Changes in anatomic position of root canal orifices in pluriradicular teeth following re-location during endodontic treatment.

Direct access to the root canals in posterior teeth for endodontic treatment is most frequently facilitated by the straightening of the coronal parts of the root canals, having as a consequence the relocation of the canal orifices on the map of the floor of the pulp chamber (Christie and Thompson, 1994). This procedure intentionally moves the coronal aspect of a canal away from the center of the chamber, while simultaneously removing internal dentin from the pulp chamber walls. The aim of this study was to evaluate the displacement resulting from the relocation of root canal orifices during the initial phase of rotary root canal treatment in molars using the dental operating microscope (DOM) and digital image processing. Forty-three molars (17 maxillary and 26 mandibular) belonging to 43 patients (aged 18-62 years) with indications for root canal treatment were endodontically treated. The differences between the initial perimeter and the perimeter of the root canal orifices polygon after relocation varied between 2.7 and 3.4mum (mean 3.0mum), while the differences between the initial area and the area after relocation varied between 2,448,456.8 and 3,249,306.6mum(2) (mean 2,848,881.7). The increase in access to the cavities and the alterations of the pulp chambers can be satisfactorily approximated by the variations of the perimeters and areas of the pulp floor polygons during root canal treatment. From a clinical perspective, these results indicate that there is a significant decrease in tooth substance in molars (except MB2).