Effect of a Toothpaste for Sensitive Teeth on the Sensitivity and Effectiveness of In-office Dental Bleaching: A Randomized Clinical Trial.

OBJECTIVES: The present study aimed to evaluate the desensitizing effect of toothpaste for sensitive teeth on patient tooth sensitivity and on bleaching efficacy of the 38% hydrogen peroxide bleaching agent used for in-office bleaching compared to a regular toothpaste in a randomized clinical trial. METHODS AND MATERIALS: Forty-eight patients having maxillary right central incisors with darkness greater than A1 were selected for the present double-blind randomized clinical trial. Patients were randomly allocated into two groups: the placebo group, which used regular toothpaste, and the experimental group, which used sensitivity toothpaste. The intervention consisted of applying toothpaste with the aid of an individual tray for a period of 4 minutes daily, starting one week before the first bleaching session and interrupting use immediately after the second session. After allocation to one of the groups, individuals received in-office dental bleaching with a 40-minute application of 38% hydrogen peroxide for two sessions with an interval of one week. The incidence and intensity of sensitivity were assessed using a visual analogue scale and a numeric analogue scale. Sensitivity was measured immediately before each session, 1 hour, 24 hours, and 48 hours after each bleaching session and four weeks after the second bleaching session. Tooth shade was evaluated using a spectrophotometer and by comparison with the VITA Classical Shade Guide (Vita Zahnfabrik, Bad Säckingen, Germany). Tooth shade was evaluated before the first bleaching session, one week after the first bleaching session, one week after the second bleaching session and four weeks after the second bleaching session. Participants and professionals who performed the bleaching, shade, and sensitivity assessments were blinded to the group of patients they were treating or assessing. For the incidence of hypersensitivity, the results were evaluated by comparing the groups at different evaluation times with the Mann-Whitney test for comparison between groups, the Friedman test for repeated measures, and the Tukey test for comparison of times. Shade change on the guide was analyzed using the Mann-Whitney test for comparison between groups and the Wilcoxon test for comparison between times. Shade change by the spectrophotometer was analyzed using the t-test for comparison between groups and the paired t-test for comparison between times. All analyses were performed with a significance level of 5%. RESULTS: There was no difference in the pattern of dental hypersensitivity between groups. For all shade measures, there was no difference between the bleaching results, and no statistically significant difference was observed between the study groups. CONCLUSION: The use of arginine-based desensitizing toothpaste did not interfere with the bleaching ability of hydrogen peroxide and was not effective in reducing the sensitivity caused by in-office tooth bleaching.

A comparison of virulence patterns and in vivo fitness between hospital- and community-acquired methicillin-resistant Staphylococcus aureus related to the USA400 clone.

Methicillin-resistant Staphylococcus aureus (MRSA) isolates genetically related to the CA-MRSA clone MW2/USA400 (ST1-SCCmecIV lineage) from the United States have emerged in hospitals in Rio de Janeiro and are associated with nosocomial bloodstream infections. To understand the virulence mechanisms involved in the adaptability of ST1 isolates as a hospital pathogen in Rio de Janeiro, we compared the virulence traits and fitness properties of the Brazilian isolates with those displayed by the CA-MRSA isolates from the United States. Similar to the USA400 from the United States, all the Brazilian isolates tested carried the genes encoding SEH and LukDE. In contrast, none of the Brazilian isolates carried the lukSF PVL, sea, sec, and sek genes. Competition experiments in mice demonstrated a significant increase in the fitness for the CA-MRSA isolates MW2 and USA400-0051 from the United States compared to other isolates. In the foreign body animal model, 83 % more North-American bacterial cells were recovered compared to the Brazilian ST1 isolates. Differences in gene expression of important virulence factors were detected. Transcription of rnaIII and psmα3 was increased about two-fold in the isolates from the United States, and sasG about two-fold in the Brazilian isolates. Thus, it is possible that the virulence attenuation observed among the Brazilian hospital isolates, associated with the acquisition of multiple resistant determinants, are consequences of microevolutionary events that contributed to the necessary fitness adjustment of this lineage, allowing a typically community-acquired MRSA (MW2/USA400) to emerge as a successful hospital pathogen (Brazilian ST1-SCCmecIV).

Virulence characteristics of genetically related isolates of group B streptococci from bovines and humans.

The present study had the objective of evaluating the pathogenic potential of the genetically related strains of Streptococcus agalactiae no. 80427 (human origin) and no. 87159 (bovine origin), and comparing the results with two other strains isolated from bovine mastitis (no. 87244) and invasive human infection (no. 90356), with no genetic or epidemiologic relationship between them or with the first 2 isolates. Virulence genes hylB (hyaluronidase) and lmb (laminin-binding protein) were detected in the 4 strains, and genes bac (beta protein) and bca (alpha protein) were only detected in human strains. The protein profile obtained using SDS-PAGE did not indicate any differences between the 4 strains. No significant difference was detected between human and bovine strains in the assays of adherence to and invasion of 16HBe cells, as well as in the resistance assay for intracellular bacterial survival in macrophages. However, the strain 87159 exhibited a greater survival in the killing test with whole human blood and was more virulent in newborn mice than the 80427 strain. The strain 87244 was not virulent in mice. These data suggest that isolates of human and bovine origins may express similar virulence attributes, leading to a possible, however limited, dissemination.

Bacteroides fragilis induce necrosis on mice peritoneal macrophages: In vitro and in vivo assays.

Bacteroides fragilis is an anaerobic bacteria component of human intestinal microbiota and agent of infections. In the host B. fragilis interacts with macrophages, which produces toxic radicals like NO. The interaction of activated mice peritoneal macrophages with four strains of B. fragilis was evaluated on this study. Previously was shown that such strains could cause metabolic and morphologic alterations related to macrophage death. In this work propidium iodide staining showed the strains inducing macrophage necrosis in that the labeling was evident. Besides nitroblue tetrazolium test showed that B. fragilis stimulates macrophage to produce oxygen radicals. In vivo assays performed in BalbC mice have results similar to those for in vitro tests as well as scanning electron microscopy, which showed the same surface pore-like structures observed in vitro before. The results revealed that B. fragilis strains studied lead to macrophage death by a process similar to necrosis.