Necrosis of cementum induced by root canal treatments in the molar teeth of rats

Abstract

In order to study the causes and evolution of cementum necrosis, root canal treatment was carried out in the mesial root of the first left lower molar in 154 white rats. Animals were sacrificed from 3 to 90 days after treatment. Histological studies allowed the following conclusions to be drawn: 1. 1. Cementum necrosis due to the chemical irritation provoked by the filling material employed, and to the toxic bacterial action of detritus caused by instrumentation, was seen extending outwards from the cementodentinal junction. Necrosis became more severe as dentine thickness decreased. 2. 2. In specimens showing infarct necrosis of the periodontal ligament, or periapical abscess, necrosis of the cementum started from the periodontal surface and spread towards the cementodentinal junction. 3. 3. Resorption of the necrotic cementum was frequently observed, causing, in some instances, total removal of cementum and dentine in the apical zone. 4. 4. When the cause provoking the necrosis was not persistent and the periodontal ligament was normal, apposition of new cementum over necrotic cementum was seen occasionally.