Objective To evaluate recently developed acidic calcium-phosphate (CaP) pastes as conservative enamel-conditioning systems for bracket bonding and investigate their effects on the shear bond strength, adhesive residues, and enamel damage in comparison to a conventional 37 % phosphoric acid (PA) gel. Materials and methods Two experimental etchant pastes consisting of hydroxyapatite and monocalcium phosphate monohydrate were prepared by mixing them with 37 % and 10 % PA solutions, respectively. These were characterized using X-ray diffraction. Metal brackets were bonded to 90 freshly extracted human premolars and assigned to three groups, depending on etchant type: 37 % PA-gel (control) and the two experimental (HPA and MPA) pastes. Shear bond strengths (SBS), adhesive remnant index scores, and enamel damage for the three groups were compared at 24 h water storage and after 5000 thermocycles. Enamel etch pattern, surface damage, and CaP precipitation were evaluated through FE-SEM. Surface Vickers micro-hardness (VHN) following etching procedures was compared to the unetched enamel surface. Results HPA and MPA pastes yielded significantly lower SBS values than 37 % PA-gel (p < 0.001), induced a milder etch pattern, unblemished enamel surfaces and CaP re-precipitation with no or minimal adhesive residues post-bracket debonding as compared to 37 % PA-gel. Moreover, the HPA paste-etched enamel revealed the highest (p < 0.001) micro-hardness value (232 VHN). Conclusions Enamel conditioning using the CaP pastes, particularly the HPA, may evoke CaP re-precipitation and cause minimal enamel damage, with greater efficiency at bracket debonding/enamel cleaning procedures. Furthermore, it yields low adhesive residues and potentially adequate bond strength for clinical performance in comparison to conventional PA gel. Clinical Significance Enamel etching with the developed paste prior to orthodontic bonding might lessen the development of white spot lesions during treatment, with the potential of reducing the prolonged chair time for clean-up and polishing usually required whenever PA is used.
Phosphorus is usually the limiting nutrient for eutrophication in inland receiving waters; therefore, phosphorus concentrations must be controlled. In the present study, a series of jar test was conducted to evaluate the optimum pH, dosage and performance parameters for coagulants alum and calcium chloride. Phosphorus removal by alum was found to be highly pH dependent with an optimum pH of 5.7-6. At this pH an alum dosage of 80 mg/l removed 83 % of the total phosphorus. Better removal was achieved when the solution was buffered at pH = 6. Phosphorus removal was not affected by varying the slow mixing period; this is due to the fact that the reaction is relatively fast.
The dosage of calcium chloride and pH of solution play an importa
In this research paper, two techniques were used to treat the drill cuttings resulting from the oil-based drilling fluid. The drill cuttings were taken from the southern Rumaila fields which prepared for testing and fixed with 100 gm per sample and contaminated with two types of crude oil, one from Rumaila oilfields with Sp.gr of 0.882 and the other from the eastern Baghdad oilfield with Sp.gr of 0.924 besides contamination levels of 10% and 15% w/w in mass. Samples were treated first with microwave with a power applied of 540 & 180 watts as well as a time of 50 minutes. It was found that the results reached below 1% w/w in mass, except for two samples they reached below 1.5% w/w in mass. Then, the sample of 1.41% w/w in mass,
... Show MoreKE Sharquie, KI Al-Hamdi, AA Noaimi, AA Al-Mohammadi, J Clin Exp Invest www. clinexpinvest. org Vol, 2011 - Cited by 1
Reintervention after balloon angioplasty is often considered inevitable in children with coarctation of the aorta (COA). The present study aimed to evaluate predictors of re-intervention after balloon angioplasty for COA, with the goal of identifying patient and procedural characteristics that may influence long-term outcomes
In this study, ultraviolet (UV), ozone techniques with hydrogen peroxide oxidant were used to treat the wastewater which is produced from South Baghdad Power Station using lab-scale system. From UV-H2O2 experiments, it was shown that the optimum exposure time was 80 min. At this time, the highest removal percentages of oil, COD, and TOC were 84.69 %, 56.33 % and 50 % respectively. Effect of pH on the contaminants removing was studied in the range of (2-12). The best oil, COD, and TOC removal percentages (69.38 %, 70 % and 52 %) using H2O2/UV were at pH=12. H2O2/ozone experiments exhibited better performance compared to
... Show MoreDeveloped and underdevelopment countries, on equal terms, face the problem of budget deficiency. Budget deficiency means that the public expenditure surpasses the public revenues. This, on the international level, is one of the most serious economic problems with many direct effects on the national economy, and depends, basically, on its finance chosen method. Looking for a solution to this problem, for this reason and many other ones, has been highlighted in spite of the many attempts to reduce the role of the governmental expenditure. Budget deficiency can not be attributed to a single unique cause since it is complex phenomenons the causes of which are related to many factors contribute to its occurrence, some of which refer t
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