4 ago. referência em Materiais Dentários, ANUSAVICE – 12ª Edição apresenta o Phillips. Materiais. Dentários a. EDIÇÃO. 7/5/13 PM Entretanto, o termo prótese dentária fixa (PDF) é o termo universalmente preferido. Phillips - Materiais Dentários; 12ª Edição - Elsevier, Artigos (em anexo). 1) All-ceramic or metal-ceramic tooth-supported fixed dental prostheses (FDPs)?. Phillips Materiais Dentarios book. Read 5 reviews from the world's largest community for readers. Este texto atualizado e amplamente revisado engloba a m.
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Área Materiais Dentários. Faculdade de Odontologia de Piracicaba, UNICAMP. Av. Limeira, Piracicaba, SP, Brasil. Fax: + Learn the most up-to-date information on materials used in the dental office and laboratory today. Emphasizing practical, clinical use, as well as the physical. PDF | A wide variety of dental products that are launched on the market becomes the correct Propriedades mecânicas dos materiais dentários restauradores: contribuição relativa dos ensaios laboratoriais .. Phillips materiais dentários.
It corresponds to resistance of a material to permanent deformation and indicates the amount of energy required to deform the material to its proportional limit. When the area under the elastic and plastic portions of a stress-strain curve is calculated, it indicates the toughness of a material.
Toughness is the resistance of a material to fracture and correspond to the amount of energy required to cause it. All these concepts can be applied in clinical situations. Since many complex forces occur and tend to deform the material tensile, compressive, shear, bending forces , the knowledge and interpretation of how these materials behave under such forces are relevant to understand the performance of the material.
When a body is subjected to axial forces in a straight line and in opposite directions, it results in tension. The resistance of the material to this load is called tensile strength 4,8.
The length alteration that results from the application of a tensile force on a body before its rupture is defined as elongation. Values of stress-strain determine a curve, characterizing the performance of the material under tensile test.
From this curve, elastic modulus, ultimate tensile strength, resilience and toughness of such product can be registered. In this test, it is common to measure the ductibility of a material. It is an important feature of metallic materials because it is the ability of the material to deform under tensile forces until the fracture moment and indicates the workability of an alloy. Rupture under low tension characterizes fragile materials, susceptible to brittle.
In these cases, tensile strength is not indicated to evaluate material reaction, because of the low cohesive condition. An alternative method of tensile strength is calculated by compressive testing.
It is a relative simple and reproducible test. It is defined as diametral compression test for tension or indirect tension 3,4,6,7,8.
Disk sample is necessary to conduct this test, where it is compressed diametrically introducing tensile stress in the material in the plane of the force application by the test Figure 4. This is calculate by the formula: Since most of mastication forces are compressive in nature, it is important to investigate materials under this condition 8. This test is more suitable to compare brittle materials, which show relatively low result when subject to tension.
Therefore, this test is applied to compare dental amalgam, impression materials, investments and cements. Materials that are more resistant under compressive forces than under tensile forces, are called malleable. To test compressive strength of a material, two axial sets of force are applied to a sample in an opposite direction, in order to approximate the molecular structure of the material.
According to ISO 11 , cylindrical-shaped specimens are tested. The dimensions of the samples should have a relation of length to diameter of 2: When this proportion is exceeded, it can result in undesirable bending of the specimen 8. Stress-strain curve of investigated material is determined as the same manner as established to tensile tests. Thus, the elastic modulus can also be determined by the ratio stress-strain in the elastic region. When a material is under axial loading as tensile or compression tests, it is stated that the stress provokes strain in an axial direction.
However, lateral strain also occurs 4,8. Then, tensile force results in material elongation in the axial direction and a reduction of the cross-section. On the other hand, compressive force leads material to increase in the cross-section and reduction of original length. If these reactions occur in the elastic limit, the ratio between lateral and axial strain is denominated Poisson's ratio. Poisson's ratio indicates that the alteration in cross-section is proportional to the deformation during the elastic range.
Brittle materials show little permanent reduction in cross-section during tensile test situations than more ductile materials. The flexural strength of a material is its ability to bend before it breaks. Flexural forces are the result of forces generated in clinical situations and the dental materials need to withstand repeated flexing, bending, and twisting.
