Root canal isthmus more prevalent in posterior teeth, Study says

The study is published in the Journal of Conservative Dentistry.

Root canal isthmus (RCI) is defined as a channel/corridor of communication between two canals that contain pulp/pulpally derived tissue. Microcomputed tomography (micro-CT) studies describe RCI to be a highly complex network that branches and extends longitudinally.

RCI is commonly seen in single roots with two canals, such as the mesial root of the mandibular molars. It has been reported that when the distance between two orifices in a single root having two canals is <3 mm, these root canals often merge before their exit.

However, if the interorifice distance (IOD) is more than 3 mm, the canals remain separate. Similarly, it can be speculated that if the root canals are closer together, the chances of RCI being present could also be very high.

The authors carried out the present study with the aim to evaluate the frequency of RCI in human permanent teeth using a sample of CBCT images obtained from an Indian subpopulation. The secondary objective of this study was to determine the IOD between the root canals and their correlation with RCI.

A total of 5881 teeth from 280 CBCT full mouth scans were analyzed. The presence or absence of complete and incomplete RCI of each tooth was identified using the map‑reading strategy. IOD was calculated by measuring the distance between the center of each root canal orifice to that of the center of the adjacent orifice at the level of the cementoenamel junction using the axial and sagittal sections. Chi‑square analysis and correlation statistics using Spearman's rank‑order test was done (P < 0.05).

The following results were observed-

1. High prevalence of RCI was found in maxillary first premolars, mesial root of mandibular molars, and mesiobuccal root of maxillary first molars, while its prevalence was low in maxillary canines and mandibular premolars and absent in maxillary incisors.
2. RCI was predominantly seen in the cervical and middle third of the root canal in all the teeth evaluated.
3. A weak negative correlation was established between the IOD and RCI for maxillary premolars, whereas a weak positive correlation was seen in maxillary first molars and mandibular second molars.

Therefore, the authors concluded that "high prevalence of RCI was found in maxillary first premolars, mesial root of mandibular molars, and mesiobuccal root of maxillary first molars, while its prevalence was low in maxillary canines and mandibular premolars and absent in maxillary incisors. RCI was seen predominantly in the cervical and middle third of the root canal in all the teeth evaluated. Vertucci's types IV, II, and III root canal patterns were seen predominantly in teeth with RCI."

They also inferred that a weak negative correlation was established between the IOD and RCI for maxillary premolars, whereas a weak positive correlation was seen in maxillary first molars and mandibular second molar.