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Microbiological Effects (microbiological + effects)

Distribution by Scientific Domains
Medical Sciences60%

Selected Abstracts

Long-Term Performance of Permeable Reactive Barriers Using Zero-Valent Iron: Geochemical and Microbiological Effects

GROUND WATER, Issue 4 2003
Richard T. Wilkin
Geochemical and microbiological factors that control long-term performance of subsurface permeable reactive barriers were evaluated at the Elizabeth City, North Carolina, and the Denver Federal Center, Colorado, sites. These ground water treatment systems use zero-valent iron filings (Peerless Metal Powders Inc.) to intercept and remediate chlorinated hydrocarbon compounds at the Denver Federal Center (funnel-and-gate system) and overlapping plumes of hexavalent chromium and chlorinated hydrocarbons at Elizabeth City (continuous wall system). Zero-valent iron at both sites is a long-term sink for carbon, sulfur, calcium, silicon, nitrogen, and magnesium. After about four years of operation, the average rates of inorganic carbon (IC) and sulfur (S) accumulation are 0.09 and 0.02 kg/m2/year, respectively, at Elizabeth City where upgradient waters contain <400 mg/L of total dissolved solids (TDS). At the Denver Federal Center site, upgradient ground water contains 1000 to 1200 mg/L TDS and rates of IC and S accumulation are as high as 2.16 and 0.80 kg/m2/year, respectively. At both sites, consistent patterns of spatially variable mineral precipitation and microbial activity are observed. Mineral precipitates and microbial biomass accumulate the fastest near the upgradient aquifer-Fe0 interface. Maximum net reductions in porosity due to the accumulation of sulfur and inorganic carbon precipitates range from 0.032 at Elizabeth City to 0.062 at the Denver Federal Center (gate 2) after about four years. Although pore space has been lost due the accumulation of authigenic components, neither site shows evidence of pervasive pore clogging after four years of operation. [source]

The effect of the VectorŽ scaler system on human teeth: a systematic review

INTERNATIONAL JOURNAL OF DENTAL HYGIENE, Issue 3 2008
DE Slot
Abstract:, Aim:, To review the available literature, considering the effect of instrumentation with the VectorŽ ultrasonic scaler on human teeth in vitro and in vivo compared to conventional ultrasonic instruments and/or hand instrumentation. The assessed effects are calculus removal, time of instrumentation, root surface aspects, cell attachment, patients' perception, bleeding upon probing, pocket depth, clinical attachment loss and microbiological effects. Materials and methods:, MEDLINE,PubMed and the Cochrane Central register of controlled trials (CENTRAL) were searched up through January 2008 to identify appropriate studies. Results:, Independent screening of the titles and abstracts of 270 MEDLINE,PubMed and 15 Cochrane papers resulted in 15 suitable publications. The studies differed in design and outcome, so this review summarizes the outcomes in a descriptive manner. Comparisons are presented against conventional ultrasonic system and scaling and root planing. Conclusion:, The VectorŽ ultrasonic scaler provided comparable clinical and microbiological periodontal healing results as scaling and root planing and conventional ultrasonic system in moderately deep pockets. The VectorŽ ultrasonic scaler may be used as a gentle root debridement device for supportive periodontal therapy, as an alternative to other conventional ultrasonic system. The operator should however consider the extra time needed for instrumentation. [source]

Cariogenicity of soluble starch in oral in vitro biofilm and experimental rat caries studies: a comparison

JOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2008
T. Thurnheer
Abstract Aims:, Common belief suggests that starch is less cariogenic than sugar; however, the related literature is quite controversial. We aimed to compare cariogenic and microbiological effects of soluble starch in both a standard animal model and an oral biofilm system, and to assess the possible substitution of the animal model. Methods and Results:, Six-species biofilms were grown anaerobically on enamel discs in saliva and medium with glucose/sucrose, starch (average molecular weight of 5000, average polymerization grade of 31), or mixtures thereof. After 64ˇ5 h of biofilm formation, the microbiota were quantitated by cultivation and demineralization was measured by quantitative light-induced fluorescence. To assess caries incidence in rats, the same microbiota as in the biofilm experiments were applied. The animals were fed diets containing either glucose, glucose/sucrose, glucose/sucrose/starch or starch alone. Results with both models show that demineralization was significantly smaller with starch than sucrose. Conclusions:, The data demonstrate that soluble starch is substantially less cariogenic than glucose/sucrose. Significance and Impact of the Study:, By leading to the same scientific evidence as its in vivo counterpart, the described in vitro biofilm system provides an interesting and valuable tool in the quest to reduce experimentation with animals. [source]

