In vivo Assessments of Bioabsorbable AZ91 Magnesium Implants Coated with Nanostructured Fluoridated Hydroxyapatite by MAO/EPD Technique for Biomedical Applications

Although magnesium (Mg) is a unique biodegradable metal which possesses mechanical property similar to that of the natural bone and can be an attractive material to be used as orthopedic implants, its quick corrosion rate restricts its actual clinical applications. To control its rapid degradation, we have modified the surface of magnesium implant using fluoridated hydroxyapatite (FHA: Ca10(PO4)6OH2 − xFx) through the combined micro-arc oxidation (MAO) and electrophoretic deposition (EPD) techniques, which was presented in our previous paper. In this article, the biocompatibility examinations were conducted on the coated AZ91 magnesium alloy by implanting it into the greater trochanter area of rabbits. The results of the in vivo animal test revealed a significant enhancement in the biocompatibility of FHA/MAO coated implant compared to the uncoated one. By applying the FHA/MAO coating on the AZ91 implant, the amount of weight loss and magnesium ion release in blood plasma decreased. According to the histological results, the formation of the new bone increased and the inflammation decreased around the implant. In addition, the implantation of the uncoated AZ91 alloy accompanied by the release of hydrogen gas around the implant; this release was suppressed by applying the coated implant. Our study exemplifies that the surface coating of magnesium implant using a bioactive ceramic such as fluoridated hydroxyapatite may improve the biocompatibility of the implant to make it suitable as a commercialized biomedical product

Clinical performance of CEREC AC Bluecam conservative ceramic restorations after five years—A retrospective study

OBJECTIVES: The aim of this study was to assess the clinical performance of CAD/CAM partial coverage posterior restorations made by CEREC AC Bluecam system after 5 years. METHODS: 159 ceramic partial coverage posterior restorations were placed in 109 patients in a private practice. The restorations were made using CEREC AC Bluecam with CEREC Blocs or Empress CAD blocks. The clinical performance of the restorations was evaluated with modified California Dental Association (CDA) guidelines, gingival and plaque indices, probing pocket depth, and bleeding on probing in a period of 5 years. Patients' satisfaction was assessed using visual analogue scale. The Kaplan-Meier method was used to analyze survival probability of the restorations (α=0.05). RESULTS: The restorations included 102CEREC Blocs and 57 Empress CAD. The survival rates of CEREC Blocs and Empress CAD blocks were 96.0% and 94.6%, respectively (P=0.67). A total of 7 (4.5%) failures were found. The failures were not significantly influenced by restoration size, type and position of teeth. The ceramic fracture was significantly more in nonvital teeth (P=0.04). The periodontal parameters were not significantly different between the restored and control teeth except plaque index. The mean score of patients' satisfaction was 94.4 ± 8.1. CONCLUSIONS: Chair-side CEREC AC ceramic partial coverage posterior restorations were clinically successful restorations with mean survival rate of 95.5% after 5 years. CLINICAL SIGNIFICANCE: Conservative chair-side CAD/CAM ceramic restorations with less reduction of tooth structure can be a successful restorative method with acceptable survival rate and patient's satisfaction

Identification of a hydrodynamic threshold in karst rocks from the Biscayne Aquifer, south Florida, USA

A hydrodynamic threshold between Darcian and non-Darcian flow conditions was found to occur in cubes of Key Largo Limestone from Florida, USA (one cube measuring 0.2 m on each side, the other 0.3 m) at an effective porosity of 33% and a hydraulic conductivity of 10 m/day. Below these values, flow was laminar and could be described as Darcian. Above these values, hydraulic conductivity increased greatly and flow was non-laminar. Reynolds numbers (Re) for these experiments ranged fro

A review of CAD/CAM use in dentistry (part II): Comparison of intraoral digital scanners used in restorative dentistry

Introduction: Intraoral imaging technology has become one of the most exciting new fields in dentistry. Three-dimensional scanning of the oral cavity is used in many dental procedures such as restorative dentistry and orthodontics. To date, a number of intraoral scanners have been developed for restorative dentistry throughout the world, and many researchers and manufacturers seek the design and development of new digital devices. Only some of these devices are currently available on the market and some others are being clinically tested. All existing intraoral scanners try to overcome the drawbacks of traditional impression processes. The aim of the present article is to provide an extensive evaluation of intraoral scanners in restorative dentistry, with special attention to their assessment principles, characteristics and performance. Review report: This review article was prepared by scientific searching in electronic sources of Pubmed and ISI Web of Science in connection with articles published in English until 2014, and with these key words: intraoral scanners and digital impression. Conclusion: Over the years there have been major advances in digital scanning systems, and a variety of digital systems have been introduced that enable the dentist to select different intraoral reconstruction methods in the extraoral environment. The ultimate goal of dentists is to provide accurate and efficient dental restorations for the patient, while maintaining patient comfort during the impression process. High-resolution dental optical scanners will enable the operator to provide high-quality restorations. With digital impression techniques, the number of operators and material variables will decrease, making restoration fabrication processes more predictable and easier

Adsorption and desorption of phosphate on limestone in experiments simulating seawater intrusion

