Histological periapical repair after obturation of infected root canals in dogs.

Histological periapical healing of infected roots obturated in one-step or with prior calcium hydroxide (Ca(OH)2) disinfection was compared. Seventy-two roots of vital dog teeth were instrumented to ISO size 45. Sixty roots were infected with dental plaque and closed. Six weeks later, apical periodontitis was radiographically confirmed in the infected roots. The teeth were divided into the following groups: group 1, one-step (n = 24)-roots were irrigated with 10 ml of saline, obturated, and permanently restored; group 2, Ca(OH)2 (n = 24)-roots were treated as in group 1, except that after saline irrigation, Ca(OH)2 dressing was placed in the canal for 1 wk before obturation; group 3, positive control (n = 12)--the roots were irrigated with saline, but the canals were not obturated; and an additional group, group 4, served as a negative control (n = 12)--these teeth that were not infected with plaque were aseptically obturated. The dogs were sacrificed after 6 months. The roots and surrounding apical tissues were prepared and histologically examined by two independent evaluators blinded to the treatment groups. A two-way ANOVA test demonstrated that the four treatment groups were significantly different from one another. The positive control showed the most inflammation, the negative control the least, and the Ca(OH)2 group had significantly less inflammation than the one-step group (p < 0.05). It is concluded that Ca(OH)2 disinfection before obturation of infected root canals results in significantly less periapical inflammation than obturation alone.