Electronic root canal length measurement before and after experimentally induced pulpitis and apical periodontitis in dogs.

The aim of the study was to examine the influence of the state of the pulp and apical periodontium on the results of electronic root canal length measurement (ERCLM) with a resistance measuring device in dogs. Pulpitis and apical periodontitis were induced by pulp exposure and contamination by the oral flora in the premolar teeth of six mongrel dogs, comprising four experimental groups (36 root canals). In a control group, measured lengths of teeth with uninfected pulps were performed on the first experimental day (44 root canals). In all animals the ERCLMs were performed on teeth with healthy pulps, and at the end of the experimental period (20, 35, 50 and 65 days) following pulp exposure. The point of measuring canal lengths was the anatomical obstacle above the apical delta. Electronically measured lengths (EML) were compared between each other and with the root canal length established by tactile-sense measurement verified radiographically. The EMLs were less accurate in teeth with healthy pulps and teeth with pulpitis in the third experimental group (dif=2.27 x 2.65 mm(2); t test, p<0.05), while they were most precise after 65 days in teeth with completely necrotic pulp and established chronic apical periodontitis (dif=0.54 x 1.36 mm(2); t test, p>0.05). These results suggest that the state of the pulp and periapical tissue may have an influence on the ERCLM.