title: Effect of canal preparation on fill length in straight root canals obturated with RealSeal 1 and Thermafil Plus.
abstract: BACKGROUND
  A common adverse effect when using thermoplasticized obturators is overextension. A canal preparation allowing for predictable obturation length would be of clinical value. This study compared straight canals instrumented to a size 40 file by evaluating the extension of 2 thermoplastic obturation systems, a 0.04 standardized taper preparation (STP) and a varied taper preparation (VTP), by evaluating the extension of 2 thermoplastic obturation systems, RealSeal 1 (RS-1) and Thermafil Plus (TP).
  
  
  METHODS
  Eighty extracted mature human premolars with single straight canals were randomly divided into 4 experimental groups (n = 20). Groups 1 and 2 were instrumented to size 40/04 at working length with STP. Groups 3 and 4 were instrumented to size 40/02 at working length with VTP. Groups 1 and 3 were obturated with RS-1, and groups 2 and 4 were obturated with TP. All groups were obturated per manufacturer's instructions. Extension of material was evaluated and assessed ordinally. Statistically significant differences were determined by logistic regression with significance level set at P < .05.
  
  
  RESULTS
  Significant differences in extrusion existed between groups 2 and 4 when controlling for type of material (P = .026) and all groups for extrusion of TP compared with RS-1 when controlling for type of preparation (P < .001).
  
  
  CONCLUSIONS
  The results indicate that when filling with RS-1 obturators, the canal can be instrumented to an STP or VTP with a low likelihood of excessive extrusion. If the clinician prefers to use TP obturators, this study validates a VTP to decrease the occurrence of overextension.
authors.affiliation: Division of Endodontics, College of Dental Medicine, Medical University of South Carolina, Charleston, South Carolina 29425-5070, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Heeren
authors.forename: Marc E
authors.initials: ME
authors.lastname: Levitan
mesh_terms: D001641:Bicuspid; D003188:Composite Resins / Q000008:administration & dosage; D003762:Dental Instruments; D005119:Extravasation of Diagnostic and Therapeutic Materials / Q000517:prevention & control*; D006171:Gutta-Percha / Q000627:therapeutic use; D006801:Humans; D016015:Logistic Models; D012387:Root Canal Filling Materials / Q000627:therapeutic use*; D012389:Root Canal Obturation; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods*
chemical_list: D003188:Composite Resins; C511498:Real Seal composite resin; D012387:Root Canal Filling Materials; D006171:Gutta-Percha