In vitro evaluation of push-out bond strength of direct ceramic inlays to tooth surface with fiber-reinforced composite at the interface.
BACKGROUND
Failure of a restoration, where a part of a ceramic inlay and/or a cusp is fractured, is a common clinical problem. The application of fiber-reinforced composites at the tooth-inlay interface may prevent undesirable fractures in dental restorations. There is little information regarding the effect of a fiber- reinforced composite layer on the push-out bond strength of ceramic inlays to tooth structure.


OBJECTIVE
The purpose of this study was to compare push-out bond strengths of ceramic inlays to tooth structure using a layer of fiber weave-reinforced composite at the tooth interface with different adhesive systems.


METHODS
Forty standardized occlusal, conically-shaped cavities, 5 mm in occlusal diameter, 3.5 mm in cervical diameter and 3.5 mm deep, were prepared in extracted human molars using a truncated cone-shaped diamond rotary cutting instrument, the dimensions of which corresponded with those of prefabricated ceramic inlays. The teeth were divided into 2 groups according to the adhesive system used. Solobond Plus was used as a total-etching system and Futurabond NR as a self-etching system. Preetched and silanized ceramic inlays were bonded to tooth structure with or without a layer of bidirectional fiber weave (StickTech). The groups without fiber-reinforced composite layer served as controls. The inlays were cemented with dual-polymerizing luting composite (Bifix QM) and light polymerized for 40 seconds from the buccal, lingual, and occlusal surfaces. Specimens were thermal cycled (6000 x 5 degrees -55 degrees C) and 3.5-mm-thick discs were prepared for the push-out test. The discs (n=10) were tested in a universal testing machine and pushed out with a cross-head speed of 1.0 mm/min. The data were analyzed with analysis of variance (ANOVA) (alpha=.05). Failure modes were analyzed using a stereomicroscope and SEM.


RESULTS
Push-out mean bond strength (SD) values in MPa of direct ceramic inlays were: Solobond Plus (control): 9.7 (3.9), Solobond Plus with fiber-reinforced composite: 10.5 (5.0), Futurabond NR (control): 8.4 (2.5), Futurabond NR with fiber-reinforced composite: 8.6 (2.2). The differences between groups were not significant for either adhesive system or with the use of fiber-reinforced composite layer at the interface. Mixed failures were observed in the control groups, whereas in the fiber-reinforced composite layer groups, failures were mostly cohesive within the fiber layer. No cohesive fracture of the tooth was observed when a layer of fiber weave was placed at the interface.


CONCLUSIONS
Within the limitations of this in vitro study, a fiber-reinforced composite layer at the bonding interface of ceramic inlay did not influence the push-out bond strength. Futurabond NR self-etching system and Solobond Plus total-etching system demonstrated similar push-out bond strengths.
Cekic
Isil
I
Department of Prosthodontics, Faculty of Dentistry, Gazi University, Ankara, Turkey. isilcekic@gazi.edu.tr
Ergun
Gulfem
G
Uctasli
Sadullah
S
Lassila
Lippo V J
LV
D000269:Adhesives / Q000737:chemistry; D000704:Analysis of Variance; D002516:Ceramics / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding / Q000379:methods*; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis; D006801:Humans; D066298:In Vitro Techniques; D007284:Inlays / Q000379:methods*; D008689:Methacrylates / Q000737:chemistry; D008963:Molar; D013718:Tensile Strength
D000269:Adhesives; D003188:Composite Resins; D003764:Dental Materials; D008689:Methacrylates; C488002:Solobond Plus adhesive; C512545:futurabond NR