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PubMed2003

[In vitro culture of cells from respiratory mucosa on foils of collagen, poly-L-lactide (PLLA) and poly-3-hydroxy-butyrate (PHB)].

BACKGROUND: The replacement of respiratory mucosa after surgical resections at different locations in the ENT-field (trachea, nasal septum, sinus maxillaris) seems to be essential or at least of great benefit for patients. Presently a satisfying solution for this challenge does not exist. Therefore we have analysed the growth of cells from respiratory mucosa on different matrices. METHODS: Cell cultures are initiated mainly by growing out cells from tissue pieces but also by seeding of cells after enzymatic dissociation (sequential trypsinization) of mucosa. Cells were cultured with serum-containing and serum-free media on 3 different foils: made of collagen, of Poly-L-lactic acid (PLLA) and Poly-hydroxybutyric acid (PHB). Culturing time was on average about 4 - 5 weeks. RESULTS: On all tested materials fibroblasts and epithelial cells have grown in principle. PLLA was the material with best properties concerning the aim of this study whereas culturing of cells on PHB only happens after surface modification by amino-functionalisation with plasma treatment. Visualisation of cells on materials of collagen could not realised by light-microscopy due to the 3-dimensional structure and the optical properties of this material. Here the cultures were analysed by cell membrane staining and by REM. We could not find a differentiation of epithelial cells with beating cilia 6 weeks after starting the culture. However 20 days after starting the culture on PLLA (good conditions for observation with light-microscope) cells with beating cilia could be observed, in our opinion resulting from dissociated cells from tissue pieces and not from proliferated cells. CONCLUSIONS: In principle the analysed materials are useful for the culturing of cells from respiratory mucosa. However, for obtaining differentiated epithelial cells the culture conditions have to be modified.

Cell Adhesion↗

PubMed2003

Intra-oral adhesive systems for ceramic repairs: a comparison.

The aim of this investigation was to compare the bond strength of restorative composite resin to dental ceramic conditioned with primers and adhesives of various commercial repair kits. Three intra-oral ceramic repair systems--Silistor (Heraeus Kulzer), Cimara (Voco), Ceramic Repair (Vivadent)--were used on all-ceramic (IPS Empress 2, Ivoclar-Vivadent) substrate. Shear bond strength of restorative composite resin to substrate was tested after thermocycling and without thermocycling (n = 10). Substrate surfaces of the specimen after loading were examined microscopically (SEM). The highest bond strengths in both water-stored (7.0 +/- 5.7 MPa) and thermocycled conditions (2.5 +/- 1.8 MPa) were obtained with the Vivadent repair system, while the lowest values were observed with the Cimara system (0.6 +/- 1.4 MPa and 0.0 +/- 0.0 MPa, respectively). Shear bond strengths appeared to be significantly affected by thermocycling (ANOVA, P < 0.05). It is concluded that there are significant differences in the bond strengths of resin composites and ceramic substrate. The roughened surface does not necessarily provide a better bond strength; the bond strength of composite decreases with storage in water and after thermocycling. Bond strength values were generally low for all of the tested materials.

Acrylates↗

PubMed2004

The effect of surface waviness on friction between Neolite and quarry tiles.

Friction is widely used as an indicator of surface slipperiness in preventing accidents in slips and falls. Surface texture affects friction, but it is not clear which surface characteristics are better correlated with friction. Highly correlated surface characteristics could be used as potential interventions to prevent slip and fall accidents. The dynamic friction between quarry tiles and a commonly used sole testing material, Neolite, using three different mixtures of glycerol and water as contaminants at the interface was correlated with the surface parameters of the tile surfaces. The surface texture was quantified with various surface roughness and surface waviness parameters using three different cut-off lengths to filter the measured profiles for obtaining the profiles of either surface roughness or surface waviness. The correlation coefficients between the surface parameters and the measured friction were affected by the glycerol contents and cut-off lengths. Surface waviness parameters could potentially be better indicators of friction than commonly used surface roughness parameters, especially when they were measured with commonly used cut-off lengths or when the viscosity of the liquid contaminant was high.

