IADR Abstract Archives
Should Separated-Files be Removed? a Stress-Analysis Study About Profit-Loss
Objectives: The aim of this finite element stress-analysis (FEA) study was to assess the effect of separated-files (SF) which were broken at two levels (at apical 4 and 9mm) on biomechanics of premolars and to determine if removal-techniques have an effect on stresses.
Methods: Six lower premolar-teeth were screened on computerized micro tomography (micro-CT), standard access-cavities were prepared, working-lengths were determined and root-canals were prepared (Protaper files, Protaper Universal, Dentsply, Switzerland). Notches were created on the final shaping-file F3 at a point 4 and 9mm from the file-tips, inserted in the canals and squeezed at the apical to break. The roots were re-screened and SFs were removed by using Masseran kit (MK; Micro Mega, France), ultrasonic-tips (UT; Satelec, Acteon group, France) and by-pass (BP) technique. Final scans were obtained and converted into three dimensional FEA models. The following conditions were then simulated: a) root-filled tooth with SF; b) root-filled tooth after removal of the SF by using with MK, UT or BP techniques. The models were loaded axially (from two directions) and vertically (300 Newton), Von mises stresses were then analyzed.
Results: SFs increased the stresses within the root. Longer SF caused more stresses within the root thus should be removed while short SFs, if cannot be removed could be kept considering the other clinical factors. Among the techniques used, removing with MK caused more stresses within the roots. Axial loading caused more stresses at cervical while the stresses moved towards the apical under vertical loading.
Conclusions: SFs increase the stresses within the root. Long SFs should be removed while short SFs can be left (considering other clinical factors that may affect the success of the treatment). Trying to remove short SFs located at apical negatively affects biomechanics of the teeth and this effect is more dramatic with MK technique.
Methods: Six lower premolar-teeth were screened on computerized micro tomography (micro-CT), standard access-cavities were prepared, working-lengths were determined and root-canals were prepared (Protaper files, Protaper Universal, Dentsply, Switzerland). Notches were created on the final shaping-file F3 at a point 4 and 9mm from the file-tips, inserted in the canals and squeezed at the apical to break. The roots were re-screened and SFs were removed by using Masseran kit (MK; Micro Mega, France), ultrasonic-tips (UT; Satelec, Acteon group, France) and by-pass (BP) technique. Final scans were obtained and converted into three dimensional FEA models. The following conditions were then simulated: a) root-filled tooth with SF; b) root-filled tooth after removal of the SF by using with MK, UT or BP techniques. The models were loaded axially (from two directions) and vertically (300 Newton), Von mises stresses were then analyzed.
Results: SFs increased the stresses within the root. Longer SF caused more stresses within the root thus should be removed while short SFs, if cannot be removed could be kept considering the other clinical factors. Among the techniques used, removing with MK caused more stresses within the roots. Axial loading caused more stresses at cervical while the stresses moved towards the apical under vertical loading.
Conclusions: SFs increase the stresses within the root. Long SFs should be removed while short SFs can be left (considering other clinical factors that may affect the success of the treatment). Trying to remove short SFs located at apical negatively affects biomechanics of the teeth and this effect is more dramatic with MK technique.