title: The effect of canal preparation on fill length in straight root canals obturated with GuttaCore.
abstract: BACKGROUND
  A common critique of using thermoplasticized carrier-based obturators is the incidence of overextension. It would be of benefit to clinicians to have a technique for canal preparation that would allow for predictable length control. This study compared straight canals instrumented to a size 40 file using a 0.04 standardized taper preparation (STP) and a varied taper preparation (VTP) by evaluating the extension of GuttaCore (GC) obturators (Dentsply Tulsa Dental, Tulsa, OK).
  
  
  METHODS
  Eighty extracted mature human premolars with single straight canals were randomly divided into 2 experimental groups (n = 40). The STP group was instrumented to size 40/.04 at the working length (WL). The VTP group was instrumented to size 40/.02 at the WL. Both groups were obturated with a size 40 GC obturator. Extension of the material, in relation to the WL, was evaluated and assessed ordinally. Statistically significant differences were determined by a 2-group chi-square test with a 2-sided P value set at P = .05 and a Fisher exact test of equal proportions.
  
  
  RESULTS
  Significant differences in extrusion existed between the STP and VTP groups when controlling for the type of apical preparation (P = .0005). The STP group resulted in a 47.2% incidence of overextension, whereas the VTP group resulted in 10.5% overextension of obturating material.
  
  
  CONCLUSIONS
  The results indicate that when filling straight canals with GC obturators the canal can be instrumented using a varied tapered canal preparation with a low likelihood of overextension.
authors.affiliation: Medical University of South Carolina, Charleston, South Carolina.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Whitten
authors.affiliation: Medical University of South Carolina, Charleston, South Carolina. Electronic address: levitanm@musc.edu.
authors.forename: Marc E
authors.initials: ME
authors.lastname: Levitan
mesh_terms: D001641:Bicuspid / Q000187:drug effects* / Q000503:physiopathology / Q000601:surgery; D003786:Dental Pulp Cavity / Q000187:drug effects / Q000473:pathology; D006171:Gutta-Percha / Q000627:therapeutic use*; D006801:Humans; D012387:Root Canal Filling Materials / Q000627:therapeutic use*; D012389:Root Canal Obturation / Q000379:methods*; D018915:Root Canal Preparation
chemical_list: D012387:Root Canal Filling Materials; D006171:Gutta-Percha
keywords: GuttaCore; overextension; thermoplastic carrier-based obturation; varied taper preparation