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The soft tissue aspiration experiment has been further developed for application during laparoscopic surgery. The new setup has been tested and validated under lab-conditions and came then to in vivo operation. It is to our knowledge the first time ever a mechanical experiment has been performed under laparoscopic conditions on the human, which enables determining corresponding constitutive model equations. As most important results, the feasibility of laparoscopic tissue aspiration has been demonstrated and, based on an ad hoc parameter for the tissue stiffness, the liver and the stomach gave significantly different responses. Furthermore, the determined constitutive behavior for one healthy human liver was in line with results obtained from tissue aspiration during open surgery. Eventually, laparoscopic tissue aspiration might qualify as minimally invasive testing method for tactile feedback systems. The presented results are preliminary and more research is required., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The purpose of this work is to study the elastoplastic properties of novel intermetallic coatings grown by hot dipping on medical steel 316 LVM and their correlation with the scratch resistance by means of instrumented ultramicroindentation techniques. Elastoplastic properties are defined by the plasticity index (PI), which correlates the hardness and the Young's modulus, and the yield strength that delimits the elastic-plastic transition. To avoid overestimations of the PI due to the so-called indentation size effect, macroscopic hardness values were determined. The PI of the coating increases from 0.6 to 0.8 with increasing immersion time. These values are always lower than those of the bare substrate (0.9) but higher than those found for ceramics (∼0.5). The increase of the PI is accompanied by a decrease in the yield strength from 0.73 to 0.34 GPa, which highlights the relevance of the compressive residual stresses and their relaxation with increasing immersion time. The higher plasticity is shown by higher apparent friction coefficients (0.159), which are always lower than those of the bare steel (0.264). Therefore, these intermetallic coatings could be considered "hard but tough" coatings, suitable for enhancing the wear resistance of the medical steel, especially when using short periods of immersion. The study provides evidence that the load-depth curve of indentation contains abundant information and that its analysis can be used to determine various mechanical properties of coatings that could be important for load bearing components., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

In a wide range of biomechanical modeling of aorta from traumatic injury to stent grafts, the arterial wall has been considered as a single homogeneous layer vessel, ignoring the fact that arteries are composed of distinct anatomical layers with different mechanical characteristics. In this study, using a custom-made nanoindentation technique, changes in the mechanical properties of porcine thoracic aorta wall in the radial direction were characterized using a quasi-linear viscoelastic model. Two layers of equal thickness were mechanically distinguishable in descending aorta based on the radial variations in the instantaneous Young's modulus E and reduced relaxation function G(t). Overall, comparison of E and G(∞) of the outer half (70.27±2.47 kPa and 0.35±0.01) versus the inner half (60.32±1.65 kPa and 0.33±0.01) revealed that the outer half was stiffer and showed less relaxation. The results were used to explain local mechanisms of deformation, force transmission, tear propagation and failure in arteries., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Objective: In order to quantitatively evaluate testicular consistency, we designed a device for measurement of testis rigidity, which reflects the resistance caused by testicular pressure and elasticity. The device was tested in experimental models of cryptorchidism and torsion., Materials and Methods: The Testis Rigidity Tester (TRT) prototype consists of a system of weights and levers. It measures the force needed for a known deformation of the testis, defined as rigidity. We inhibited testis descent in 10 18-day-old Lewis rats; another 10 age-matched rats underwent sham operation. At the age of 40 days we measured testicular rigidity using the TRT. Additionally, left testes of eight adult Lewis rats underwent 720 degrees torsion; rigidity was measured by the TRT before and 1h after torsion. To investigate repeatability of TRT measurements, the rigidity of five twisted testes was measured 10 times by three researchers., Results: The TRT revealed a significant decrease of rigidity in undescended testes and an increase in twisted testes. Measurements were repeatable, independent of the observer., Conclusion: The TRT is a safe, reliable and objective device that successfully measured the altered rigidity in experimental models of testicular disease., (Copyright (c) 2010 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.)

