Observation of depth and incidence of the mesial groove between the mesiobuccal and mesiolingual orifices in mandibular molars.

The purpose of this study was to analyze the mesiolingual-mesiobuccal groove indentations at the pulpal floor in mandibular first and second molars. The depth and incidence of occurrence were assessed. Sixty freshly extracted, mature teeth were kept in a 2.5% sodium hypochlorite for 5 to 7 days. The teeth were accessed without touching the floor of the chamber. The dental debris was washed thoroughly and then the patency and the presence of two mesial canals were established with a #10 file. The teeth were placed in 2.5% sodium hypochlorite for 3 to 5 days and later rinsed and air-dried before placement in centrifuge tubes. A vinyl polysiloxane impression material was injected into the chambers, and the teeth were centrifuged. The impressions were carefully removed and then measured by using a dissecting microscope and a transparent millimeter ruler. The ruler, at zero, placed at the mid-floor area of the impression and viewed from the mesial, measured (to the nearest 0.5 mm) the depth of the mesial groove between the mesiolingual and mesiobuccal canals. Due to imperfect impressions, 50 teeth were included in the study. The recorded average in depth was 1.0 mm. Some of the impressions had depths measuring 3.5 mm. This could be a significant space when considering the limitations of instrumentation techniques. There is the question of whether this area may remain untouched, thereby effecting the prognosis of treatment in both vital and nonvital teeth. Modifications in access preparation and/or an increased emphasis on irrigation and intracanal medication may be needed.