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W C Martin

Publications and source records attributed to W C Martin.

12 recordsLinked to original sources
PubMed2001

Implant abutment screw rotations and preloads for four different screw materials and surfaces.

STATEMENT OF PROBLEM: Chronic implant screw loosening remains a problem in restorative practices. Some implant manufacturers have introduced abutment screws with treated surfaces in an effort to increase preload and reduce potential loosening. Purpose. This study evaluated the materials and surfaces of 4 commercially available abutment screws on preload generation. MATERIAL AND METHODS: Twenty of each of the following abutment screws-Gold-Tite (Gt), TorqTite (Tt), gold alloy (Ga), and titanium alloy (Ta)-were divided into 2 groups. Measurements were recorded for each abutment screw on a mounted 3.75 x 18 mm external hex implant with a titanium abutment. Rotational angle measurements were conducted on the 4 abutment screws at 20 and 32 Ncm. Removal torque values were recorded and used to indirectly generate preload values. Random implant block specimens were sectioned and qualitatively evaluated with an SEM. RESULTS: At 20 and 32 Ncm, the largest rotational angles were recorded for the Tt groups: 21.2 +/- 3.1 degrees and 38.1 +/- 8.7 degrees, respectively. The greatest preload values at 20 and 32 Ncm were calculated for the Gt groups: 596.8 +/- 101.2 N and 1015.3 +/- 191.2 N, respectively. SEM analysis of the 4 implant block specimens revealed mating thread contacts located in the middle portion of the superior surface of the abutment screw thread. The greatest number of mating thread contacts were seen in the Gt implant block specimen (14 of 20 possible thread contacts). CONCLUSION: The Gt and Tt abutment screws with enhanced surfaces that help reduce the coefficient of friction produced greater rotational angles and preload values than the conventional gold alloy and titanium alloy screws.

Algorithms↗
PubMed1993

Distribution of the bundle-forming pilus structural gene (bfpA) among enteropathogenic Escherichia coli.

Enteropathogenic Escherichia coli (EPEC) express an inducible bundle-forming pilus (BFP) associated with the presence of the EPEC adherence factor (EAF) plasmid and localized adherence (LA) on HEp-2 cells. The cloned structural gene (bfpA) encoding BFP was found to be specific for EPEC, as homologous sequences were found only in EPEC and not in other enteropathogens. The bfpA probe was slightly more sensitive than the EAF probe; among EPEC strains with LA, the bfpA and EAF probes hybridized with 99% and 96% of the strains, respectively. Immunoblotting of whole cell lysates of BFP-positive, EAF-positive or -negative, and LA-positive or -negative EPEC strains revealed variations in the size (18,500-21,000) of the expressed structural subunit of BFP, suggesting differences in processing that may account for discrepancies between the bfpA, EAF, and LA. Because the bfpA probe consists primarily of sequences encoding an important EPEC virulence factor, in contrast to the unknown function of sequences contained in the EAF probe, the bfpA probe may be useful in epidemiologic studies to detect EPEC.

Carcinoma, Squamous Cell↗
PubMed1992

Aggregative adherence fimbriae I of enteroaggregative Escherichia coli mediate adherence to HEp-2 cells and hemagglutination of human erythrocytes.

Strains of enteroaggregative Escherichia coli (EAggEC) have been implicated in several studies as important agents of persistent diarrhea among infants in the developing world. We have previously shown that the aggregative adherence (AA) property of EAggEC is associated with the presence of a 60-MDa plasmid which confers AA when introduced into E. coli HB101. Here, we report the cloning of the AA determinant from EAggEC strain 17-2 into the 21.5-kb cosmid vector pCVD301. TnphoA mutagenesis of the AA cosmid clone pJPN31 implicated an AA region of approximately 12 kb. Transmission electron microscopy of HB101 (pJPN31) revealed the presence of bundle-forming fimbriae, which were absent in AA- TnphoA insertion mutants. The presence of these fimbriae, AA, and hemagglutination (HA) of human erythrocytes were all concurrently lost by single-insertion mutations. A 14-kDa protein was seen on polyacrylamide gel electrophoresis and Western blotting (immunoblotting) of surface shear preparations from fimbriated clones. Twelve of nineteen volunteers fed EAggEC 17-2 developed rises in antibodies to the 14-kDa protein as determined by Western blot. We have termed the cloned bundle-forming fimbriae aggregative adherence fimbriae I (AAF/I); positivity with a previously described EAggEC probe and human erythrocyte HA appear to correlate with the presence of AAF/I.

Antibodies, Bacterial↗
PubMed1990

Practical and economical method for using biotinylated DNA probes with bacterial colony blots to identify diarrhea-causing Escherichia coli.

A simple and economical method was developed for using biotinylated DNA probes to hybridize with bacterial colonies belonging to the various categories of diarrhea-causing Escherichia coli. Simplification and cost containment were achieved by using Whatman no. 541 filter papers instead of nitrocellulose, by minimizing the concentration of proteinase K (an expensive but necessary reagent used to pretreat the colony blots prior to hybridization with biotin-labeled DNA probes) and by reusing hybridization solution containing labeled probe DNA. After exposing the colony blots to lysing solution and steam, followed by lysozyme (1.5 mg/ml), sucrose (25%), and proteinase K (10 micrograms/ml) treatments, biotinylated probes were used to detect enterotoxigenic, enteropathogenic, enterohemorrhagic, diffuse adherence, and enteroinvasive categories of diarrhea-causing E. coli with a high level of sensitivity and specificity. Three independent observers who were experienced in reading DNA blots recorded remarkably similar results, while less satisfactory results were obtained when the blots were read by an inexperienced observer. This technique will be useful in laboratories in which radioactive isotopes are unavailable or impractical and in which budgets are restricted.

Biotin↗
PubMed1990

Oligonucleotide probe for detection of the enteropathogenic Escherichia coli (EPEC) adherence factor of localized adherent EPEC.

The enteropathogenic Escherichia coli adherence factor (EAF) probe detects isolates of enteropathogenic E. coli that exhibit localized adherence to HEp-2 cells. A 21-base oligonucleotide probe was constructed on the basis of a sequence from within the 1-kb EAF probe and was shown to have greater sensitivity and specificity than the EAF fragment probe in detecting localized adherent E. coli.

Adhesins, Escherichia coli↗
PubMed1978

Benign retroperitoneal emphysema associated with upper gastrointestinal endoscopy.

It is important to realize that retroperitoneal emphysema may be seen as a complication of upper gastrointestinal endoscopy. Because of the increased frequency of endoscopic and associated procedures, it is important to realize that these striking roentgenographic findings may be associated with a benign clinical condition that will resolve with expectant management alone. Clinically, we might be forced to differentiate this complication with pathological perforation from the original lesion or with free perforation by the instrument depending on the clinical conditions.

Aged↗