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Biomedical subjects

R Wächter

Publications and source records attributed to R Wächter.

At least 19 recordsLinked to original sources
PubMed2004

[Are there olfactory evoked alterations of breathing patterns?].

BACKGROUND: It is controversially discussed whether strictly olfactory stimuli are able to evoke changes of breathing patterns. A number work groups argue that the more or less noticeable irritative component of odors are responsible for a respiratory response. Other work groups regard changes of breathing pattern as an indicator for an intact smell ability during "pure" olfactory stimulation. METHODS: 12 normosmic young volunteers were repeatedly challenged with hydrogensulfide (H (2)S) for two seconds on inspiration in concentrations just above the threshold using a flow olfactometer. Clean air stimuli were presented randomly as control blanks. The breathing patterns were registered with a differential pressure transducer occluding one nostril via a tube. The signals were digitized and recorded on a PC. Nine parameters were calculated for each breath using a custom made LabView (R) software. The breath during stimulation was compared to the average of five breathing cycles prior to stimulation. An increase or reduction of each parameter was equally regarded by means of their absolute value. The sum was termed respiration index (RI). RESULTS: The mean RI (all trials of each test person) stimulated with H (2)S varied from 201 to 570; stimulated with clean air from 85 to 188. The difference was significant (p < 0,001). A significant group-difference for each single trial was seen as well. There was no significant increase or decrease of RI during 15 successive stimulations with H (2)S. CONCLUSIONS: Detectable short H (2)S-stimuli are able to evoke alterations of breathing patterns which can be identified by computer. Respiration-olfactometry is suitable to objectify odor perception.

Adult↗
PubMed2001

Immunolocalization of plasma-membrane H+-ATPase and tonoplast-type pyrophosphatase in the plasma membrane of the sieve element-companion cell complex in the stem of Ricinus communis L.

Plasma-membrane-located primary pumps were investigated in the sieve element (SE)-companion cell complex in the transport phloem of 2-week-old stems of Ricinus communis L. and, for comparison, in stems of Cucurbita pepo L. and in the secondary phloem of Agrobacterium tumefaciens-induced crown galls as a typical sink tissue. The plasma-membrane (PM) H+-ATPase and the tonoplast-type pyrophosphatase (PPase) were immunolocalized by epifluorescence and confocal laser scanning microscopy (CLSM) upon single or double labeling with specific monoclonal and polyclonal antibodies. Quantitative fluorescence evaluation by CLSM revealed both pumps in one membrane, the sieve-element PM. Different PM H+-ATPase antibody clones, raised against the PM H+-ATPase of Zea mays coleoptiles, induced in mouse and produced in mouse hybridoma cells, discriminated between different phloem cell types. Clones 30D5C4 and 44B8A1 labeled sieve elements and clone 46E5B11D5 labeled companion cells, indicating the existence of different phloem PM H+-ATPase isoforms. The results are discussed in terms of energization of SE transporters for retrieval of leaking sucrose, K+ and amino acids, as one of the unknown roles of ATP found in SEs. The function of the PPase could be related to phloem sucrose metabolism in support of ATP-requiring processes.

Antibodies, Monoclonal↗
PubMed2001

[Cortical thickness of the mandible with special reference to miniplate osteosynthesis. Morphometric analysis of autopsy material].

Thirty-two human mandibles were marked with three typical fracture lines: a low condylar fracture, a fracture of the mandibular angle, and one through the mental foramen on each side. The mandibles were sectioned at the fixation sites of the miniplate screws. The thickness of the cortical layer was measured with a scaled magnifying glass at the points of anthropological interest and at the marked screw holes. The inferior cortical layer turned out to be thickest in the anterior area. In contrast, it was very thin at the mandibular angle, which might explain the higher complication rate in treating fractures in this region. The thickness of the lingual cortex increased up to the symphysis, whereas the buccal cortical layer showed a decline in size from the mandibular angle up to the chin. The cortical bone at the alveolar ridge was porous. The cortical supply for miniplate osteosynthesis at the condylus ranged from 1.1 mm up to 1.74 mm, which seems to be limited, but due to the small diameter of the condylus most common screws obtain additional anchorage in the inner cortex. The thickness of the cortical layer at the mandibular angle increased from 1.47 mm at the ramus up to 1.97 mm at the beginning of the corpus, reaching 2.14-2.38 mm for the lower plate at the mental foramen. The results for the upper plate were slightly lower.

Bone Plates↗
PubMed1998

[Mandibular osteomyelitis after mandibular conduction anesthesia].

Several complications following a mandibular nerve block were reported in the literature. In some cases pterygomandibular abscess formation may be caused by mandibular needle injections. There is no report of odontogenic osteomyelitis of the ascending mandibular ramus in the literature. Here two patients with osteomyelitis of the ascending ramus following a mandibular nerve block injection are presented.

