Ion release and cytotoxicity of stainless steel wires.
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Heat treatment is generally applied to orthodontic stainless steel (SS) wires to relieve the stresses that result from their manipulation by orthodontists. The quality and thickness of the oxide films formed on the surface of heat-treated wires can vary, and it is believed that these oxide films can influence the properties of heat-treated wires. The aim of this study was to investigate the influence of heat treatment and cooling methods on the amount of metal ions released and to examine the cytotoxicity of heat-treated wires. In this study, four types of SS wires (Remanium, Permachrome, Colboloy and Orthos) with a cross-sectional area of 0.41 x 0.56 mm were investigated. These wires were heat-treated in a vacuum, air, or argon environment, and were cooled in either a furnace or a water bath. Four control groups and 24 experimental groups were classified according to the type of wires, heat treatment conditions and cooling methods. In each group, the amount of nickel released as well as its cytotoxicity was investigated. The concentration of dissolved nickel ions in artificial saliva was measured for a period of up to 12 weeks. In all groups, the concentration of dissolved nickel ions in artificial saliva was lowest for the vacuum heat treatment-furnace cooling group and a significant difference was shown compared with the other experimental groups. The concentration of dissolved nickel ions in artificial saliva was highest in the groups heat-treated in air (P < 0.05), while the amount of nickel released was highest in the Remanium and Colboloy (P < 0.05). The cytotoxicity was mild in all the experimental groups but the response index of the air groups was slightly higher than in the other groups. According to these results, SS wires retain their high corrosion resistance and low ion release rate when heat-treated in a vacuum and cooled in a furnace. (+info)
Galvanic corrosion between orthodontic wires and brackets in fluoride mouthwashes.
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The aim of this investigation was to determine the influence of fluoride in certain mouthwashes on the risk of corrosion through galvanic coupling of orthodontic wires and brackets. Two titanium alloy wires, nickel-titanium (NiTi) and copper-nickel-titanium (CuNiTi), and the three most commonly used brackets, titanium (Ti), iron-chromium-nickel (FeCrNi) and cobalt-chromium (CoCr), were tested in a reference solution of Fusayama-Meyer artificial saliva and in two commercially available fluoride (250 ppm) mouthwashes, Elmex and Meridol. Corrosion resistance was assessed by inductively coupled plasma-atomic emission spectrometry (ICP-MS), analysis of released metal ions, and a scanning electron microscope (SEM) study of the metal surfaces after immersion of different wire-bracket pairs in the test solutions. The study was completed by an electrochemical analysis. Meridol mouthwash, which contains stannous fluoride, was the solution in which the NiTi wires coupled with the different brackets showed the highest corrosion risk, while in Elmex mouthwash, which contains sodium fluoride, the CuNiTi wires presented the highest corrosion risk. Such corrosion has two consequences: deterioration in mechanical performance of the wire-bracket system, which would negatively affect the final aesthetic result, and the risk of local allergic reactions caused by released Ni ions. The results suggest that mouthwashes should be prescribed according to the orthodontic materials used. A new type of mouthwash for use during orthodontic therapy could be an interesting development in this field. (+info)
The effect of different solutions on the bond strength of soft lining materials to acrylic resin.
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In this study, we investigated the effect of different solutions--coffee, tea, Turkish coffee, artificial saliva, mouthwash, denture cleanser, and distilled water--on the bond strength of soft lining materials (one acrylic- and three silicone-based) to acrylic resin. Acrylic specimens (40x10x10 mm) were prepared for the bond strength test. The specimens were stored in different solutions and tested after 24 hours, seven days, and 30 days. Using analysis of variance, the bond strength of soft lining materials to acrylic resin was found to be related to the type of material, storage time, and storage solution. Visco-gel had the lowest bond strength to cured acrylic resin, where its strength ranged from 0.149 MPa to 0.784 MPa. The bond strength of Visco-gel was also found to increase with time. Molloplast-B and Ufi Gel P demonstrated better bond strength than Visco-gel and Mollosil. (+info)
Color change of newly developed esthetic restorative material immersed in food-simulating solutions.
