15. Which one is the disadvantage of step back technique? a. Increase chances of iatrogenic errors b. Taper of canal preparation can be altered by changing the interval between the consecutive instruments. c. Permit straighter access to the apical region d. Removes bulk of tissue and microorganisms before apical shaping c. Allows deeper penetration of irrigants

The disadvantage of the step back technique is:<br /><br />b. Taper of canal preparation can be altered by changing the interval between the consecutive instruments.<br /><br />The step back technique involves removing a small amount of dentin at the apex of the root canal, then cleaning and shaping the canal before repeating the process. This technique can be effective for removing bulk tissue and microorganisms before apical shaping, allowing deeper penetration of irrigants, and permitting straighter access to the apical region. However, the disadvantage is that it can alter the taper of the canal preparation by changing the interval between the consecutive instruments. This can lead to a more constricted canal, which may make it more difficult to clean and shape the canal effectively.