Influence of cement thickness on the bond strength of tooth-colored posts to root dentin after thermal cycling.
OBJECTIVE
The purpose of this study was to evaluate the effect of different resin cement thickness on the push-out bond strength of different posts (CAD/CAM zirconia post (ZR post)) and an individually formed glass fiber reinforced composite post (IPN post) prior to and after thermal cycling (TC).


METHODS
Post spaces with a height of 9 mm and a diameter of 1.5 mm were drilled in 80 mandibular premolar teeth. Two groups (n = 40) were formed according to the posts used (IPN posts or ZR posts). Then the specimens were randomly assigned into two sub-groups according to the post diameter: (1) 1.5 mm in diameter and (2) 1.2 mm in diameter (n = 20/per group). All posts were luted with a self-adhesive luting agent according to the manufacturer's instructions by using endo tips. Half of the samples (n = 10) were submitted to thermal cycling (5000 cycles, 5-55 °C). Thereafter, four 2-mm thick horizontal sections were obtained and subjected to push-out test. Failure modes were assessed quantitatively and morphologically. The data were statistically analyzed with a three-way analysis of variance (ANOVA) (p < 0.05). Statistical differences in failure modes were investigated by chi-square tests at a significance level of p < 0.05.


RESULTS
Push-out bond strengths were significantly influenced both by the post diameter and thermal cycling. Larger (1.5 mm) diameter post results were statistically higher than 1.2 mm results (p < 0.05). Moreover, TC significantly increased the bond strength results (p < 0.05). There was no significant difference between ZR and IPN posts (p = 0.219).


CONCLUSIONS
The bond strengths of ZR and IPN posts were significantly decreased when the resin cement layer was thick. In addition, thermal cycling drastically influenced bond strengths of the tested post materials.


CONCLUSIONS
The fit between tooth-colored endodontic posts and post spaces should be as tight as possible.
Department of Prosthodontics, Faculty of Dentistry, Gazi University, Ankara, Turkey. ferhanegilmez@gmail.com
Ferhan
F
Egilmez
Gulfem
G
Ergun
Isil
I
Cekic-Nagas
Pekka K
PK
Vallittu
Lippo V J
LV
Lassila
D000704:Analysis of Variance; D016009:Chi-Square Distribution; D003188:Composite Resins; D017076:Computer-Aided Design; D001840:Dental Bonding; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis; D003804:Dentin; D017220:Dentin-Bonding Agents / Q000737:chemistry; D005898:Glass; D006358:Hot Temperature; D006801:Humans; D011176:Post and Core Technique; D019279:Resin Cements / Q000737:chemistry; D014092:Tooth Root; D015019:Yttrium; D015040:Zirconium
D003188:Composite Resins; D017220:Dentin-Bonding Agents; D019279:Resin Cements; C009753:fiberglass; C499362:yttria stabilized tetragonal zirconia; D015019:Yttrium; D015040:Zirconium