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At least 37 records · Page 2Linked to original sources
PubMed2005

Effects of 50 Hz electromagnetic fields on electroencephalographic alpha activity, dental pain threshold and cardiovascular parameters in humans.

Recent studies indicate that exposure to extremely low frequency magnetic fields (ELF MFs) influences human electroencephalographic (EEG) alpha activity and pain perception. In the present study we analyse the effect on electrical EEG activity in the alpha band (8-13 Hz) and on nociception in 40 healthy male volunteers after 90-min exposure of the head to 50 Hz ELF MFs at a flux density of 40 or 80 microT in a double-blind randomized sham-controlled study. Since cardiovascular regulation is functionally related to pain modulation, we also measured blood pressure (BP) and heart rate (HR) during treatment. Alpha activity after 80 microT magnetic treatment almost doubled compared to sham treatment. Pain threshold after 40 microT magnetic treatment was significantly lower than after sham treatment. No effects were found for BP and HR. We suggest that these results may be explained by a modulation of sensory gating processes through the opioidergic system, that in turn is influenced by magnetic exposure.

Adult↗
PubMed1997

Effect of post-cure temperature and heat duration on monomer conversion of photo-activated dental resin composite.

OBJECTIVES: This research evaluated the relationship between post-cure heating temperature and duration on the monomer conversion of a commercial light-activated resin composite. METHODS: Disc-shaped composite specimens (10 x 1 mm) were initially light-cured and then submitted to one of the following post-cure. CONDITIONS: None (control), 50 degrees, 75 degrees, 100 degrees or 125 degrees C for 0.5, 1, 3, 5, or 7 min. After curing, specimens were stored in the dark at room temperature. Monomer conversion of all specimens was then determined using infrared spectroscopy. RESULTS: Post-cure temperature was 12 times more influential than was heal duration on the extent of resin cure. The extent of cure increased linearly with an increase in post-cure temperature. Post-cure specimens that were heated between 3 and 7 min demonstrated equivalent cure values. All post-cure healing conditions resulted in significantly higher cure values than the light-cured only control. SIGNIFICANCE: Physical properties of post-cure heated composites may change with respect to aging and water, but monomer conversion values of post-cure heated materials remain unaltered. Results of this study validate the use of relatively high temperatures for increasing the extent of monomer conversion. Such increases may lead to more biocompatible restorations.

Analysis of Variance↗
PubMedDate not supplied

Actinomyces spp. in supragingival plaque of ethnic Chinese preschool children with and without active dental caries.

Very limited molecular epidemiological data are available on the role of Actinomyces spp. in the pathogenesis of caries in the primary dentition. Therefore, we investigated their distribution in supragingival plaque of ethnic Chinese preschool children from Singapore and Hong Kong, either with or without active caries. Plaque samples were taken from intact interproximal enamel areas using dental floss. Bacterial genomic DNA of each sample was extracted and variable regions of 16S ribosomal DNA amplified and labelled with digoxigenin. Oligonucleotide probes specific for Actinomyces bovis, Actinomyces gerencseriae, Actinomyces israelii, Actinomyces meyeri, Actinomyces odontolyticus, catalase-negative Actinomyces naeslundii (genospecies 1 and 2) and catalase-positive Actinomyces naeslundii genospecies 2 (previously Actinomyces viscosus serotype II) were used to detect these species using Southern hybridization with a Minislot and Miniblotter system. A. odontolyticus, A. gerencseriae and A. meyeri were detected with similar frequency in both Singapore and Hong Kong samples or in those with and without active caries. However, the prevalence of A. naeslundii was significantly different in the two locales (p<0.05). A. odontolyticus (88.7%), A. gerencseriae (56.6%) and A. naeslundii (50.9%) were detected in a majority of the samples and the positive hybridization signals of A. gerencseriae in the caries-active group were stronger than from the caries-free group. A. bovis and A. israelii were undetectable in any of the samples. These data imply that A. odontolyticus, A. naeslundii and A. gerencseriae may play an important role in supragingival plaque formation on primary teeth in ethnic Chinese, with others such as A. meyeri contributing.

Actinomyces↗