[Study on fatigue resistance of mechanical nickel-titanium files by phase-locked infrared flaw detection method].

Purpose: The fatigue resistance of mechanical nickel-titanium files was tested by phase-locked infrared flaw detection method, in order to timely detect instrument wear, providing reference for clinical safe use and timely abandonment of nickel-titanium files.

Methods: Twenty sets of mechanical nickel-titanium files were selected from Reciproc-Blue(RB), MTWO and S3 respectively, and resin simulated root canals with 60° and 90° bending were prepared, which were divided into 6 subgroups. The fatigue value after use, the number of uses before breaking and the length of fracture of file 25# of each group of files were recorded and compared with SPSS 26.

[Comparison of clinical effects of different irrigant solutions combined with different agitation techniques in the treatment of chronic apical periodontitis with fistula].

Purpose: To evaluate the effect of combination of auxiliary irrigation technology and root canal irrigation solution in the treatment of chronic apical periodontitis with fistula, and try to seek a more effective and minimally invasive therapeutic strategy.

Methods: One hundred and fifty patients with fistulous chronic apical periodontitis who were diagnosed in Hefei Stomatological Hospital from January 2021 to January 2022 were randomly divided into 6 groups, 25 cases in each group. The 6 groups were as follows, group A: 0.