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Biomedical subjects

J S Reid

Publications and source records attributed to J S Reid.

72 records · Page 4Linked to original sources
PubMedDate not supplied

Transmission of water through a biocompatible polyurethane: application to circulatory assist devices.

The permeability characteristics of a water-segmented polyurethane (Biomer) system under the conditions encountered in circulatory-assist devices were investigated. A diffusion cell and permeability system providing precise control of membrane boundary conditions and allowing continuous measurement of water vapor transmission was designed. Liquid water at 37 degrees C was used as the donor fluid and the system incorporated a constant-flow nitrogen carrier gas and an optical dew point sensor downstream to determine the water vapor mass flow rate as a function of time. The mass flow rate was then numerically integrated and plotted against time to allow calculation of effective diffusion coefficient (D) by the dynamic time lag method. Steady-state permeabilities were found to be insensitive to donor chamber hydrostatic pressure (50-200 mm Hg) indicating that bulk flow is not a transport mechanism in these membranes. The permeability coefficient (P) was independent of membrane thickness (H) over the four samples tested (0.0102, 0.0148, 0.0269, and 0.0366 cm), with an average value of 3.29 X 10(-4) cm2/s. Thus, diffusion was Fickian with negligible boundary layers. A plot of lag time versus H2 was linear (R = 0.98) yielding a value for D of 2.18 X 10(-7) cm2/s. A water-Biomer partition coefficient was determined for each sample with an average value of 1525, indicating a moderately hydrophilic membrane with a water sorption of 6.3% at 37 degrees C. Since water transport is by Fickian diffusion in the absence of bulk flow, liquid water cannot be expected to accumulate in circulatory-assist devices unless a condensing surface is maintained within the system.

Biocompatible Materials↗
PubMedDate not supplied

Production of a nonwettable enamel surface.

A water-repellent enamel surface was achieved using a new material that is a combination of fumed silicon dioxide and a silane. The effects of this coating on enamel were studied. In vitro studies suggest that the material produces good water and saliva repellency. However, no reduction in bacterial colonization between treated and control enamel occurred. results of in vivo investigations of coated and control Styroflex strips showed a reduction in deposits on the former. Retention with or without previous acid etching of the enamel was poor.

Dental Bonding↗
PubMedDate not supplied

Comparison of total nutrient admixture stability using two intravenous fat emulsions, Soyacal and Intralipid 20%.

The safe clinical use and physical stability of a total nutrient admixture (TNA) system containing a soybean oil emulsion (Intralipid) has been reported. A study was conducted to compare the physical stability of four admixtures which were divided into two groups based upon the ratios (1:1:1 and 2:1:1) of amino acids (8.5%), dextrose (70%), and fat emulsion (20%). The fat component in each group contained either a new soy bean fat emulsion, Soyacal, or Intralipid. The quantities of all electrolytes, trace elements and vitamin additives were the same. All solutions were stored at 4 degrees C for 28 days and then held at ambient temperature for 5 days for a total 33-day study period. Each admixture was serially analyzed on days 0, 1, 2, 3, 5, 7, 14, 21, 28, 29, 30, 31, 32, and 33. Examination of gross visual appearance and determinations of pH were performed. Osmolality was measured by means of freezing point depression (Advanced Digimatic Osmometer, Advanced Instruments, Inc., Needham Heights, MA). A Brookhaven particle analyzer was used to measure lipid particle size and particle size distribution. Electron and light microscopy were used to verify maximum particle size and distribution on days 0, 7, 14, 21, 28, and 29. The type of lipid emulsion used did not affect the pH or osmolality of the admixtures. Admixtures prepared with the 2:1:1 ratio had slightly higher pH (0.07) and lower osmolality (350 mOsm/kg). The range of mean diameters for the admixtures prepared with Soyacal and Intralipid were 0.283 to 0.310 micron and 0.314 to 0.351 micron, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMedDate not supplied

The treatment of erosion using porcelain veneers.

Two cases reported here demonstrate the use of porcelain veneers to restore lost tooth tissue due to erosion. The veneers have advantages compared with other restorations in terms of aesthetics and resistance to wear. The patients described in these two reports have been seen over periods of two and three years and have been satisfied with the results, with each reporting no further pain.

Adolescent↗
PubMedDate not supplied

Patient and operator attitudes toward rubber dam.

The increasing reliance of modern dentistry on adhesive materials, has acted as a renewed incentive for the use of rubber dam. A safe, dry field in a comfortable patient, with the teeth and colored rubber dam contrasting, are the major advantages to the operator. Few articles have assessed the reactions of either the patient or the operator; in this study, it is accepted well.

Adolescent↗
PubMedDate not supplied

An in-vitro investigation of microleakage and gap size of glass ionomer/composite resin "sandwich" restorations in primary teeth.

Eighty extracted primary molars were divided into four groups of twenty teeth. Class II cavities were prepared in all teeth with equal numbers of proximal boxes having cavosurface margins either in enamel, or dentin/cementum. Each group was allocated to an open or closed sandwich technique using glass ionomer as a lining. Following the placement of the composite resin restorations, the gap size measured at the proximal box was greatest for the closed sandwich group with the cavosurface margin on enamel (0.203 microns) or dentin/cementum (0.174 microns). Microleakage scores were measured at the proximal box and were greatest for the closed sandwich group with the cavosurface margin on dentin/cementum. The best result was obtained for the open sandwich group with the cavosurface margin on enamel.

Analysis of Variance↗
PubMedDate not supplied

Dentinal dysplasia type I: review of the literature and report of a family.

A family is reported with dentinal dysplasia type I affecting both dentitions. Presenting features included unusual mobility of the teeth, followed by early exfoliation; normal clinical shape of the crowns of the teeth, but with an amber color without any sign of attrition or abnormal loss of enamel. Radiographic findings showed pulp-chamber and root-canal obliteration, poor root formation, radiolucent linear appearance of the pulp chamber parallel to the cementoenamel junction and frequent periapical radiolucencies. Histological studies have reported large masses of calcified tubular dentin, atypical osteodentin, and also true denticle.

Adult↗