In Situ and In Vitro Effects of Two Bleaching Treatments on Human Enamel Hardness.

The aim of this study was to evaluate in vitro and in situ the effects of two bleaching treatments on human enamel surface microhardness. Sixty enamel slabs from recently extracted thirty molars were used. The specimens were polished with sandpapers under water-cooling. The enamel samples were randomly divided in four groups, treated with 10% hydrogen peroxide (HP) or Whitening Strips (WS) containing 10% hydrogen peroxide and using two conditions: in vitro or in situ model. For in situ condition, six volunteers wore an intra-oral appliance containing enamel slabs, while for in vitro condition the specimens were kept in deionized water after the bleaching protocols. The bleaching treatments were applied one-hour daily for 14 days. Similar amounts of bleaching agents were used in both conditions. Before and after bleaching treatments, microhardness was measured. Statistical analysis (ANOVA and Tukey test) showed that in the in situ condition there was no statistically significant microhardness reduction in the bleached enamel (p>0.05). Significant decrease in hardness was observed for enamel slabs bleached with both treatments in the in vitro condition (p<0.05). Regarding the bleaching agents, in situ results showed no difference between HP and WS, while in vitro WS produced the lowest hardness value. It could be concluded that there was no deleterious effect on enamel produced by any of the bleaching protocols used in the in situ model. The reduction of hardness was only observed in vitro.

In Situ and In Vitro Effects of Two Bleaching Treatments on Human Enamel Hardness

Abstract The aim of this study was to evaluate in vitro and in situ the effects of two bleaching treatments on human enamel surface microhardness. Sixty enamel slabs from recently extracted thirty molars were used. The specimens were polished with sandpapers under water-cooling. The enamel samples were randomly divided in four groups, treated with 10% hydrogen peroxide (HP) or Whitening Strips (WS) containing 10% hydrogen peroxide and using two conditions: in vitro or in situ model. For in situ condition, six volunteers wore an intra-oral appliance containing enamel slabs, while for in vitro condition the specimens were kept in deionized water after the bleaching protocols. The bleaching treatments were applied one-hour daily for 14 days. Similar amounts of bleaching agents were used in both conditions. Before and after bleaching treatments, microhardness was measured. Statistical analysis (ANOVA and Tukey test) showed that in the in situ condition there was no statistically significant microhardness reduction in the bleached enamel (p>0.05). Significant decrease in hardness was observed for enamel slabs bleached with both treatments in the in vitro condition (p<0.05). Regarding the bleaching agents, in situ results showed no difference between HP and WS, while in vitro WS produced the lowest hardness value. It could be concluded that there was no deleterious effect on enamel produced by any of the bleaching protocols used in the in situ model. The reduction of hardness was only observed in vitro.

Resumo O objetivo deste estudo foi avaliar in vitro e in situ os efeitos de dois tratamentos clareadores sobre a microdureza do esmalte dental humano. Sessenta blocos de esmalte obtidos de trinta molares recentemente extraídos foram utilizados. Os espécimes foram polidos com lixas sob refrigeração com água. As amostras de esmalte foram divididas aleatoriamente em quatro grupos e tratadas com 10% de peróxido de hidrogênio (HP) ou fitas de clareamento (WS) contendo 10% de peróxido de hidrogênio, testadas em duas condições experimentais: in vitro ou in situ. Para o ensaio in situ, seis voluntários foram selecionados e usaram um aparelho intra-oral contendo blocos de esmalte, enquanto que para a condição in vitro, os espécimes foram mantidos em água deionizada após os protocolos de clareamento. Os tratamentos clareadores foram aplicadas durante uma hora/dia durante 14 dias. Quantidades semelhantes de agentes de clareamento foram usadas nas duas condições. Antes e após os tratamentos de clareamento, a análise da microdureza foi realizada. A análise estatística (ANOVA e teste de Tukey) mostrou que, na condição in situ não houve redução estatisticamente significante na microdureza do esmalte clareado (p>0,05). Diminuição significativa na dureza foi observada nos blocos de esmalte clareados, em ambos os tratamentos, na condição in vitro (p <0,05). Em relação aos agentes de clareamento, os resultados in situ não mostraram nenhuma diferença entre a HP e WS, enquanto que in vitro, WS produziu o menor valor de dureza. Conclui-se que não houve nenhum efeito deletério na dureza do esmalte, em nenhum dos protocolos de clareamento ao usar um modelo in situ. A diminuição da dureza foi observada somente na condição in vitro.