Accidental Falls↗

PubMed2000

The impact of head angle on monaural and binaural performance with directional and omnidirectional hearing aids.

OBJECTIVE: To evaluate the impact of head turn and monaural and binaural fittings on the sentence reception thresholds of hearing-impaired listeners wearing directional and omnidirectional hearing aids. DESIGN: Sentence reception thresholds were measured for 20 listeners fit monaurally and binaurally with behind-the-ear hearing aids set in both directional and omnidirectional modes. All listeners exhibited symmetrical, sloping, sensorineural hearing loss. The aided performance across these four fittings was evaluated for three different head and body angles. The three angles reflected body turns of 0 degrees, 15 degrees, and 30 degrees as measured relative to the primary sound source, with 0 degrees denoting the listener directly facing the sound source. Listeners were instructed to keep their heads in a fixed horizontal position and turn their heads and bodies to face visual targets at the three test angles. Sentences from the Hearing in Noise Test presented with a background of five, spatially separated, uncorrelated samples of cafeteria noise served as test material. All testing was performed in a moderately reverberant (Rt = 631 msec) "living room" environment. RESULTS: Participants generally performed significantly better when fit with directional versus omnidirectional hearing aids, and when fit binaurally versus monaurally across test conditions. The measured "binaural advantage" was reduced with increasing head angle. Participants performed significantly better with a 30 degree head angle than when directly facing the primary speaker. This "head turn advantage" was most prominent for monaural (versus binaural) conditions. Binaural and head turn advantages were not significantly different across directional and omnidirectional modes. CONCLUSIONS: These data provide additional support for the use of directional hearing aids and binaural amplification to improve speech intelligibility in noisy environments. The magnitude of these advantages was similar to that reported in previous investigations. The data also showed that hearing aid wearers achieved significantly better speech intelligibility in noise by turning their heads and bodies to a position in which they were not directly facing the sound source. This head turn advantage was in good agreement with the increase in Directivity Index with head turn and reflected the fact that hearing aids are generally most sensitive to sounds arriving from angles other than directly in front of the hearing aid wearer. Although these data suggest that many monaural hearing aid wearers may significantly improve speech intelligibility in noise through the use of head turn, the interaction between this advantage and the potential loss of visual cues with head turn is unknown.

Adult↗

PubMedDate not supplied

Mechanical characteristics of eight femoral intramedullary nailing systems.

OBJECTIVE: There are few nonproprietary papers addressing the mechanical strength of intramedullary nails; none address the characteristics of the proximal and distal ends of these devices. Our objective was to provide such data. DESIGN: Independent testing of eight femoral intramedullary nail systems at the proximal, middle, and distal regions was undertaken to evaluate strength and flexural rigidity (stiffness). METHODS: Each device, usually a reconstruction nail, was forty-two to forty-six centimeters in length. Four or five nails of each available size (range 9 to 13 millimeters in diameter) were tested for each system. The nails were cut into proximal, middle, and distal thirds. Each nail section was loaded to failure using a four-point bend test on a custom fixture (modification of the American Society of Testing Materials standard test). RESULTS: Significant variations (p < 0.05) were found in strength and stiffness between the middle and the proximal or distal aspects of some rods. A significant difference (p < 0.05) was observed when comparing the properties of earlier designs with the properties of more recent designs. Newer rod designs all performed in a similar manner with regard to strength. Strength and rigidity increased with increasing rod diameter in some but not all systems. CONCLUSIONS: Although none of the newer designs appeared to have superior static strength, the individual systems had significant variations in their mechanical properties (bending rigidity), particularly in the proximal and distal sections. It is important that the surgeon become familiar with the individual characteristics of strength and rigidity for the particular devices available and how these might impact fracture healing. Consideration of this information could alter the decision to select one system over another in a complex fracture situation.

Femoral Fractures↗

PubMed2002

Biomechanical consequences of secondary congruence after both-column acetabular fracture.

