In-vitro evaluation of the effect of different variables on measured adhesive bond strength values
Attar, Moaz H.
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Statement of problem: Bond strength of dental adhesives to dentine can be affected by multiple factors contributed in preparation, adhesion process, and materials condition. Purpose: The aim of this in vitro study was to determine the effect of various factors attributed to the adhesion process on shear bond strength to dentine. Methods: For all specimens tested, extracted human teeth were embedded in acrylic bases. The coronal aspect of each tooth was sliced to expose a flat surface of dentine. Dentine surface were prepared using 600 grit wet diamond disc. Materials applied using Ultradent jig in combination with 2.38 mm diameter plastic inserts for the first and second chapter, and a special jig in combination with 2.38 Teflon inserts created for the second and all remaining chapters. Adhesives cylinders of 2.38 mm diameter were bonded to dentine surfaces. All specimens were stored in water for 24 hours. Shear bond strength was tested in shear mode using notched blade and Instron machine at 0.5 mm/min. Different variables were tested including photopolymerization duration, photopolymerization intensity, special jig, compsite thickness, material's aging, bonding agent aging and bottle open time, photopolymerizing distance, and the effect of applying primer/conditioner of two resin modified glass ionomers (RMGI) on shear bond strength to dentine. Results: Different photopolymerizing intensity and duration produced significant statistical results. The special jig significantly reduced the variance in shear bond strength compared to Ultradent jig. composite thickness at 5 mm has significantly reduced shear bond strength compared to 2.3 mm thicknesses. Materials expiration resulted in less shear bond strength in all materials groups tested except for Z100. Shear bond strength with bonding agent bottle open time significantly different when the bottle reached ½ full and less. Increasing photopolymerization distance reduced energy perceived. There was significant difference in shear bond strength when photopolymerzing distance increased to 3 mm in comparison to direct contact and 6 mm and between direct contact, 3, 6 mm and 9 mm. Conclusions: Different factors affecting to the process of bonding dental materials to dentine produced a significant effect on shear bond strength to dentine. Both curing time and intensity had a significant effect on shear bond strength (P=0.001). A new experimental specimen preparation device demonstrated good potential for lower variability and preparation. Different composite thicknesses significantly affected shear bond strength. The best shear bond strength was achieved using 2 mm thickness with 2140 intensity at both 10 and 40 seconds. Shear bond strength at 3 mm thickness was decreases compared to 2 mm with 2140 at both 10 and 40 seconds but was not significant. Shear bond strength was significantly decreased at 5 mm thickness at 2140 mw/cm2 intensity for both 10 and 40 seconds.At 5 mm thickness, shear bond strength was significantly increased at lower intensity of 600 and 40 seconds than 2140 mw/cm2 photopolymerization intensity and both 10 and 40 seconds. At 2 and 3 mm, shear bond strength was significantly increased for 2140 mw/cm2 over 600 mw/cm2 at both durations of 10 and 40 seconds. There was significant difference between expired composites and non-expired one. Shear bond strength was significantly decreased toward half full bottle. Shear bond strength was sharply decreased toward near empty bottle with extended period of time. Shear bond strength at 3 mm was significantly greater than direct contact and 6 mm. There was no significant difference in shear bond strength at direct contact and 6 mm distance. Shear bond strength at 10 mm was significantly lower. Using Ketac Nano primer significantly increased shear bond strength for Ketac Nano RMGI. There was no significant difference in shear bond strength when applying GC RMGI with or without its conditioner.
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 firstname.lastname@example.org.Thesis (DScD) --Boston University, Henry M. Goldman School of Dental Medicine, 2010 (Department of Restorative Sciences and Biomaterials).Includes bibliographic references: leaves 252-263.
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