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Biomedical subjects

J Willer

Publications and source records attributed to J Willer.

18 recordsLinked to original sources
PubMed2000

Temporal summation and a C-fibre reflex in the rat: effects of morphine on facilitatory and inhibitory mechanisms.

In intact rats, an inhibitory mechanism counteracts the increase in excitability of a flexor reflex, which is seen in spinal animals following temporal summation of C-fibre inputs; the Rostral Ventromedial Medulla is involved in this inhibitory mechanism. Electromyographic responses elicited by electrical stimulation of the sural nerve were recorded from the biceps femoris in four types of preparations, namely intact, sham-operated, Rostral Ventromedial Medulla-lesioned and decerebrate-spinal rats. The excitability of the C-fibre reflex was tested during and following high intensity homotopic electrical conditioning stimuli. Morphine (2 mg/kg) did not significantly change the basal test response but increased the excitability of the spinal cord during conditioning. This effect was triggered by the strength of inputs, involved the Rostral Ventromedial Medulla and was probably related to some forms of motor stimulation through dopaminergic transmission. While wind-up was not reduced, the inhibition related to Diffuse Noxious Inhibitory Controls, which occurred following the conditioning period, did. In spinal animals where inhibitory mechanisms disappear, the depressive effects of morphine were unmasked for both wind-up and post-conditioning facilitations. All effects of morphine were completely reversed by naloxone.

Analgesics, Opioid↗
PubMed1998

[3-D imaging of the facial surface by topometry using projected white light strips].

Three-dimensional registration of the facial surface by methods which are currently in use is difficult because of the long measuring times required by point-based imaging systems. Artifacts caused by movement appear, e.g., blinking. Also the production of a facial plaster-cast model for measuring is not an adequate solution. In order to acquire data of the facial surface in a contact-free manner, a system is needed that has short measuring times, is able to record data of complex surfaces and at the same time does no harm to the open eyes. The method described here represents a new development of an industrial high tech CAD/CAM system. Unlike customary point-based imaging systems, the stripe projection method works using entire planes. Structured light is aimed at the surface to be measured, recorded by videocamera and calculated by triangulation; then the different views are combined by computer. The system has an optic sensor that can record approximately 500,000 measuring points within seconds (ca. 1.7s). Test persons' faces and plaster-cast models of them (n = 15) were measured comparatively and serially (n = 5) to test the validity and reliability of the method for maxillofacial procedures. These investigations show that this method is appropriate for recording three-dimensional soft-tissue profiles. First studies on patients before and after dysgnathia operations were undertaken. A prospective long-term study for collecting data on pre- and postoperative dysgnathia patients has been begun. Initially, it will record the changes in facial soft tissue on the basis of skeletal displacement. Later, predictions about the soft-tissue changes subsequent to dysgnathia surgery can be worked out on the basis of stored data matched with three-dimensional bone data.

Adolescent↗
PubMed1998

Computer-assisted milling of dental restorations using a new CAD/CAM data acquisition system.

BACKGROUND: Recent technologic innovations have created possibilities for restorative dentistry, such as computer-aided design and computer-aided manufacturing (CAD/CAM). PURPOSE: This article presents a new CAD/CAM process that has been developed for the fabrication of dental restorations. METHODS: This process uses an improved imaging technique, successfully applied in other industries. Imaging is accomplished with 2-dimensional line grids projected onto an object, which allows for a mathematical reproduction of prepared and unprepared tooth surfaces, including those that are outside the direct line of light. The relative position of the sensor to the surface of the object is controlled automatically. CONCLUSIONS: This system, which is undergoing clinical testing, allows the generation of various types of highly accurate dental restorations (inlays, onlays, crown, and fixed partial dentures) from a number of different materials. Acquired digitized data points are directly translated from the sensor to the electronic controls of the milling machine to provide various manufacturing possibilities, including copy milling and accurate reproduction of occlusal tooth surfaces in various materials.

Computer-Aided Design↗
PubMed1987

The privatization of health care and physicians' perceptions of access to hospital services.

Health care in the United States is increasingly delivered by for-profit providers, by multi-facility corporations, and under conditions of price-based competition. The joint influence of these three trends is examined through data drawn from a 1984 survey of physicians conducted by the American Medical Association. For-profit ownership and price competition are reported to restrict admission for the poor and uninsured; the effects of system affiliation are shown to be more complex. Policy responses to future restrictions on access are discussed.

Attitude of Health Personnel↗
PubMedDate not supplied

Long-term results after placement of dental implants: longitudinal study of 1,964 implants over 16 years.

In a retrospective study, Kaplan-Meier implant survival analyses were conducted on 883 patients with 1,964 implants of various systems placed, followed up, documented, and statistically evaluated at an oral surgery and dentistry practice between January 1981 and January 1997. The goal of this study was to evaluate the success of osseointegrated implants of the Brånemark, Frialit-1 (Tübinger Implant), Frialit-2, and IMZ systems and Linkow blade implants. For all systems, mandibular implants were generally more successful than maxillary implants. The preprosthetic loss rate was 1.9%, and 4.3% of implants were lost after prosthetic treatment. The lowest loss rates were seen with implants in intermediate and distal extension spaces and with single-tooth replacements using IMZ, Frialit-2, and Brånemark implants. In edentulous arches, implants of the IMZ and Brånemark systems had the lowest failure rates.

Adolescent↗