Accuracy of Apex Locator NaOCL-level Readings During Three Root-canal-irrigation Methods

Objectives: To investigate the accuracy of the apex locator readings against digital x-ray (gold standard) regarding liquid level measurement during root canal irrigation with sodium hypochlorite (NaOCL) and Omnipaque^TM solution (OS), respectively, across three irrigation methods: negative pressure irrigation with a normal needle, positive pressure irrigation with a side-hole needle, and positive pressure irrigation with an open-ended needle.
Methods: Ten extracted lower premolars (for orthodontic treatment purposes) with single roots were prepared for virtual root canal obturation by K-files and Rivo-s shaping instruments. Every canal was irrigated three times with NaOCL (5.25%) by negative pressure irrigation (Al-Jajeh device, -0.35 to -0.40 Bar, patent #5928/Syria) using a normal needle (NN), positive pressure irrigation (Lego-robot device, 3ml/min.) using a side-hole needle (PS), and positive pressure irrigation (Lego-robot device, 3ml/min.) using an open-ended beveled needle (PO). During irrigation, the needles were connected to the apex locator device. The same procedures were repeated for irrigation with OS under digital visualisation on EasyDent^® computer program. Spearman correlation coefficients for the apex locator and digital x-ray readings were calculated across the three irrigation methods. Chi-square analysis was carried out to test the significance of the differences among the three irrigation methods in terms of liquid overflow beyond the apex.
Results: The correlation coefficients were 0.7, 0.8 and 0.9 for NN, PS and PO, respectively. The differences among NN, PS and PO in terms of irrigation liquid overflow beyond the apex were significant (P<0.05). There were more overflow observations with PS and PO, whilst no overflow observation was reported with NN.
Conclusions: The accuracy of apex locator readings for NaOCL level in the root canal was high across the three irrigation methods, when compared with digital x-ray readings using OS. Al-Jajeh device was more effective in terms of NaOCL irrigation and evacuation, and therefore preventing NaOCL overflow beyond the apex.