This study investigates the potential release of from carbonate aquifers exposed to seawater intrusion. Adsorption and desorption of in the presence of deionized water (DIW) and seawater were conducted on a large block of Pleistocene age limestone to simulate the effects of seawater intrusion into a coastal carbonate aquifer at the laboratory scale. The limestone showed strong adsorption of in DIW, while adsorption was significantly less in the presence of seawater. Dissolution of CaCO3 was found to prevent adsorption at salinities less than 30 psu. Adsorption of was limited at higher salinities (30–33 psu), due to competition with ions for adsorption sites. At a salinity3 precipitated. Concentrations of between 2 and 5 μmol/L were released by desorption when the limestone was exposed to seawater. The results of this study suggest that as seawater intrudes into an originally freshwater coastal aquifer, adsorbed may be released into the groundwater. Consequently, adsorbed is expected to be released from coastal carbonate aquifers world-wide as sea level continues to rise exposing more of the freshwater aquifer to seawater

Biodegradable Magnesium Bone Implants Coated with a Novel Bioceramic Nanocomposite

Magnesium (Mg) alloys are being investigated as a biodegradable metallic biomaterial because of their mechanical property profile, which is similar to the human bone. However, implants based on Mg alloys are corroded quickly in the body before the bone fracture is fully healed. Therefore, we aimed to reduce the corrosion rate of Mg using a double protective layer. We used a magnesium-aluminum-zinc alloy (AZ91) and treated its surface with micro-arc oxidation (MAO) technique to first form an intermediate layer. Next, a bioceramic nanocomposite composed of diopside, bredigite, and fluoridated hydroxyapatite (FHA) was coated on the surface of MAO treated AZ91 using the electrophoretic deposition (EPD) technique. Our in vivo results showed a significant enhancement in the bioactivity of the nanocomposite coated AZ91 implant compared to the uncoated control implant. Implantation of the uncoated AZ91 caused a significant release of hydrogen bubbles around the implant, which was reduced when the nanocomposite coated implants were used. Using histology, this reduction in the corrosion rate of the coated implants resulted in an improved new bone formation and reduced inflammation in the interface of the implants and the surrounding tissue. Hence, our strategy using a MAO/EPD of a bioceramic nanocomposite coating (i.e., diopside-bredigite-FHA) can significantly reduce the corrosion rate and improve the bioactivity of the biodegradable AZ91 Mg implant

.

گوی مارکوویتز درتعیین سهم هریک از سهام در سبد دارایی، برمبنای انتخاب بهینه سهام برای حداکثر نمودن درآمد انتظاری سبد استوار است، از یک طرف، این الگو امید ریاضی ارزش هر سهم را در الگو وارد مینماید. ازطرف دیگر، این مدل کوواریانس نوسانات ارزشی سهام را ثابت و برونزا درنظر میگیرد. بنابراین دراین مقاله از طریق ترکیب نظریات مارکوویتز و شارپ و پیشنهاد مدلی جدید الگوی جامع تری را معرفی میکنیم که نسبت به مرزسنتی مارکوویتز کاراتر خواهد بود. به عبارت دیگر از طریق درونزا نمودن کوواریانسهای نرخهای بازدهی مربوط به سهام واقع شده در پرتفولیوی اختیار شده در مدل توسعه یافته مدل مارکوویتز، بازده انتظاری مدل پیشنهادی، همواره در هر سطح مشخص ریسک، بزرگتر یا مساوی با بازده انتظاری مدل سنتی مارکوویتز خواهد بود. در الگوی پیشنهادی، سهم بخش ریسک غیرسیستماتیک که طبق نظریه شارپ بازار برای آن پاداشی را درنظر نمیگیرد در هر سطح از ریسک پرتفولیو، همواره در پایینترین سطح ممکن قرار میگیرد. برتری نظریه پیشنهادی هم از طریق نظری و هم از طریق عملی با یافتن سبد بهینه سهام شرکتهای بزرگ سیمان، فعال در بورس تهران در مقایسه با نظریه مارکوویتز تأیید میشو

The Role of Mediatory Factors of Hope and Forgiveness in Personality Traits Effect on Marital Satisfaction of Couples on the Verge of Divorce

The main objective of this study was to investigate the role of mediatory factors of personality traits, hope and forgiveness in marital satisfaction of couples on the verge of divorce. The methodology used in this study was correlation method and the statistical sample included married couples on the verge of divorce in Mashhad, Iran, which 180 couples from counseling centers were selected in random. For data collection purpose, four questionnaires were used, including Five Factor Model of NEO Personality Inventory Revised (60-question form), Enrich Marital Satisfaction Scale (47-question form), Family Forgiveness Scale, by Pollard et al. and Schneider’s Hope scale (1991). Data analysis was performed by applying the statistical method of analysis with recursive models. Results confirmed the desired evaluation of the investigation model. They also revealed that sense of duty has a positive and significant effect and neuroticism has a negative and significant impact on the marital satisfaction. Also, hope and forgiveness have mediatory roles in this relationship. Moreover, results showed the positive and significant effect of experientialism on the marital satisfaction but hope and forgiveness, as personality traits, have no mediatory roles in this relation. therefore consequence, neuroticism and sense of duty have effect on the marital satisfaction through hope and forgiveness, as personality traits. each of three variables including personality traits, hope and forgiveness can result in increasing the marital satisfaction of married couples on the verge of divorce