title: Torsional resistance of crowns cemented to composite cores involving three stainless steel endodontic post designs.
abstract: BACKGROUND
  There are no studies analyzing the effects of a crown in relationship to torsional resistance for a titanium-reinforced core material supported by a post.
  
  
  OBJECTIVE
  This study investigated the effects of post design on the torsional resistance of a crown supported by a titanium-reinforced composite core material (Ti-Core) and 3 endodontic posts (AccessPost, Flexi-Post, and ParaPost).
  
  
  METHODS
  Three groups of 10 specimens per group were studied. A total of 30 recently extracted human single-rooted (incisors) teeth with their crowns removed were used. Post holes preparations were created according to manufacturer's instructions. All posts were cemented using Flexi-Flow with titanium cement. Scotchbond Multi-Purpose bonding system was used as the bonding system for all groups. All cores were fabricated with Ti-Core with titanium core material with hard copper bands as the matrix. The Ti-Core core material was allowed to set for 1 hour. Metal crowns were fabricated and cemented with zinc phosphate cement. Specimens were placed in a special jig and a clockwise torsional force was applied. Torsional force was measured on a Lebow 1102-200 torque transducer and recorded on a Hewlett Packard 7015B X-Y recorder in inch x ounce. A 1-way analysis of variance (ANOVA) was used to test for statistical significance (P < .001).
  
  
  RESULTS
  The torsional values (inch x ounce) were AccessPost 77.2 +/- 30.3, Flexi-Post 162.2 +/- 51.2, and ParaPost 60.9 +/- 28.4. SNK and Scheffé comparison tests revealed that the Flexi-Post group had significantly greater resistance to torque loading than the AccessPost and ParaPost groups, which were statistically similar to each other.
  
  
  CONCLUSIONS
  Post design has an effect on torsional resistance of a crown supported by titanium-reinforced core build-up and post. The threaded split-shank design of the Flexi-Post dowel offers significantly greater resistance to torsional loading than the passive posts studied.
authors.affiliation: Essential Dental Laboratories, South Hackensack, N.J., USA. eds@pipeline.com
authors.forename: B I
authors.initials: BI
authors.lastname: Cohen
authors.forename: B
authors.initials: B
authors.lastname: Penugonda
authors.forename: M K
authors.initials: MK
authors.lastname: Pagnillo
authors.forename: A
authors.initials: A
authors.lastname: Schulman
authors.forename: E
authors.initials: E
authors.lastname: Hittelman
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins; D003442:Crowns; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis; D017220:Dentin-Bonding Agents; D006801:Humans; D007180:Incisor; D011176:Post and Core Technique; D019279:Resin Cements; D013193:Stainless Steel; D018709:Statistics, Nonparametric; D019415:Torque
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents; D019279:Resin Cements; C084018:Scotchbond Multi-Purpose; D013193:Stainless Steel; C079578:Ti-Core composite resin