Effects of induced precocious puberty on cranial growth in female Wistar rats.

This investigation examined the effects of pharmacologically induced precocious puberty on cranial growth in Wistar rats. Forty-eight female newborn Wistar rats were divided into two groups: a control group (C) and an experimental group (E), with four subgroups of six animals each. The time interval from birth until sacrifice differed between the subgroups, and was set at 30, 60, 90, and 120 days. An intramuscular single dose (300 µg) of steroid hormone danazol was administered on day 5 after birth, as a means of inducing precocious puberty. Alizarin (2 mg/100 g) was administered to three animals in each subgroup three days prior to sacrifice. Body mass and dates corresponding to the beginning of the oestrous cycle were recorded. Craniometric measurements were undertaken. Histological analysis using light and fluorescence microscopy was then carried out to qualitatively and quantitatively evaluate the spheno-occipital synchondrosis and to visualize bone deposition patterns. The results were analysed with a Student's t-test and analysis of variance. Precocious puberty was effectively induced and differences between groups denoted an earlier maturation in the experimental rats. In qualitative analysis, a significant increase of total synchondrosis width was noted only in group E60, in comparison with C60, and an increase in the E90 subgroup cortical bone width compared with the C90 subgroup. Histomorphometrically, a statistical difference between total width values of subgroups E60 (434.3 µm) and C60 (323.5 µm) was detected. However, body mass and macroscopic measurements did not show statistically significant differences. An appropriate model for studying bone growth associated with precocious puberty in Wistar female rats was not achieved using steroid hormone danazol, when evaluated at 30 day intervals.

Clareação dentária: revisão de literatura e sua interferência na colagem de braquetes ortodônticos / Tooth bleaching: reviw of literature and interference in orthodontic brackets bonding

A primeira descrição de clareação de dentes escurecidos e não-vitais foi feita em 1864, por Truman. Desde então, várias técnicas de clareação, com o uso dos mais diversos materiais, têm sido descritas e utilizadas por pacientes. A preocupação dos pacientes com a estética dentária, incluindo cor e arranjo dos dentes, vem crescendo consideravelmente, aumentando a possibilidade de pacientes com necessidade de tratamento ortodôntico já haverem sido submetidos a algum tipo de clareação dentária. Objetivo deste trabalho foi realizar uma análise crítica da influência da clareação de dentes vitais sobre a força de adesão ao esmalte. Concluiu-se que existe uma discrepância de resultados encontrados na literatura a respeito da diminuição da força de adesão dos braquetes aos dentes clareados, mas que as alterações causadas pela clareação existem tornando-se necessário um período de, pelo menos, 7 dias de espera para que a colagem dos braquetes ortodônticos seja realizada com maior segurança.