In vitro evaluation of push-out bond strength of direct ceramic inlays to tooth surface with fiber-reinforced composite at the interface

• Published in: The Journal of prosthetic dentistry Vol. 97; no. 5; pp. 271 - 278
• Main Authors: Cekic, Isil, DDS, Ergun, Gulfem, DDS, PhD, Uctasli, Sadullah, DDS, PhD, Lassila, Lippo V.J., DDS, MSc Eng
• Format: Journal Article
• Language: English
• Published: United States Mosby, Inc 01.05.2007
• Subjects: Adhesives - chemistry; Analysis of Variance; Ceramics - chemistry; Composite Resins - chemistry; Dental Bonding - methods; Dental Marginal Adaptation; Dental Materials - chemistry; Dental Restoration Failure; Dental Restoration, Permanent - methods; Dental Stress Analysis; Dentistry; Humans; In Vitro Techniques; Inlays - methods; Methacrylates - chemistry; Molar; Tensile Strength
• ISSN: 0022-3913; 1097-6841
• DOI: 10.1016/j.prosdent.2007.04.002

Statement of problem 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. Purpose 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. Material and 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 × 5°-55°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) ( α =.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. Conclusion 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.