2007 Volume 50 Issue 2 Pages 266-276
This study experimentally investigated the histopathological influence of the root canal open space following pulp removal in monkey teeth on the periapical and intracanal healing. Twenty fully developed maxillary and mandibular multirooted posterior teeth in a crab-eating monkey (Macaca irus) were used for this experiment. Pulp removal procedures were performed under general and local anesthesia, while using a rubber dam for all teeth. The root canal length was determined by using an electronic device (Endodontic Meter S, Onuki). After the canals of teeth were prepared on the apex, in most of them penetration a small-size reamer was done approximately 1.0mm beyond the apex. The canals were then irrigated alternately with 6% sodium hypochlorite (Purelox®) and 3% hydrogen peroxide, and sterile saline was used for washing. Sterile cotton pellets were placed in the canal orifices. All the cavities were carefully lined with zinc phosphate cement and then sealed with Clearfil Posterior® (Kuraray). The teeth were radiographed. Thirty-one months after the experiment, the animal was killed with intracardiac injections of 10% formalin. After decalcification by 20% formic acid, serial paraffin sections were cut at 8μm and stained with hematoxylin eosin and Gram stained for light microscope observation. The results were as follows: 1. In many teeth there were radiographically visible pathological changes. A widespread diffusely demarcated radiolucency was sometimes seen around the periradicular areas of mandibular molars 31 months later. In some cases of apical radiolucency, bone sclerosis appeared surrounding the entire periapical radiolucency. 2. In many teeth granulation tissue bridges had grown into or through the dead space of an unfilled root canal. 3. Most of the teeth developed root resorption which correlates with the presence of chronically inflamed granulation tissue. Maxillary third molars exhibiting slight root resorption showed the deposition of calcific repair tissue, called osteodentin, within the empty canal extending into the pulp chamber floor. 4. The top of the invaded granulation tissue in the apical canal became necrotic and there were infections in many teeth. Colonies of microorganisms with inflammatory cell infiltration of polymosphonuclear leukocytes in the necrotic tissue area were observed. 5. Pathological diagnosis of the radicular lesions was thought to be granuloma or chronic abscess in many cases.
