Effectiveness of different excavation methods on removal of artificially demineralized dentin

The aim of this study was to evaluate the effectiveness of three mechanical methods for removal of demineralized dentin. A total of thirty sound human third molars indicated for extraction. After extraction, the teeth were cleaned and stored properly. The occlusal enamel was removed with a diamond wheel to expose a flat dentin surface, and each tooth was sectioned longitudinally in the buccal-lingual direction. One half of each tooth was entirely covered with an acid-resistant varnish, except for an occlusal area of 16 mm2, and was submitted to pH-cycling model to produce demineralized dentin. The other half of each tooth was maintained with mineralized dentin. The pH-cycling procedure was taken in 8 days. Halves of teeth were reassembled with cyanoacrylate adhesive. Samples were randomly allocated into three groups according to the method of removal of demineralized dentin: G1 – steel bur, G2 – polymer bur; G3 – hand excavation. The procedure of demineralized dentin removal was performed by a single operator. Digital images were obtained and cavities depths were measured (µm) using MacBiophotonics ImageJ software. Knoop microhardness measurements (kgf/mm2) were performed in all samples at 10 to 200 µm depth from the bottom of cavities. Data for cavity depth and microhardness were analyzed using One-Way ANOVA and the post hoc tests (p<0.05). The steel bur provided a larger wear, resulting in a deeper depth after the removal of the demineralized dentin, followed by the hand excavator and the polymer bur had a lower depth. The hardness values obtained with the steel bur were higher, indicating that there was a higher standard of demineralized dentin removal, followed by the hand excavator. The use of polymer bur left dentin with low values of hardness, indicating that demineralized tissue still remained. The polymer bur looks to be more selective in the removal of the demineralized dentin when compared with the steel bur and the hand excavator.O objetivo do estudo foi avaliar a efetividade de três métodos mecânicos na remoção de dentina desmineralizada. Utilizaram-se 30 terceiros molares humanos hígidos, indicados para extração. Após a extração, os dentes foram devidamente limpos e armazenados. Removeu-se o esmalte oclusal com um disco de diamante para expor uma superfície plana de dentina e seccionou-se cada dente longitudinalmente, no sentido vestíbulo-lingual. Uma metade de cada dente foi totalmente coberta com um verniz ácido resistente, com exceção de uma área oclusal de 16 mm2, e submetida à ciclagem de pH para produzir dentina desmineralizada. A outra metade de cada dente foi mantida com a dentina mineralizada. A dentina desmineralizada foi criada por meio de procedimento de ciclagem de pH durante 8 dias. As metades dos dentes foram unidas novamente com adesivo de cianoacrilato. Alocaram-se aleatoriamente as amostras em três grupos, segundo o método de remoção da dentina desmineralizada: G1 – broca de aço esférica; G2 – broca de polímero; G3 – cureta de dentina. Um único operador realizou o procedimento de remoção de dentina desmineralizada. Após a remoção da dentina, as metades dos dentes foram separadas, incluídos em resina acrílica e polidas. As imagens digitais foram obtidas e as profundidades das cavidades foram medidas (µm) com o uso do programa MacBiophotonics ImageJ. Realizaram-se medidas de dureza Knoop (kgf/mm2) em todas as amostras de 10 a 200 microns a partir do fundo das cavidades. Os dados de profundidade da cavidade e microdureza foram analisados utilizando One-Way ANOVA e os testes post hoc (p