Intracanal Aspiration Technique for Root Canal Irrigation : Part 2. Development of Newly Designed Aspiration Needles

Abstract

We have developed a new root canal irrigation system: intracanal aspiration technique(IAT), where irrigants are aspirated through a needle positioned near the apical canal end. The application of IAT was limited to wide canals because 24G standard needles were used. The aim of this study was to develop newly designed aspiration needles for narrower canals in IAT. In Study 1, two types of newly designed aspiration needles with a tip diameter of 27G were used. The size of the basal part of Type 1 and 2 needles was equivalent to 21 and 23G, respectively. Twenty-one root canals were instrumented to #35 file size, and divided into three groups(Groups 1-3)of 7 teeth each. Seven root canals(Group 4) were instrumented to #50 file size. The roots were fixed in a plastic case and surrounded with normal saline agar colored by 1% acid red solution. In Groups 1, 2 and 4, each root canal was irrigated using IAT with aspiration needle of Type 1, 2 and 24G, respectively. Each needle was connected to a Root ZX™® and positioned 2 mm from the apical root end. In Group 3, root canals were irrigated conventionally. Each canal was irrigated with 9ml of 14% EDTA for 3 minutes, and then with 6ml of 6% NaClO for 2 minutes. The meter value of Root ZX™® during irrigation and the discolored area of agar around the apical root end were measured. In Study 2, the flow rate at -20kPa was measured with newly designed aspiration needles of 24G and 27G. In Study 1, indicated meter values of Root ZX™® for Groups 1, 2 and 4 were significantly closer to the apex than those of Group 3(p<0.05). Discolored areas in Groups 1, 2 and 4 were significantly smaller than those of Group 3 (p<0.05). The results of Study 2 suggested that the optimal needle for IAT may consist of a 23G basal part of 32.5 mm in length and 27G tip part of 5mm in length. It was concluded that the newly designed aspiration needles for IAT could be effective in the canal with the small apical diameter of 0.35mm.