Evaluation of superficial microhardness in dental enamel with different eruptive ages

This study evaluated the superficial microhardness of enamel in teeth at different posteruptive ages (before eruption in the oral cavity, 2-3 years after eruption, 4-10 years after eruption and more than 10 years after eruption). The study sample was composed of 134 specimens of human enamel. One fragment of each tooth was obtained from the flattest central portion of the crown to produce specimens with 3 x 3 mm. The enamel blocks were minimally flattened out and polished in order to obtain a flat surface parallel to the base, which is fundamental for microhardness testing. Microhardness was measured with a microhardness tester and a Knoop diamond indenter, under a static load of 25 g applied for 5 seconds. Comparison between the superficial microhardness obtained for the different groups was performed by analysis of Student's t test. The results demonstrated that superficial microhardness values have a tendency to increase over the years, with statistically significant difference only between unerupted enamel and that with more than 10 years after eruption. According to the present conditions and methodology, it was concluded that there were differences between the superficial micro-hardness of specimens at different eruptive ages, revealing an increasing mineralization. However, this difference was significant only between unerupted specimens and those with more than 10 years after eruption.

A sem study of prismless enamel in non-erupted human deciduos teeth

The frequency, structure, and thickness of the prismless enamel layer in the bucal and lingual surfaces of nonerupted anterior deciduous teeth were described. The samples were fixed in a modified Karnovsky solution, longitudinally fractured in liquid nitrogen and observed by scanning electron microscopy. The aprismatic area was observed in the incisal and perpendicular to the enamel outer surface. Some depressions were observed on the enamel surface. The statistical analysis showed no significant differences related to prismless enamel thickness among upper and lower central incisors, lateral incisors and canines, which varied from 4,19 to 5.15um.

Microscopia eletrônica de varredura da camada de esmalte aprismático de dentes decíduos humanos näo erupcionados / Scanning electron microscopy of prismless enamel layer in human non-erupted deciduous teeth

Avaliou-se o esmalte aprismático em dentes decíduos anteriores näo erupcionados, através da microscopia eletrônica de varredura. A camada aprismática foi observada nas faces vestibular e lingual de todas as amostras, apresentando uma espessura média de 6,2 micrometros. Estruturalmente constituiu-se de cristas de hidroxiapatita dispostos paralelamente entre si e perpendiculares à superfície dental