Response of human pulps after professionally applied vital tooth bleaching.

AIM: To evaluate in vivo the microscopic pulpal response in sound human premolar teeth subjected to vital tooth bleaching with a 38% hydrogen peroxide (H(2)O(2)) bleaching gel (Opalescence X-tra Boost) catalysed or not by a halogen light source. METHODOLOGY: Twelve pairs of sound maxillary and/or mandibular premolar teeth from 12 to 18-year-old patients were selected and randomly assigned to the following experimental (n = 10) and control (n = 4) groups: group 1: bleaching gel + halogen light; group 2: bleaching gel; group 3: no treatment (control). The teeth were extracted 2-15 days after bleaching and were subjected to routine laboratory processing for histological analysis of the pulpal response under light microscopy. RESULTS: In almost all specimens of the experimental groups, the pulp tissue exhibited histological characteristics of normality. Only one specimen in each group exhibited some dilated and congested blood vessels among a discrete number of mononuclear inflammatory cells in the peripheral pulp region related to the buccal surface of the tooth. These specimens had a slight disruption to the odontoblastic layer, which characterized discrete tissue disorganization. Some deposition of reactionary dentine occurred in only one specimen of group 2. CONCLUSIONS: Professionally applied vital tooth bleaching with a 38% H(2)O(2) gel with or without activation by a halogen light source did not cause damage to the pulp tissue of sound human premolar teeth.

Discharge of the nile river: a barometer of short-period climate variation.

Eight events of climate variation with durations of the order of 100 years have been found in the history of annual Nile River discharge dating from the year 622. They cease during the "little climatic optimum" in the North Atlantic and then reappear and intensify; this behavior suggests that control is from the belt of the polar westerlies.