File Name: materials in dentistry principles and applications .zip
Zohaib Khurshid. Comprehensive, covering all subjects taught in a dental assisting program.
- Dental Material Books
- Amalgam (dentistry)
- Advanced Dental Biomaterials
- Dental Biomaterials Principles and Applications (2nd Edition)
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Dental Material Books
Dental amalgam is a liquid mercury and metal alloy mixture used in dentistry to fill cavities caused by tooth decay. In July the EU prohibited amalgam for dental treatment of children under 15 years and of pregnant or breastfeeding women. Early amalgam was made by mixing mercury with the filings of silver coins. The American Dental Association ADA was founded in its place in , which has since then strongly defended dental amalgam from allegations of being too risky from the health standpoint.
Amalgam has been used for many years for restorations, commonly known as fillings. Prior to many compositions were tried but few were successful when placed in the oral environment.
Around , small amounts of copper and occasionally zinc were added. Zinc acts as a scavenger because it prevents oxidation of the other metals in the alloy during the manufacturing process. Zinc accomplishes this by combining readily with oxygen to form zinc oxide. In a new amalgam alloy, called Dispersalloy, was introduced with the addition of a spherical silver-copper eutectic particle to the traditional lathe-cut Ag 3 Sn particle in a ratio of The mixture of these two types of particles is known as admix alloy.
The increased copper in the silver-copper eutectic reacted preferentially with tin so that Sn 8 Hg could not form. Early results from the clinical use of this new amalgam showed an improvement in marginal integrity. Dental amalgam is produced by mixing liquid mercury with an alloy made of silver, tin, and copper solid particles. Small quantities of zinc, mercury and other metals may be present in some alloys.
This combination of solid particles is known as amalgam alloy. It is important to differentiate between dental amalgam and the amalgam alloy that is commercially produced and marketed as small filings, spheroid particles, or a combination of these, suitable for mixing with liquid mercury to produce the dental amalgam. Amalgam is used most commonly for direct, permanent, posterior restorations and for large foundation restorations, or cores, which are precursors to placing crowns.
The reaction between mercury and alloy when mixed together is termed an amalgamation reaction. The standard composition of alloy prior to is referred to as conventional amalgam alloy. More recently post , there has been a change in the compositional standard of the alloy due to better understanding of structure-property relationships for the materials.
To fabricate an amalgam filling, the dentist uses a mixing device to blend roughly equal parts by mass of shavings of a silver-base alloy with mercury until the shavings are thoroughly wetted. The dentist packs the plastic mass, before it sets, into the cavity. Amalgam is a mixture of two or more metals alloy with mercury which has been purified first by distillation to remove impurities. Currently, [ when? The composition of the alloy powder is controlled by ISO standard for dental amalgam alloy ISO to control the properties of amalgam.
Creep or plastic deformation happens when subjected to intra-oral stresses such as chewing or grinding. Creep causes the amalgam to flow and protrudes from the margin of the cavity forming unsupported edges.
Corrosion occurs when an anode and cathode are set up in the presence of electrolytes, creating an electrolytic cell. The multiphase structure of dental amalgam can contribute as an anode or cathode with saliva as electrolytes. Corrosion may significantly affect the structure and mechanical properties of set dental amalgam. It will break down releasing corrosion products and mercury.
Some of the mercury will combine rapidly with unreacted alloy and some will be ingested. The chances of ditching are further increased. The corrosion however is still much lower than conventional amalgam. In spite of that, it is thought that corrosion actually offers a clinical advantage.
The corrosion products will gather at the tooth-amalgam interface and fill the microgap marginal gap which helps to decrease microleakage. Even so, there are no reports of increased marginal leakage for the copper-enriched amalgams indicating that sufficient quantities of corrosion product are produced to seal the margins. Microleakage is the leakage of minute amounts of fluids, debris, and microorganisms through the microscopic space between a dental restoration and the adjacent surface of the cavity preparation.
