title: Effect of cement type on retention of a tapered post with a self-cutting double thread.
abstract: OBJECTIVE
  The aim of this in vitro study was to examine the effect of varying the cement type on the retention of a prefabricated tapered titanium post with a self-cutting double thread (Perma-tex activ).
  
  
  METHODS
  A total of 130 suitable roots from extracted human permanent teeth were selected. Post holes were prepared using the instruments supplied with the post system. One-hundred-twenty posts (medium size) were luted with one of four luting agents: a zinc-phosphate cement (Harvard), a glass-ionomer cement (Ketac Cem), a compomer luting agent (Dyract Cem), and a new capsulated composite luting system (Compolute). The cement groups were subdivided into three treatment groups with 10 posts each: group 1 (4-week water storage at 37 degrees C), group 2 (4-week water storage at 37 degrees C, 4000 cycles 5-55 degrees C), group 3 (4-week water storage at 37 degrees C, 4000 cycles 5-55 degrees C, 3 x 4 min mechanical stress: 40N vibrations). Another 10 posts inserted without cement and stored like group 1 served as a control. Retention was measured on a universal testing machine (Zwick Z050/TH3A) with a crosshead speed of 0.1cm/min. Data were analyzed using ANOVA with a Bonferroni or Tamhane adjustment for multiple comparisons (significance level alpha=0.05).
  
  
  RESULTS
  In group 1, Dyract Cem was significantly more retentive than the other three cements and the control group (no cement). In group 2, Compolute demonstrated significantly higher retention than Harvard and Ketac Cem. In group 3, Compolute, Dyract Cem, and Ketac Cem obtained higher retentive values than Harvard without differing from one another. Within the cement groups, thermocycling (group 2) caused a significant decrease in retention compared to group 1 only for Dyract Cem. All cements except Compolute were different from group 1 after a combination of thermocycling and mechanical stress (group 3).
  
  
  CONCLUSIONS
  The retention of the tapered post with a self-cutting double thread was significantly influenced by the cement type used.
authors.affiliation: Department of Operative Dentistry, Periodontology and Paediatric Dentistry, School of Dentistry, University of Greifswald, Rotgerberstr. 8, D 17489 Greifswald, Germany. rosin@uni-greifswald.de
authors.forename: M
authors.initials: M
authors.lastname: Rosin
authors.forename: C
authors.initials: C
authors.lastname: Splieth
authors.forename: M
authors.initials: M
authors.lastname: Wilkens
authors.forename: G
authors.initials: G
authors.lastname: Meyer
mesh_terms: D000704:Analysis of Variance; D020770:Compomers; D003738:Dental Cements / Q000737:chemistry*; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D005899:Glass Ionomer Cements; D006358:Hot Temperature; D006801:Humans; D008277:Magnesium Oxide; D008422:Materials Testing; D008689:Methacrylates; D011076:Polycarboxylate Cement; D011176:Post and Core Technique; D019279:Resin Cements; D017640:Silicates; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D013718:Tensile Strength; D015034:Zinc Oxide; D015036:Zinc Phosphate Cement
chemical_list: C418025:Compolute; D020770:Compomers; D003738:Dental Cements; C088486:Dyract; D005899:Glass Ionomer Cements; D008689:Methacrylates; D011076:Polycarboxylate Cement; D019279:Resin Cements; D017640:Silicates; D008277:Magnesium Oxide; D015036:Zinc Phosphate Cement; C074226:Harvard Cement; C040235:Ketac-cem; D015034:Zinc Oxide