instrumentation errors

Question 1

what is zipping?
what causes it?

Answer 1

• A tear-drop shape that may be formed in the apical foramen during preparation of a curved canal
• when a file extends through the apical foramen and subsequently transports that outer wall

Question 2

aetiology of zipping?

Answer 2

• failure to pre-curve the files
• forcing instruments into a curved canal
• use of large, stiff instruments to bore out a curved canal

Question 3

how to prevent zipping?

Answer 3

• pre-curved files for curved canals
• use of incremental filing technique
• use of flexible files

Question 4

what is transportation? What causes it?
what problems may this cause?

Answer 4

• Removal of canal wall structure on the outside curve in the apical half of the canal
• due to
  the tendency of files to restore themselves to their original linear shape during canal preparation
• may lead
  to ledge formation and possible perforation.

Question 5

what is a ledge in endodontics?

Answer 5

An artificial irregularity created on the surface of the root canal wall that impedes the placement of
instruments to the apex of an otherwise patent canal.