title: Effect of dowel space preparation and composite cement thickness on retention of a prefabricated dowel.
abstract: OBJECTIVE
  This investigation examined what effect cement thickness had on retention of prefabricated endodontic dowels luted with a composite resin cement (Panavia 21 OP; J Morita, Irvine, CA) into canals previously obturated with gutta percha and a eugenol-based sealer.
  
  
  METHODS
  Sixty-four single-rooted teeth were decoronated, filed, cleaned, and sequentially shaped with sizes 2-5 Gates Glidden drills (Dentsply/Maillefer, Tulsa, OK) and 0.12 taper rotary instrumentation. Teeth were then divided into 4 groups of 16 specimens each. All specimens were obturated with gutta percha and a eugenol-based sealer. Dowel space preparation and dowel cementation were completed 1 week after obturation. Ten-millimeter-deep dowel spaces were prepared using dowel drills with 4 different diameters: size 5 Parapost drill (Group 1; Coltene/Whaledent, Mahwah, NJ); size 5.5 Parapost drill (Group 2; Coltene/Whaledent); size 6 Gates Glidden drill (Group 3; Dentsply/Maillefer); size 6 Parapost drill (Group 4; Coltene/Whaledent). Size 5 Paraposts were then cemented with Panavia 21 OP. After 48 hours of storage, specimens were mounted in polyvinyl chloride (PVC) pipe with acrylic, and the dowels were removed in tensile mode using a universal testing machine at 1 mm/min, with data recorded in kilograms.
  
  
  RESULTS
  (all values in kilograms) Group 1 (Parapost 5) mean = 15.07, 95% confidence interval (CI) = +/-6.11; Group 2 (Parapost 5.5) mean = 25.60, 95% CI = +/-7.39; Group 3 (Gates-Glidden 6) mean = 43.15, 95% CI = +/-7.81; Group 4 (Parapost 6) mean = 37.75, 95% CI = +/-6.35. Analysis of variance and Bonferroni tests revealed that Group 3 had significantly greater mean retention strength values than Group 1 and Group 2 (p <.05), and that Group 4 had significantly greater mean retention strength values than Group 1 (p <.05).
  
  
  CONCLUSIONS
  Paraposts cemented with Panavia 21 OP showed significantly greater retention in oversized dowel spaces compared with dowel spaces prepared with the manufacturers' matched dowel-drill set.
authors.affiliation: Department of Restorative Dentistry, University of the Pacific School of Dentistry, San Francisco, CA 94115, USA. mhagge@sf.uop.edu
authors.forename: Mark S
authors.initials: MS
authors.lastname: Hagge
authors.forename: Ralan D M
authors.initials: RD
authors.lastname: Wong
authors.forename: James S
authors.initials: JS
authors.lastname: Lindemuth
mesh_terms: D000704:Analysis of Variance; D002484:Cementation; D003188:Composite Resins / Q000737:chemistry*; D016001:Confidence Intervals; D001840:Dental Bonding; D017268:Dental Prosthesis Retention; D017220:Dentin-Bonding Agents / Q000737:chemistry; D005054:Eugenol / Q000627:therapeutic use; D006171:Gutta-Percha / Q000627:therapeutic use; D006801:Humans; D006813:Humidity; D008422:Materials Testing; D010710:Phosphates / Q000737:chemistry; D011176:Post and Core Technique / Q000295:instrumentation; D019279:Resin Cements / Q000737:chemistry*; D012387:Root Canal Filling Materials / Q000627:therapeutic use; D012389:Root Canal Obturation; D018915:Root Canal Preparation; D013223:Statistics as Topic; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors; D019231:Tooth Preparation, Prosthodontic / Q000295:instrumentation / Q000379:methods*
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents; C093719:Panavia TPN-S; D010710:Phosphates; D019279:Resin Cements; D012387:Root Canal Filling Materials; D005054:Eugenol; D006171:Gutta-Percha