OBJECTIVES: To create a both-column acetabular fracture model with secondary congruence and to determine the intraarticular loading characteristics present in simulated single-leg stance. HYPOTHESIS: The normal contact pressures on the weight-bearing portion of the acetabulum in simulated single-leg stance are different from those present in a both-column fracture model exhibiting secondary congruence. DESIGN: Cadaveric Biomechanical model. SETTING: Biomechanical testing laboratory. SPECIMENS: Nine fresh frozen cadaveric hemipelves. INTERVENTION: Both-column fracture model with secondary congruence of the acetabular articular surface with respect to the femoral head was created and tested using Materials Testing Machine (MTS Systems Corp., Minneapolis, MN) and Fuji pressure-sensitive film (Sensor Products, Inc., East Hanover, NJ). OUTCOME MEASUREMENTS: Testing data recorded and analyzed comparing the fractured and unfractured states. RESULTS: With respect to the intact specimen, the contact area, mean pressure, and peak pressure in the dome region all increased (p < 0.003) in the both-column model. The contact area in the anterior articular region decreased (p < 0.02) as did the mean pressure (p < 0.032). The posterior articular region demonstrated a trend toward decreased contact area and increased mean and peak pressures. Descriptively, the stress concentration shifted toward the fracture in all cases with the most anterior and most posterior articular regions having little contact in the fracture model. CONCLUSIONS: In the authors' both-column model of secondary congruence, the stress concentration during simulated single-leg stance was increased significantly in the dome of the acetabulum adjacent to the fracture line.

Acetabulum↗

PubMed1996

An ultrasound indentation system for biomechanical properties assessment of soft tissues in-vivo.

An ultrasound indentation system for biomechanical assessment of soft tissues in vivo was developed. The pen-size, hand-held probe was composed of an ultrasound transducer and a load cell. The ultrasound transducer was at the tip of the probe serving also as the indentor. The thickness and deformation of the soft tissue layer were determined from the ultrasound echo. A compressive load cell was connected in series with the ultrasound transducer to record the force response. A validation experiment was performed on porcine tissues. Force and deformation acquired with the present system was in good comparison with those obtained from a Housfield material testing machine. Material constants were obtained via a curve-fitting procedure by predicting the force transient response from the deformation-time data using a quasilinear viscoelastic model. In addition, deformation in the fat and in the muscle could be differentiated. The potential applications of this type of indentation probes are many. The specific application of this current development is for stump tissue assessment in the design of prosthetics.

Adipose Tissue↗

PubMed1993

Mechanical properties of metal connectors soldered by gas torch versus an infrared technique.

PURPOSE: The ultimate tensile strength and percentage elongation of solder joints of three alloy systems were tested. MATERIALS AND METHODS: Solder joints were formed using either an infrared soldering machine or gas-oxygen torch. Intact solder materials were used as controls. RESULTS: There were no significant differences in percentage elongation among different treatment methods of the solders or among various solder materials. All intact solder materials possessed significantly higher ultimate tensile strength than the joints made with either method. For high-noble and noble alloy solders, there were no significant differences in ultimate tensile strength of joints made with either method. For base metal alloy solder, the ultimate tensile strength of joints made with the infrared technique was significantly higher than that made with the gas-oxygen torch technique. CONCLUSIONS: The infrared technique can be used as an alternative to the gas-torch technique for soldering high-noble and noble alloys. It is superior to the gas-torch technique for soldering a cobalt-chromium alloy.

Analysis of Variance↗

PubMed1994

In vitro fracture behavior of ceramic and metal-ceramic restorations.

