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Biomedical subjects

E J Richter

Publications and source records attributed to E J Richter.

At least 19 recordsLinked to original sources
PubMed2001

Monitoring in-shoe plantar pressures, temperature, and humidity: reliability and validity of measures from a portable device.

OBJECTIVE: To investigate the reliability and validity of measures obtained from a portable electronic device used to monitor changes in plantar pressure, temperature, and humidity that occur within the shoe during prolonged activity. DESIGN: Descriptive study comparing electronic sensor output with criterion values. SETTINGS: Indoor level walkway for pressure data; uncontrolled, outdoor environment for step count data; enclosed environmental control chamber for humidity and temperature data. PARTICIPANTS: Convenience sample of 4 healthy, sensate subjects. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Correlations between sensor output and criterion measures were determined for pressure and temperature data. The absolute differences between sensor output and criterion values of temperature, humidity, and step count were also determined. RESULTS: Pressure measurements from electronic sensors correlated highly with criterion values (r > or =.82), both before and after prolonged use. Relative humidity sensor output were within 5% of hygrometer values. In-shoe temperature data correlated highly with criterion values (r > or =.99), and differed from known temperatures by.50 degrees +/-.84 degrees C and.96 degrees +/- 1.56 degrees C at the forefoot and heel, respectively. Electronic step counts recorded at the central forefoot were within 1 step of visual step counts. Pressure tracings obtained from the device during different weight-bearing activities revealed qualitatively distinct pressure patterns. CONCLUSION: The device provides valid and reliable measures of in-shoe plantar pressures, temperature, and humidity during prolonged activity.

Diabetic Foot↗
PubMed2001

In-shoe multisensory data acquisition system.

Patients with diabetes and peripheral neuropathy are susceptible to unnoticed trauma on the foot that can cause skin breakdown. We have designed an electronic system in a shoe that monitors temperature, pressure, and humidity, storing the data in a battery-powered device for later uploading to a host computer for data analysis. The pressure sensors are located at the heel, and under three metatarsal heads. Temperature sensors are located under the medial metatarsal head and under the heel. The humidity sensor is located in the toe of the shoe. Correlations of data from pressure sensors with known values were high (r > 0.85), even after extended use. Although data currently are being collected for descriptive purposes, the design potentially can be used to provide feedback to patients.

Data Display↗
PubMed1999

Cell culture tests for assessing the tolerance of soft tissue to variously modified titanium surfaces.

The aim of our research project was to achieve an improvement in the integration of enossal dental implants in the region of peri-implantary soft tissue. Improvement in the adhesion of the gingiva of the surface of enossal implants was to be achieved by modification of the titanium surface. The effect of different modifications on the biocompatibility of the modified titanium surfaces was tested: sulfur dioxide plasma treatment of titanium; acetylene plasma treatment of titanium followed by sulfur dioxide plasma etching; plasma nitration of titanium; replacement of titanium by glycidoxypropyltrimethoxy silane; coating titanium with poly[(ethene-co-vinyl acetate)-graft-vinyl chloride] and coating titanium with fibronectin. Determination of the chemical composition of the surface was carried out using X-ray photospectroscopy. The adsorption of fibronectin at the surface of the titanium was tested using an Enzyme Linked Immunosorbent Assay. In selected in vitro tests with human gingival fibroblasts, cell morphology was assessed using scanning electron microscopy and light microscopy. Cell proliferation and protein synthesis, as well as the activity of mitochondrial dehydrogenases were evaluated. By means of centrifugation and by determining initial cell adhesion, the adhesion of gingival fibroblasts was investigated. According to the kind of modification made to the titanium surfaces, it was possible to observe differences in the cellular behavior of gingiva fibroblasts on the differently modified surfaces of the implants. Coating the titanium using fibronectin produced optimization of cell growth and improvement in the adhesion of gingiva fibroblasts to the implant surface. In contrast, modification of the titanium with poly[(ethene-co-vinyl acetate)-graft-vinyl chloride] generally resulted in a deterioration of the biocompatibility of the surface. A marked correlation between the cellular compatibility of the modified titanium and the surface modification made did not become apparent. One reason for this is the large number of parameters determining the interaction between implant and tissue.

