Ebook Sturdevant’s Art and science of operative dentistry: Part 2
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Ebook Sturdevant’s Art and science of operative dentistry: Part 2
10Clinical Technique for Amalgam RestorationsLEE w. BOUSHELL, ALDRIDGE D. WILDER, JR., SUMITHA N. AHMEDDental amalgam (tilvrr amalgam or simply amalga Ebook Sturdevant’s Art and science of operative dentistry: Part 2am) is a metallic, polycrystallinc restorative material originally composed of a mixture of silver-tin alloy and mercury. Current alloys that are amalgamated with mercury are silver-tin-copper. The unset silver-colored mixture is pressed (condensed) into a tooth defect (cavitation) that has been spe Ebook Sturdevant’s Art and science of operative dentistry: Part 2cifically prepared to retain the amalgam. The material is then contoured to restore the tooth’s form so that, when the material hardens, the tooth isEbook Sturdevant’s Art and science of operative dentistry: Part 2
returned to normal function (Fig. 10.1). Amalgam has been the primary direct restorative material in the United States for more than 150 years. It has10Clinical Technique for Amalgam RestorationsLEE w. BOUSHELL, ALDRIDGE D. WILDER, JR., SUMITHA N. AHMEDDental amalgam (tilvrr amalgam or simply amalga Ebook Sturdevant’s Art and science of operative dentistry: Part 2ve nature of amalgam restorations has benefited many people. According to the U.S. Public Health Service, “hundreds of millions of teeth have been retained that otherwise would have been sacrificed because restorative alternatives would have been too expensive for many people.'1In addition to being Ebook Sturdevant’s Art and science of operative dentistry: Part 2cost effective, amalgam has the unique property of being "self-scaling." Self-scaling occurs when percolation of oral fluids (i.e., microlcakagc) betwEbook Sturdevant’s Art and science of operative dentistry: Part 2
een the amalgam restoration and the prepared cavity walls results in corrosion of the amalgam and a subsequent accumulation of corrosion products in t10Clinical Technique for Amalgam RestorationsLEE w. BOUSHELL, ALDRIDGE D. WILDER, JR., SUMITHA N. AHMEDDental amalgam (tilvrr amalgam or simply amalga Ebook Sturdevant’s Art and science of operative dentistry: Part 2scaling process is self-limiting and requires several months. Amalgam is the only restorative material with an interfacial seal that improves over time.>7Amalgam was introduced to the United States in the 1830s. Initially, amalgam restorations were made by dentists filing silver coins and mixing the Ebook Sturdevant’s Art and science of operative dentistry: Part 2 filings with mercury, creating a puttylike mass that was placed into the defective tooth. As knowledge increased and research intensified, major advaEbook Sturdevant’s Art and science of operative dentistry: Part 2
ncements in the formulation and use of amalgam occurred. Concerns about mercury toxicity in the use of amalgam were, however, expressed in many countr10Clinical Technique for Amalgam RestorationsLEE w. BOUSHELL, ALDRIDGE D. WILDER, JR., SUMITHA N. AHMEDDental amalgam (tilvrr amalgam or simply amalga Ebook Sturdevant’s Art and science of operative dentistry: Part 2e is attributed in part to increased interest in tooth-colored composite resin restorations and the minimally invasive nature of their preparation steps. Concerns have been raised that the preparation used when planning foramalgam may result in unnecessary weakening of teeth because of the demand fo Ebook Sturdevant’s Art and science of operative dentistry: Part 2r additional removal of tooth structure so as to accommodate amalgams strength and retention requirements. While it is true that preparations for compEbook Sturdevant’s Art and science of operative dentistry: Part 2
osite resin restorations may allow smaller, more conservative preparations for very early caries lesions, treatment of more advanced lesions may resul10Clinical Technique for Amalgam RestorationsLEE w. BOUSHELL, ALDRIDGE D. WILDER, JR., SUMITHA N. AHMEDDental amalgam (tilvrr amalgam or simply amalga Ebook Sturdevant’s Art and science of operative dentistry: Part 2terial over amalgam may Ik based on the assumption that both materials will perform equally well over time for all patients. However, a growing body of evidence suggests that the risk of developing secondary caries adjacent to amalgam restorations is at least two times less likely than that of compo Ebook Sturdevant’s Art and science of operative dentistry: Part 2site resin restorations in high caries risk patients, and therefore the reduction/phase-out of dental amalgam may have been premature."" The decline oEbook Sturdevant’s Art and science of operative dentistry: Part 2
f amalgam use is also due to perceived concerns over individual and environmental safety relative to the presence of elemental mercury in amalgam rest10Clinical Technique for Amalgam RestorationsLEE w. BOUSHELL, ALDRIDGE D. WILDER, JR., SUMITHA N. AHMEDDental amalgam (tilvrr amalgam or simply amalga Ebook Sturdevant’s Art and science of operative dentistry: Part 2nly appropriate and absolutely essential. Following best management practices for amalgam waste, as presented by the American Dental Association, results in appropriate amalgam use.1’Types of Amalgam Restorative MaterialsLow-Copper AmalgamLow-copper amalgams were primarily used before the early 1960 Ebook Sturdevant’s Art and science of operative dentistry: Part 2s. When the setting reaction occurred, the material was subject to corrosion because of the formation of a tin-mercury phase (gamma-2). The corrosionEbook Sturdevant’s Art and science of operative dentistry: Part 2