PURPOSE: Failed crowns and failure load data were studied to gain insights into the fracture behavior of prostheses under incisal-directed, load-to-failure testing. MATERIALS AND METHODS: Incisor crowns (n = 68) were fabricated: two all-ceramic groups (feldspathic veneer on high-strength core), differing in core design, and two metal-ceramic groups, differing in metal oxidation time (30 seconds v 3 minutes). Crowns were loaded to failure on their incisal edge. Gross visual, microscopic, and elemental microprobe analyses of failed crowns were coupled with Weibull analysis of the failure load data. RESULTS: Failure loads were higher for the normal oxidation time (TN) than for the extended oxidation time (TE) metal-ceramic crowns (P < .02), but both groups had indistinguishable Weibull moduli indicating the possibility of a common failure origin. Fracture behavior and Weibull results both implicated the oxide layer as being the origin of failure. The ratio of fracture loads (TE/TN) corresponded well with calculated oxide-volume ratios. Failure loads were lower for the all-ceramic than for the metal-ceramic crowns (P < .001). Fifty percent of the all-ceramic crowns failed by delamination of veneering glass alone, leaving a thin layer of residual glass on the core surface. Scanning electron microscope views showed that delamination occurred 10 to 50 microns away from the core-veneer interface. Electron microprobe elemental analysis of the core-veneer interface showed that residual core infiltration glass was not present on the core surface and that chemical alterations in the veneering glass were apparently limited to less than a 2- to 3-microns thick layer. CONCLUSIONS: Failure for both restorative systems involved interfacial stresses with crack propagation occurring at or near the core-veneer interface. The weaker interface in the metal-ceramic system probably resulted from an increase in surface oxide volume, irrespective of any change in its adherence or physical properties. For the ceramic crowns, delamination crack fronts appeared to propagate through chemically unaltered veneering porcelain. Both the Weibull moduli and characteristic strengths were indistinguishable between either of the two ceramic core designs or between groups failing from delamination with or without core cracking/failure. This is consistent with delamination being the primary fracture process during failure. Clinical implications should not be drawn from results of this study because no correlation is known to have ever been established between clinical behavior and incisal load-to-failure results.

Aluminum Oxide↗

PubMed2004

Methodology for rheological testing of engineered biomaterials at low audio frequencies.

A commercial rheometer (Bohlin CVO120) was used to mechanically test materials that approximate vocal-fold tissues. Application is to frequencies in the low audio range (20-150 Hz). Because commercial rheometers are not specifically designed for this frequency range, a primary problem is maintaining accuracy up to (and beyond) the mechanical resonance frequency of the rotating shaft assembly. A standard viscoelastic material (NIST SRM 2490) has been used to calibrate the rheometric system for an expanded frequency range. Mathematically predicted response curves are compared to measured response curves, and an error analysis is conducted to determine the accuracy to which the elastic modulus and the shear modulus can be determined in the 20-150-Hz region. Results indicate that the inertia of the rotating assembly and the gap between the plates need to be known (or determined empirically) to a high precision when the measurement frequency exceeds the resonant frequency. In addition, a phase correction is needed to account for the magnetic inertia (inductance) of the drag cup motor. Uncorrected, the measured phase can go below the theoretical limit of -pi. This can produce large errors in the viscous modulus near and above the resonance frequency. With appropriate inertia and phase corrections, +/- 10% accuracy can be obtained up to twice the resonance frequency.

Ear, Middle↗

PubMed2003

Effect of surface roughness on flexural strength of veneer ceramics.

The strength of ceramic restorations depends on the occlusal surface roughness of the veneering porcelain, which is influenced by the final preparation. The hypothesis of the study was that roughnesses below a critical microscopic defect size--based only on fracture mechanics considerations--also affect flexural strength. The bending failure stress was evaluated on standard specimens of 4 veneer ceramics with 4 different surfaces of defined roughnesses, respectively. A linear correlation was found between roughness and failure stress. A "roughness-free" failure stress value was predicted for each tested material. This theoretical value can represent the "true" strength of the respective ceramic material. We conclude from our results that the final preparation of a ceramic restoration is critical to the strength of the material, and that ceramic veneering materials can be compared more objectively with respect to their strength by means of roughness-free strength values.

Air Abrasion, Dental↗

PubMedDate not supplied

Penetration of ciprofloxacin into bone: a new bioabsorbable implant.