Adult↗
PubMed1998

Use of the "double barrel" free vascularized fibula in mandibular reconstruction.

PURPOSE: Microvascularized fibula transplants have become established in reconstruction of the mandible. However, because of the limited diameter of the fibula compared with the height of the mandible, the vertical distance between the reconstructed segment and the occlusal plane can be substantially large. This is a particular problem in nonatrophic or dentate mandibles, especially when rehabilitation with dental implants or an implant-borne denture is contemplated. The large leverage forces resulting from the high vertical dimension of the prosthetic construction can lead to overloading of the osseointegrated implants and endanger the longevity of the prosthetic restoration. This article describes experience with a new method of circumventing this problem. PATIENTS AND METHODS: This procedure was used in eight patients. A fibula graft corresponding to at least twice the length of the mandibular defect was harvested, halved perpendicular to its length, and the resulting struts folded on top of each other to form a "double barrel." The struts are then fixed to each other with screws and plates and stabilized in the defect using a reconstruction plate. RESULTS: Compared with the conventional one-strut fibula transplant, the "double-barrel" graft achieved more bone height and appreciably reduced the vertical distance to the occlusal plane. CONCLUSIONS: This technique creates better conditions for prosthetic rehabilitation. In comparison with the iliac graft, the fibula is easier to harvest, more reliable regarding anastomosis, and is associated with less postoperative morbidity.

Adult↗
PubMed1998

[Selection of the method of surgical approach in plate osteosynthesis of mandibular fractures].

BACKGROUND: Plateosteosynthesis by intraoral approach of mandibular fractures gives the best cosmetical result but presents a rather difficult procedure. AIMS: Comparison of intra- versus extraoral approach in plateosteosynthesis of mandibular fractures. METHODS: Plate type, experience of the surgeon, age and sex of the patient, as well as hospital stay and rate of the septic complications were analysed retrospectively in 248 patients of the OMF Department (University Freiburg) with mandibular fractures with respect in view of the operative approach used. RESULTS: The method of osteosynthesis was found to be the strongest determinant. Concerning the surgical approach significant correlation was found between age and sex, and surgical experience. Operative approach was found to have no effect on hospitalization and septic complications. CONCLUSION: Operative approach does not have either medical nor economical consequences in the surgical management of mandibula fractures.

Age Factors↗
PubMed1996

[Late results of 15 years and longer after mandibular condyle fractures].

A sample of 91 patients who had suffered from condylar fractures in the years 1970-1977 could be followed up. The mean follow up period was 19.8 years. As a prognostic relevant parameter the patient's age at the time of the accident as well as the type of the fracture where taken into account. Clinically young (8-11 years at the time of the accident) patient's with no or low grade dislocation showed the best results. Almost 36% of the patients with high grade dislocation or luxation presented measurable pathological changes during function. The condylar movement was assessed by using 3D-optoelectronic measurement. Despite severe radiographic alterations and hindered condylar translation in cases with high grade dislocation or luxation, mouth opening was not restricted in the majority of the patients. It seems that the lack of condylar translation is compensated by extensive rotation.

Adolescent↗
PubMed1995

[Complications of surgical wisdom tooth removal of the maxilla. A clinical and roentgenologic study of 1,013 patients with statistical evaluation].

In a retrospective study the condition of the alveolar process in the region of the maxillary tuberosity after operative removal of impacted upper third molars was evaluated. Basically the clinical records of 1013 patients were explored. 371 patients were checked clinically, from 355 patients X-ray examinations were taken. There was at least one year between operation and follow-up examination. Pain was the reason for removal of the upper wisdom teeth in 32.9% of the patients. The most common intraoperative complications were oro-antral fistulae (11.3%). Most of the patients 70.9%) showed regular wound healing. Postoperative complications were seen more often and for a longer period in young female patients. In most cases (87.7%) there was a complete bony regeneration of the alveolar process in the area of the maxillary tuberosity. Contrary to our expectations cyst formations were very rare (0.59%).

Adolescent↗
PubMed1994

[3-D CT for the demonstration of findings in compound skull injuries].

Conventional radiographs, axial CT with multiplanar 2-D and 3-D-CT reformations were obtained in 20 patients presenting with craniofacial injuries, to evaluate the capabilities of 3-D-CT. The image quality was assessed by two readers. Sagittal and oblique components as well as comminuted fractures could be detected by 3-D-CT reconstructions similarly to axial CT with 2-D reformations. Displacements over 2 mm were confidently documented by 3-D-CT images. 3-D-CT reconstructions allow an improved demonstration of rotational components of fractured fragments. 3-D-CT images are not as accurate as 2-D-CT in the primary detection of fractures in the relevant anatomic regions. Among 3-D-CT reconstructions, the lateral and partly the facial regions are adequately visualised.

