<prompt> Problems encountered during instrumentation :Ledging.Stripping lateral wall Perforation .Zipping.All of the above.  <response>: Problems Encountered during InstrumentationLoss of working length due to a blockage of the canal systemLedging shelf formationBreakage of instrumentDeviation from the normal canal anatomyZipping ellipticationStrippinglateral wall perforationInadequate canal preparationOverinstrumentation beyond apical constrictionOver preparation excessive removal of tooth structureUnder preparation insufficient canal preparation 