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Dual-cure (DC) resins are mainly used as cements due to high initial color (generally yellow) and large color shift (ΔE*) after polymerization as compared to light-cured resins. However, even as cements, this color shift is clinically unacceptable, especially when used to cement thin veneers. Objective To develop a novel DC initiator system with both lower initial color (less yellow, i.e., whiter) and smaller ΔE*. Methods The effect of using an allyl thiourea (T)/cumene hydroperoxide (CH) self-cure (SC) initiator system in combination with a photo-co-initiator, p-octyloxy-phenyl-phenyl iodonium hexafluoroantimonate (OPPI), in a commercial DC resin cement (PermaFlo DC, Ultradent Products, Inc.) was investigated. Initial color and ΔE* were assessed for 6 weeks in vitro under accelerated aging conditions (75 °C water bath). Rockwell15T hardness was used to assess degree of cure (DoC) and the three-point bending test was used to assess mechanical properties. Results PermaFlo DC (control) was significantly harder than all experimental groups without OPPI but had up to three times higher initial color and four times greater color shift (ΔE* = 27 vs. 8). With OPPI, hardness in the experimental groups increased significantly and several were comparable to the controls. Initial color and ΔE* increased slightly (ΔE* = 9), but was still 3 times less than that of PermaFlo DC. DC samples containing OPPI had comparable modulus and ultimate transverse strengths to those of the controls. Conclusions DC resins that use the T/CH initiator system are weaker but have extremely low color and ΔE*. The addition of OPPI increases DoC and mechanical properties to clinically acceptable levels and maintains extremely low color and ΔE*. Significance With this novel initiator system, DC resins potentially can now have comparable color and color stability to light-cure resins and be used in broader esthetic dental applications to improve color stability and reduce shrinkage stress in restorative composites.

Dimethacrylate dental composite resins exhibit inherently low toughness. Toughening of these materials may reduce the incidence of marginal and bulk fracture of composite restorations. Objective: To determine if dimethacrylate dental restorative materials can be rubber-toughened, and if so, to identify a possible mechanism. Methods: A filler composed of aggregates of polybutadiene/silica as well as irregularly-shaped silica slabs was produced by mixing silica with polybutadiene in dichloromethane. The dried filler was subsequently ground and sieved to

Administration of morphine or ethanol to rats produces a decrease in regional brain calcium in vivo. This effect is selectively antagonized by the stereospecific narcotic antagonist naloxone. Reserpine and the dopamine-acetaldehyde conjugate salsolinol also produce a depletion of regional brain calcium, but only the salsolinol depletion is antagonized by naloxone. Experiments with naloxone provide evidence for two calcium-sensitive pools in the central nervous system.

— The in vivo administration of a single dose of morphine produces a decrease of tissue calcium in the rat brain. This decrease is observed to be linear, dose-dependent, time-dependent and to occur to an equal degree in 8 discrete brain regions. This effect of morphine is blocked by naloxone and exhibits a high degree of sterospecificity. The reserpine induced decrease of brain calcium was not antagonized by naloxone. Differentiation of this response using reserpine and naloxone indicates the possibility of calcium pools in the central nervous system. The results are discussed in terms of a specific effect of opiate drugs and the role of calcium in opiatereceptor interactions.

Synaptosomal membranes accumulate 3–6 times more Ca2+ in the presence of ATP (50–1000 μM) than basal Ca2+ accumulation (-ATP). The location of this Ca2+ accumulation appears to reside on the cytosolic face of the synaptosome since lysed synaptosomes accumulate 4-times more Ca2+ than intact synaptosomes. The inclusion of mitochondrial inhibitors, oligomycin (0.7 μg/ml), sodium azide (100 μM) and dinitrophenol (100 μM) differentiate mitochondrial from nonmitochondrial Ca2+ accumulation under conditions that are [Ca2+]- and ATP-dependent. In the presence of low concentrations of ATP (200 μM), the Ca2+ accumulation process remains independent of the presence of mitochondrial inhibitors when Ca free 2+ =2.5 μM. When Ca free 2+ is increased to 6.8 μM, mitochondrial inhibitors differentiate mitochondrial from nonmitochondrial accumulation. These studies suggest that optimal conditions for the measurement of Ca2+ accumulating mechanisms in synaptosomal membranes depend on both [Ca2+] and ATP. Use of these assay conditions provide evidence that ATP-dependent Ca2+ uptake may be a viable mechanism for the regulation of synaptosomal Ca2+ levels.