This topic is going to describe the uses of amalgam in dental treatment and explain the proprieties of dental amalgam that made it the most consumer dental filling ,also this topic will discuss the toxic effects of mercury in dental amalgam. Dental amalgam is one of the oldest dental materials that used in the oral cavity to replace the function and anatomy of the damaged teeth. Dental amalgam used from hundreds of years that the earliest use of amalgam as restorative dental materials was a silver paste , which used to restore the tooth as 659 .A.D. in China. Before the invention of dental amalgam dentists restored the damaged teeth by using of a filling material such as stone chips, resin, cork, turpentine, gun, lead, and gold leaf. But, the invention of dental amalgam reduce the use of this materials, because of the superior proprieties of the amalgam filling. The extensive use of dental amalgam restoration was over the last 150 years. But, the use of dental amalgam is going down, because of the decrease of dental caries in the children and young adults, result from the use of fluoride and the increase of dental care. Even though dental amalgam still take the first place in dental fillings, because it's ability to continuance in the oral cavity more than any other dental filling such as composite. In addition dental amalgam has many properties made it very resistance material. For example its' strength resists forces of mastication against fracture, and it has a good ability to oppose corrosion and forces placed in the mouth more than any other dental filling. Beside, as dr. Robert G. Craig defined dental amalgam as ( a mixture of silver alloy with mercury. That the silver alloy is a fine powder that is composed mostly of silver, and copper. So, when the silver and mercury are mixed, a chemical reaction occurs and forms dental amalgam). So, this topic is going to analytic the dental amalgam uses, properties, and the toxic compound of the amalgam.
Firstly, today amalgam restoration material is used in the following situations. If the patient has lost the structure of the tooth by carious lesion and other reasons such as accident, facture or trauma. That the tooth may lose its' function and ability to assist the masticator system to chew the food, or may the patient has such pain in the damage tooth. So, the dentist remove the damage structure and replace it by amalgam filling to back the anatomy and the function of the tooth. In addition to this, dental amalgam restoration used in the posterior teeth, because of the high forces applied on this teeth, and because of the color of amalgam. So, it can not be used on the interior teeth where the esthetic is an important factor. Furthermore, dental amalgam restoration used when the cost is the first priority of patient worry. Some patient do not have the ability to stand the high cost of other dental fillings or restorations which used in the treatment such as composite or fixed partial denture. As a result dental amalgam restoration is the first choice for the poor patient who are make the high percent of the patients, so in this situation the dentist should choose a low cost material that have the ability to continue on the mouth of the patient. An other use of dental amalgam filling is that when the structural lose of the tooth is excessive that the filling would be more subject to fracture. So that, dental amalgam is requirement because its' strength and ability to appose the masticatory forces and attrition. In addition to this, dental amalgam can be used to assist the fixed partial denture and the removable partial denture which need enough tooth structure to fix in the place on the abutment tooth, that if the abutment tooth was lost most of its' structure it should assist with amalgam or other restoration. Moreover, dental amalgam filling could be used with all ages, so it can be used in children and young adult patients. However, dental amalgam restoration is not used when esthetics are important factors. Such as in the interior teeth and in the lingual surfaces of this teeth. That the color of dental amalgam is a metal which appear in the treated teeth like black spot, and this annoy the patient who care about their appearance, so they prefer the esthetic restorations, such as, composite or ceramic veneers. Furthermore, dental amalgam restoration can not be used with patient who have a history of allergy to mercury or other amalgam components such as cupper or zinc. This components could cause hypersensitivity and other problems for this kind of patients. Another situation that we can not use dental amalgam filling when the amount of the lost tooth structure is very large, that the amalgam filling can not assist with tooth structure, so that it would be subject to fracture. In this case dental amalgam filling should be covered with a crown restoration.
Secondly, amalgam filling is a superior restorative dental material that satisfying many functions in the dental treatment because of many properties it has. It is inexpensive and easy to use during dental placement. That it can be shaped for a short time so it can be carried and filled into the cavity preparation, and then formed in one treatment setting. So that, it would reduce the work time in the mouth of the patient. As a result, the patient would be more comfortable and the dentist would have more time for other patients. Moreover, the longevity of dental amalgam is more when it compared with other materials such as composite. That dental amalgam could fit in the oral cavity for ten years, but composite can not stay more than tow to three years. This advantage of dental amalgam assist the low cost of this filling because the patient does not have to replace the filling for along time. So, in ten years the patient would pay one time with dental amalgam but with composite he or she would pay tow or three times to fill his or her tooth with composite in this ten years. Another property of dental amalgam restoration is that its' strength and ability to resist fracture against the forces applied in the oral cavity more than composite and other dental filling. As dental material properties and manipulation book ( pg. 95-96) : (the strength of dental amalgam restoration should be high enough to resist the applied forces on the amalgam restoration in the mouth. That a fracture may occur in the bulk or the marginal of the dental amalgam restoration. If any of this types of fracture occur the restoration should be remove and replaced). So that, dental amalgam restoration is a subject to chewing or other forces so the strength of dental amalgam restoration is an important clinical characteristic to put up with that forces. However, dental amalgam restoration has a few weakness such as dimensional change. As dental material properties and manipulation book ( pg. 97) : (when a freshly mixed amalgam is condensed into the cavity preparation, the ideal result is that the amalgam neither expands or contracts as it sets. Expansions could result in post placement sensitivity or protrusion from the cavity, where as contraction would leave gaps prone to leakage between the restoration and the tooth. Dimensional change is negative of the amalgam contracts and positive if it expands during sitting. In general, most amalgams expands or contract only slightly overall during sitting, but the dimensional change should not be an expansion or contraction more than 20 micrometers / centimeter). So, the dimensional change of dental amalgam restoration should be small to prevent the leakage of the mouth product ( the saliva; the food; and acids) between the restoration and the margins of the cavity preparation to reduce the percent of the carious lesion in this areas. Another weakness of dental amalgam restoration is that tarnish and corrosion. As dental material properties and manipulation book ( pg. 98_99) : ( tarnish is a surface phenomenon that can result in a discolored restoration. And corrosion result from chemical reaction that penetrate into the body of the amalgam. With tarnish, the chemical reaction between the amalgam and the oral cavity are restricted to the amalgam surface. Although tarnish may be undesirable esthetically, it will not often destroy the restoration. Corrosion, on the other hand, eventually leads to failure of the restoration. Tarnish and corrosion occur more on amalgams with rough surfaces. Thus a will polished amalgam limits this problems). So, tarnish and corrosion occur in most of metals which reduce the good properties of the metals as amalgam. Furthermore, the strength of amalgam filling is more than the strength of tooth structure, because of this difference an excessive wear occur on the teeth which facing the amalgam restoration.