Titanium dioxide (TiO(2)) coatings exhibit desirable properties as biocompatible coatings. In this paper we report on mechanical properties and deformation behavior of (TiO(2)) nanotubes grown on pure titanium substrates through anodic oxidation. Characterization of the as-processed coatings was conducted using scanning electron microscopy (SEM). Nanoindentation, using Interfacial Force Microscopy (IFM), was employed to probe the Young's modulus of the nanotubes. Using the IFM technique, the modulus of the nanotube coating may be measured with minimal contribution from the underlying Ti substrate. The modulus of the (TiO(2)) nanotube coating was estimated at 4-8 GPa. This technique was also used to study the inelastic deformation behavior of the nanotubes. (TiO(2)) nanotubes were found to inelastically deform by "tube crushing" in the immediate vicinity of indenter tip, increasing the local density. This increase in local density caused an increase in the Young's modulus from roughly 4 GPa to 30 GPa in the first 30 nm of indentation. Densification and the resulting increase in elastic modulus are related to the total work of inelastic deformation, irrespective of the loading history.

Load response of viscoelastic-plastic materials depends on the load magnitude and history, and can be described by rheological models consisting of springs and dashpots. The parameters in these models can be obtained by instrumented indentation. Time-dependent properties are determined best from the time course of indenter displacement under constant load, but one must consider also the initial loading history. For characterization of instantaneous elastic and plastic response, fast loading and unloading are necessary. The paper summarizes the formulae for indentation into elastic-plastic and viscoelastic-plastic materials, and proposes a procedure for testing and data evaluation. Its application is illustrated on the indentation of human enamel.

The brain deformation that occurs during neurosurgery is a serious issue impacting the patient "safety" as well as the invasiveness of the brain surgery. Model-driven compensation is a realistic and efficient solution to solve this problem. However, a vital issue is the lack of reliable and easily obtainable patient-specific mechanical characteristics of the brain which, according to clinicians' experience, can vary considerably. We designed an aspiration device that is able to meet the very rigorous sterilization and handling process imposed during surgery, and especially neurosurgery. The device, which has no electronic component, is simple, light and can be considered as an ancillary instrument. The deformation of the aspirated tissue is imaged via a mirror using an external camera. This paper describes the experimental setup as well as its use during a specific neurosurgery. The experimental data was used to calibrate a continuous model. We show that we were able to extract an in vivo constitutive law of the brain elasticity: thus for the first time, measurements are carried out per-operatively on the patient, just before the resection of the brain parenchyma. This paper discloses the results of a difficult experiment and provide for the first time in vivo data on human brain elasticity. The results point out the softness as well as the highly non-linear behavior of the brain tissue.

Objectives: The purpose of the current study was to examine the influence of simulated masticatory loading regimes, to which all-ceramic crown or bridge restorations will routinely be subjected during their service-life, on the performance of a yttria-stabilised tetragonal zirconia polycrystalline (Y-TZP) dental ceramic., Methods: Ten sets of 30 Y-TZP ceramic discs (13 mm diameter, 1.48-1.54 mm thickness) supplied by the manufacturer were randomly selected. Six groups were loaded for 2000 cycles at 500 N (383-420 MPa), 700N (536-588 MPa) and 800 N (613-672 MPa) with three groups maintained dry and the remaining three groups loaded while immersed in water at 37+/-1 degrees C. A further two groups underwent extended simulated masticatory loading regimes at 80 N (61-67 MPa) for 10(4) and 10(5)cycles under dry conditions. The mean bi-axial flexure strengths, standard deviations and associated Weibull moduli (m) were determined. The surface hardness was also determined using the Vickers hardness indentation technique., Results: No significant difference (P>0.05) was identified in the bi-axial flexure strength of the simulated masticatory loading regimes and the control specimens loaded dry or wet. A significant increase in m was identified for the Y-TZP specimens following loading while immersed in water (8.6+/-1.6, 8.5+/-1.6 and 10.3+/-1.9) compared with the control (7.1+/-1.3). However, the extended loading regime to 10(5)cycles resulted in a significant reduction in the m of the Y-TZP specimens (5.3+/-1.0) compared with the control. Localised areas of increased surface hardness were identified to occur directly beneath the spherical indenter., Conclusions: The occurrence of localised areas of increased surface hardness could be the result of either a transformation toughening mechanism or crushing and densification of the material beneath the indentor manifested as the formation of a surface layer of compressive stresses that counteracted the tensile field generated at the tip of a propagating crack which increased the Weibull modulus of the Y-TZP specimens. The reduced reliability of the Y-TZP specimens loaded to 80 N for 10(5)cycles was associated with the accumulation of subcritical damage as a result of the extended nature of loading.

