Biomedical subjects
Publications and source records attributed to H Visser.
The advantage of electrosurgery in minor dental surgery is demonstrated with regard to contraindications and especial precautions. In reports of case some indications are presented in combination with the treatment procedure.
The purpose of this study was to evaluate the suitability of CO2 laser and two different electronically controlled electrosurgical units in periodontal surgery; both of the electrosurgical generators were recently designed for application in medicine. The study was performed on freshly butchered pig jaws. In addition to the management of the devices, the macroscopic and histologic effects of laser and high frequency energy on palatal gums, alveolar bone, tooth structures and filling materials were investigated. The handling of the electrosurgical units was efficient and smooth, the incisions showed accurate and reproducible results. In contrast to this the laser was uncomfortable to work with, additional safety arrangements were required and lesions in teeth and alveolar bone occurred easily. While the electronically controlled electrosurgical generators offer interesting aspects in some indications, CO2 laser seems to be unsuitable for periodontal surgery.
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A method for measuring and documentation of the physical characteristics of electronic root canal length determination instruments is presented and illustrated by evaluation of ten different devices. Important parameters such as the influence of the capacitive component in alternating current resistances are presented by means of impedance-charts. All devices examined worked with alternating current; regarding frequency, signal form and resistances, which the devices interpreted as "Apex", the measurements obtained varied. The advantages of this method for clinical and experimental studies are discussed by the author.
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11 electrosurgical units of several manufactures were analysed by physical measurements. Conventional units and those with constant output voltage demonstrate nearly identical behavior in their voltage- and power-characteristics at load-impedance occurring during dental electrosurgery. So far there are no advantages of simple voltage control. We did not find technical deficiencies concerning security in the modern units examined.
The reliability of an electronic detector for caries in pits and fissures was tested by means of physical measurements, histological sections and clinical evaluation. The device measures the ohmic resistance of the tooth, technical data are given. First we compared measurements and histological sections of teeth due for extraction. The results indicated a high sensitivity of the device for caries, false positive diagnoses did not occur. Based on this, a clinical evaluation on 179 teeth was performed. Under practical conditions the sensitivity of the electronic detector (0.77) was lower than in the first part of the study; conventional diagnosis revealed more carious lesions in dentine (sensitivity: 0.82).
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Retinae from neonatal mice were explanted in toto, with or without the retinal pigment epithelium (RPE) and adjoining mesenchymal cells, and maintained in organ culture for up to 3 weeks. The explants remained flat, rosette formation was minimal and histogenetic changes followed in the normal sequence. After 11, 14 and 21 days in vitro the three cellular layers--the outer nuclear layer including well differentiated rod and cone perikarya, the inner nuclear layer and the ganglion cell layer--with the intervening plexiform layers were comparable to those of the in vivo eyes. Electron microscopic analysis revealed that in the explants without RPE the nuclear layers developed as in vivo, but receptor outer segments (ROS) were not formed. When the RPE was present, receptor inner segments appeared normal and ROS including profuse disc structures were developed. Presence of synaptic elements was also recognized. Mesenchymal cells, when present differentiated into choroidal and scleral tissues and appeared to play a supportive role for the RPE cells. The system is described in detail and its suitability for the analysis of various cellular and metabolic factors in the development of the retina is discussed.
It was the goal of this study performed in two subsequent technical courses of operative dentistry to find out if the first "professional" contact of dental students with amalgam resulted in a increased mercury excretion. At six different points in time urine analyses using (flame-free) cold vapor nuclear absorption spectroscopy were performed. At the first measurement, prior to working with amalgam, the median values were at 0.53 micrograms Hg/g creatinine (summer term 88) and 1.46 micrograms Hg/g creatinine (winter term 88/89). At the end of the course the median values have increased to 2.49 micrograms Hg/g creatinine (summer term 88) and 2.56 micrograms Hg/g creatinine (winter term 88/89). In the subsequent vacations the Hg values in the students' urine clearly decreased.
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Measures of gait and balance were undertaken in 11 elderly ambulant patients suffering from senile dementia of Alzheimer type of moderate severity, and in an equal number of healthy non-demented age- and sex-matched controls. Valid results were obtained in nine pairs. Compared with the controls the demented patients had significantly shorter step length, lower gait speed, lower stepping frequency, greater step-to-step variability, greater double support ratio and greater sway path. The findings are consistent with the view that transcortical pathways participating in the integration of gait are damaged in senile dementia of Alzheimer type. The findings may help to explain the increased incidence of falls in patients with brain failure.
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