Thirdly, dental amalgam filling contain mercury, which is an important source of poisons in the dental amalgam. As dental material properties and manipulation book (pg. 93) : (mercury is a dense metal that is liquid at room temperature). And dental amalgam restoration release high amount of mercury which is one of the most toxic materials that used in the history of dental treatment, and this release cause many problems in the body when it absorbed by the tissues. Such as, it causes injury to the brain of children. As holisticmed.com: (in February, 1998, a group of the world's top mercury researchers announced that mercury from amalgam fillings can permanently damage the brain, kidneys, and immune system of children). So that, the dental amalgam used with children should be observer to prevent such damage and reduce the toxic affects of mercury. In addition to this, dental amalgam fillings cause neurological problems, and gastrointestinal problems. An epidemiological study of mercury display that there is relation between mercury and symptoms of gastrointestinal problems, and it may cause interference in sleep or in memory. Also, it could be responsible of concentration problems and lake of initiative, restlessness, bleeding gums and other mouth disorders. Furthermore, amalgam restoration is the largest source of mercury that people could contaminant with. That the World Health Organization conduct a general studies of inorganic mercury in 1991 determined that the absorption mercury is appraised to be approximately four times higher from amalgam fillings than fish consumption. Also, the cumulative of poison from dental amalgam fillings affect the organs of the body and it builds up in the brain, pituitary, adrenals, and other parts of the body. Moreover, a research by Dr. Boyd Haley reported the relationship between mercury and Alzheimer's disease which is a disease affect the central nervous system and cause dementia. This relationship depend on the exposed level of mercury vapor. So, people should reduce the exposed level of mercury by removing of dental amalgam in such case. Furthermore, mercury released from dental amalgam could be a potential contributory factor assist other disease such as Parkinson's disease, which is a nervous disease characterized by trembling and lack of muscle control. Also, it could cause reproductive disorders, allergies, cancer, and many other disease.
In conclusion, dental amalgam filling is one from the most dental materials, that science could produce over the last tow century. And it will have the first place in the restorative materials in the future, because of the brilliant properties that it has. Even though, the fast development of science in the last century, it can not produce an other dental material could compete dental amalgam filling. Moreover, as we see, the reduce of using dental amalgam filling is not because the invention of better dental material, but it because of the community realization to the important of the protection from dental diseases by the prevention of carious lesion, and increasing the dental care in children that when we prevent the carious lesion in the childhood, this reduce the risk of dental disease by aging. In addition to this, the scantest try to improve the properties of dental amalgam restoration, and reduce the weaknesses of this material by adding other elements to the mixture of amalgam or changing the percentage of copper, silver, zinc, or mercury in amalgam mixture. For example, the silver alloy which used n dental amalgam filling was contain tow to four percent by weight of copper which is low amount. However, the scientists discovered when they were trying to improve the silver alloy that a higher percent ( 13 Ùª to 30 Ùª ) of copper produce amalgam filling with higher strength, less corrosion, and better longevity at the margins of the cavity preparation. Also, the replacement of zinc from the silver alloy produce better amalgam because zinc can cause undesirable expansion of the amalgam when contaminated with saliva. Besides, the particles of the powder either irregularly shaped or spherical shaped, but scientists discovered that when they mix the tow of the spherical and irregular in the same powder, the alloy would require greater packing or condensation forces during placement than amalgam with spherical or irregular particles alone as ( dental amalgam material properties and manipulation book ). Never the less, toxic of mercury is reduced by the condensation of amalgam and by using the exact percent of mercury to the silver alloy that the producer required. In addition to this, when the mercury is mixed with the powder very will and the dentist condense the amalgam filling in the cavity preparation in the right way, that would reduce the toxic of mercury in the dental amalgam in high percent. Finally, dental amalgam serve the humanity for a long time. So, for the people who are against amalgam filling they should try to combine the abilities to develop a new mixture of amalgam to reduce the weaknesses of this dental material.
Sources:
http://www.holisticmed.com/dental/amalgam/ http://en.wikipedia.org/wiki/Amalgam_(dentistry http://www.qualitydentistry.com/dental/amalgam/amalgam4.htm
http://www.amalgam.org
DENTAL MATERIALS PROPERTIES AND MANIPULATION BOOK
DENTAL MEDIUM ELECTRONIC VERSION MAGAZINE
