Three-year randomised clinical trial to evaluate the clinical performance, quantitative and qualitative wear patterns of hybrid composite restorations.
(27/56)
The effects of erroneous mixing of zinc carboxylate cements.
(29/56)
The mechanical properties of luting agents are determined by the mixing ratio of powder and liquid. The purpose of this in vitro study was to evaluate the therapeutic range of zinc carboxylate cements by investigating the mechanical properties of such cements when formulated using erroneous powder/liquid ratios. Using the recommended powder/liquid ratio as a standard, four different mixing ratios (25% and 50% more or less powder) were used to prepare each carboxylate cement (Aqualox, Carboco, Durelon). A veneering composite (Sinfony) was used as control. Vickers hardness and three-body abrasion were evaluated. In each carboxylate cement, both a 25% and 50% increase in liquid content resulted in significantly lower Vickers hardness, whereas a higher powder content altered the saturation concentration but did not result in increased hardness; this effect was particularly obvious in Carboco. Durelon showed a linear relationship between wear and powder/liquid ratio, whereas Carboco and Aqualox displayed a more exponential increase in wear in mixings with an increased liquid content. The mechanical properties of carboxylate cements were altered in mixtures with an increased liquid content, but not in those with a high powder content. Mixing ratio errors greater than 25% may significantly affect the clinical performance of carboxylate cements. (+info)
Improved brushing durability of titanium dioxide coating on polymethylmethacrylate substrate by prior treatment with acryloxypropyl trimethoxysilane-based agent for denture application.
(30/56)
The purpose of this study was to determine whether the brushing durability of a titanium dioxide coating on a polymethyl methacrylate (PMMA) substrate was improved by prior treatment with an acryloxypropyl trimethoxysilane-based agent. Titanium dioxide coatings were obtained by spray-coating substrates with or without prior treatment. Structure was investigated using IR, SEM, and an EPMA. Effect on durability against brushing was determined with a brush-wear test machine utilizing a commercial denture brush. A thin layer comprised of siloxane and TiO(2) was formed on a PMMA substrate by prior treatment with an acryloxypropyl trimethoxysilane-based agent and spray-coating of TiO(2). Prior treatment demonstrated improved stability against brushing, whereas the titanium coating was removed after less than 1x10(5) brushing cycles without prior treatment. This suggests that prior treatment with an acryloxypropyl trimethoxysilane-based agent would confer improved durability against brushing-induced stress on a TiO(2) coating in its application to dentures. (+info)
Masticatory efficiency in denture wearers with bilateral balanced occlusion and canine guidance.
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Wear of opposing teeth by posterior composite resins--evaluation of newly developed wear test methods.
(32/56)
In the present study, enamel wear against indirect composite resins was evaluated using two newly designed wear test methods: a rotating sliding wear test and a buff wear test. For the composite resins investigated in this study, their surface morphologies were examined using a scanning probe microscope after buff-polishing. After the wear tests, enamel was worn down by hard fillers that protruded from the abraded resin matrices. Notably, enamel wear was induced by composite materials with a Vickers hardness number (VHN) greater than 45 and that the amount of enamel wear increased with increasing hardness of the composite material. Therefore, 45 VHN was the critical hardness value for composite resins at which antagonistic enamel wear would occur. Besides, the D-value obtained from the buff wear test indicated not only the relative wear resistance of the composite resin itself, but also its potential risk to induce antagonistic enamel wear. (+info)