The implantation of antibiotic-containing cement beads became standard adjuvant local antibiotic therapy of chronic osteomyelitis. The new developed bioabsorbable drug carrier system of polyglycolic acid with the antibiotic Ciprofloxacin was tested in vitro and in vivo. The goal of this study was to determinate the penetration depth of Ciprofloxacin into bone cortex and marrow. Two monofil, PGA cylinders, 3.2 x 5 mm in size, containing 3 mg of Ciprofloxacin each, were implanted into the proximal part of both femora of 18 rabbits (New Zealand white). After sacrifice, the concentration of Ciprofloxacin in micrograms/g cortex and marrow was measured with high-performance liquid chromatography in relation to the distance from the test material at day 2, as well as at 1, 2, 3, 4, and 6 weeks postimplantation. For a distance up to 5 mm, marrow levels of the drug exceeded cortical levels at day 2 (5000 to 240 micrograms/g). At a distance of 5-10 mm, cortex levels were similar to marrow levels after 2 weeks and were higher than marrow levels at week 3. This observation could be made at a distance between 10 and 15 mm only after 2 days. Later, marrow concentrations again exceeded that in cortex. At a distance of more than 15 mm, antibiotic levels were low and approximated. After 6 weeks, at 5 mm distance, a bactericidal drug concentration of about 2 micrograms/g in bone marrow could be measured. Drug penetration into cortical bone in bactericidal concentrations of about 2 micrograms/g was achieved at up to 30 mm in the first few days.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Sensitivity of chick embryo to various solvents used in egg injection studies.

Two experiments were conducted to study the sensitivity of developing chicken embryos to various solvents used as vehicles and their effect on hatchability. No significant differences on embryonic mortality were observed between the sham-injected control and corn oil-injected groups. Acetone, ethylene glycol, and ethanol (0.10 ml/egg) significantly reduced the percentage hatchability and showed a high embryonic mortality during the first week of incubation. Levels of cottonseed oil (0.05-0.10 ml) and propylene glycol (0.05-0.15 ml) were well tolerated by the developing embryo but were slightly inferior to corn oil. Levels of 0.05-0.15 ml of corn oil are suitable vehicles for fat soluble compounds in studies involving the injection of eggs. Higher levels of solvent can be injected at later incubation periods. The choice of the best solvent must be made depending upon (1) solubility of test material, (2) amount of test material needed, (3) toxicity of the solvent at the appropriate levels, (4) route of administration, and (5) stage of development.

Acetone↗

PubMed1998

Superior-inferior stability of the shoulder: role of the coracohumeral ligament and the rotator interval capsule.

OBJECTIVE: To study the superior-inferior stabilizing functions of the coracohumeral ligament (CHL) and the rotator interval capsule (RIC) with use of a material testing machine. MATERIAL AND METHODS: The axial translations of the humerus with the superior-inferior translation force of 30 N applied were recorded under the following joint capsule conditions: (1) intact, (2) vented, (3) the CHL sectioned, and (4) the RIC incised in six cadaver shoulders. The order of sectioning was changed for conditions 3 and 4 in six other cadaver shoulders. RESULTS: With the arm in internal and neutral rotations, venting the capsule significantly increased the superior-inferior translation, which was unaffected by further sectioning of the CHL and the RIC. With the arm in external rotation, only the CHL contributed significantly to inferior stability, whereas both this ligament and the RIC contributed to superior stability to a lesser degree. CONCLUSION: The CHL is a stabilizer in superior inferior directions with the arm in external rotation, and the intra-articular pressure that is maintained by the intact RIC is a stabilizer in superior-inferior directions with the arm in internal and neutral rotations. These findings may provide a scientific background to support closure of the interval space to stabilize the shoulder and may explain part of the superior instability observed in shoulders with rotator cuff tears.

Aged↗

PubMed2001

Hydroxylapatite implants with or without collagen in the zygomatic arch of rats. Histological study.

The authors studied the behavior of calcium phosphate materials used as inlay implants into bone cavities prepared in the zygomatic arch of rats. Fifty male albino rats were divided into four groups as follows: group I-preparation of bone cavities which did not receive any implant material as controls; group II-implants of Interpore 200; group III-implants of experimental hydroxylapatite; group IV-implants of experimental hydroxylapatite combined with collagen. The animals were sacrificed after 5, 15, 30, 60 and 120 days and the specimens were submitted to histological analysis. Results showed that the experimental hydroxylapatite used in group III presented better osteogenic properties compared to the other materials. All tested materials were biocompatible, although group IV presented a more intense inflammatory response.

Animals↗

PubMed2001

Reliability of in vitro microleakage tests: a literature review.

