Patch testing to plants.
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Dermatitis, Contact↗
Biomedical subjects
J C Mitchell
Publications and source records attributed to J C Mitchell.
Management of cleft lip and palate in primary care.
Cleft lip and palate malformations are the most common congenital craniofacial abnormalities. Patients with these deformities require coordinated care involving multiple disciplines from birth throughout adolescence. The primary care provider plays a vital role in facilitating the provision of care for these patients, who often have numerous health care needs, including feeding difficulties, speech disorders, chronic ear infections, and dental and orthodontic problems. The emotional issues of patients with these deformities and their families are significant and include disrupted parent and child bonding, body image disturbances, and impaired socialization. The role of the primary care provider is to be a stable source of support for these patients and to assist in coordinating care for the many physical and emotional problems they may have.
Child, Preschool↗
Crystallographic characteristics of plasma-sprayed calcium phosphate coatings on Ti-6Al-4V.
The purpose of this study was to investigate the crystallographic characteristics of 3 sets of plasma-sprayed hydroxyapatite (HA) coatings prepared with different degrees of crystallinity on Ti-6Al-4V substrates. X-ray diffraction analyses were performed on the coatings to determine mean percent crystallinity, calcium phosphate phases present, average crystallite size, and residual strain. The mean percent crystallinity for the 3 sets of coatings ranged from 49 to 60%. The coatings that achieved the highest crystallinity consisted almost entirely of HA. As the coating crystallinity decreased, increasing amounts of alpha- and beta-tricalcium phosphate and tetracalcium phosphate were detected. The mean HA crystallite size for the 3 sets of coatings ranged from 0.02 to 0.05 micron. Differences in mean interplanar spacing for selected crystallographic planes of HA, compared with the pure ICDD (International Center for Diffraction Data) powder standards, implied that the coatings were in an uneven state of tensile strain.
Alloys↗
Microwave oven interference with cardiac pacemakers.
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Animals↗
Ultraviolet-mediated antibiotic activity of species of Compositae caused by polyacetylenic compounds.
A survey of North, Central, and South American composites, and of certain polyacetylenic compounds occurring in them, confirmed that the ultraviolet-mediated antibiotic activity against Candida albicans can be ascribed to the presence of particular polyacetylenes and their thiophene derivatives. Leaves, stems, roots, and achenes were assayed separately. An attempt was made to relate the phototoxic activity of specific compounds to their chemical structures. Most composites tested were not phototoxic against Candida, but many were antibiotic. The antibiotic activity also appears to be caused by polyacetylenes. Of 65 sequiterpene lactones assayed, only a few were found to be antibiotic, and only one, glaucolide G, was phototoxic.
Alkynes↗
New high-palladium casting alloys: Part 2. Effects of heat treatment and burnout temperature.
Castings simulating a maxillary central incisor coping were fabricated from five representative high-palladium alloys, using burnout temperatures of 1,400 degrees F and 1,500 degrees F, with a carbon-free phosphate-bonded investment. Three castings of each alloy were individually prepared at each burnout temperature. Each casting was sectioned into two specimens, and one specimen was subjected to simulated porcelain firing heat treatment. Polished and etched specimens in as-cast and heat-treated conditions were examined with optical and scanning electron microscopes. Mean values of Vickers hardness (1-kg load) were determined for each alloy and condition. It was observed that the simulated porcelain firing cycles caused major changes in as-cast bulk microstructures for the three first-generation alloys, while only subtle alterations were observed for the two second-generation alloys. In addition, complex regions associated with oxidation processes were found near the surfaces of all the heat-treated alloys. While the as-cast microstructure and the hardness of each alloy did not vary appreciably for the two burnout temperatures, the incidence of hot tearing in one first-generation alloy was substantially reduced at the lower burnout temperature. Statistically significant decreases in hardness generally occurred in the high-palladium alloys after the simulated porcelain firing cycles, but the relatively small changes (usually 10% or less) should not have any clinical significance. Other clinically relevant applications are also discussed.
Dental Alloys↗
New high-palladium casting alloys: studies of the interface with porcelain.
This investigation studied the metal ceramic interface for two representative high-palladium alloys each of the Pd-Cu-Ga and Pd-Ga systems, using scanning electron microscopy and x-ray energy dispersive spectroscopy. The Pd-Cu-Ga alloys produced complex subsurface oxidation regions with thickness ranging from 15 to 20 microns for one alloy and 5 to 10 microns for the other alloy. Ga, In, and Sn accumulated at the interfaces, and Ga-rich deposits were found in the subsurface scale. One Pd-Ga alloy presented a surface oxidation region which dissolved in the ceramic, producing "islands" rich in Pd and Ga with a width that ranged from 1 to 2 microns. These islands were separated from the alloy by a band rich in Ga and Si which was 1 to 2.5 microns thick. While the other Pd-Ga alloy presented similar interfacial microstructures, the "islands" formed for this alloy were relatively sparse. The Pd-Cu-Ga alloys had a more favorable interface for metal ceramic bonding, which agrees with previous characterization of bond failures between these alloys and dental porcelain.
Copper↗
Microstructures of plasma-sprayed hydroxyapatite-coated Ti-6Al-4V dental implants.
The purpose of this study was to investigate the microstructure of plasma-sprayed hydroxyapatite coatings and the elemental composition near the coating-substrate interface for two commercial implants, using the scanning electron microscope. Both coating surfaces and cross-sectioned specimens were examined. The results indicated that while the surface microstructures of both implants were consistent with the plasma-spraying process, the scale of the constituents was much finer for one product. In cross-section, both coatings exhibited minimal porosity and intimate contact with the titanium alloy substrate. It was found that limited interdiffusion of titanium and calcium occurred near the interface.
Alloys↗