led to the rapid breakdown of amalgam restorations. Subsequent research led to the development of high-copper amalgam materials. Currently low-copper 10Clinical Technique for Amalgam RestorationsLEE w. BOUSHELL, ALDRIDGE D. WILDER, JR., SUMITHA N. AHMEDDental amalgam (tilvrr amalgam or simply amalga Ebook Sturdevant’s Art and science of operative dentistry: Part 2 unless otherwise specified, the term amalgam306CHAPTER 10 oinkaiTechniqu • Fig. 10.1 Clnkal example of an amaigam restoration. (From rtatnck CD. Eakle ws, Bird WF. Dental materials. Cữvca! appữcations for dental assistants and dental nygrervsfs, ed 2. St. Louis. Saunders. 2011Jrefers to high-copper Ebook Sturdevant’s Art and science of operative dentistry: Part 2 dental amalgam. The increase in copper content to 12% or greater designates an amalgam as a high-copper type. The advantage of the added copper is thEbook Sturdevant’s Art and science of operative dentistry: Part 2
at it preferentially reacts with the tin and reduces the formation of the more corrosive phase (gamma-2) within the amalgam mass. This change in compo10Clinical Technique for Amalgam RestorationsLEE w. BOUSHELL, ALDRIDGE D. WILDER, JR., SUMITHA N. AHMEDDental amalgam (tilvrr amalgam or simply amalga Ebook Sturdevant’s Art and science of operative dentistry: Part 2sealing of the restoration, which reduces microleakage. These materials may provide satisfactory clinical performance for more than 12 yeans.1'”1' High-copper amalgams arc available with admixed or spherical alloy structure.Admixed AmalgamAdmixed amalgam contains irregularly shaped and sized alloy p Ebook Sturdevant’s Art and science of operative dentistry: Part 2articles, sometimes combined with spherical shapes, which arc mixed to form a mass that is placed into the tooth preparation. The irregular shape of mEbook Sturdevant’s Art and science of operative dentistry: Part 2
any of the particles results in a mass that requires greater condensation pressure (which many dentists prefer) and permits the dentist to displace ma10Clinical Technique for Amalgam RestorationsLEE w. BOUSHELL, ALDRIDGE D. WILDER, JR., SUMITHA N. AHMEDDental amalgam (tilvrr amalgam or simply amalga Ebook Sturdevant’s Art and science of operative dentistry: Part 2rcury to form the mass that is placed into the tooth preparation. Because of the shape of the panicles, the material is condensed into the tooth preparation with little condensation pressure. This advantage is combined with its high early strength to provide a material that is well suited for very l Ebook Sturdevant’s Art and science of operative dentistry: Part 2arge amalgam restorations such as complex amalgams or foundations.1New Amalgam AlloysBecause of the concern about mercury toxicity, new compositions oEbook Sturdevant’s Art and science of operative dentistry: Part 2
f amalgam have been promoted as mercury-free or low-mercuryamalgam restorative materials. Alloys with gallium or indium or alloys using cold-svelding 10Clinical Technique for Amalgam RestorationsLEE w. BOUSHELL, ALDRIDGE D. WILDER, JR., SUMITHA N. AHMEDDental amalgam (tilvrr amalgam or simply amalga Ebook Sturdevant’s Art and science of operative dentistry: Part 2rsal replacement for current amalgam materials.” ■'Important Amalgam PropertiesThe linear coefficient of the thermal expansion of amalgam is 2.5 times greater than that of tooth structure, but it is closer to that of tooth structure than the linear coefficient of thermal expansion of composite." Alt Ebook Sturdevant’s Art and science of operative dentistry: Part 2hough the compressive strength of high-copper amalgam is similar to tooth structure, the tensile strength is lower, making amalgam restorations proneEbook Sturdevant’s Art and science of operative dentistry: Part 2
to fracture during flexure." '■ "■ Usually, high-copper amalgam fracture is a bulk fracture, not a marginal fracture. All amalgams are brittle and haw10Clinical Technique for Amalgam RestorationsLEE w. BOUSHELL, ALDRIDGE D. WILDER, JR., SUMITHA N. AHMEDDental amalgam (tilvrr amalgam or simply amalga Ebook Sturdevant’s Art and science of operative dentistry: Part 2ion within the tooth) and a 90-degrce marginal configuration.Creep and flow relate to the deformation of a material under load over time. High-copper amalgams exhibit no clinically relevant creep or flow. ' * Because amalgam is metallic in structure, it also is a good thermal conductor. At minimum, Ebook Sturdevant’s Art and science of operative dentistry: Part 2a dentin desensitizer should be used immediately prior to amalgam placement to limit sensitivity secondary to rapid fluid movement in the dentinal tubEbook Sturdevant’s Art and science of operative dentistry: Part 2
ules caused by thermal changes. A liner or base should be placed in areas of deep caries removal prior to amalgam placement to limit thermal sensitivi10Clinical Technique for Amalgam RestorationsLEE w. BOUSHELL, ALDRIDGE D. WILDER, JR., SUMITHA N. AHMEDDental amalgam (tilvrr amalgam or simply amalga Ebook Sturdevant’s Art and science of operative dentistry: Part 2sertion into a tooth preparation and. when hardened, its ability to restore the tooth to proper form and function. The tooth preparation not only must remove the fault in the tooth and remove weakened tooth structure, but its form must also allow the amalgam material to function properly. The requir Ebook Sturdevant’s Art and science of operative dentistry: Part 2ed tooth preparation form must allow the amalgam to (1) possess a uniform specified minimum thickness for strength (so that it will not flex and fractEbook Sturdevant’s Art and science of operative dentistry: Part 2
ure under load), (2) produce a 90-degree amalgam angle (butt-joint form for maximum edge thickness) at the margin, and (3) be mechanically retained inGọi ngay
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