This in vivo study aimed to compare both antimicrobial effects and influence on periradicular tissue inflammation between nanosilver solution with calcium hydroxide during chronic apical periodontitis treatments.

The cone-beam computed tomography (CBCT) was photographed after the establishment of a chronic apical periodontitis model with 30 double fangs of 3 beagle dogs. Root canals were divided into 3 groups according to the random number table method with 10 teeth for each group, which were sealed into 0.1% nanosilver solution, calcium hydroxide paste or rinsed with 1% sodium hypochlorite alone. The dogs were harvested 4 weeks later and the CBCT was performed again, the area of lesion before and after the intracanal medicament was measured by DCTViewer 2.0; the bacteriostatic depth of root canal and the degree of inflammation of periapical tissue were measured under optical microscope after partial root and periapical tissue stained. The data from each group were compared using the SPSS 24.0 statistical software for the homogeneity of the experimental data and the normality test to compare the area of periradicular lesion, the bacteriostatic depth of root canal, the degree of inflammation of periapical tissue.

The area of periradicular lesion of the three groups decreased than before, the reduction areas were (4.8 ± 3.4) , (1.6 ± 1.6) and (2.2 ± 2.6) mm² in coronal plane with a statistically significant difference between the groups (F = 5.607, P = 0.002) . There was also statistically significant difference between the groups in sagittal plane which were (6.3 ± 3.9) , (4.1 ± 4.6) and (1.3 ± 2.8) mm², (F = 6.869, P<0.001) . The bacteriostatic depth of root canal of the three groups were 243 (159, 372) , 123.5 (90, 134) and 104.5 (81, 135) μm and there was statistically significant difference between these groups (χ² = 18.519, P<0.001) . The inflammation degree of three samples were 0, four samples were 1 and three samples were 2 in the group of 0.1% nanosilver solution. The degree of one sample in calcium hydroxide paste group was 0, five samples were 1, three samples were 2 and one sample was 3, while in the blank group the degree of one sample was 0, three samples were 1, four samples were 2, two samples were 3 with no statistically difference between the groups (χ² = 3.955, P = 0.052) .

0.1% nanosilver solution could promote the healing of periradicular lesions more effectively, had bacteriostasis more effectively in root canal and no significant inflammatory response on periapical tissue.