Retentive Strengths of Fiber Posts

Objective:

To compare the retentive strengths of active and passive fiber posts bonded to root canal dentin or composite core material.

Methods: 

The active fiber post systems used in this in-vitro study were Flexi-Post Fiber and Flexi-Flange Fiber.  The passive fiber post systems used were ICEPost, ParaPost Fiber, and FibreKor. Post-core retention samples were created by embedding post heads into the manufacturer recommended core material.  Post-tooth retention samples were created by instrumenting extracted human anterior teeth and post placement according to the manufacturer's instructions. All samples (14 per group) were cured at 37șC for 24 hours before testing. Retentive strengths were determined with a universal testing machine. In the statistical analysis, the different sizes of posts tested were grouped according to the size of the reamer used to prepare the post space.  Statistical testing was performed using 3-way ANOVA.  Significant results (P<0.05) were further analyzed using the Student-Newman-Keuls test.

Results: 

Post-core retentive strengths (N) were as follows:

Post Brand	Approximate Reamer Diameter (mm)
	1.2	1.4
Flexi-Flange Fiber	461±53	561±60
Flexi-Post Fiber	363±33	517±54
FibreKor	355±50	602±53
ParaPost Fiber	370±51	595±37
ICEPost	265±47	366±46

The post-tooth retentive strengths (N) were as follows:

Post Brand	Approximate Reamer Diameter (mm)
	1.2	1.4
Flexi-Flange Fiber	347±39	420±51
Flexi-Post Fiber	372±46	433±44
FibreKor	267±59	307±56
ParaPost Fiber	227±58	314±58
ICEPost	224±29	276±45

All factors and interactions were significant (P<0.001).  The larger reamer diameter significantly increased retention for both testing methods (P<0.05).  The post-tooth retentive strength was significantly weaker than the post-core retentive strength (P<0.05).  The active fiber posts had significantly greater post-tooth retention than the passive fiber posts (P<0.05).

Conclusions:

When subjected to a tensile force, the post-tooth interface should debond before the post-core interface.  The post-tooth retentive strengths of the active fiber posts were significantly greater than those of equivalently sized passive fiber posts.