Mechanical properties and bond strength of dual-cure resin composites to root canal dentin.
OBJECTIVE
To evaluate the regional mechanical properties of dual-cure resin composites and their regional bond strengths to root canal dentin.


METHODS
One of the following dual-cure resin composites was placed in artificial post spaces: Unifil Core (UC), Clearfil DC Core (DC), Build-It FR (BI), Clearfil DC Core-automix (DCA), and photo-cured for 60s. After 24h storage, each specimen was serially sliced to harvest eight hour-glass shaped specimens for measurement of regional ultimate tensile strength (UTS), and the remaining eight semi-circular slabs were polished for the measurement of Knoop Hardness Number (KHN). For the microtensile bond strength (muTBS) test, post cavities were prepared in human premolar roots, and the cavity surfaces treated with Clearfil SE Bond and photo-cured for 10s. The post spaces were then filled with one of the above resin composites and photo-cured for 60s. After 24h storage, each specimen was serially sliced into 8, 0.6x0.6 mm-thick beams for the muTBS test. The data were divided into coronal and apical regions and analyzed using ANOVA and post hoc test (alpha=0.05).


RESULTS
UTS and KHN were affected by the type of dual-cure resin composite and region (p<0.0001). There was no relationship between UTS and KHN for each material. The auto-mix type of resin composite possessed superior UTS to that of the hand-mix type. muTBS among the four composite materials were not significantly different at both apical and coronal regions (p>0.05). Regional differences in bond strengths were found for all materials (p<0.05).


CONCLUSIONS
The UTS and KHN of the dual-cure resin composites varied among each material, however, differences in the mechanical properties of the resin core materials did not affect their adhesion to root canal dentin.
Aksornmuang
Juthatip
J
Department of Prosthetic Dentistry, Faculty of Dentistry, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand. juthatip.a@psu.ac.th
Nakajima
Masatoshi
M
Foxton
Richard M
RM
Tagami
Junji
J
D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry*; D003786:Dental Pulp Cavity / Q000648:ultrastructure*; D003804:Dentin / Q000648:ultrastructure*; D006244:Hardness; D006801:Humans; D008027:Light; D008422:Materials Testing; D011176:Post and Core Technique; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013718:Tensile Strength; D013997:Time Factors; D019231:Tooth Preparation, Prosthodontic
C483702:Build-it composite resin; C469237:Clearfil Core; C438313:Clearfil SE Bond; D003188:Composite Resins; D003764:Dental Materials; D019279:Resin Cements; C500741:Unifil Core