In patients, root canal treatments are often done when the pulp has become infected or necrotic. In this animal study, pulps are surgically exposed and bacteria introduced. Bacterial by-products will then leach out of the apical foramina into surrounding bone and cause a reaction by the body. This reaction typically involves loss of bone (resorption), which is visible on dental radiographs. For patients, the appropriate treatment is cleaning and filling of root canals and verifying the result (ideally bone fill) with radiographs. The same techniques will be used in the experiments to treat teeth that have been experimentally infected with bacteria from the animals' own flora.
Ultimately, we expect bone fill-in into the bony lesion. In order for that to happen, bone has to be deposited, enabled by biologic mediators from the surrounding tissues or distant sites that shift the reaction from defense to build-up. Very little is known in this field except for the signal that requests bone-producing cells to start laying down bone (RANK-RANKL). The conditions under which this signal is given and by what entity are not clear; the present experiments are designed to determine the time course of healing and to address the question which mediators play a role in healing.
In the experiments, we will be able to control the conditions of root canal treatment and the overall immune defense of the animals. The tissues will be harvested for microscopic evaluation, including measurement of lesion size and composition of tissues. This will allow us to figure out which of the factors are likely to increase the chance of successful root canal treatments in human patients.