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Original scientific paper

Dentin Bond Strength and Reliability of Experimental Bioactive Composites

Josipa Vukelja
Matej Par
Zrinka Tarle
Eva Klarić Sever

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Weibull analysis of bond strength
Aim: To compare differences in outcomes of statistical approaches of reliability analysis (Weibull) and conventional statistics for bond strength of experimental remineralizing composites and disclose changes that would not be discernible by using just one statistical approach.
Materials and Methods: Experimental composites were made by blending a Bis-GMA/TEGDMA resin with bioactive glass (BG) and inert fillers (barium glass and silica) in a centrifugal mixer. Inert fillers were admixed to the total filler load of 70 wt%. Control composite incorporated only inert fillers (70 wt%). Two remineralizing composites with 10 or 40 wt% of BG were marked as bioactive-10 and bioactive-40. Dentin substrates were prepared from intact third molars, polished under the water using P600 silicon carbide paper and embedded into an acrylic resin. Composite cylinders (d=3mm, h=2mm) were bonded on dentin substrates using a two-step self-etch bonding agent (Clearfil SE Bond 2, Kur- aray). Specimens were stored at 37 °C in distilled water and fractured in shear mode after 1 week and
1 year. Per experimental group 20 samples were prepared in order to obtain the optimal sample size for Weibull analysis (total n=120 for the whole study).
Results: Mean bond strengths measured after 1 week and 1 year were statistically similar for the control composite (21.9 vs. 24.0 MPa) and for bioactive-10 (19.6 vs. 19.1 MPa). Nevertheless, Weibull statistics identified a significant decrease in bond reliability after aging: Weibull moduli were decreased from 13.5 to 3.9 for the control composite and from 12.3 to 3.8 for bioactive-10. For bioactive-40, mean bond strength declined significantly after 1 year (8.1 vs. 6.8 MPa) but its reliability remained unchanged, as identified by statistically similar Weibull moduli.
Conclusions: A decrease in dentin bond strength after 1 year was identified using Weibull analysis in the control and experimental bioactive composite, while conventional statistics were incapable to distin- guish changes in mean bond strength.


dentin bond strength, Weibull analysis, reliability, bioactive glass 45S5, shear bond strength adhesives, dental materials, composite resins,

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