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Root canal anatomical complexities, such as isthmus, may limit the action of the endodontic instruments, irrigant solutions and intracanal medications, leading to endodontic treatment failure.ObjectivesThis in vitro study assessed the type, position and incidence of isthmus in human permanent molars.Material and MethodsOne hundred and twenty eight upper and lower first and second permanent molars were analyzed. The roots were embedded in transparent resin, and then split at different distances from the apex (1.0-2.5-4.0-5.5-7.0 mm). Following the sample examination in stereomicroscope, the data were submitted to chi-square statistical test at a 5% significance level.ResultsThe highest isthmus incidence was at 7.0 mm from the root apex in all samples, except the distal root of lower molars (at 5.5 mm). In upper and lower molars, type V (complete isthmus with a continuous opening between the two main root canals) was the most common classification of isthmus (28.8%). In the mesial root of first and second mandibular molars, type IV had the highest incidence (36% and 23.9%, respectively).ConclusionIt was concluded that isthmus was widely found in flat roots, with a low percentage in areas close to the apex. In upper and lower molars, these structures were most frequently found at 7 mm from the apex.

Understanding the correct use of basic statistics leads to fewer errors in reporting the results of studies performed and in the interpretation of their conclusions.

SUMMARY:The purpose of this work was to study the morphology and morphometry of the mental foramen (MF), as well as to evaluate its morphological configuration; in addition to taking measures of its localization using as a parameter the distances of the foramen to the inferior border of the mandible and at the alveolar ridge. 80 dry mandibles were analyzed using the test of Qui-square and T test, with 5% of significance. Its average distance, on the right side, at the inferior edge of the mandible (IEM) was of 12.96(± 1.57) mm and of the alveolar ridge (AR) was of 12.82(± 3.4) mm. On the left side it was found distant of IEM 12.96(± 1.32) mm and of the AR 12.82(± 3.22)mm. The largest horizontal diameter found was of 3.32 (± 0.91) mm to the right and 3.25 (± 0.86) mm to the left side while the largest vertical diameter was of 2.38 (± 0.63) mm on the right and of 2.39 (± 0.58) mm on the left side. It was predominantly found in the oval form, on the right side, of which 98.3% presented as a larger diameter the horizontal (type I). On the left side, all the oval foramens were classified as of type I. 76 (95%) appeared single on both sides. As to the localization related to the mandibular dentition, it was localized in similar statistic proportions between the 1 st and 2 nd premolars and above the 2 nd premolar, in 45.17% of the mandibles, on the right side. On the left side it was predominantly found between the 1 st and 2 nd premolars 48.48% of the mandibles. The study of the MF is of vital importance to the acupuncture practice, as well as to modern surgical procedures, like anesthesia, requiring a detailed and precise study of the morphology and morphometry of the area.