The calcifying potential of the pulpless open apex in untreated teeth of dogs.

Pulpectomies were performed on 22 immature premolars (44 root canals) from 3 young dogs. The root canals remained unfilled and the access cavities were sealed with amalgam. After observation periods of 7, 15 and 45 days, the apical and periapical regions of the teeth were evaluated histopathologically. Hard tissue formation was found in 32 open apices. The apical calcification occurred only in specimens with intracanal vital tissue. The severity of periapical inflammatory response had no relationship to the presence or absence of apical hard tissue formation. No apical bridging was seen in specimens where epithelial proliferation had occurred.