Micro versus Macro Shear Bond Strength Testing of Dentin-Composite Interface Using Chisel and Wireloop Loading Techniques

Shear bond strength (SBS) testing is a commonly used method for evaluating different dental adhesive systems. Failure mode analysis provides valuable information for better interpretation of bond strength results. The aim of this study was to evaluate the influence of specimen dimension and loading technique on shear bond strength and failure mode results. Eighty macro and micro flowable composite cylindrical specimens of 1.8 and 0.8 mm diameter, respectively, and 1.5 mm length were bonded to dentinal substrate. Four study groups were created (n = 20): Macroshear wireloop, Gp1; Microshear wireloop, Gp2; Macroshear chisel, Gp3; and Microshear chisel, Gp4. They were tested for SBS using chisel and wireloop loading devices followed by failure mode analysis using digital microscopy and SEM. Two- and one-way ANOVA were used to compare stress at failure values of different groups while the Kruskal–Wallis test was used to compare between failure modes of the tested groups. Gp4 recorded the highest mean stress at failure 54.1 ± 14.1 MPa, and the highest percentage of adhesive failure in relation to the other groups. Specimen dimension and loading technique are important parameters influencing the results of shear bond strength. Micro-sized specimens and chisel loading are recommended for shear testing.

I Unplugged What?

Dear KV, I'm sure by now you've read about the latest large systems failure, and I wondered if you'd share your thoughts on how such a large company can fail so miserably at infrastructure. I'm probably lobbing a softball, but how is it possible that these large and pervasive failures happen?

Brake systems: a mind of their own

Brake systems fitted to current production vehicles are not the relativity straightforward hydraulic systems that many people expect. Rather they have evolved into complex systems which are on their own deliberately capable of affecting the behaviour of a vehicle. Crucially they depend on computers, software and electronic sensors to allow them to form a model of how the vehicle is expected to behave on the road and how it is actually behaving. Like any artefact they can, and do fail. This paper provides a high-level overview of the braking systems currently in place, how these systems act and present some examples of how they have failed in practice. Index words: vehicles; vehicle electronics; electronic control; software; brake systems; failure modes

Decentralization and District-Level Decentralization in Amhara Region

This paper examines the process of decentralization and district level decentralization programs in the Amhara region. It addresses the decentralization processes in Imperial, Derg, and EPRDF regimes. The depth and degree of decentralization in the three consecutive regimes were different as the process of decentralization in the current government meant to be deeper and extensive and pushed powers, functions, and roles into the local government. The process of decentralization in the current government has transferred powers and functions to the districts. However, the district level decentralization process has faced many challenges. The paper revealed that unclear assignments of powers and functions, executive dominations, upward accountabilities, top-down planning, lack of skilled manpower, lack participatory systems, failure of the councils in holding the executive accountable, lack of adequate budget, lack of revenue mobilization capacity, lack of responsiveness, and accountability among councils were the main challenges that impede in the process of the DLD process.