In situ and in vitro effects of bleaching with carbamide peroxide on human enamel.

This study evaluated in vitro and in situ the potential adverse effects of 10% carbamide peroxide on human enamel using microhardness, calcium loss and surface morphology analysis. Twenty-four enamel slices (4 mm2) were obtained from recently extracted premolars. The specimens were polished under water-cooling down to 1,200-grade sandpaper. After initial microhardness readings (100 g), the specimens were randomly divided into two groups for in situ and in vitro conditions. The specimens were covered with 10% carbamide peroxide for eight hours. After removing the bleaching gel, the in vitro specimens were stored in deionized water and the in situ specimens, included in an intra-oral appliance, were placed in the oral cavity of four volunteers. These cycling sequences took place for 14 days. Upon conclusion of the bleaching treatment, new microhardness readings were performed on all specimens. Calcium dosage was assessed from the bleaching gel collected after initial exposure on day one, then from gel collected between days two and seven and gel collected between day eight and 14 using an atomic absorption spectrophotometer. Surface morphology was observed from two non-treated control specimens and two specimens of each experimental bleached group under SEM evaluation. Statistical analysis (ANOVA and Tukey tests) disclosed that specimens bleached in situ showed similar microhardness to unbleached specimens and had statistically higher (p < 0.01) hardness than in vitro bleached specimens. The loss of calcium in the in vitro situation at 14 days was 2.5 times higher than the in situ condition. SEM micrographs demonstrated that surface alterations were more pronounced in the in vitro condition. The adverse effects of carbamide peroxide on enamel were evident in specimens bleached in vitro but were not seen in situ. The presence of saliva could prevent the demineralizing effect of bleaching gel in situ.

Expression of NO-synthase in cells of foreign-body and BCG-induced granulomata in mice: influence of L-NAME on the evolution of the lesion.

The microbicidal activity of macrophages in an inflammatory milieu has been related to the production of a large number of cytokins and intermediary metabolites of oxygen and nitrogen among them, nitric oxide (NO). Considering that granulomatous inflammation is predominantly composed of macrophages and epithelioid cells, we decided to investigate the participation of NO in this peculiar type of inflammation. Two models were used: glass cover slip implantation into the subcutaneous tissue of mice and, the inoculation of live bacillus Calmette-Guérin (BCG) into the footpad of the animals. Using a histochemical method for the detection of NO synthase and of the concentration of citrulin metabolized by cells obtained from cover slips implanted on different time intervals or BCG-activated peritoneal cells, it was possible to demonstrate that epithelioid cells do not produce NO. Cells from granuloma induced by BCG inoculation express NO synthase, with different degrees of reactivity with a higher intensity in the cytoplasm of cells located in the edge of the lesions. The expression of NO synthase in the cytoplasm of these cells decreases with the age of the lesions. It could also be demonstrated that in mice treated with l-name, an inhibitor of NO metabolism, the lesions induced by BCG lost the granulomatous architecture, were necrotic, and had a significant increase in the bacillary load of the lesion. These data allow us to conclude that NO production by macrophages is a determining factor in the organization of the granulomatous lesion and that it also controls the bacterial load in BCG-induced lesions in mice.

In vitro study of enamel erosion caused by soft drinks and lemon juice in deciduous teeth analysed by stereomicroscopy and scanning electron microscopy.

The erosion caused in vitro by cola-type and guaraná-type beverages (the latter is a soft drink sold in Brazil), and a canned lemon juice on the enamel of human deciduous teeth was analyzed. Morphological analysis of affected enamel was done using stereomicroscopy and scanning electron microscopy (SEM). The harmful effect of all test products on deciduous enamel was clearly demonstrated. Stereomicroscopy showed loss of gloss and an alteration in normal color of enamel, with irregular loss of dental tissue in variable degrees. Such a loss became more serious as the time of incubation increased. Different degrees of solubilization of enamel prisms were demonstrated by SEM, affecting initially the sheaths and the heads of prisms and later their tails. Areas of erosion increased in proportion to the time of incubation. All the products showed a great erosive potential on human deciduous dental enamel.

Influence of long-term treatment of the rat with clebopride on the morphology of the mammary gland.

The substituted benzamides or orthopramides are used to treat gastrointestinal and psychotic disorders. The orthopramide clebopride, a potent dopaminergic antagonist, blocks emesis in dogs and stereotyped behavior in rodents. Since the release of prolactin is inhibited by dopamine, antidopaminergic drugs may be useful to increase lactation in nursing mothers. The present work examines the morphological and histological alterations produced by long-term treatment of puerperal and virgin female rats with clebopride. Clebopride induced significant hyperplasia of parenchymal secretory units and stimulated milk secretion in both groups of rats. However, only in virgin rats was mammary weight significantly increased.