PULPAL AND PERIAPICAL TISSUE-REACTIONS AFTER EXPERIMENTAL PULPAL EXPOSURE IN RATS

The purpose of this study was to investigate histologically and histom etrically the changes in pulpal and periapical tissues after pulpal ex posure in rats. All animals received a pulpal exposure in the left man dibular first molar. Animals were killed at 1 to 56 days after pulpal exposure, and their mandibles were evaluated histologically and histom etrically. Histologically, pulpal necrosis extended gradually from the upper part of the pulpal tissue to the apex, with inflammation starti ng in the periapical tissue at an early stage. As the periapical lesio n developed, alveolar bone and cementum resorption was also found. His tometrically, the length of pulpal necrosis increased gradually from 1 to 28 days. The vertical length of the periapical lesion after 14 day s was significantly increased, while the horizontal length and the ove rall area after 7 days were also significantly increased. The periapic al lesion extended in a mesiodistal direction at first and then in a v ertical direction before expansion ceased.