Adolescent↗
PubMed1993

[Effect of adaptation and compensation mechanisms on postoperative function of patients with tumors of the oral cavity].

To examine adaptation and compensation mechanisms on oral function, the tongue and the floor of the mouth of five healthy volunteers were immobilised with a plastic plate. The functional results of this group were compared with the postoperative results of patients with tumours in the area of the anterior floor of the mouth and the edge of the tongue. Swallowing, sucking, and speech functions were used to assess oral function. Unhandicaped swallow and sucking functions were determined as average value (reference value 100%) in a control group with 20 healthy adults. The results of the study demonstrate the adaptive ability of the tongue and underline the importance of keeping the remaining structures free to move. In cases of resection in the area of the anterior floor of the mouth, however, careful soft tissue reconstruction plays a far greater role, since the remaining structures do not adapt as easily.

Adaptation, Psychological↗
PubMed1992

AO reconstruction plate systems for the repair of mandibular defects 3-DBRP versus Thorp-system.

The AO-maxillofacial division offers two different reconstruction plate systems for the repair of mandibular defects--the conventional 3-dimensionally-bendable reconstruction plate (3-DBRP) and the titanium hollow screw and reconstruction plate (THORP). Both systems were investigated and compared under identical conditions in an experimental study. The results of this investigation show a higher incidence of instability using the THORP-system. We believe that for the THORP, the anchorage applying only two screws in each bone stump as recommended by Raveh et al. (1984), is not sufficient to bear full functional loading immediately.

Animals↗
PubMed1991

Increase of temperature during osteotomy. In vitro and in vivo investigations.

Direct temperature measurements using copper-constantan thermocouples were performed during in vitro and in vivo bone cuttings while the load of the oscillating saw and irrigation were varied. Very high temperatures during continuously applied load were observed. Consequent irrigation may reduce temperature elevation, but only intermittent sawing combined with irrigation diminishes temperature elevation adequately, which allows for an osteotomy without discernible bone damage. In practice, the available oscillating saws should be handled with great care, which implies that the osteotomy should be performed with maximum irrigation and intermittent use.

Animals↗
PubMed1991

[Is it possible to differentiate between odontoameloblastoma and fibro-odontoma? Critical position on basis of 18 cases in DOSAK list].

An attempt was made to differentiate between odontoameloblastoma and ameloblastic fibro-odontoma by means of histological criteria based on 29 cases referred to the DOSAK-bone tumor register. After critical revision 18 appropriate cases have been selected for evaluation. We divided them into 4 odonto-ameloblastomas and 14 ameloblastic fibro-odontomas in accordance with the WHO classification. With respect to localisation, clinical symptoms, radiography, frequency of recurrencies and age no major difference was found between the two "entities". In our sample a decisive histological differentiation was not possible. This supports our hypothesis that there is only one entity.

Ameloblastoma↗
PubMed1990

Radiation and osteosynthesis. Dosimetry on an irradiation phantom.

An irradiation phantom was used to measure dose increases using the backscatter of different materials (titanium, steel, lead, aluminium). Telecobalt-60 and 8-MV photons were used for the irradiation. The irradiation dose was measured by means of a defined X-ray film blackening. The most important parameter was to find out whether under simulated conditions, undesirable hot spots occur. We were able to demonstrate that a 12.5 to 16% increase in the radiation dose can be observed for titanium and steel at a distance of 0.45 mm from the metal specimen. A comparison between titanium and steel did not demonstrate a relevant advantage for titanium. Therefore, adjuvant percutaneous radiation therapy should not have any influence on the life of the implant, if the soft tissue layer is of sufficient thickness. The available literature is reviewed and presented in tables.

Aluminum↗
PubMed1990

[The use of osteosynthesis screws in child mandibles. Anatomical and mechanical considerations].

Thirty seven child mandibular skeletons were analysed radiographically and computer tomographically to establish if there is enough room for osteosynthesis screws. The study demonstrated that in the primary and early mixed dentition there is not enough room in the canine or post-canine region to allow the installation of an osteosynthesis screw without damaging the inferior dental nerve or teeth buds. However, in the later stage of permanent tooth eruption the entire caudal portion of the mandibular body seems to provide sufficient room for osteosynthesis screws. SEM examinations of implant beds of 100 2 mm AO miniscrews inserted into the mandibles of eight fresh cadavers aged eight to twelve years showed cracks, as well as signs of squashing, crushing and shearing stress, regardless of whether the screws were pretapped or not. When, during screw insertion, the axis of the screw deviated by at least 10 degrees from the axis of the tap, two crossing thread courses resulted.

Bone Screws↗