Root Canal Wall Dentin Structure in Uninstrumented but Cleaned Human Premolars: A Scanning Electron Microscopic Study.

INTRODUCTION: Conventional endodontic treatment includes instrumentation of the canals in most cases to size #25/.06 or larger, which changes the original canal wall anatomy. In recent years, energy-driven equipment, such as photon-induced photoacoustic streaming (Fotona LLC, Dallas, TX) and a multisonic GentleWave system (Sonendo Inc, Laguna Hills, CA), have been introduced to facilitate cleaning of minimally instrumented canals or even uninstrumented canals. The purpose of this study was to examine root canal wall anatomy in premolar teeth cleaned by a noninstrumentation method after #10 K-file patency examination.

METHODS: Twenty-four freshly extracted human premolars were accessed, and patency was established by a #10 K-file. Seventeen teeth were treated by the GentleWave system using 3% sodium hypochlorite, and 7 untreated teeth served as negative controls. The dentin surface in the coronal, middle, and apical thirds of the root canal was examined by scanning electron microscopy after tooth splitting. The canal wall structures were assessed using a predefined scale of 4 parameters: calcospherites, surface irregularities, dentinal tubule openings, and tissue debris.

RESULTS: A clean surface of mineralized dentin was exposed with no organic tissue remnants or debris left in the root canal system, including the isthmus areas between the 2 canals. The uninstrumented root canals showed an irregular dentin structure in many areas, including previously unreported fingerlike projections. The isthmus areas had no or only a few dentinal tubule openings. The dentin structures were well preserved in the test group, whereas in the untreated control teeth tissue debris covered most of the dentin surface.

CONCLUSIONS: Root canal wall dentin in premolars cleaned with a noninstrumentation method showed a wide structural variety, especially in the middle and apical region. No organic tissue remnants or dentin debris were detected.