The effect of dowel space on the bond strengths of fiber posts.
OBJECTIVE
The purpose of this study was to evaluate the effect of the degree of mismatch between post space and post diameters on the bond strength of a fiber-reinforced resin post.


METHODS
Thirty-two extracted human maxillary central incisors and canines were endodontically treated and assigned to four groups: Group 1--Canal prepared with a D.T. Light Post #1 drill (control); Group 2--Canal prepared with a D.T. Light Post #2 drill; Group 3--Canal prepared with a D.T. Light Post #3 drill; Group 4--Canal prepared with a Gates Glidden #6 drill. A D.T. Light Post size 1 was then luted into the canal using One-Step Adhesive and Post Cement Hi-X. A push-out test was performed on three sections of each root to measure push-out bond strengths. Data were analyzed with ANOVA and Bonferroni's test at p < 0.05. Two extra teeth for each group were restored in the same fashion and processed for SEM observation.


RESULTS
(in MPa): Group 1: 15.7 +/- 6.9; Group 2: 14.7 +/- 6.5; Group 3: 14.0 +/- 5.0; Group 4: 14.0 +/- 5.1. The variable "post space" resulted in no statistically significant difference in mean bond strengths (p > 0.05). For the variable "root region," the coronal third (17.5 +/- 6.0) resulted in statistically greater mean bond strengths than the apical third (12.3 +/- 6.0) at p < 0.008. The middle third (14.0 +/- 5.3) resulted in no statistically significant different mean bond strengths from the coronal third at p > 0.119 and from the apical third at p > 0.999. Under the SEM, some areas of the canal system still displayed residual gutta-percha, which resulted in debonding of the interface between the resin cement and dentin. Areas with incomplete dentin hybridization were observed in localized areas of all groups.


CONCLUSIONS
The diameter of the post space did not affect the push-out bond strengths. Bonding at the coronal level of the root canal is more reliable than bonding at the apical level. The presence of residual gutta-percha and the deficient dentin hybridization may result in deficient seal of the resin-dentin interface.
Perdigão
Jorge
J
Division of Operative Dentistry, Department of Restorative Sciences, University of Minnesota, 515 SE Delaware Street, Minneapolis, MN 55455, USA. perdi001@umn.edu
Gomes
George
G
Augusto
Vitor
V
D000704:Analysis of Variance; D001840:Dental Bonding / Q000379:methods*; D003804:Dentin / Q000648:ultrastructure; D006801:Humans; D011176:Post and Core Technique / Q000295:instrumentation*; D018915:Root Canal Preparation / Q000295:instrumentation / Q000379:methods*