Incidence of micro-cracks in the root dentine during various re-treatment techniques an in-vitro study

Introduction: ProTaper Universal retreatment system is a Ni-Ti rotary instrument that is used for removal of filling material from the root canal. Wave One is a reciprocating instrument used for the preparation of root canals. Although Wave One is fundamentally used for the preparation of root canals, studies have evaluated their use in removal of root filling material. Root fractures may occur as a result of retreatment procedures resulting in dentinal defects (i.e. craze lines or micro-cracks) that propagate with repeated stress application through occlusal forces.

Aim: To compare the incidence of dentinal defects caused by reciprocating and rotary techniques during retreatment procedures.

Methodology: 53 extracted single-rooted teeth were selected. The biomechanical preparation was done followed by obturation with cold lateral compaction technique. Five canals received no further treatment (control group). Forty-Eight teeth were divided into Six groups (n=8) to undergo the removal of root filling. In Groups 1,2 and 3, the root filling was removed using ProTaper Retreatment files, Wave One files and Gates Glidden drills respectively and canals were not refilled. In groups 4,5 and 6, the root filling was removed using ProTaper Retreatment files, Wave one file, and Gates Glidden drills, the canals were then refilled using a conventional cold lateral compaction technique. Roots were sectioned horizontally at 3mm, 6mm and 9 mm from the root apex and observed under a stereomicroscope at 20 X magnification. Defects were categorized as no defect, incomplete defect, and
fracture. The difference between the groups was analyzed using the statistical analysis.