title: The impact of post space preparation with Gates-Glidden drills on residual dentin thickness in distal roots of mandibular molars.
abstract: BACKGROUND
  Posts frequently are used to retain buildups. The authors examined the effects of post space preparation with Gates-Glidden drills on residual dentin thickness in distal roots of mandibular molars.
  
  
  METHODS
  The authors embedded 26 root-treated mandibular molars in endodontic cubes and sectioned them perpendicularly to their long axis at 1.8-millimeter intervals. They placed Gates-Glidden drills nos. 3, 4, 5 and 6 sequentially to 5 mm short of working length in the distal canals. After using each drill size, the authors measured the dentin thickness from light microscopic images of the tooth slices.
  
  
  RESULTS
  The authors analyzed data to detect changes resulting from canal instrumentation. They performed statistical analysis by partitioning the variability in a nested analysis of variance. Strip perforations occurred with a no. 4 Gates-Glidden drill 7.3 percent of the time and more frequently with larger drills. After endodontic treatment alone, the canal wall on the furcal side was less than 1 mm thick 82 percent of the time and less than 0.5 mm thick 17.5 percent of the time.
  
  
  CONCLUSIONS
  Dentin thickness correlates inversely to post space diameter. A no. 4 Gates-Glidden drill caused strip perforations in 7.3 percent of the canals studied, and therefore the authors recommend that Gates-Glidden drills larger than a no. 3 not be used in these roots. After endodontic treatment, the furcation-side dentin thickness was less than 1 mm in 82 percent of the teeth.
  
  
  CONCLUSIONS
  Post space preparation in mandibular molars carries significant risk of perforation. Post space in such teeth should be limited to the endodontically prepared canal.
authors.affiliation: Department of Endodontics, Nova Southeastern University, Fort Lauderdale, FL, USA.
authors.forename: Sergio
authors.initials: S
authors.lastname: Kuttler
authors.forename: Alex
authors.initials: A
authors.lastname: McLean
authors.forename: Samuel
authors.initials: S
authors.lastname: Dorn
authors.forename: Alberto
authors.initials: A
authors.lastname: Fischzang
mesh_terms: D003762:Dental Instruments / Q000009:adverse effects; D003804:Dentin / Q000033:anatomy & histology*; D004867:Equipment Design; D006801:Humans; D008334:Mandible; D008963:Molar; D011176:Post and Core Technique; D018915:Root Canal Preparation / Q000009:adverse effects / Q000295:instrumentation*