Cell Adhesion↗
PubMed1998

[Characterization of the properties of differently modified titanium surfaces for dental implantology. 1: Methods for surface analysis].

Contact between the biological environment and biomaterials takes place at their surfaces. The biocompatibility of a material is determined by interactions at the interface between implant and biological system. The physicochemical surface properties of the materials used, for example, chemical composition, wettability, surface energy and electrical surface charge, therefore play an important role. Within the framework of the investigations described here, specific modifications of the surfaces properties of titanium are effected using various methods with the aim of achieving a positive influence on cell growth and cell attachment. To characterize the physicochemical surface properties, X-ray photoelectron spectroscopy (XPS) have been used. In addition to the clearly altered chemical composition of the modified material surface, it proved possible to determine significant changes in the thermodynamic properties with the aid of contact angle measurements and the determination of surface energy. On the basis of these results, important information about possible interactions at the interface between implant and tissue can be obtained.

Biocompatible Materials↗
PubMed1998

[Characterization of the properties of differentially modified titanium surfaces for dental implantology. 2: In vitro biocompatibility studies].

The aim of the present study was to determine whether specific surface modifications are capable of improving the biocompatibility of a titanium surface, and whether there is a correlation between the physico-chemical properties of the implant material and its biocompatibility. To this end, the properties of titanium surfaces were modified using various methods or the latter were coated with various materials. Plasma treatments under different atmospheric conditions (N2-plasma, SO2-plasma, acetylene plasma) as well as plasma polymerization were used to affect the biological response. Characterization of the physico-chemical surface properties by means of X-ray photoelectron spectroscopy (XPS), contact angle measurements and the calculation of surface tensions or surface energy provided important information on the interactions at the interface between the implant material and the aqueous environment. The influence of the respective surface modification on cell proliferation, cell viability and the activity of mitochondrial dehydrogenases was evaluated in specific in vitro tests with human gingiva fibroblasts. It was show that different modifications of the titanium samples induce different biological responses of the gingiva fibroblasts. The results confirm the existence of correlations between thermodynamic surface properties and cellular reactions under in vitro conditions.

Cell Division↗
PubMed1992

Bone regeneration around titanium dental implants in dehisced defect sites: a clinical study.

Insufficient bone volume can be a significant problem when placing dental implants. This clinical study was designed to evaluate bone regeneration potential at dehisced dental implant sites. Nineteen titanium dental implants with exposed threads were studied. To create a secluded space for bone formation, an expanded polytetrafluoroethylene (e-PTFE) membrane was placed over the exposed implant sites secured with an implant cover screw and completely covered with the flap. Three membranes perforated the overlying soft tissue during the healing time and were removed prematurely. The remaining membranes were removed after an uneventful healing period of 4.5 to 6 months. Fourteen of 19 dehisced implant sites were completely covered with newly formed bonelike tissue; 4 implants demonstrated partial bone fill at reentry and 1 implant showed partial fill with soft tissue. In five implant sites a reentry was performed between 6 and 9 weeks; nonmineralized fibrous tissue was found to fill the space under the membrane. At 16 of the 19 implant sites there were similar dehiscence-type defects that were evaluated as a group. These dehiscences varied from 2.0 to 9.0 mm. The percentage of bone fill at reentry ranged from 28.4% to 100% (mean 89.6%; SD 22.51; SE 5.63) and was highly significant (P < .0001). Six to 12 months after prosthesis connection, 12 of the 19 implants were available for radiographic interpretation and an average bone loss of 1.73 mm (SD = 0.43) was measured. This surgical application of an e-PTFE membrane suggested a viable clinical method for enhancing bone formation around dental implants.

Adult↗
PubMed1990

Dental implant abutment resembling the two-phase tooth mobility.

Natural teeth and dental implants have differing degrees of mobility thus causing a potential biomechanical problem when connected by fixed bridgework. The clinical follow-up often discloses marginal bone loss around an implant neck probably due to high stress factors. An implant with a built-in compliance resembling the tooth mobility could be advantageous for stress distribution. With axial loading the proposed 'elastic'-test model accomplishes this demand. By means of theoretical and experimental studies this 'elastic'-test model is optimized and compared with a stiff implant-model. The results show a 20 times reduction of stress accumulation in bone with the 'elastic'-test model.

