Abstract This study was designed to investigate the resistance to dislodgment provided by MTA HP, a new high-plasticity calcium silicate-based cement. Biodentine and White MTA Angelus were used as reference materials for comparison. Three discs 1 ± 0.1 mm thick were obtained from the middle third of the roots of 5 maxillary canines. Three 0.8-mm-wide holes were drilled on the axial surface of each root disc. Standardized irrigation was performed. Then the holes were dried with paper points and filled with one of the three tested cements. The filled dental slices were immersed in a phosphate-buffered saline (PBS) solution (pH 7.2) for 7 days before the push-out assessment. The Kruskal-Wallis test was applied to assess the effect of each endodontic cement on the push-out bond strength. Mann-Whitney with Bonferroni correction was used to isolate the differences. The alpha-type error was set at 0.05. All specimens had measurable push-out values and no premature failure occurred. There were significant differences among the materials (p <0.05). The Biodentine specimens had the highest push-out bond strength values (p < 0.05). MTA HP had significantly higher bond strength than White MTA (p < 0.05). MTA HP showed better push-out bond strength than its predecessor, White MTA; however, Biodentine had higher dislodgment resistance than both MTA formulations.
O objetivo do presente estudo foi avaliar as alteracoes morfologicas relacionadas com a idade em canais radiculares mesial de primeiros molares inferiores. Cinquenta e seis especimes foram selecionados para este estudo. Os especimes foram distribuidos em quatro grupos etarios (n. 14): a) Grupo de criancas menores de 13 anos, b) grupo de adolescentes (de 14 a 19 anos), c) Grupo de jovens adultos (de 20 a 39 anos ) e d) Grupo de adultos (acima de 40 anos). Apos as extracoes os elementos foram cuidadosamente limpos, esterilizados, identificadas e armazenadas em agua. A fim de melhorar a limpeza, foram colocados numa solucao de hipoclorito de sodio a 1%, durante quatro horas e enxaguados em 10 vol. peroxido de hidrogenio durante 8 horas. Depois, uma tecnica de diafanizacao foi realizada para ilustrar a anatomia do canal radicular. As imagens digitalizadas de todas as amostras foram obtidas atraves da utilizacao de um estereoscopio. Os canais foram visivelmente mais simples em adultos mais velhos: eles foram bem definidas e estreito, por vezes, demasiado estreito. Nucleo de calcificacao nao foi encontrado e havia apenas alguns restos de espacos internucleares. O sistema de canal apareceu mais limpa, mais clara e mais bem definida do que nas outras faixas etarias. Pode-se concluir que ha uma correlacao entre as alteracoes do envelhecimento e morfologicas nos canais radiculares mesial de primeiros molares inferiores.
The aim of this study was to evaluate age-related morphological canal changes in mesial root canals of mandibular first molars of known ages. Fifty-six specimens were selected for this study and distributed into the following four age groups (n. 14): a) Group of children under 13 years, b) Group of adolescents (from 14 to 19 years), c) Group of young adults (from 20 to 39 years) and d) Group of older adults (over 40 years). The specimens were in perfect condition because after extraction they were carefully cleaned, sterilized, identified and stored in water. In order to improve the cleaning, they were placed in 1% sodium hypochlorite solution for four hours and rinsed in 10 vol. hydrogen peroxide for 8 hours. After that, a clearing technique was performed to illustrate root canal anatomy. Digitalized images of all samples were obtained by use of a stereomicroscope. Canals were noticeably simpler in older adults: they were sharply defined and narrow, sometimes too narrow. Calcification nuclei were not found and there were only a few remains of internuclear spaces. The canal system appeared cleaner, clearer and more sharply defined than in the other age groups. It may be concluded that there is a correlation between aging and morphological changes in the mesial root canals of mandibular first molars.