It is moving the position of canal’s normal anatomic foramen to a new location on the external root surface.
It Occurs apical to curvature.
Transportation occurs when the angle of access and angle of incidence differ.
The angle of access refers to the orientation of the instrument as it slides down the body of the root canal.
The angle of incidence refers to the turn required to follow the path of the root canal.
EXTERNAL TRANSPORTATION
• Occurs mainly due to failing to precurve files, using large instruments.
Original apical foramen is torn.
• When the instrument is overused - the elastic memory of the instrument may create the teardrop and tearing of the apical foramen
• Another form of external transportation is direct perforation.
• begins with a ledge or apical blockage.
• continues its misdirection until it perforates the root surface.
INTERNAL TRANSPORTATION
• occurs when foramen is clogged with dentin mud.
• perforate the external root surface through a false path.
LEDGING
• leding is Iatrogenically created root canal wall irregularity .
• it Impedes the placement of instrument
• Caused by
– forcing uncurved instrument in a curved canal.
– Rapid advancement in file size.
• Identified by Loss of tactile sensation on instrument - loose feeling instead of binding at the apex.
ZIPPING
• It is transposition of the apical portion of the canal.
• Causes
– failure to precurve the files
– Forcing the instrument in curved canal.
– Use of large , stiff instruments.
files placed in a curved canal will cut more on the outer portion of the canal wall.
ELBOW
• Creation of an ‘elbow’ is associated with zipping
• narrow region of the root canal at the point of maximum curvature as a result of the irregular widening.
• Elbow prevents obturation in the apical portion of the canal
STRIP PERFORATION
Strip perforation occurs in the middle part of the inner curve of a root canal if excessive dentine is removed by over instrument.
