RADIOGRAPHIC AND MICROBIOLOGIC EVALUATION OF POSTTREATMENT APICAL ANDPERIAPICAL REPAIR OF ROOT CANALS OF DOGS TEETH WITH EXPERIMENTALLY-INDUCED CHRONIC LESION

The objective of the present study was to evaluate radiographically an d bacteriologically apical and periapical repair in dogs' teeth with i nduced chronic periapical lesions with the use of two different operat ive techniques (techniques 1 and 2). The study was conducted on 40 roo t canals of upper and lower premolars from two dogs aged approximately 12 months. Periapical lesions were induced by leaving the root canals exposed to the oral environment for 5 days and then sealing them with zinc oxide-eugenol for 45 days. After this period, radiographic exami nation revealed the occurrence of a radiolucent lesion and endodontic treatment was started. The two techniques did not differ in terms of c hemomechanical preparation, final filling, or type of cement, but diff ered in terms of irrigating solution and the presence of an antibacter ial dressing. Thus 4% to 6% hypochlorite and hydrogen peroxide (10 vol umes) were used in technique 1 during chemomechanical preparation and an antibacterial dressing based on calcium hydroxide was applied betwe en sessions, whereas Dakin's fluid (0.5% sodium hypochlorite solution) and a final filling with no antibacterial dressing were used in techn ique 2. After chemomechanical preparation, the root canals were filled with gutta-percha cones and Sealapex (Sealapex-Sybron, Kerr, Sao Paul o, Brazil), and the animals were killed 270 days after the final filli ng. Blocks were cut into 6-mum sections and stained by the Brown and B renn method. Radiographic, histomicrobiologic and statistical analysis permitted us to conclude the following: radiographically there was a marked reduction or even the disappearance of the radiolucent area pre sent before treatment with greater success in the group treated with t echnique 1 (group I) than in the group treated with technique 2 (group II); the extent of bacterial invasion of dentinal tubules was greater and more intense in group II than in group I; and the amount of micro organisms detected in the ramifications of the apical delta and in the lumen of the root canal was intense in group II and mild or absent in group I.