Biocompatible Materials↗
PubMed1989

Basic biomechanics of dental implants in prosthetic dentistry.

A discussion of loads applied to implants must include the clinical consideration that not only rigid implant types are used, such as the Tübingen immediate implant and the TPS screw implant without shock absorber, but also systems with inherent resilience integrated in the implant design, such as the IMC and Flexiroot implants. The common goal of all of these implant systems is to achieve a stable anchorage of the implant body in the bone tissue, that is, contact osteogenesis or osteointegration. In the implant-to-bone interface region there is an implant mobility resulting from the elasticity of the bone. The question of whether additional implant-integrated elastic elements are necessary to simulate the periodontal attachment is controversial.

Biomechanical Phenomena↗
PubMed1989

The value of angiography in cerebrovascular disease.

The expanding availability of digital subtraction angiography has essentially contributed in lowering the risks in the use of angiography of the cerebral arteries. The best results in imaging the cerebral artery are achieved by conventional subtraction angiography after selective catheterisation. This is, however, only important for diagnosis in intracerebral pathological changes distal of the Circulus Willisi or in connection with preoperative interventional radiological treatment. Pre-clinical diagnosis of patients with cerebrovascular occlusive disease as well as clinical diagnosis with Doppler and B-scan US sonography can be optimally complemented by DSA using 4-5 French catheters entered in the thoracic ascending aorta. Using this technique, the sensitivity and specificity with an image-matrix of 512 is diagnostically adequate and includes an only limited examination risk. Complication with lasting neurological defects will be least observed after intravenous pre-atrial application of contrast media and most after selective angiography of the carotid artery. Here the extent of the multiple arteriosclerotic obliteration is of essential importance. The quality of interpretation of the diagnostic findings essentially depends on indications not only about the grade of obliteration but also on the morphological details. At present DSA with application of contrast media into the thoracic ascending aorta in combination with the duplex-scan method represent the optimum for the diagnosis of cerebrovascular disease. In spite of lower specificity intravenous application of contrast media has to be preferred for post-operative controls and controls of progressing disease with "screening".

Carotid Arteries↗
PubMed1989

[Comparative studies on different full and veneer-ceramic crowns].

Under quasi-clinical conditions, Dicor, Hi-Ceram, Ceraplatin and PFM (porcelain butt margin) crowns with ceramic shoulders manufactured by commercial laboratories for the same metal master die were examined for marginal defects under the electron microscope. With equal cementing conditions and points of measurement for all crowns, the PFM crowns were found to be significantly superior to the other crown types. However, this result becomes relativistic in view of the great statistical variances involved.

Crowns↗
PubMed1989

[Acceptance of polytetrafluoroethylene by subcutaneous connective tissue].

The suitability of extended PTFE as a supporting matrix for subepithelial connective tissue was studied histologically. The main question was whether tissue was able to grow within the implant. After a maximum of seven months post-implantation, no signs of vascularisation but only isolated cells were found within the implant. The histological examination showed neither inflammation nor encapsulation of the implant.

Animals↗
PubMed1989

[Studies on marginal fit of Dicor crowns].

Dicor crowns may present marginal defects, among other reasons because they require preparation of a circular ledge with rounded internal line angles. In studying this problem, 21 teeth that could no longer be saved were prepared in vivo and provided with Dicor crowns in our hospital. After remaining in place for 3 months these teeth were extracted. Subsequently their marginal areas were studied by SEM and histological preparations were made and measured. The marginal defects of Dicor crowns revealed slightly less favorable values than the Hi-Ceram crowns investigated one year ago, but these values are still within the range of clinical acceptability.

Ceramics↗
PubMed1989

[Dicor glass ceramic crowns].

Within a period of 36 months 103 Dicor glass ceramic crowns have been inserted. Total loss of function occurred in 8 of the restored teeth in the form of loss, partial or total fracture of the crown. In 15 cases a partial loss of function was observed due to esthetic damage, abrasions or cement washouts. Before treatment 73 teeth had been sensitive on probing, after restoration 4 of them required endodontic treatment. Many of the reasons for loss of function could be found. These results suggest that, although sensitive to technical errors, this technique provides highly qualified single tooth restaurations.

Ceramics↗