Cementum is a nonuniform connective tissue that covers the roots of human teeth. Investigation of the physical properties of cementum may help in understanding or evaluating any possible connection to root resorption. A variety of engineering tests are available to investigate these properties. However, the thickness of the cementum layer varies, and this limits the applicability of these techniques in determining the physical properties of cementum. Hardness testing with Knoop and Vickers indentations overcame some of these limitations, but they prohibited the retrieval and retesting of the sample and therefore the testing was restricted to one area or section of the tooth. Another limiting factor with the existing techniques was the risk of artifacts related to the embedding material such as acrylic. A new method to investigate the physical properties of human premolar cementum was developed to obtain a 3-dimensional map of these properties with the Ultra Micro Indentation System (UMIS-2000; Commonwealth Scientific and Industrial Research Organization, Campbell, Australia). UMIS-2000 is a nano-indentation instrument for investigation of the properties of the near-surface region of materials. Premolars were harvested from orthodontic patients requiring extractions and then mounted on a newly designed surveyor that allowed sample retrieval and 3-dimensional rotation. This novel method enabled the quantitative testing of root surface cementum, on all 4 root surfaces, extending from the apex to the cementoenamel junction at 60 different sites.

Objectives: The presence of a resin component in resin-modified glass-ionomer cements (RMGICs) results in considerable water sorption which may affect the surface hardness of the materials. This study investigated the effect of long-term storage in aqueous solutions on the surface hardness of RMGICs., Methods: The surface micro-hardness of four RMGICs stored in either distilled water or artificial saliva was measured using the Wallace microindentation tester at regular time intervals up to 360 days., Results: There was a substantial increase in hardness during the first day of storage when RMGICs were kept in distilled water. All RMGICs except one liner/base material reached their maximum hardness within 7 days and maintained their hardness for up to 1 year. RMGICs stored in artificial saliva were relatively softer and showed a decrease in surface hardness with time., Conclusions: The post-hardening reaction overcame the plasticising effect of water when RMGICs were stored in distilled water. However, progressive and high water uptake of specimens stored in artificial saliva resulted in a decrease in their surface hardness.

The tensile strengths of compacts of different crystal forms of aspirin, sulfathiazole, and barbital were determined with a modified tablet hardness tester. For each material, the tensile strength could be correlated with the amount of plastic flow and/or crushing undergone by each crystal form during compression.

New instrumentation to measure the flexure breaking strength of capsule-shaped tablets was developed. It consisted of a mechanical linkage to apply the breaking load at a uniform rate and a strain-gauge instrumented cantilever beam to convert the load to a proportional millivolt response on a recorder. A recorder tracing was obtained of increasing load with time, with a break in the tracing denoting the tablet's flexure breaking strength. Measurements were made for different tablet hardnesses, and a plot of tablet hardness versus flexure breaking strength yielded a profile of the mechanical strength of the tablet. The instrumentation was shown to have application for determining the effects of tablet thicknesses, tablet ingredients, tablet sizes, cup depths, and bisect dimensions on tablet strength.

The instrumentation of a tablet breaking-strength tester, for the automatic recording of hardness values, is described. A comparison is made between a computerized hardness tester and another identical model hardness tester from the same manufacturer ("standard"). Three lots of placebo tablets at different hardness values were compared. No significant difference was observed between the computerized unit compared with the "standard" unit.

A rapid, simplified method of checking the calibration of a new motorized pendulum type of tablet hardness tester and the accuracy and precision of three testers were determined. Two force gauges were calibrated, and both gauges were used by two operators to determine the accuracy of the new testers. The calibration method using the force gauge was reliable for checking the accuracy. The results show the various new testers to be in calibration and to give reproducible results.

Tabletability factors were developed through the use of an automated tabletability tester, and the applicability of these factors to actual manufacturing procedures was tested by the large-scale manufacturing of tablets. Use of this approach does not require knowledge of the tablet's physical properties, e.g., moisture content, porosity, particle size, fluidity, and angle of repose.