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Recently, an esthetic tooth coating material has been developed. The material consisted of a primer solution, a base coat, and a top coat. The purpose of this study, therefore, was to evaluate the color change of this tooth coating material and two resin composites after immersion in food-simulating, staining solutions. To this end, the newly developed coating material with and without its top coat, a flowable resin composite, and a hybrid resin composite were employed for the evaluation. The specimens were subjected to an experimental 24-hour staining cycle: 7-hour immersion in coffee, green tea or red wine, then 17-hour immersion in artificial saliva solution containing 0.3% mucin. After 24 hours, 3 days, 1, 2, and 4 weeks of immersion, the color changes of all specimen surfaces were measured. Compared with the other materials, the deltaE* value of coating material without its top coat tended to increase as the immersion period increased until 4 weeks. On the other hand, the deltaE* value of coating material with its top coat measured the lowest among the materials tested. Based on the results obtained, it was concluded that when using this recently developed tooth coating material in dental clinics, its top coat should be properly applied. (+info)
Effects of welding pulse energy and fluoride ion on the cracking susceptibility and fatigue behavior of Nd:YAG laser-welded cast titanium joints.
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In this study, the cracking susceptibility and fatigue behavior of Nd:YAG laser-welded cast Ti joints (welding pulse energy: 11, 15, and 18 J) in fluoride-containing (0 and 0.5% NaF) artificial saliva were evaluated using constant elongation rate test (CERT) and fatigue test (FT), respectively. Both CERT and FT were also carried out in open air as controls. Results showed that increasing the welding energy increased the elongation and fatigue life, but decreased the tensile strength, of cast Ti joints in open-air environment. With a welding energy of 11 J, the fluoride ions in the artificial saliva increased the cracking susceptibility and decreased the fatigue life of Ti joints. When the welding energy exceeded 15 J, the presence of fluoride ions still increased the cracking susceptibility, but did not reduce the fatigue life of Ti joints. Rupture of Ti joints--if it occurred--occurred only at the welded metal (versus the non-welded part). (+info)
Hyposalivation in elderly patients.
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Saliva is a key element in oral homeostasis, oral function and maintenance of oral health. Dry mouth has multiple oral health consequences and affects quality of life. The incidence of dry mouth and its public health impact are increasing due to the aging population, the effects of some systemic diseases, and medical management and commonly prescribed medications that reduce saliva production. In this paper, we review the causes of dry mouth and its impact on health. The role of dental providers and current management of dry mouth is presented. (+info)
Chlorhexidine preserves dentin bond in vitro.
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Loss of hybrid layer integrity compromises resin-dentin bond stability. Matrix metalloproteinases (MMPs) may be partially responsible for hybrid layer degradation. Since chlorhexidine inhibits MMPs, we hypothesized that chlorhexidine would decelerate the loss of resin-dentin bonds. Class I preparations in extracted third molars were sectioned into two halves. One half was customarily restored (etch-and-rinse adhesive/resin composite), and the other was treated with 2% chlorhexidine after being acid-etched before restoration. Specimens were stored in artificial saliva with/without protease inhibitors. Microtensile bond strengths and failure mode distribution under SEM were analyzed immediately after specimens' preparation and 6 months later. With chlorhexidine, significantly better preservation of bond strength was observed after 6 months; protease inhibitors in the storage medium had no effect. Failure analysis showed significantly less failure in the hybrid layer with chlorhexidine, compared with controls after 6 months. In conclusion, this in vitro study suggests that chlorhexidine might be useful for the preservation of dentin bond strength. (+info)
Evaluation of the solubility of dental cements in artificial saliva of different pH values.
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The aim of this study was to determine the solubility of dental cements in artificial saliva of different pH values. A total of 180 specimens--20 specimens (20 mm diameter x 1.5 mm thickness) for each dental cement-were prepared. After the specimens were weighed, they were set in the media with different pH values. After 24 hours, 72 hours, seven days, and 28 days, the specimens were taken out, dried in a desiccator, and re-weighed. Percentage of solubility at each time period was calculated as 100 per cent times weight loss divided by the initial weight of the specimen. Analysis of variance and LSD multiple comparison test were applied. It was found that cement type, storage time, and medium pH exerted statistically significant (p<0.001) effects on solubility. Among the tested cement types, zinc phosphate cement (Adhesor Carbofine) presented the highest solubility. In terms of medium pH, the cements seemed to be most stable in the medium with pH 7. (+info)