2026 Volume 4 Issue 1 Pages 22-28
The objective of root canal treatment is to reduce the presence of bacteria in the root canal. The root canal is mechanically enlarged to enable the removal of bacteria from within, but this alone is known to be insufficient. As a result, the root canal is normally irrigated at the same time. However, because intracanal bacterial infections are caused by a variety of microbial biofilms attached to the dentinal surface in the vicinity of the apex, passive root canal irrigation that consists solely of rinsing the root canal with irrigant is insufficient to secure adequate bacterial removal. Hopes are therefore being pinned on active root canal irrigation utilizing special delivery systems. Among these, the SmartLite Pro EndoActivator is a sonic wave-based irrigator that is considered to provide efficient, safe irrigation. However, many points remain unclear regarding the durability of the tip, the part that is inserted into the root canal. Our objective in this study was to investigate the effect on root canal cleaning performance of increased wear on the tip, the consumable component of the EndoActivator. We performed objective assessments of changes in cleaning performance, the tip damage rate, and changes in surface morphology depending on the number of uses and following autoclave sterilization. We first penetrated a transparent model root canal with a ＃10K file, then used an NiTi rotary file to carry out root canal shaping up to ＃30. The shaped root canal was filled with water, and the EndoActivator (with a small tip) was used and subsequently sterilized by autoclaving at 121℃ for 20 min. The apical 8 mm of the transparent model root canal that had been shaped to ＃30 was filled with root canal filling paste (Vitapex, Neo Dental Chemical Products, Tokyo, Japan). The 8 mm above this was filled with water and irrigation was conducted with EndoActivator tips that had previously been used differing numbers of times. Five tips each were used 8, 16, or 24 times, with five unused tips as the Control group. After irrigation, the transparent model root canal was photographed with a stereomicroscope/digital camera system (Stemi 508, Carl Zeiss, Oberkochen, Germany). Cleaning performance of different groups was assessed in terms of the root canal filling removal rate, calculated from measurements of the surface area of Vitapex removed from within the root canal. The proportion of cleaned surface area removed was 18.03±2.9％ for the Control group, 13.75±4.13％ for tips used 8 times, 10.56±1.6％ for tips used 16 times, and 7.16±3.04％ for tips used 24 times. The cleaned surface area tended to be smaller for tips that had been used multiple times than in the Control group. Splitting of the tip during use was also seen in some tips that had been used 24 times. With continued EndoActivator tip use, the cleaning rate decreased with increasing number of uses, but no changes in surface conformation were identified despite the use of autoclaving. These results suggest that when EndoActivator are used repeatedly, they should be replaced after approximately eight uses, and that use beyond 16 times requires particular caution, with close attention paid to the risk of tip breakage.
