Papers by Keyword: Dental Cement

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Authors: Robert G. Hill, E. De Barra, S. Griffin, G. Henn, J. Devlin, P.V. Hatton, I.M. Brook, K. Johal, G. Craig
Authors: Ali Zamanian, Mana Yasaei, F. Moztarzadeh, Saeed Hesaraki, Masoud Hafezi
Abstract: Calcium hydroxide cement used in dentistry has advantages of proper alkaline pH, releasing calcium ions and promoting tissue regeneration. However, it also has some drawbacks such as high solubility and low strength. In this study, the properties of nano-hydroxyapatite (nHA) added calcium hydroxide cement was investigated for overcoming these drawbacks. Stoichiometric nHA powder was synthesized using orthophosphoric acid and calcium hydroxide. 5, 10 and 15 percent (in w/w) of synthesized nHA powder was added to commercial calcium hydroxide cement and the obtained nanocomposite was characterized by setting time, compressive strength, pH, Ca dissolution, antibacterial tests and SEM. Nanometric size and purity of synthesized apatite was confirmed by XRD and TEM. Setting time increased by increasing the content of nHA. SEM micrographs showed less microporosity for sample with 5% nHA. Adding 5% nHA to calcium hydroxide cement increased compressive strength to 60%, while further additions had an adverse effect. Adding nHA slightly decreased pH and increased Ca dissolution. The antibacterial test revealed that inhibition zone was about 2-2.5 mm for calcium hydroxide cement and sample with 5% nHA and less than 1 mm for other samples. Finally, nanocomposite with 5% nHA exhibited adequate properties to overcome the drawbacks of calcium hydroxide cements.
Authors: Wasana Khongwong, Kanungnuch Keawsupsak, Saengdoen Daungdaw, Pornpen Siridamrong, Arjin Boonruang
Abstract: Dental resin composite cements were prepared with simply mixing method of Part A and Part B. The material components in Part A were composed of Bis-GMA, TEDGMA, 4-META, SiO2 nanopowders and BPO. The components in Part B were Bis-GMA, TEDGMA, 4-META, SiO2 nanopowders and 2,2¢-(4-methylphenylimino) diethanol. Before using SiO2 nano-filler in the formulation of Part A and Part B, it had to be coated with methacryloxypropyltrimethoxysilane (MPS) which served as a silane coupling agent. Therefore, the optimum amount of MPS (1, 1.2, 1.5 and 2%) and SiO2 nano-filler (20, 27.27 and 33.33 wt%) used to fabricate the composites were investigated. The homogeneous mixture of Part A and Part B at mass fraction of 1:1 was formed into the bar shape with dimension of 25 mm x 2.0 mm x 2.0 mm and then cured under light source for 20 s. Then flexural strength was measured using the universal testing machine. Depth of cure was tested using mould which was perforated in cylindrical shape of 6 mm in depth and of 4 mm in diameter. The result showed that composite with 27.27 wt% of salinized SiO2 nanopowders by 1.5% of MPS showed the highest flexural strength of 65 MPa and depth of cure of more than 5 mm which were accepted according to ISO 4049. This study could be concluded that using a proper amount of MPS to silanize SiO2 nanopowders and using an optimum amount of SiO2 nanopowders significantly improved the flexural strength of dental resin composite cements.
Authors: J.C. Murphy, M.P. Hofmann, J.L. O’Beirne, K.S. Coomaraswamy, R.M. Shelton
Abstract: Mineral trioxide aggregate (MTA) is a slow setting Portland cement (PC) based dental material for endodontic applications. The present study investigated the effect of adding either CaCl2 or Plaster of Paris (PoP) as setting accelerators on the development of the material properties and microstructure with reaction time for a PC based model system. Mechanical strength, density and relative porosity were measured after 1, 10 and 30days and the microstructure was assessed using scanning electron microscopy (SEM). The strength of all cements increased with time whereas material density and relative porosity decreased due to the progress of the hydration reaction. Cements with 5-10% CaCl2 in the liquid phase had a higher final strength and lower porosity than cements modified with 20wt% PoP in the cement powder, whilst PoP modified cement had a shorter setting time of 15min compared with 60min for 10% CaCl2 addition. The microstructure of the two modifications were noticeably different, with the CaCl2 modified cement having more interconnected needle-like crystals than seen in PoP modified cements, which may explain the higher strength of this cement.
Authors: George J. Mattamal
Abstract: Since the Medical Device Amendments of 1976 were enacted, the FDA considers Tissue Adhesives as “Transitional Devices” that are classified as Class III medical devices and are marketed in the United States subsequent to the approval of a Pre-market Approval Application (PMA). On February 9, 2006, Regulatory & Clinical Research Institute, Inc. submitted a petition to FDA to reclassify tissue adhesive transitional medical devices for skin approximation from Class III to Class II (special controls). FDA consulted with the General and Plastic Surgery Devices Advisory Panel, and on August 25, 2006, in a public meeting, the panel unanimously recommended that the tissue adhesive transitional medical devices for topical approximation of skin be classified from class III into Class II. Consequently, since June 30, 2008, following the effective date of the FDA Final Rule [1] that reclassified tissue adhesive transitional medical devices for skin approximation, any firm submitting a Premarket Notification [510(k)] for a tissue adhesive for the topical approximation of skin will need to address the issues covered in the published “Class II Special Control Guidance Document: Tissue Adhesive for the Topical Approximation of Skin, dated May 30, 2008” [2]. Accordingly, the firm needs to show that its device meets the recommendations of the published Class II guidance document or in some other way provides equivalent assurances of safety and effectiveness. Also, the author provides a short regulatory description of US FDA, under what laws its operates, how FDA evaluates new medical devices for marketing as Class I, Class II, and Class III [3].
Authors: George J. Mattamal
Abstract: A brief description of the uses and clinical applications of synthetic cyanoacrylate polymer adhesive/glues that have been cleared and/or approved as medical devices by FDA since the Medical Device Amendments of 1976 were enacted. This includes cyanoacrylate Class I devices (Exempt and not Exempt devices), Class II cyanoacrylate devices such as Dental Cements and Orthodontic Bracket Adhesives, and Class III (PMA) devices such as Dermabond™, Indermil™ Tissue Adhesive, and Trufill® n-Butyl Cyanoacrylate Embolic Agent. By citing an example of recently FDA approved Class III (PMA) devices in the Cyanoacrylate technology, the author provides a brief discussion of the FDA approval process of medical devices. It includes the FDA issues regarding the published guidance document for "Cyanoacrylate Topical Tissue Adhesives" that will provide guidance to regulatory personnel and manufacturers in the preparation of IDE applications and in the development of valid scientific evidence to support PMA applications for cyanocrylate tissue adhesives intended for topical approximation of skin and others. Also, the author provides a short regulatory description of US FDA; under what laws its operates, how FDA evaluates new devices for marketing, and how the device regulatory system works, for example, Class I, Class II, and Class III cyanoacrylate medical devices.
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