title: Comparative Analysis of Crack Propagation in Roots with Hand and Rotary Instrumentation of the Root Canal -An Ex-vivo Study.
abstract: BACKGROUND
  Success of any endodontic treatment depends on strict adherence to 'endodontic triad'. Preparation of root canal system is recognized as being one of the most important stages in root canal treatment. At times, we inevitably end up damaging root dentin which becomes a Gateway for infections like perforation, zipping, dentinal cracks and minute intricate fractures or even vertical root fractures, thereby resulting in failure of treatment. Several factors may be responsible for the formation of dentinal cracks like high concentration of sodium hypochlorite, compaction methods and various canal shaping methods.
  
  
  OBJECTIVE
  To compare and evaluate the effects of root canal preparation techniques and instrumentation length on the development of apical root cracks.
  
  
  METHODS
  Seventy extracted premolars with straight roots were mounted on resin blocks with simulated periodontal ligaments, exposing 1-2 mm of the apex followed by sectioning of 1mm of root tip for better visualization under stereomicroscope. The teeth were divided into seven groups of 10 teeth each - a control group and six experimental groups. Subgroup A & B were instrumented with: Stainless Steel hand files (SS) up to Root Canal Length (RCL) & (RCL -1 mm) respectively; sub group C & D were instrumented using ProTaper Universal (PTU) up to RCL and (RCL -1mm) respectively; subgroup E & F were instrumented using ProTaper Next (PTN) up to RCL & (RCL -1 mm) respectively. Stereomicroscopic images of the instrumentation sequence were compared for each tooth. The data was analyzed statistically using descriptive analysis by 'Phi' and 'Cramers' test to find out statistical significance between the groups. The level of significance was set at p< 0.05 using SPSS software.
  
  
  RESULTS
  Stainless steel hand file group showed most cracks followed by ProTaper Universal & ProTaper Next though statistically not significant. Samples instrumented up to 1mm short of working length (RCL-1mm) showed lesser number of cracks.
  
  
  CONCLUSIONS
  All groups showed cracks formation, the stainless steel group being the highest. Working 1mm short of apex reduces the incidence of crack formation.
authors.affiliation: Post Graduate Student, Department of Conservative Dentistry and Endodontics, J.S.S Dental College and Hospital , Mysuru India .
authors.forename: Manju Raj
authors.initials: MR
authors.lastname: Kumari
authors.affiliation: Professor and Head of the Department, Department of Conservative Dentistry and Endodontics, J.S.S Dental College and Hospital , Mysuru, India .
authors.forename: Manjunath Mysore
authors.initials: MM
authors.lastname: Krishnaswamy
keywords: Apical root crack; Instrumentation length; Protaper next; Protaper universal; Root canal instrumentation; Stainless steel K file