This study examined, histologically, the healing of intentionally damaged root surfaces of replanted teeth with either uninfected or infected root canals treated with short- and long-term calcium hydroxide. Thirty beagle dog incisors were randomly divided into four groups. In group 1, uninfected obturated incisors were extracted, the roots were longitudinally grooved and the teeth were replanted within 2 min. In group 2 the root canals were artificially infected followed by extraction, longitudinal grooving, and replantation as described in group 1. Fourteen days after replantation, the root canals were fully instrumented and medicated with intracanal calcium hydroxide. One week later the root canals were permanently obturated with gutta-percha and sealer. The teeth in group 3 were treated as described in group 2 but after 1 wk the calcium hydroxide dressing was repacked for the duration of the study. In group 4 (positive control) the teeth were treated as described in groups 2 and 3 but no endodontic treatment was performed. After 8 wk, sacrifice and histological preparation were carried out. In group 1 complete cemental repair was seen in all teeth. In groups 2 and 3, complete and incomplete cemental repair was seen in seven and two teeth, respectively. An ankylotic area was present in one tooth in group 3. None of the teeth in group 4 showed cemental repair. It was concluded that short- and long-term calcium hydroxide treatment resulted in similar healing patterns when endodontic treatment is initiated 14 days after replantation of teeth.