A new nanofiber-reinforced hybrid composite (NovaPro Fill, Nanova) was recently introduced with reportedly improved mechanical properties. The purpose of this study was to compare the properties (flexural strength/modulus, degree of conversion [DC], depth of cure, and polymerization shrinkage) of the nanofiber composite to those of traditional hybrid composites (Filtek Z250, 3M ESPE; Esthet-X HD, Dentsply). To determine flexural strength and modulus, composite was placed in a rectangular mold, light-cured, stored for 24 hours, and then fractured in a universal testing machine. For degree of conversion, composite was placed in a cylindrical mold, light-cured, and stored for 24 hours. Measurements were made at the top and bottom surfaces using Fourier Transform Infrared Spectroscopy. To determine depth of cure, composite was placed in a cylindrical mold and light-cured. Uncured composite was scraped until polymerized resin was reached. Remaining composite was measured and divided by two. Polymerization shrinkage was determined by placing the composite material on a pedestal in a video-imaging device while light-curing. Shrinkage was determined after 10 minutes. Data were analyzed with one-way analysis of variance and Tukey post hoc test per property (α=0.05). Compared to Filtek Z250, NovaPro Fill had significantly lower flexural strength and modulus, greater volumetric shrinkage, and similar depth of cure, but greater top and bottom DC. Compared to Esthet-X HD, NovaPro Fill had similar flexural strength, shrinkage, and top and bottom DC, but significantly greater depth of cure and flexural modulus.
furthering the study of dental materials. It has been his organization, deadlines, answers to my endless questions and continual help that have been the basis of my successfully completing this project. I would also like to thank Mr. Dan Sellers and Dr. Wen Lien. Mr. Sellers was gracious enough to spend his time running the samples in the Instron machine for me. Dr. Lien was very helpful in creating the SEM images contained within this thesis. Their time and services are greatly valued. v ABSTRACT Objective: This study evaluated the shear-bond strength of a resin-modified glassionomer (RMGI) restorative material (Fuji II LC, GC Corporation) to a new siloranebased composite (Filtek LS, 3M/ESPE) and a methacrylate-based composite (Filtek Z250, 3M/ESPE) in a sandwich technique with various combinations of surface treatments and bonding agents. Methods: The RMGI was bonded to Filtek LS or Z250 using the proprietary adhesive (Filtek LS System Adhesive (LSA), 3M/ESPE) or methacrylate-based (Clearfil SE Bond (CSE), Kuraray) self-etch adhesive systems. Molds were filled with the RMGI and the surface was prepared in one of four ways: no treatment, etched with phosphoric acid, bur-roughened, or both burroughened and etched. Either the LSA or CSE adhesive system was applied according to the manufacturer"s instructions. Next, either Filtek LS or Z250 was bonded to the RMGI, creating 16 groups of 10 specimens each. Specimens were stored for 24 hours at 37°C in 100% humidity and tested in shear (Instron). A mean and standard deviation was determined per group. A three-way ANOVA was used to evaluate the effect of surface preparation (4-levels) and bonding agent (2-levels) on the shear-bond strength of composite (2-levels) to RMGI (alpha=0.05). Results: A significant difference in bond strength was found based on composite (p<0.001) and bonding agent (p<0.001) but not on surface treatment (p=0.699) with no significant interactions (p>0.05) (see Table 1). Conclusions: Surface modifications did not affect the shear-bond strength of the silorane or methacrylate composites to the RMGI. The new silorane composite (Filtek LS) had significantly lower bond strength to the RMGI compared to the methacrylate composite (Filtek Z250). The vi new silorane system adhesive agent (Filtek LS System Adhesive) had significantly higher bond strength to the RMGI compared to the methacrylate adhesive agent (Clearfil SE Bond). The greatest bond strengths to the RMGI were produced when using the silorane system adhesive agent with the methacrylate composite. vii Table 1-Mean Shear Bond Strength Resin Composite
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