PURPOSE: The literature contains conflicting data about in vitro microleakage evaluations and their usefulness and reliability. No standardization has yet been established. Here we consider features of published studies that might affect the results of the in vitro microleakage tests. MATERIALS AND METHODS: We reviewed 144 in vitro microleakage studies, published in 14 international reviews between 1992 and 1998, which comprised 917 sets or groups of experiments. The published studies were entered in a database and compared using selected literature criteria: sample, cavities, restoration procedures, thermocycling and mechanical cycling, evaluation method. RESULTS: The methods employed vary widely. The most frequent methodological choices (%) were (1) specimen storage after extraction: duration (unspecified, 59.2), medium (distilled or deionized water, 33.8), temperature (unspecified, 52.2), additives (none, 47.0); (2) aging method (79.1): duration before aging (< 24 h, 35.9); medium and temperature of storage before aging (distilled or deionized water, 26.8; 37 degrees C, 54.3); (3) medium of cycling (tap water, 50.5), number of cycles ([250-500], 34.6), number of baths (2, 84.0), bath temperature (5 degrees C to 55 degrees C, 60.6), immersion dwell time (30 s, 44.3); (4) tracer: type (basic fuchsin, 40.7), time of immersion (after thermocycling and/or mechanical cycles, 64.1), immersion duration (basic fuchsin: 24 h, 59.5); assessment of dye penetration of sections (91.7): direction (perpendicular, 88.5), number (1, 47.1). CONCLUSION: The great variability in the methods used in these 144 studies prevented meta-analysis and comparison of the results, thus reducing the value of these methods.

Coloring Agents↗

PubMed1999

An inexpensive alternative approach to bone compression analyses.

A new method for testing the compression strength of vertebrae was developed and implemented using minimal resources and time expenditure. The device digitally measured and analyzed the torque and force necessary to load rat lumbar and thoracic vertebrae to failure. The system was calibrated using a series of known lead masses. Similar to other standardized force/compression and torque devices, this method has been shown to provide reliable and reproducible results. Furthermore, although vertebrae were the only specimens used to collect data in these initial studies, this measurement system could be altered quite easily to allow for a variety of test materials.

Animals↗

PubMed2003

Cost effective and advanced phosphorus removal in membrane bioreactors for a decentralised wastewater technology.

Future stringent phosphorus regulations (down to 50 microg/L in some cases) together with the availability of more cost effective and/or innovative membrane processes, are the bases for this project. In contrast to conventional activated sludge plants, process parameters are not optimised and especially enhanced biological phosphorus (Bio-P) removal in membrane bioreactors (MBRs) are not proven yet. Current practice of P-removal in MBRs is the addition of coagulants in a co-precipitation mode. Enhanced biological phosphorus removal, when adapted to MBR technology, might be a cost-effective process. For very stringent effluent criteria additional P-adsorption on activated clay after membrane filtration can be also an interesting solution. The objective of this research project is to identify and test various phosphorus removal processes or process combinations, including MBR technologies. This should enable us to establish efficient and cost effective P-removal strategies for upgrading small sewage treatment units (up to 10,000 PE), as needed in some decentralised areas of Berlin. In particular, enhanced Bio-P removal technology was developed and optimised in MBR. Combinations of co-precipitation and post-adsorption will be tested when low P-values down to 50 microg/L are required in the effluent. One MBR bench-scale plant of 200 to 250 L and two MBR pilot plants of 1 to 3 m3 each were operated in parallel to a conventional wastewater treatment plant (Ruhleben WWTP, Berlin, Germany). The MBR bench-scale and pilot plants were operated under sludge ages of respectively 15 and 25 days. In both cases, Bio-P was possible, and phosphorus effluent concentration of about 0.1 mg/L could be achieved. A similar effluent quality was observed with the conventional WWTP. Investigations with lab columns indicated that P-adsorption could lead to concentrations down to 50 microg/L and no particle accumulation occurred in the filter media. The three tested materials exhibited great differences in break-through curves. Granulated ferric hydroxyde (GEH) showed higher capacity than activated alumina and FerroSorpPlus.

Adsorption↗