Title Presence of an Isthmus Decreases the Success Rate of Surgically Treated Molars
Clinical Question In teeth requiring endodontic microsurgery, does the presence of an isthmus affect the success rate of surgically treated molars?
Clinical Bottom Line In endodontic microsurgery, teeth that have isthmuses have lower success rates than teeth without isthmuses. An isthmus is formed by the connection of two canals and may contain remnant tissue and bacteria. Therefore, bacteria can grow, resulting in endodontic failure. A recent retrospective study shows that the presence of an isthmus can result in failure of endodontic microsurgery treatment.
Best Evidence  
PubMed ID Author / Year Patient Group Study type
(level of evidence)
27238415Kim/2016106 teeth Case series
Key resultsSurvival rate at 4 years after surgery was 61.5% when an isthmus was present and prepared. The survival rate after 4 years was 87.4% when an isthmus was absent and unprepared. A multivariate Cox proportional hazards regression analysis showed that the adjusted hazard ratio for failure was 6.01 times higher for the isthmus-present teeth than for the isthmus-absent teeth (P < .05).
27912820Floratos/2016Narrative review
Key resultsIsthmuses are present in premolars and molars in approximately 80% to 90% of cases at the 3-mm level from the apex. Apical root resection alone, without root-end preparation and root-end filling of canals and the isthmus, usually fails.
Evidence Search endodontic[All Fields] AND ("microsurgery"[MeSH Terms] OR "microsurgery"[All Fields]) AND isthmus[All Fields] AND success[All Fields]
Comments on
The Evidence
One article is a case series, and the other is a narrative review. These are not the high level of evidence represented by a systematic review or randomized clinical trial. Also, all cases in the case series study were treated by one surgeon. The results could be different if there had been more than one operator.
Applicability In a patient who receives endodontic microsurgery treatment, the presence of an isthmus can be a cause of failure of the treatment. It helps both the surgeon and the patient to predict that the presence of an isthmus can decrease the success rate, particularly in molars and premolars.
Specialty (Endodontics)
Keywords Endodontic Microsurgery, isthmus, Success rate
ID# 3282
Date of submission 11/13/2017
E-mail alelyani@livemail.uthscsa.edu
Author Ahmed Alelyani
Co-author(s) e-mail
Faculty mentor
Faculty mentor e-mail
Basic Science Rationale
(Mechanisms that may account for and/or explain the clinical question, i.e. is the answer to the clinical question consistent with basic biological, physical and/or behavioral science principles, laws and research?)
None available
Comments and Evidence-Based Updates on the CAT
None available