Frequency and type of canal isthmuses in first molars detected by endoscopic inspection during periradicular surgery

By von Arx T

Date: 03/2006
Journal: JOE

Purpose: to assess the presence of a canal isthmus in molars during periradicular surgery using an endoscope, and to determine the type of canal isthmus present at the cut root face

N= 32 first maxillary molars and 56 first mandibular molars


•During the periradicular surgery, affected roots were resected approximately 3–4 mm from the apex.

•Methylene blue utilized for vital tissue staining to help in locating the periodontal ligament, accessory canals, unfilled canals, canal isthmuses, cracks and root fractures.

•The cut root faces were inspected with a rigid endoscope –Fig.

1- following apical root-end resection.

•The number of canals at the cut root face and the presence and type of canal isthmuses were recorded.

•Isthmuses were classified according to Hsu & Kim (1997) – Fig. 2

Most highlighted Results: 

•Canal isthmus was present in 76% of MB roots in maxillary first molars but never in DB or P roots.

•Presence in MB root of 1st mandibular molars = 83%, In D roots = 36% •None of the canal isthmuses had been obturated by orthograde canal filling • 💡Clinical significance: Understanding possible causes of failure is the first step towards properly diagnosing and choosing proper treatment methods