A preliminary in vitro study of the incidence and position of the root canal isthmus in maxillary and mandibular first molars
Article first published online: 16 APR 2003
International Endodontic Journal
Volume 36, Issue 4, pages 276–280, April 2003
How to Cite
Teixeira, F. B., Sano, C. L., Gomes, B. P. F. A., Zaia, A. A., Ferraz, C. C. R. and Souza-Filho, F. J. (2003), A preliminary in vitro study of the incidence and position of the root canal isthmus in maxillary and mandibular first molars. International Endodontic Journal, 36: 276–280. doi: 10.1046/j.1365-2591.2003.00638.x
- Issue published online: 16 APR 2003
- Article first published online: 16 APR 2003
- Received 5 November 2001; accepted 17 October 2002
Aim To investigate in vitro the incidence and position of the root canal isthmus in extracted mesiobuccal roots of maxillary and mesial roots of mandibular first molars.
Methodology Fifty maxillary and 50 mandibular molars were included in the study. The mesiobuccal roots of maxillary molars and the mesial roots of mandibular molars were sectioned from their crowns in the furcation region and embedded in clear resin. Transverse serial 1-mm-thick sections from the apical 6 mm were prepared. The apical side of each section was stained with India ink and observed through a light microscope. The sample images were saved to disk using a digital camera and the root canals in terms of the number present and the incidence and classification of isthmuses.
Results In the mesiobuccal root of the maxillary first molars, 70% had one canal, whereas 29.5% had two canals. In the mesial root of mandibular molars, 41% had one canal, whereas 59% had two canals. In some sections, more than two canals were found close to the apical foramen. The isthmus incidence was greatest 3–5 mm from the apex. In teeth having two canals, a complete or partial isthmus was frequently observed in the sections between 3 and 4 mm from the apex. Of the isthmuses present, 22% were complete and 37% partial in mandibular molars and 17.3% were complete and 11.7% partial in maxillary molars.
Conclusions The incidence of isthmus in the mesiobuccal root of the maxillary first molars and in the mesial root of the mandibular first molars was high, particularly in sections 3–5 mm from the apex. Cleaning the isthmus is a major challenge during root canal treatment.