A high flexural strength is desired once these materials are under the action of chewing stress that might induce permanent deformation. Specimens are placed on two supports and a load is applied at the center. This test is known as three-point bending test Figure 5. The load at yield is the sample material's flexural strength that is calculated by the following formula: The complexity of the oral environment and geometric diversity of cavities filled with restorations make it difficult to precisely define clinical failure processes and to associate routinely measured mechanical properties with dental materials performance.
The behavior of these materials under the action of stresses, which are relatively low but intermittent, shows the resistance to fatigue 8. This method permits measurement of a fatigue limit, with no fracture, at a given number of stress cycles. Compressive fatigue curves are generated when different materials are submitted to cyclic compressive stress.
Tests are made with the test machine operation in a given loading frequency. The presence of defects in the microstructure of the restoration or specimen submitted to high or low stresses leads to the development of cracks.
As clinical environment influences are critical factors due to the relatively low stress, these cracks will turn into fracture of the material. Major laboratory tests are performed to investigate products based on their bulk features. However, surface characteristics are also a determinant factor when the material is in service in oral environment.
Surfaces characteristics can influence on polishing ability, on the scratching occurrence and on the resistance to load application.
Then, surface hardness is a parameter frequently used to evaluate material surface resistance to plastic deformation by penetration 3,4,8, Hardness is not an intrinsic material property dictated by precise definitions in terms of fundamental units of mass, length and time.
A hardness property value is the result of a defined measurement procedure. The usual method to achieve hardness value is to measure the depth or area of an indentation left by an indenter of a specific shape with a specific force applied for a specific time. There are four common standard test methods for expressing the hardness of a material: Brinell, Rockwell, Vickers, and Knoop.
Each of these methods is divided into a range of scales, defined by a combination of applied load and indenter geometry. The Brinell hardness test method consists of indenting the material with a 10 mm diameter hardened steel or carbide ball subjected to a load. It is the oldest method to measure surface hardness and is applicable to test metal and alloys. The Rockwell hardness test method consists of indenting the test material with a diamond cone or hardened steel ball indenter.
This method is useful to evaluate surface hardness of plastic materials used in Dentistry.
The Vickers hardness test method consists of indenting the test material with a diamond indenter, in the form of a right pyramid with a square base and an angle of degrees between opposite faces subjected to a load of 1 to Kgf. The load is normally applied for 10 to 15 seconds. The two diagonals of the indentation left in the surface of the material after removal of the load are measured using a microscope and their average calculated.
The area of the sloping surface of the indentation is calculated. It is suitable to be applied to determine the hardness of small areas and for very hard materials. Knoop hardness is more sensitive to surface characteristics of the material.
The Knoop indenter is a diamond ground to pyramidal form that produces a diamond shaped indentation having approximate ratio between long and short diagonals of 7: When measuring the Knoop hardness, only the longest diagonal of the indentation is measured and this is used in the following formula with the load used to calculate KHN: Knoop hardness test is applied to evaluate enamel and dentine structures.
One of the major difficulties is the requirement of a high polished flat surface that is more time-consuming and more care taking compared to other tests. Comparing the indentations made with Knoop and Vickers Diamond Pyramid indenters for a given load and test material, there are some technical differences as follow Hardness tests are extremely used and have important applicability on Dentistry. Hardness test can evaluate the degree of mineralization of a dental substrate 15,16 for example.
A specific force applied for a specific time and distance provides important data in studies assessing the ability of enamel and dentin remineralization after different treatments as happens in unbalanced situations of des-remineralization. Another important use of this test is to evaluate the degree of polymerization of resin composite and resin cements. Hardening and depth of cure of these materials can be obtained using Vickers and Knoop micro-hardness test.
Since there are many products on the market, it becomes a difficult task to dentists to select dental materials. Even thought mechanical tests have not reached the level of clinical simulation, they represent an important parameter of analyses. A study of the physical and chemical properties of four resin composite luting cements.
Int J Prosthodont. Evaluation of mechanical properties of dual cure resin cements.
Flexural strength of resin cements. Cienc Odontol Bras. Dental water-based cements; Anusavice KJ. In: Anusavice KJ. Rio de Janeiro: Elsevier; Resin-based filling materials; International Organization for Standardization. Dentistry — polymer-based filling, restorative and luting materials; Dental luting agents: a review of the current literature.
Influence of activation modes on diametrical tensile strength of dual-curing resin cements.