Microleakage can risk recurrent caries. An amalgam restoration develops its strength slowly and may take up to 24 hours or longer to reach a reasonably high value. At the time when the patient is dismissed from the surgery, typically some 15—20 minutes after placing the filling, the amalgam is relatively weak.
In addition, amalgam restorations are brittle and susceptible to corrosion. The solid particles of the alloy are either spherical or irregularly shaped microspheres of various sizes or a combination of the two. The low-copper alloys have either irregular or spherical particles. High-copper alloys contain either spherical particles of the same composition unicompositional or a mixture of irregular and spherical particles of different or the same composition admixed.
The properties of set amalgam depends upon the alloy composition—particle size, shape and distribution—and heat treatment control the characteristic properties of the amalgam. During trituration, mercury diffuses into the silver-tin particles. Then, silver and tin dissolve, to a very limited extent, into the mercury.
As this occurs, the particles become smaller. The set amalgam consists of unreacted gamma particles surrounded by a matrix of gamma 1 and gamma 2. In high copper alloy, copper is added to improve mechanical properties, resistance to corrosion and marginal integrity. The higher copper content is supplied as two types:. These alloys are usually spherical. When liquid mercury is mixed with these alloys, it diffuses into the surface of these particles forming Ag 2 Hg 3 as well as Cu 6 Sn 5 .
The difference in eta prime phase of admixed alloy and unicomposition alloy is that in unicomposition alloy, Cu 6 Sn 5 crystals are much larger and rod-shaped than those in admixed alloy. Copper added in unicomposition causes removal of gamma2 phase. Amalgam is tolerant to a wide range of clinical placement conditions and moderately tolerant to the presence of moisture during placement.
Mercury has properties of a bacteriostatic agent whereas certain methacrylate polymers for example TEGMA, triethylene glycol methacrylate composing the matrix of resin composites "encourages the growth of microorganisms". In the Casa Pia study in Portugal — , 1, posterior restorations were placed and However, there is low-quality evidence to suggest that resin composites lead to higher failure rates and risk of secondary caries than amalgam restorations.
These are some of the reasons why amalgam has remained a superior restorative material over resin-base composites. The New England Children's Amalgam Trial NECAT , a randomized controlled trial , yielded results "consistent with previous reports suggesting that the longevity of amalgam is higher than that of resin-based compomer in primary teeth   and composites in permanent teeth. For example, when a more conservative preparation would be beneficial, composite is the recommended restorative material.
These situations would include small occlusal restorations, in which amalgam would require the removal of more sound tooth structure,  as well as in "enamel sites beyond the height of contour". Dental amalgam does not by itself bond to tooth structure.
This was recognized as a shortcoming by early practitioners such as Baldwin. The practice did not become universally accepted and eventually fell into disuse. Until the s, most amalgam restorations placed worldwide were done without adhesives, although in the s a polycarboxylate -based adhesive liner was formulated specifically for this purpose  In the mids the first reports of the use of resins to bond amalgam to etched tooth structure, much like is done for composite resins, appeared in the literature.
For large cavity restorations, features such as pins, slots, holes and grooves can be used for the retention of large amalgam restorations, but they do not reinforce the amalgam or increase its strength.
There is no current scientific evidence to justify the extra cost and effort associated with the use of adhesively bonded amalgam restorations in comparison with nonbonded amalgam restorations. The placement of amalgam restorations can potentially cause sensitivity post-operatively. According to R. Weiner, a protective layer or liner should be placed prior to the placement of amalgam to act as a buffer, helping to reduce sensitivity to the tooth.
Examples of lining materials include zinc oxide eugenol , zinc phosphate, glass ionomer cement , zinc poly-carboxylate and resin. A varnish can be applied to the cavity wall to provide a good marginal seal. The varnish should be insoluble in water and is usually composed of a resin in a volatile solvent. When applied to the cavity, the solvent evaporates, leaving the resin behind to seal the dentinal tubules. The amalgam can then be packed into the cavity. Concerns have been raised about the potential for mercury poisoning with dental amalgam when used in a dental filling.
