Characterization of new-generation indirect resin composites
Ghulman, Motaz A.
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OBJECTIVES: To evaluate physical and mechanical properties of four indirect resin composites in-vitro. Materials and Methods: Four indirect resin composites: Gradia (GC), Sculpture (Pentron), Sinfony (3M-ESPE), Tescera (Bisco), and Z-100 (3M-ESPE) as a control, were investigated for the following parameters: Mechanical properties: Cylindrical resin specimens were prepared (ANSI/ADA specifications) and tested for compressive and diametral tensile strengths in an Instron testing machine. Rectangular bars were prepared for flexural strength anda modulus testing in a three-point bending test. Resin discs for microhardness testing were prepared and Vickers microhardness was tested in a Buehler microhardness tester. Effect of aging and thermocycling on properties: Specimens for the flexural strength and modulus testing were prepared then aged for 1, 3, or 8 weeks at 60[degrees]C, or thermocycled for 500, 1000 or 2000 cycles. Flexural strength and modulus changes as an effect of aging and thermocycling were calculated. Resin discs for micrchardness and degree of conversion testing were prepared then aged for 24 hours, 3, 8, 12 or 18 weeks at 37[degrees]C. FTIR spectroscopy was used to measure the effect of aging on degree of conversion. Vickers microhardness changes as an effect of aging were calculated. Resin discs for color stability were prepared then aged in distilled water at 60[degrees]C for 24 hours, 1, 3, 8, 12 or 18 weeks. A Minolta colorimeter was used to measure colors at various intervals. Color changes were calculated. Toothbrush abrasion wear: A special toothbrush abrasion machine was used to evaluate in vitro wear of rectangular resin composite plates after 60,000 cycles of toothbrushing in dentifrice/water slurry. Bond strength: The 4 indirect resins were tested with 4 resin cements: Illusion (BISCO), Link-Max (GC), Lute-It (Pentron), and Rely-X ARC (3M-ESPE) with their respective adhesive systems. Shear bond strength of resin cements to the indirect composites was tested in an Instron testing machine. ANOVA was performed for all parameters tested, followed by Tukey test. Correlation analysis was performed between the different variables tested in this study. Results and Conclusions: Mechanical properties: Z-100 exhibited higher compressive and diametral tensile strength than most of the other materials tested. Z-100 also exhibited higher microhardness, flexural strength and flexural modulus than all other materials tested. In general, indirect resin composites did not exhibit better mechanical properties than the direct resin tested. Effect of aging and thermocycling on properties: Accelerated aging and thermocycling significantly decreased the flexural strength of all resin composites tested except Sinfony. The indirect resins showed less decrease in flexural strength than the direct resin, indicating better resistance to environmental changes, although flexural strength values for the direct resin were relatively high. No significant effect of aging or thermocycling was revealed on flexural modulus of resins tested. Degree of conversion of indirect resin composites widely ranged from 30.77% with Sinfony to 86.39% with Tescera, while Z-100 exhibited 53.95%, indicating that indirect resins do not always have higher degree of conversion than direct resins. Accelerated aging significantly increased the degree of conversion and microhardness of some resin composites tested. Tescera showed less increase in degree of convsion and microhardness than Sinfony, which showed higher increase than all other resins. Accelerated aging caused significantly progressive color changes to all resins tested with time. The direct resin had a [Delta] E*=4.17 at 8 weeks, and reached 7.17 at 18 weeks. The indirect resins showed less change of color ([Delta] E* less than 4 over the entire test period), indicating better color stability than direct resin. Toothbrush abrasion wear: Sculpture and Tescera exhibited the lowest in vitro wear. There was a high inverse correlation (r=-.88) between surface microhardness and wear (P=.042). Microhardness may have some predictive value for wear resistance. Bond strength: Significantly higher bond strengths were found for Gradia and Sinfony (p=.027). Link-Max hed significantly higher bond strength to Gradia (35.5 MPa, p=.001). All cement systems tested produced adequate bond strengths (ranging from 12.89 to 35.5 MPa), but certain cement-resin combinations exhibited significantly higher bond strengths. Consistently acceptable bond strength values were produced when materials from the same manufacturer were used.
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact email@example.com.Thesis (DScD) --Boston University Henry M. Goldman School of Dental Medicine, 2003 (Restorative Sciences and Biomaterials).Includes bibliography: leaves 186-208.
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