Bonding of Composite Resin to Alumina and Zirconia Ceramics with Special Emphasis on Surface Conditioning and Use of Coupling Agents

Dental oxide ceramics have been inspired by their biocompability and mechanical properties which have made durable all-ceramic structures possible. Clinical longevity of the prosthetic structures is dependent on effective bonding with luting cements. As the initial shear bond strength values can be comparable with several materials and procedures, long-term durability is affected by ageing. Aims of the current study were: to measure the shear bond strength of resin composite-to-ceramics and to evaluate the longevity of the bond; to analyze factors affecting the bond, with special emphasis on: the form of silicatization of the ceramic surface; form of silanization; type of resin primer and the effect of the type of the resin composite luting cement; the effect of ageing in water was studied regarding its effect to the endurance of the bond. Ceramic substrates were alumina and yttrium stabilized zirconia. Ceramic conditioning methods included tribochemical silicatization and use of two silane couplings agents. A commercial silane primer was used as a control silane. Various combinations of conditioning methods, primers and resin cements were tested. Bond strengths were measured by shear bond strength method. The longevity of the bond was generally studied by thermocycling the materials in water. Additionally, in one of the studies thermal cycling was compared with long-term water storaging. Results were analysed statistically with ANOVA and Weibull analysis. Tribochemical treatment utilizing air pressure of 150 kPa resulted shear bond strengths of 11.2 MPa to 18.4 MPa and air pressure of 450 kPa 18.2 MPa to 30.5 MPa, respectively. Thermocycling of 8000 cycles or four years water storaging both decreased shear bond strength values to a range of 3.8 MPa to 7.2 MPa whereas initial situation varied from 16.8. Mpa to 23.0 MPa. The silane used in studies had no statistical significance. The use of primers without 10-MDP resulted spontaneous debonding during thermocycling or shear bond strengths below 5 MPa. As conclusion, the results showed superior long-term bonding with primers containing 10-MDP. Silicatization with silanizing showed improved initial shear bond strength values which considerably decreased with ageing in water. Thermal cycling and water storing for up to four years played the major role in reduction of bond strength, which could be due to thermal fatigue of the bonding interface and hydrolytic degradation of the silane coupled interface.Yhdistelmämuovin sidostaminen alumiinioksidiin ja zirkoniaan painottaen pintakäsittelyä ja sidostusaineiden käyttöä. Hammaslääketieteelliset kokokeraamiset rakenteet ovat tulleet mahdollisiksi oksidikeraamien biologisuuden ja erinomaisten mekaanisten ominaisuuksien ansiosta. Proteettisten rakenteiden kestävyys on riippuvainen onnistuneesta ja tehokkaasta sementoinnista. Vaikka useiden tuotteiden ja menetelmien takaamat sidoslujuudet ovat vertailukelpoisia alkutilanteessa, kestävyyteen ja riittävään sidoslujuuteen vaikuttaa keinotekoinen vanhentaminen. Tämän väitöskirjatyön tavoitteet olivat: mitata yhdistelmämuovin repäisysidoslujuutta keraamiin ja arvioida sen kestävyyttä; edelleen eritellä sidokseen vaikuttavia tekijöitä painottaen: silikoinnin muoto keraamisella pinnalla; silanoinnin muoto; primerin ja resiinin tyyppi; yhdistelmämuovisementin vaikutus; vedessä vanhentamisen vaikutus sidoskestävyyden arvioimiseksi. Keraamiset substraatit olivat alumiinioksidi ja yttriastabiloitu zirkonia. Keraamin esikäsittelytapoihin kuuluivat tribokemiallinen silikointi ja kaksi silaania. Kaupallista tuotetta käytettiin referenssinä. Erilaisia esikäsittelyresiini- ja yhdistelmämuovisementtikombinaatioita tutkittiin. Sidoslujuus testattiin repäisylujuusmenetelmällä. Sidoksen pitkäikäisyys tutkittiin pääasiallisesti termosyklaamalla. Lisäksi yhdessä osatutkimuksessa pitkäaikaisvesisäilytystä verrattiin termosyklaamiseen. Tulokset analysoitiin varianssianalyysillä ja Weibull analyysillä. Tribokemiallinen käsittely käyttäen 150 kPa:n ilmanpainetta tuotti 11,2 – 18,4 MPa:n sidoslujuuden ja vastaavasti 450 kPa:n ilmanpaine 18,2 – 30,5 MPa:n sidoslujuuden.. 8000 kerran termosyklaaminen tai neljän vuoden vesihaudesäilytys laskivat molemmat repäisylujuusarvot 3,8 – 7,2 MPa:iin alkutilanteen vaihdellessa 16,8. – 23,0 MPa.:n välillä. Käytetyllä silaanilla ei ollut tilastollista merkitsevyyttä.. Ilman 10-MDP:tä sisältäviä primereitä tapahtui spontaania koekappaleiden irtoamista tai repäisylujuusarvot jäivät alle 5 MPa:n. Johtopäätöksenä tulokset osoittivat parasta pitkäaikaissidosta primereillä, joissa on 10-MDP:tä. Silikointi ja silanointi osoittivat alkutilanteessa korkeita sidoslujuusarvoja, jotka pienenivät huomattavasti vesihauteessa vanhennettaessa. Termosyklaus ja vesisäilytys neljän vuoden ajan toimivat pääasiallisina tekijöinä sidoslujuuden vähenemisessä, joka voi johtua termisestä väsymisestä sidostumisalueella ja silaanin sidostumisalueen hydrolyyttisestä rappeutumisesta.Siirretty Doriast

