Group 2: The significance of modulus of elasticity and fracture toughness for resin composites
Kelly Griffith, Lance Gunter, Joshua Haentges, Erik Hageman, Zohra Hasham, Nellab Hashimi
Modulus of elasticity is defined as the comparative stiffness of a material. A stiffer material will have a higher elastic modulus. Fracture toughness is the amount of stress required to propagate a preexisting flaw. It describes resistance of a material with a pre-existing flaw to fail. These two properties will be evaluated for resin composites in our paper through journal articles.
Packable composites have a higher filler load and elastic modulus than flowable composites. Packing might also reduce shrinkage. Flowables have less filler and are used as liners and sealants. They cannot withstand much force, but this helps relieve stress due to shrinkage. However, this may be counteracted because they shrink upon curing. Flowable and packable composite resins were tested for shear strength 30 minutes, 1 day, and 1 week, after curing under constant pressure. The dimethacrylate resins tested were: Alert/- Flow It, Filtek P 60/Filtek Flow, Admira/Admira Flow—an ormocer resin—and a microfill composite resin. The resins increased in strength over one week. The packable composites were stronger than the flowables, but variable between manufacturers. The ormocer resin had a lower elastic modulus than other packable resins. Although the flowables have lower elastic moduli, they shrink more, so shrinkage stress might not be better than packable composites. (Helvatjoglu et al)
The article by Dr. Nuray Attar focused on the comparison of the flexural strength and elastic modulus of condensable and hybrid composite resins. The study focused on fou...
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Helvatjoglu-Antoniades M, Papadogiannis Y, Lakes RS, Dionysopoulos P, and
Papadogiannis D. Dynamic and Static Elastic Moduli of Packable and Flowable Composite
Resins and Their Development After Initial Photo Curing. Dent Mater. 2006; 22: 450-459.
Kostantinos M, Silikas N, and Watts DC. Correlation of Filler Content and Elastic Properties of
Resin Composites. Dent Mater. 2008; 24: 932-939.
Nuray, A. A Comparison of the Flexural Strength and Elastic Modulus of Condensable and
Hybrid Composite Resins. ARASTIRMA , 30, 42-50.
Roberts JC, Powers JM, and Craig RG. Fracture Toughness of Composite and Unfilled
Restorative Resins. Dent Res 1977; 56(7): 748-753.
Sabbagh J, Vreven J, and Leloup G. Dynamic and Static Moduli of Elasticity of Resin-based
Materials. Dent Mater. 2002; 18: 64-71.
Laws such as the lever law and Euler’s Buckling Theorem come into play when testing and competition begins. A structure of wood and glue surely has much more to offer than meets the eye.
Karaman E, and Ozgunaltay G. Polymerization Shrinkage of Different Types of Composite Resins and Microleakage With and Without Liner in Class II Cavities. Operative Dentistry 2014; 39(2):00-00.
Adhesion of resin materials to tooth structure has been a challenge in the history of adhesive dentistry. Currently, bond durability is one of the main research topics in adhesive dentistry. Regardless of the improvements in bonding technology, resin dentin bonds show limited durability for both etch and rinse and self-etch adhesive systems.
Stiffness The effect that this additive has on the polymer in terms of stiffness is that the fillers are very useful because it makes the polymers very strong and stiff. This makes it hard to break.
Denture teeth can be made of acrylic poly(methyl methacrylate) (PMMA) or composite resins. PMMA is a polymer - a material made the from joining of methyl methacrylate monomers. Properties of PMMA include resistance to abrasion, chemical stability and a high boiling point. (Jun Shen et al. 2011). However, weak flexure and impact strength of PMMA are of concern as they account for denture failure. (Bolayir G, Boztug A and Soygun K. 2013). Composite denture teeth are made of a three distinct phases - filler, matrix and coupling agents. Out of the types of composite teeth available, nano-filled composite teeth are preferred. Composite teeth have a PMMA coating around the tooth and a high content of filler particles. This gives them strength, higher resistance to forces than acrylic teeth and provides compete polymerization due to the PMMA coating. (Anusavice, K. J., Phillips, R. W., Shen, C., & Rawls, H. R, 2012). If the interface between the PMMA denture base and PMMA or composite teeth was weak, the denture will not be able to sustain occlusal forces, making the base-teeth interface, an entity of significance.
Elastic Bands and Hooke's Law Aim: To investigate elastic bands, whether they follow Hookes Law.
Theoretical prediction of tensile modulus Young’s modulus is the stiffness of a material at the elastic stage of the deformation process. It is enhanced by adding micro and nano-particles to a polymer matrix as hard particles have much higher stiffness than the matrix [16]. There are 181 Page 2 of 12 J Polym Res (2016) 23:181 many theoretical models [16] such as Paul model, Modified rule of mixtures model, and Counto model thatmay be used to predict the moduli of particulate polymeric composites. It is to be noted that these models make a number of assumptions.
The melt flow index (MFI) is a measure of the ease of flow of the melt of a thermoplastic polymer. It is defined as the mass of polymer, in grams, flowing in ten minutes through a capillary of a specific diameter and length by a pressure applied via prescribed alternative gravimetric weights for alternative prescribed temperatures.Polymer processors usually correlate the value of MFI with the polymer grade that they have to choose for different processes, and most often this value is not accompanied by the units, because it is taken for granted to be g/10min. Similarly, the test load conditions of MFI measurement is normally expressed in kilograms rather than any other units. The method is described in the similar standards ASTM D1238 and
The structural torsional stiffness is calculated through finding the torque applied to the handle and dividing it by the angular deflection of the handle that is resulted from the torsional loading. It is expressed in term of Nm/degree of angular deflection. This calculation is shown below in figure 3.1
Young’s modulus describes the stiffness of the structure as the ratio of stress to strain. if the structure is very stiff a large stress is required to produce a given strain and young’s modulus is large.
The purposes of this lab were to determine a relationship between percent cold working and hardness, determine the effect cold working has on microstructure, and last but not least relate dislocation theory to the observed data. Determining the relationship between percent cold working and hardness involved using a cold roller and running our cartridge brass (70 wt.% Cu, 30 wt.% Zn) sample through it until the percent given was reached by each group. This is a good material because it is well suited to cold-forming because of its high strength and ductility. Each group was assigned a specific percent to reach. The percent’s were 0, 10, 20, 30 40, and 50 respectively. After our percent was given a top and bottom were decided and this was so the sample was ran through the same way every time. The percent cold work is found using this equation % CW = t1-t2/t1 * 100, multiplying by 100 to get the percent, t1 is the original thickness of the sample and t2 is the thickness after running it through.
...der is the compressive strength. This is important because most of the mastication forces act upon compression. You can use this test to see which dental material is able to resist the most occlusal forces. Another property to consider is called flexural strength. This is defined as the ability of a material to bend before it breaks. It is important to have a high flexural strength when making dental materials because the materials must be able to be repeatedly bent under the action of chewing.
Charles and Keith uses synthetic materials and polyurethane to ensure affordable prices of their products (Singapore Press Holding, 2009). However, the qualities of the products are not compromised despite its inexpensive prices. The managing director Charles Wong reassured the customers that although the ...
Exothermal energy of polymer cure (as in epoxy adhesives), allows determination of the degree and rate of cure.
The chemical properties of the material used in present model is as shown in table 5.1