Effect of cement type on retention of a tapered post with a self-cutting double thread

Objectives: The aim of this in vitro study was to examine the effect of var ying the cement type on the retention of a prefabricated tapered titanium p ost 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 wit h the post system. One-hundred-twenty posts (medium size) were luted with o ne of four luting agents: a zinc-phosphate cement (Harvard), a glass-ionome r cement (Ketac Gem), a compomer luting agent (Dyract Gem), and a new capsu lated composite luting system (Compolute). The cement groups were subdivide d into three treatment groups with 10 posts each: group 1 (4-week water sto rage at 37 degreesC), group 2 (4-week water storage at 37 degreesC, 4000 cy cles 5-55 degreesC), group 3 (4-week water storage at 37 degreesC, 4000 cyc les 5-55 degreesC, 3 x 4 min mechanical stress: 40 N vibrations). Another 1 0 posts inserted without cement and stored like group I served as a control . Retention was measured on a universal testing machine (Zwick Z050/TH3A) w ith a crosshead speed of 0.1 cm/min. Data were analyzed using ANOVA with a Bonferroni or Tamhane adjustment for multiple comparisons (significance lev el alpha = 0.05). Results: In group 1, Dyract Cem was significantly more retentive than the o ther three cements and the control group (no cement). In group 2, Compolute demonstrated significantly higher retention than Harvard and Ketac Gem. In group 3, Compolute, Dyract Gem, and Ketac Cem obtained higher retentive va lues than Harvard without differing from one another. Within the cement gro ups, thermocycling (group 2) caused a significant decrease in retention com pared to group 1 only for Dyract Gem. All cements except Compolute were dif ferent from group 1 after a combination of thermocycling and mechanical str ess (group 3). Conclusions: The retention of the tapered post with a self-cutting double t hread was significantly influenced by the cement type used. (C) 2000 Elsevi er Science Ltd. All rights reserved.