Random testing of interrupt-driven software

ManuscriptInterrupt-driven embedded software is hard to thoroughly test since it usually contains a very large number of executable paths. Developers can test more of these paths using random interrupt testing-firing random interrupt handlers at random times. Unfortunately, na¨ıve application of random testing to interrupt-driven software does not work: some randomly generated interrupt schedules violate system semantics, causing spurious failures. The contribution of this paper is the design, implementation, and experimental evaluation of RID, a restricted interrupt discipline that hardens embedded software with respect to unexpected interrupts, making it possible to perform random interrupt testing and also protecting it from spurious interrupts after deployment. We evaluate RID by implementing it in TinyOS and then using random interrupt testing to find bugs and also to drive applications toward their worst-case stack depths

On the Complexity of Spill Everywhere under SSA Form

Compilation for embedded processors can be either aggressive (time consuming cross-compilation) or just in time (embedded and usually dynamic). The heuristics used in dynamic compilation are highly constrained by limited resources, time and memory in particular. Recent results on the SSA form open promising directions for the design of new register allocation heuristics for embedded systems and especially for embedded compilation. In particular, heuristics based on tree scan with two separated phases -- one for spilling, then one for coloring/coalescing -- seem good candidates for designing memory-friendly, fast, and competitive register allocators. Still, also because of the side effect on power consumption, the minimization of loads and stores overhead (spilling problem) is an important issue. This paper provides an exhaustive study of the complexity of the ``spill everywhere'' problem in the context of the SSA form. Unfortunately, conversely to our initial hopes, many of the questions we raised lead to NP-completeness results. We identify some polynomial cases but that are impractical in JIT context. Nevertheless, they can give hints to simplify formulations for the design of aggressive allocators.Comment: 10 page

Memory safety and untrusted extensions for TinyOS

Journal ArticleSensor network applications should be reliable. However, TinyOS, the dominant sensor net OS, lacks basic building blocks for reliable software systems: memory protection, isolation, and safe termination. These features are typically found in general-purpose operating systems but are believed to be too expensive for tiny embedded systems with a few kilobytes of RAM. We dispel this notion and show that CCured, a safe dialect of C, can be leveraged to provide memory safety for largely unmodified TinyOS applications. We build upon safety to implement two very different environments for TinyOS applications. The first, Safe TinyOS, provides a minimal kernel for safely executing trusted applications. Safe execution traps and identifies bugs that would otherwise have silently corrupted RAM. The second environment, UTOS, implements a user-kernel boundary that supports isolation and safe termination of untrusted code. Existing TinyOS components can often be ported to UTOS with little effort. To create our environments, we substantially augmented the CCured toolchain to emit code that is safe under interrupt-driven concurrency, to reduce storage requirements by compressing error messages, to refactor direct hardware access into calls to trusted helper functions, and to make safe programs more efficient using whole-program optimization. A surprising result of our work is that a safe, optimized TinyOS program can be faster than the original unsafe, unoptimized application

Optimal Two-Level Speed Assignment for Real-Time Systems

Reducing energy consumption is one of the main concerns in the design and implementation of embedded real-time systems. For this reason, the current generation of processors allows to vary voltage and operating frequency to balance computational speed and energy consumption. This technique is called dynamic voltage scaling (DVS). When applying DVS tohard real-time systems, it is important to provide the worst-case computational requirement; otherwise the timing constraints may be violated. However, the probability of a task executing for its worst-case execution time is very low. In this paper,we show how to exploit probabilistic information about the execution time of a task in order to reduce the energy consumed by the processor. Optimal speed assignments and transition points are found using a very general model for the processor. The model accounts for the processor idle power and time/energy overheads due to frequency transitions. We also show how these results apply to some significant cases

Memory safety and untrusted extensions for TinyOS

technical reportSensor network applications should be reliable. However, TinyOS, the dominant sensor net OS, lacks basic building blocks for reliable software systems: memory protection, isolation, and safe termination. These features are typically found in general-purpose operating systems but are believed to be too expensive for tiny embedded systems with a few kilobytes of RAM. We dispel this notion and show that CCured, a safe dialect of C, can be leveraged to provide memory safety for largely unmodified TinyOS applications. We build upon safety to implement two very different environments for TinyOS applications. The first, Safe TinyOS, provides a minimal kernel for safely executing trusted applications. Safe execution traps and identifies bugs that would otherwise have silently corrupted RAM. The second environment, UTOS, implements a user-kernel boundary that supports isolation and safe termination of untrusted code. Existing TinyOS components can often be ported to UTOS with little effort. To create our environments, we substantially augmented the CCured toolchain to emit code that is safe under interrupt-driven concurrency, to reduce storage requirements by compressing error messages, to refactor direct hardware access into calls to trusted helper functions, and to make safe programs more efficient using whole-program optimization. A surprising result of our work is that a safe, optimized TinyOS program can be faster than the original unsafe, unoptimized application