PubMed Health⌕ Search

Biomedical subjects

W M Mansfield

Publications and source records attributed to W M Mansfield.

5 recordsLinked to original sources
PubMed1999

Long-term reliability of semiadjustable articulator interchangeability.

PURPOSE: Interchangeability between articulators allows mounted casts to be accurately transferred from one articulator to another. The purpose of this study was to evaluate the interchangeability of Whip-Mix model #2240 articulators (Whip-Mix Corporation, Louisville, KY) that had been in clinical use for between 1 and 6 years. MATERIALS AND METHODS: Forty-six Whip-Mix model #2240 articulators that had been in clinical use by students, practitioners, or laboratory technicians for between 1 and 6 years were evaluated for interchangeability using the Whip-Mix #2245 check system. The horizontal tolerance of the check system was 94 microns. The articulators were also evaluated in the vertical dimension at four locations around the check system cylinders using 26-micron shimstock. Vertical discrepancies between the cylinders were recorded as the thickness of 0, 1, 2, or more than 2 pieces of shimstock. RESULTS: Thirty-eight of the articulators (83%) passed the test for interchangeability. These articulators were interchangeable with other Whip-Mix model #2240 articulators fabricated over a 5 1/2-year period (December 1990 to August 1996). In the vertical dimension, most articulators had discrepancies < or = 26 microns. Three articulators (6.5%) had vertical discrepancies greater than 52 microns. CONCLUSIONS: (1) Eighty-three percent of Whip-Mix model #2240 articulators that had been in clinical use for between 1 and 6 years remained interchangeable within a tolerance of 94 microns in the horizontal dimension. (2) Only three articulators in this study (6.5%) had a vertical discrepancy at any location between the cylinders greater than 52 microns. (3) The model #2240 articulator has the potential to remain interchangeable during clinical use.

Dental Articulators↗
PubMed1977

Time, rate, and temperature factors in the onset of high-pressure convulsions.

An interrupted compression profile technique was used to develop data to separate the effects of time and pressure factors governing increase of high-pressure neurological syndrome (HPNS) convulsion threshold pressures (the compression rate effect) during different compression profiles. A single differential equation fits all data available to date for compression rate effect on convulsion thresholds of CD-1 mice (three distinct types of compression profile; mean compression rates 12-1,000 atm/h). The process leading to increase in HPNS convulsion pressure is initiated at the very beginning of compression, proceeds at increasingly rapid rates as higher pressures are attained, and approaches a limiting upper convulsion pressure. The convulsion threshold pressure in any given experiment is independent of the compression rate prevailing during the time immediately preceding onset of the seizure. The magnitude of the compression rate effect in the CD-1 mouse is independent of chamber temperature over a range of 27-36 degrees C, and rectal temperatures of 29.2-37.5 degrees C. The bearing of these results on the design of optimal compression schedules and on the analysis of the neurological mechanisms underlying the HPNS is discussed.

Animals↗
PubMed1975

Rate factors in development of the high-pressure neurological syndrome.

The effect of varying the pressure/time profile upon development of tremors and convulsions of the high-pressure neurological syndrome was studied in adult mice and squirrel monkeys and in baby mice. Two distinct response patterns were observed. In the adults rapid compression produces early onset of convulsions; convulsions subside rapidly when animals are held at constant pressure just above the convulsion point; and interrupted compression schedules show that total compression time rather than instantaneous compression rate at the moment seizures develop is the controlling parameter. Baby mice up to 12 days of age, by contrast, fail to show any perceptible relation between compression rate and convulsion threshold pressure (Pc); their seizures continue for a considerable period of time after a constant pressure level just above the convulsion threshold has been reached; and interrupted compressions of type a fail to change their convulsion threshold. Together with supplementary data regarding tremor thresholds and the transient increase of convulsion thresholds by prior seizures these results lead to a proposed schema describing these phenomena in terms of a pressure-dependent primary event predisposing to tremors and convulsions; a time-dependent event counteracting the convulsions (absent in baby mice); and a transient effect of prior convulsions, raising subsequent Pc.

Age Factors↗