Effect of dentin bonding and ferrule preparation on the fracture strength of crowned teeth restored with dowels and amalgam cores.
BACKGROUND
It is necessary to obtain an adequate bond at the core/dentin junction where the majority of failures occur. The effect of recently developed dentin bonding agents on the fracture resistance of endodontically treated teeth at the amalgam core/dentin junction is unclear.


OBJECTIVE
The purpose of this study was to evaluate the effects of 2 dentin bonding agents and a ferrule preparation on the fracture resistance of crowned mandibular premolars incorporating prefabricated dowel and silver amalgam cores.


METHODS
Sixty extracted mandibular second premolars were divided into 6 groups of 10 each. The coronal portion of each tooth was removed at the cemento-enamel junction (CEJ) in the first 3 groups. In the other groups, teeth were sectioned 1 mm above the CEJ to create a ferrule. After root canal preparations, prefabricated dowels (ParaPost) were placed. The first group served as a control and was tested without application of bonding agents and without incorporation of a ferrule design. In the second and third groups, respectively, an autopolymerizing adhesive (Superbond D-Liner) and a dual-polymerizing adhesive (Panavia F) were applied to tooth surfaces before restorative procedures. For the fourth (ferrule) group, no bonding agent was applied, but a 1-mm ferrule preparation was used. In the fifth (ferrule+D-Liner) and sixth (ferrule+Panavia F) groups, respectively, autopolymerizing and dual-polymerizing bonding agents were used in conjunction with the ferrule preparation. After amalgam core fabrication, Ni-Cr full cast crowns for each group were prepared and cemented. All specimens were stored in water for 1 week and thermal cycled 1000 times between 5 degrees and 55 degrees C. A compressive shear load was applied at an angle of 135 degrees to the crown, and the maximum load at fracture (N) was recorded. The data were analyzed with 1-way ANOVA and Tukey Honestly Significant Difference tests (alpha=.05).


RESULTS
Significantly higher fracture strength values were demonstrated for the ferrule+Panavia F (652.5 N), ferrule+D-liner (649.1 N) and ferrule (592.4 N) groups, respectively, than for the other groups. The next highest fracture strength values were found for the D-Liner (485.0 N) and Panavia F (486.3 N) groups. The control group (376.6 N) demonstrated the lowest fracture strength in all test groups (P<.001).


CONCLUSIONS
A ferrule preparation or a bonding agent designed for silver amalgam core-dentin bonding can each increase the fracture strength for teeth receiving cast crowns after endodontic therapy and dowel and amalgam core restorations.
Aykent
Filiz
F
Department of Prosthodontics, Faculty of Dentistry, Selcuk University, Konya, Turkey. faykent@hotmail.com
Kalkan
Mustafa
M
Yucel
Munir Tolga
MT
Ozyesil
Atilla Gokhan
AG
D000704:Analysis of Variance; D001840:Dental Bonding / Q000379:methods*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D011176:Post and Core Technique; D014082:Tooth Fractures / Q000517:prevention & control*; D019231:Tooth Preparation, Prosthodontic / Q000379:methods*; D016474:Weight-Bearing
D017220:Dentin-Bonding Agents