Factors Affecting the Removal Time of Separated Instruments

Present status and future directions: Removal of fractured instruments

“…Additionally, the retrieval success rate was found to be favourable when the canal curvature was low and the curvature radius was >4 mm (Alomairy, 2009; Cujé et al, 2010; Estrela et al, 2008). Fractured instruments located in curved canals >30° required long times to remove in both the preparation and retrieval phases; contrastingly, fractured instruments below 3.1 mm could be easily removed using ultrasonic instruments regardless of canal curvature (Terauchi et al, 2021). Taken together, the retrieval success rate is negatively and positively correlated with the canal curvature and radius, respectively, due to increased visibility and accessibility (Alomairy, 2009; Fu et al, 2011).…”

“…Therefore, compared with nonmechanical methods, mechanical methods, especially those using ultrasonics, allow higher success rates, minimally invasive preparation and faster instrument retrieval (Cujé et al, 2010; Fu et al, 2011; Nagai et al, 1986; Nevares et al, 2012; Terauchi et al, 2021). However, the success rates of instrument retrieval using ultrasonics widely vary from 33% to 100%, with the average retrieval time ranging from 3 to >60 min (Alomairy, 2009; Nagai et al, 1986; Terauchi et al, 2007, 2021) due to differences in the instrument retrieval protocols according to the location and visibility of the fractured instrument (Al‐Fouzan, 2003; Cujé et al, 2010; Ramirez‐Salomon et al, 1997; Ruddle, 1997; Terauchi et al, 2021; Ward et al, 2003). Nonetheless, compared with nonmechanical methods, mechanical retrieval methods are more reliable and practical; accordingly, they are frequently used in clinical settings.…”

“…Moreover, instrument retrieval using the Canal Finder System has an overall success rate of only 68% (Hülsmann & Schinkel, 1999). Compared with the aforementioned systems, ultrasonics are safer, more conservative in dentin sacrifice and more successful even in posterior teeth in both the preparation and retrieval steps (Cujé et al, 2010; Terauchi et al, 2007, 2021). Nonetheless, all the aforementioned protocols are not standardized for predictable instrument retrieval, which is attributed to their differences in the success rates of instrument retrieval.…”

“…Nonetheless, all the aforementioned protocols are not standardized for predictable instrument retrieval, which is attributed to their differences in the success rates of instrument retrieval. However, a recent study suggested that fractured instruments visible under a DOM can be predictably removed using ultrasonic instruments alone through a single standardized retrieval protocol that minimizes potential variables (Terauchi et al, 2021) compared with the aforementioned nonstandardized protocols (Table 1).…”

“…First, the canal is filled with soybean oil or EDTA when the canal curvature is >30° or <30°, respectively, to facilitate instrument retrieval with ultrasonics. Most fractured instruments (94%) <4.6 mm can be removed solely with ultrasonics within 10 s in the retrieval phase (Terauchi et al, 2021).…”