Morphological analysis of the enamel organ in rats treated with fluoxetine

Purpose: Previous studies have evaluated the presence of serotonin in the dental epithelia and mesenchyme during odontogenesis, suggesting its participation in tooth development. Materials and methods: Here, we used fluoxetine, a selective serotonin re-uptake inhibitor, at a dose of 10 mg/kg, administered for 20 days during pregnancy in 12 Wistar rats to examine the influence of this drug on the development of the enamel organ of the upper first molars of rat fetuses at 17 days of intra-uterine life (i.u.l.), and at one, five and ten days postpartum. The pregnant rats were anesthetized with xylazine at 10 mg/kg and ketamine at 25 mg/kg. The fetuses were removed and beheaded; their jaws were removed, and the upper jaws were exposed. The tissues were fixed in Bouin's fixative, decalcified in 5 percent nitric acid for 4 - 12 h, conventionally processed for microscopy, and embedded in paraffin. Serial sections of approximately 5 mm were obtained and stained with hematoxylin and eosin, as well as periodic acid-Schiff. Results and conclusion: Morphological analysis showed no structural changes in the experimental group compared to the controls, suggesting that, at the dose used, fluoxetine does not interfere with serotonin-mediated development of the enamel organ or the process of amelogenesis.

A histomorphometrical study of the effects of ethanol on enamel formation in rat mandibular molars during pregnancy

The consumption of alcohol during pregnancy causes fetal congenital malformations, including craniofacial and orodental defects, as a result of interference with normal embryonic development. In this work, we examined the effects of alcohol on tooth development and enamel formation in rats. Alcohol was administered to female rats in the drinking water starting at a concentration of 1% followed by weekly increases to 5%, 10%, 15%, 20% and 25%. In the seventh week, the rats were mated and continued to receive 25% alcohol until delivery. On postnatal day 5, three offsprings of each mother were killed and their hemimandibules removed, processed and embedded in araldite. Sections 1 µm thick were cut and stained with 1% toluidine blue and histomorphometric analysis of the dental germ and enamel matrix was done. During the postnatal period, the body weights of the offspring from treated dams were significantly smaller than the controls. In addition, the relative volumes of the tooth germ and enamel matrix were always smaller in the offspring of dams treated with alcohol. These results indicated that the ingestion of alcohol during pregnancy interfered with the development of the tooth germ and the secretion of the enamel matrix.

Are there structural alterations in the enamel organ of offspring of rats with alloxan-induced diabetes mellitus?

A hipoplasia de esmalte é a mais comum dentre as alterações de desenvolvimento do dente humano, e ocorre com freqüência em dentes decíduos de filhos de mães diabéticas. O presente estudo experimental analisou, por meio de microscopia óptica e morfometria, o órgão do esmalte de incisivos inferiores de filhotes de ratas com diabetes aloxânico, induzido previamente à gestação. Os resultados mostraram que não foram observadas pela microscopia óptica alterações significantes nos germes dentais dos animais descendentes de ratas diabéticas, com exceção de um caso. A análise morfométrica dos órgãos do esmalte de ratos nascidos de mães diabéticas tratadas e não tratadas evidenciou as seguintes diferenças estatisticamente significantes: menor espessura da matriz de esmalte, menor altura dos ameloblastos e área de seus núcleos. Nos animais nascidos de ratas diabéticas tratadas, observou-se núcleos dos ameloblastos mais elípticos e aumento da área correspondente ao interstício do retículo estrelado. Estes resultados indicam que há alterações estruturais no órgão do esmalte de descendentes de ratas com diabetes aloxânico as quais poderiam induzir a hipoplasia do esmalte dental visto por microscopia eletrônica de varredura, possivelmente refletindo as alterações metabólicas observadas nesta condição. Estudos futuros devem ser realizados a fim de determinar se estas alterações são transitórias ou permanentes.

Amelogenina, amelogênese imperfecta e estrutura do esmalte dental / Amelogenin, amelogenesis imperfecta and enamel structure

O presente artigo discute os recentes avanços na área de biologia molecular e suas implicaçöes na medicina e odontologia. Os autores fazem uma análise de gene da amelogenina, que é a principal proteína implicada na formaçäo do esmalte dental, correlacionando a expressäo dessa molécula com a etiologia da amelogênese imperfecta, assim como sua importância nas características físicas e na estrutura do esmalte dental

Kinetics of labelled precursors incorporated in the enamel matrix during amelogenesis as shown by radioautography

The kinetics of (3)H-tymidine and (3)H-proline incorporated by ameloblasts and enamel, were studied in undecalcified mouse incisors from birth to 6 days of age. Serial cross sections of unfixed right incisors were cut with a cryotome. The left incisors were fixed in paraformaldehyde, embedded in polybed as to get sagital 1 mum-thick sections. (3)H-thymidine was used to determine the apparent daily migration rate of ameloblasts, which was 513 mum in the unfixed sections and 610 mum/p.d. in the fixed ones. The semi-thin epon-embedded sections were also used to measure the lengths of the regions of the secretory and post-secretory zone of amelogenesis and to determine their growth during the experimental period. (3)H-proline was used to show the fate of the enamel proteins by correlating the radiactivity, determined by silver grain counts, with the migration rate of the ameloblasts. The results showed that the (3)H-proline labeled protein reached a peak of radiactivity at 4 h over ameloblasts and between 24 and 48 h after injection over enamel. In the unfixed section of the righ incisor a second peak of reaction was shown at48 h over ameloblasts and at72 h over enamel matrix. All these peaks were related to ameloblasts and enamel of the secretory zone. These results were interpreted as the evidence of reabsorption and reutilization of labeled proteins broken down in the young enamel, but may also be explained as secretion of low molecular weight proteins which are not kept by fixation. Another evidence of reutilization of labeled compounts for the biosynthesis of enamel proteins were given by the labeling of ameloblasts and enamel formed after birth at a considerable time after the pulse of (3)H-proline.