The effect of citric acid on repair after delayed tooth replantation in dogs.

An experimental study of maxillary incisors in dogs was carried out to test the hypothesis that demineralization of denuded root surfaces by citric acid to expose collagen matrix fibrils might improve the rate of periodontal regeneration after replantation of traumatically avulsed and dried teeth, provided that the root surface is not traumatized during replantation or postoperatively. Experimental teeth (group 4) were allowed to dry in air for 45 min. A mid-portion of the root was then root-planed extensively, treated with citric acid for 3 min, rinsed with saline, and replanted. The apical region and a cervical collar were not instrumented, ensuring precise reseating and stability of the tooth during the postoperative period. Control teeth were either replanted immediately (group 1), bench-dried for 45 min and replanted (group 2), or bench-dried and the entire root surface root-planed and acid-treated before replantation (group 3). Histological examination of block specimens after 21 days of healing showed complete periodontal regeneration in group 1 and, by contrast, a high rate of ankylosis, inflammatory resorption, and surface resorption in group 2. Root planing and acid treatment of bench-dried teeth (group 3) did not improve the healing response, whereas the mid-root region of teeth in group 4 showed an absence of inflammatory resorption and less ankylosis than groups 2 and 3. These preliminary observations indicate that the frequency of adverse healing results after delayed replantation can be reduced by removing nonvital soft tissue remnants, demineralizing the root surface, and preventing mechanical trauma to the root surface in the postoperative period.