Effect of calcium hydroxide pastes on uninstrumented canal wall studied with scanning electron microscopy

Calcium hydroxide (Calpha(OH)2) paste has been used as a root canal dressing for long time and promotes healing of vital pulp and periapical tissues. The aim of this study was to evaluate the dissolving effect of calcium hydroxide paste mixed with different vehicles on uninstrumented canal walls using scanning electron microscopy (SEM). Twenty one recently extracted single-root teeth were used. The crowns were removed and the root sections were divided longitudinally into two halves. The pulp tissue was removed and the specimens were randomly divided into 7 groups. The control group was immediately fixed without any treatment. The canals in the other groups were filled with the different calcium hydroxide pastes: group 1 (n = 6), with saline solution; group 2 (n = 6) with propylene glycol; group 3 (n = 6) with propylene glycol and camphorated p-monochlorophenol; group 4 (n = 6) with sodium hypochlorite; group 5 (n = 6) with chorhexidine 1%, group 6 (n = 6) with iodine potassium iodide 0.1/0.2%. The specimens were kept in an incubator at 100% humidity and 37 degrees C, removed after 14 days, and washed ultrasonically for 10 min. Then they were fixed with glutaraldehyde and examined with scanning electron microscopy The percentage of organic remains and paste were evaluated and scored. The data were analyzed using the Kruskal- Wallis test. In groups 1, 5 and 2 there were more cavities without organic remains than in the other groups (p < 0.05). However, there was no difference among them (p > 0.05). The paste in group 3 cleaned only 5%. In groups 4, 6 and 7 (control) the canals walls were wholly covered with fiber, cells, and residual paste, the percentage cleaned was 0. This study shows that Calpha(OH)2 pastes with saline solution, with chlorhexidine and with propylene glycol have a greater dissolving effect on the canal walls than the other pastes evaluated.