PubMed Health⌕ Search

Biomedical subjects

J R Kelly

Publications and source records attributed to J R Kelly.

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

Isolation of Neisseria meningitidis from anogenital specimens from homosexual men.

By use of the fluorescent antibody technique, the authors examined 663 consecutive anogenital isolates from men that satisfied the presumptive criteria for Neisseria gonorrhoeae of the Center for Disease Control (Atlanta, Ga.). Most urethral isolates (364 of 368; 98.9%) from men presumed to be heterosexual were confirmed as N. gonorrhoeae. In contrast, urethral (98 of 114; 86%) and anal (136 of 175; 78%) isolates from homosexual men contained N. gonorrhoeae significantly less often (P less than 0.001). Most the isolates with negative results in the fluorescent antibody test for N. gonorrhoeae were shown to be Neisseria meningitidis by use of sugar fermentation reactions. Homosexual men sampled at two bathhouses for gay men were more likely to have oropharyngeal Neisseria isolated from anogenital cultures than were homosexual men screened in a clinic for gay men. Reliance on presumptive criteria for the identification of N. gonorrhoeae in anogenital cultures taken from homosexual men is inappropriate.

Anal Canal↗
PubMedDate not supplied

Fracture surface analysis of dental ceramics: clinically failed restorations.

Fractography was used to study all-ceramic restorations that had failed clinically. Some basic tenets of fracture mechanics and fractography are reviewed and related to the examination of clinically failed all-ceramic restorations. Dicor and Cerestore restorations that had failed either at trial placement or 17 to 36 months postcementation were evaluated. Failed Dicor restorations were studied to determine the origin of failure and calculate the intraoral stress at failure. Descriptive information regarding crack origin and crack path were obtained from failed restorations constructed of first-generation Cerestore. A majority of the crowns apparently failed from the internal surface, indicating this as the highest tensile surface and/or the location of the largest flaws. Flaws were identified as being related to fabrication or inherent in the ceramic microstructure.

Aluminum Oxide↗
PubMedDate not supplied

Influence of surface preparation on the strength and surface microstructure of a cast dental ceramic.

The effect of three surface preparations on the flexural strength of a cast glass-ceramic (Dicor) was studied. The microstructure of the external and fracture surfaces was evaluated using electron microscopy. It was found that there was no difference in strength for the "as-cast/cerammed," acid-etched, or glazed shading porcelain specimens. A significant increase in strength (twofold) was observed when the "ceram layer" was mechanically removed from the surface of the ceramic. Scanning electron microscopy revealed that the "ceram layer" was 25 to 100 microns thick and consisted of crystal "whiskers" oriented perpendicular to the external surfaces. It was observed in both the laboratory and the clinically failed specimens that a zone of strength-limiting porosity was associated with this "ceram layer." Potential origins of the crystal "whiskers" and the porosity were discussed.

Acid Etching, Dental↗
PubMedDate not supplied

Compatibility of ceramic-ceramic systems for fixed prosthodontics.

This study evaluated dilatometric data for predicting ceramic-ceramic compatibility for porcelains fired on central incisor copings (n = 72) of high expansion colored IPS-Empress porcelain. Nine body porcelains (leucite 0 wt% to 51 wt%) were each fired onto eight copings. Cracks were detected at 10 x magnification using transilluminating light. Failure was defined as the presence of at least one crack and probability of failure (Pf) as the ratio of failed to total crowns. Thermal contraction coefficients (alpha) were determined using four bars of each porcelain following the protocol of ISO 9693. Absolute differences in thermal contraction, magnitude of delta alpha, between core and test porcelains were plotted against Pf and curve fit. Significant differences in alpha were found among the porcelains tested (ANOVA, 95% Tukey); the alpha values ranged from 7.92 to 17.83 x 10(-6)/degree C; Pf ranged from 0 to 1. Compatible porcelains (no cracks during any firing of all eight crowns) had magnitude of delta alpha values less than 1 x 10(-6)/degree C. Absolute values (magnitude of delta alpha) were surprisingly predictive of Pf given the very different cooling rates (dilatometry versus dental lab) and the relatively complex crown shape. Standard dilatometry may be useful for predicting the compatibility of ceramic-ceramic systems. Three porcelains, IPS-Empress dentin, Duceram, and Will-Ceram were successfully used for veneering IPS Empress cores.

Aluminum Oxide↗