Assessment of mode of failure
fracture
To determine the type of failure, the failed teeth were examined under a stereomicroscope (SZ1145TR Olympus; Japan 1990) by using software (Toup view, version 3.7). It was classified as follows [
Favorable or restorable failure: When the failure or fractured line or area was found to be above the cervical line of restored teeth.Non-favorable or non-restorable or catastrophic failures: were present when the fracture line or failure occurred at the cervical line or extended beyond it. Vertical root fracture is also included.