Major health and professional organizations regard amalgam as safe    but questions have been raised  and acute but rare allergic reactions have been reported. Critics argue that it has toxic effects that make it unsafe, both for the patient and perhaps even more so for the dental professional manipulating it during a restoration. However, research is inadequate to determine the chance of harm occurring and therefore placement and removal should be avoided during pregnancy if possible.
In response to The Minamata Convention on Mercury, the European Commission has confirmed its position that individual nations should work to gradually scale down the use of dental amalgam.
Dental amalgam is thought to be relatively safe to be used as a restorative material as it is used in low doses. Amalgam vapour can be released through chewing but this is minimal. However, there is an increased release of mercury following the exposure of electromagnetic fields generated by MRI machines. Resin composite, glass ionomer cements and ceramic or gold inlays can be used as alternatives to amalgam.
In the United States, dental offices have typically disposed of amalgam waste down the drain. The wastewater is sent to the local sewage treatment plant, which is not designed to treat or recycle mercury or other heavy metals. The mercury contaminates the sludge processed at the treatment plant, and thereby can spread the mercury in surrounding communities, if the sludge is land-applied for disposal.
Dental amalgam is the largest source of mercury received by U. The U. Environmental Protection Agency EPA promulgated an effluent guidelines regulation in which prohibits most dental practices from disposing dental amalgam waste down the drain. Most dental offices in the U.
The separator captures the waste material, which is then recycled. The European Commission has issued a Waste Directive that classifies amalgam waste as a hazardous waste. The waste should be separated from other waste by fitting amalgam separators in all dental practices. Mercury can cross the placenta leading to stillbirths and birth defects.
Advanced Dental Biomaterials is an invaluable reference for researchers and clinicians within the biomedical industry and academia. Zohaib Khurshid is graduated with B. Up to date, he published 50 plus scientific papers in high impact factor journals, and he edited 3 dental books with the Asian publisher. His research interests cover natural materials incorporation in dental biomaterials, oral antimicrobial peptides, dental implant materials, salivary proteins and peptides, salivary diagnostics and regenerative dental materials. He is a reviewer and an editorial member of for highly indexed dental journals. Shariq Najeeb is a dentist, academician, author and a researcher. His research project in Sheffield focused on the production of a novel, inexpensive tissue regenerative material.
Dental amalgam is a liquid mercury and metal alloy mixture used in dentistry to fill cavities caused by tooth decay. In July the EU prohibited amalgam for dental treatment of children under 15 years and of pregnant or breastfeeding women. Early amalgam was made by mixing mercury with the filings of silver coins. The American Dental Association ADA was founded in its place in , which has since then strongly defended dental amalgam from allegations of being too risky from the health standpoint. Amalgam has been used for many years for restorations, commonly known as fillings. Prior to many compositions were tried but few were successful when placed in the oral environment.
You will be redirected to Cut and paste the pictures, then fold into a book. Browse hundreds of dental equipment and technology products and learn how they can complement your skillset and enhance your practice. Real Tooth Morphology can replace a dental textbook as a learning tool and has the advantage of being able to demonstrate the points shown using real 3D tooth models rather than flat diagrams. The book is designed to function as a stand-up display, providing ease of use to the photographer when used chairside.
Advanced Dental Biomaterials
The Second Edition of this textbook for dental assisting, dental hygiene, and first-year dental students retains its well-organized, easy-to-follow format, with enhanced content, tables, illustrations, and display boxes. Expanded chapters cover preventative materials, abrasion and polishing, dental implants and composites. Coverage of new materials includes ceramics, dental cements, and new gold alloys for PFM restorations.
Powers PhD Author. Master the use of dental materials with this all-in-one guide to restorative materials and procedures! It begins with fundamentals and moves on to advanced skills in the manipulation of dental materials, providing insight on the latest advances and research along the way. From an expert author team led by Ronald Sakaguchi, this comprehensive resource is considered to be the standard in the field of dental restorations.
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Dental Biomaterials Principles and Applications (2nd Edition)
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