In step back technique, the file used for measuring working length is 25 no and it is the first file to be used for Phase 2 i.e. step back technique, the file used for recapitulation will be
**Core Concept**
The step-back technique is a method used in endodontics to determine the working length of a root canal, ensuring the correct placement of the endodontic file. This technique involves gradually removing the file from the canal while maintaining a gentle back-and-forth motion, allowing the dentist to measure the length of the canal accurately.
**Why the Correct Answer is Right**
In the step-back technique, the first file used for Phase 2 is typically a larger file, which is used to recapitulate the canal and remove any remaining dentin or debris. The correct file size is essential to ensure that the canal is adequately cleaned and shaped without causing damage to the surrounding tooth structure. The file used for recapitulation should be larger than the 25 file, which was used for measuring the working length.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the file used for recapitulation should be larger than the 25 file, and a smaller file would not be effective in removing dentin or debris.
**Option B:** This option is incorrect because the 25 file was used for measuring the working length and is not suitable for recapitulation.
**Clinical Pearl / High-Yield Fact**
In the step-back technique, it is essential to use a larger file for recapitulation to ensure thorough cleaning and shaping of the canal, while avoiding damage to the surrounding tooth structure.
**Correct Answer: C. 35 or 40 file.**