneurysm (AAA) distensibility may be an independent predictor of growth and rupture, possibly because it reflects changes in aortic wall structure and composition. AIM: to determine whether AAA distensibility is related to circulating markers of elastin and collagen metabolism. METHODS: sixty-two male patients of median age (IQR) 68 (65-72) years with asymptomatic AAA of median (IQR) diameter 42 (37-45) mm were prospectively studied. Pressure-strain elastic modulus (Ep) and stiffness (beta) were measured using an ultrasonic echo-tracker (Diamove). Serum elastin peptides (SEP), plasma elastin-alpha1-antitrypsin complex (E-AT), procollagen III-N-terminal propeptide (PIIINP) were measured by enzyme-linked immunoassay. RESULTS: age and smoking adjusted Ep and beta were significantly inversely related to SEP (r=-0.33 and r=-0.31 respectively, both p<0.02) and E-AT (r=-0.27 and r=-0.27 respectively, both p<0.05) both of which indicate elastolysis. By contrast, there was a significant positive correlation between PIIINP, indicative of increased collagen turn-over, and both Ep and beta (both r=0.45, p<0.01 unadjusted correlations). CONCLUSION: increased elastolysis is associated with increased AAA wall distensibility; whereas increased collagen turn-over is associated with reduced distensibility.

Adult↗

PubMed2004

The effect of mechanical undercuts on the strength of composite repair.

BACKGROUND: The authors conducted an in vitro study to test the hypothesis that undercuts prepared in old composite restorations could improve the strength between the restoration and a flowable composite as repair material. METHODS: The authors used three composites to fabricate cylinders as repair substrates. The etched-only group was ground, etched, dried and built up with a flowable composite. For the undercut group, the authors introduced arrays of fissures on the surfaces before preparing the specimens for subsequent buildup in the manner described for the etched-only group. They made nonrepaired cylinders for baseline measures of strength. They sliced all finished cylinders into slender bars with a diamond saw. Flexure strength values were determined by a three-point-bending test. RESULTS: Nonrepaired bars exhibited statistically significantly higher flexure strength values than did repaired bars, as determined by Wilcoxon rank sum test. Two-way general linear model showed that both material (P < .0001) and undercut (P = .0207) exhibited a statistically significant influence on the repaired flexure strength. Repair substrate with elastic modulus close to that of repair material exhibited a greater percentage of recovery of the respective cohesive strength. Compared with the etched-only group, the undercut group yielded a higher mean flexure strength with one composite but a lower mean flexure strength with the other two. Examination of the fractured surfaces showed that a significant number of undercuts were filled only partially. CONCLUSION: Flexure strengths of repaired specimens always were lower than the cohesive flexure strengths of the materials being repaired. Undercuts did not generally improve repair strength. CLINICAL IMPLICATIONS: Small undercuts on the surface of composite often are difficult to fill completely, resulting in areas of stress concentration that result in no improvement in the repair strength.

Analysis of Variance↗

PubMedDate not supplied

Hydroxyapatite/poly(epsilon-caprolactone) composite coatings on hydroxyapatite porous bone scaffold for drug delivery.

Hydroxyapatite (HA) porous scaffold was coated with HA and polycaprolactone (PCL) composites, and antibiotic drug tetracycline hydrochloride was entrapped within the coating layer. The HA scaffold obtained by a polymeric reticulate method, possessed high porosity ( approximately 87%) and controlled pore size (150-200 microm). Such a well-developed porous structure facilitated usage in a drug delivery system due to its high surface area and blood circulation efficiency. The PCL polymer, as a coating component, was used to improve the brittleness and low strength of the HA scaffold, as well to effectively entrap the drug. To improve the osteoconductivity and bioactivity of the coating layer, HA powder was hybridized with PCL solution to make the HA-PCL composite coating. With alteration in the coating concentration and HA/PCL ratio, the morphology, mechanical properties, and biodegradation behavior were investigated. Increasing the concentration rendered the stems thicker and some pores to be clogged; as well increasing the HA/PCL ratio made the coating surface be rough due to the large amount of HA particles. However, for all concentrations and compositions, uniform coatings were formed, i.e., with the HA particles being dispersed homogeneously in the PCL sheet. With the composite coating, the mechanical properties, such as compressive strength and elastic modulus were improved by several orders of magnitude. These improvements were more significant with thicker coatings, while little difference was observed with the HA/PCL ratio. The in vitro biodegradation of the composite coatings in the phosphate buffered saline solution increased linearly with incubation time and the rate differed with the coating concentration and the HA/PCL ratio; the higher concentration and HA amount caused the increased biodegradation. At short period (<2 h), about 20-30% drug was released especially due to free drug at the coating surface. However, the release rate was sustained for prolonged periods and was highly dependent on the degree of coating dissolution, suggesting the possibility of a controlled drug release in the porous scaffold with HA+PCL coating.

Absorbable Implants↗