Clinical and microbiological effects of different antimicrobials on generalized aggressive periodontitis

JOURNAL OF CLINICAL PERIODONTOLOGY, Issue 4 2006
Christiana Xajigeorgiou
Abstract Aim: To evaluate and compare the effects of adjunctive metronidazole plus amoxicillin, doxycycline and metronidazole on clinical and microbiological parameters in patients with generalized aggressive periodontitis. Material and Methods: Forty-three patients participated in this randomized clinical trial divided into four groups. Six weeks after scaling and root planning (SRP), groups 1,3 received adjunctive metronidazole, plus amoxicillin, doxycycline and metronidazole respectively, and group 4 acted as controls. Clinical recordings concerning probing depth, probing attachment level and bleeding on probing were performed at baseline, 6 weeks after SRP and 6 months from baseline. Subgingival samples were analysed using the ,checkerboard' DNA,DNA hybridization for Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, Tannerella forsythia and Treponema denticola. Results: All treatments resulted in improvement of clinical parameters (ANOVA p>0.05). Systemic administration of metronidazole plus amoxicillin or metronidazole resulted in statistically significant greater reduction of the proportion of sites > 6mm than SRP (z -test, p<0.05). These antimicrobials yielded a significant effect on levels of important periodontal pathogens for 6 months. Conclusion: Adjunctive metronidazole plus amoxicillin or metronidazole alone (when A.actinomycetemcomitans is not involved) is effective in deep pockets of aggressive periodontitis patients. [source]

Microbiological effect of photodynamic therapy (PDT) in healthy volunteers: a comparative study using methyl aminolaevulinate and hexyl aminolaevulinate cream

CLINICAL & EXPERIMENTAL DERMATOLOGY, Issue 6 2007
A. Yung
Summary Background., Acne vulgaris is a common skin problem that affects up to 90% of adolescents. Colonization of the duct with Propionibacterium species is one of the factors implicated in the development of acne. Owing to the increasing incidence of antibiotic resistance, there has been an greater interest in the development of new methods to treat acne. Early studies have shown that photodynamic therapy (PDT) with aminolaevulinic acid (ALA) can lead to prolonged improvement in acne. Newer derivatives of ALA such as methyl aminolaevulinate hydrochloride (MAL) and hexyl aminolaevulinate hydrochloride (HAL) have been developed for use in PDT, with the potential benefits of higher lipophilicity and penetration potential. Objectives., To determine the microbiological effect and tolerability of a single application of HAL-PDT and to compare it with MAL-PDT in healthy volunteers. Methods., This was a randomised double-blind study to examine the microbiological effects and safety of a single application of MAL-PDT and HAL-PDT on normal skin in 18 healthy volunteers. Bacterial skin samples for Propionibacterium spp. and Micrococceae were obtained at baseline and 2, 4, 7 and 14 days. Results., Following PDT with MAL and HAL, a statistically significant transient reduction in mean density of Propionibacterium spp. 2 days after treatment using each agent (P < 0.05 for both) was found. There were no significant changes in mean number of Micrococceae for the duration of the study period. Treatment with HAL-PDT and MAL-PDT was well tolerated. Overall, HAL-PDT was associated with fewer side-effects compared with MAL-PDT (P < 0.01) over the 14 day study period. Conclusion., HAL-PDT and MAL-PDT transiently reduce density of Propionibacterium spp. density to a similar degree in normal healthy individuals. The transient reduction in Propionibacterium spp. suggests that the prolonged antiacne effect of PDT relies on factors independent of bacterial density. HAL-PDT appears to be better tolerated than MAL-PDT. [source]