Comparison Of Four Kinds Of Room Curing Polymethylmethacrylate Material Properties

Room curing PMMA material is at room temperature by redox initiated polymerization, fast curing is made. It is widely used in dental clinic one of the repair materials, mainly used in full denture relining, making temporary substrate, individual trays, temporary crowns and so on, but room curing PMMA material has a low molecular weight, residual monomer and more mechanical strength disadvantages such as low and easy to change color. Present new room curing PMMA materials have wide application in China, but its mechanical properties of the study also been reported. This study selected four kinds of typical room curing PMMA material ShangHai (simple type), Heraeus-Meliodent (fiber type), Nisshin - Natural (fiber type), Tokuyama-REBASEⅡ(hard-liner type). At room temperature under 20℃, with a stainless steel mold material operations in strict accordance with the standard specimen preparation, to ensure test accuracy and consistency.In this study, the specimens produced in full accordance with testing standards, and strictly control the temperature, the material powder liquid ratio of influencing factors such as pressure polymerization conditions, through the observation of the specimen, remove air bubbles, defects of the specimen, as far as possible reduce the impact of human factors, so that comparable among the groups.Room temperature curing PMMA material to resist the mouth complex role forces, bending strength and impact bending strength of denture base capacity is a measure of the importance of indicators. Bending strength reflects the material fracture under static load when the energy absorbed. Brittle materials is the inherent characteristics of PMMA, for brittle materials, tensile test is difficult to make the best use of bending test. Bending test specimen size 60 mm×20 mm×5 mm, each of 10 specimen materials. In the CSS-44100 electronic universal testing machine for testing. TOKUYAMA bending strength and Nisshin, Heraeus, the ShangHai were significantly different (P <0. 05), Nisshin and TOKUYAMA, Heraeus significant difference (P <0. 05), Heraeus and TOKUYAMA, Nisshin significant difference (P <0. 05); on ShangHai and Nisshin, Heraeus no significant difference (P> 0. 05). TOKUYAMA lowest flexural strength, flexural strength into the approximate date the highest. Four kinds of curing at room temperature flexural strength of PMMA order: Nisshin≥ShangHai≈Heraeus> TOKUYAMA.For TOKUYAMA bending strength does not meet the standards, may be two reasons:①Due to the hard-liner-type room temperature curing PMMA material, likely to join a plasticizer, reducing its strength,②the less liquid, non-dough stage, production of small bubbles generated when the specimen. Specific reasons to be further studied its chemical composition.Heraeus all day and into the fiber-type room temperature curing PMMA material, the bending strength than Nisshin Heraeus, there are two possible reasons:①fiber content, length or texture different, leading to different bending strength;②its solution may agent in a certain amount of high boiling point acrylate, naked as the day the high level of transparency was observed. Specific reasons to be further studied its chemical composition.Elastic modulus is the elastic resistance, said material is adaptability. The larger the elastic modulus, the more difficult material the elastic deformation. As with the deflection is inversely proportional to the thickness of the specimen and other factors into account, so elastic modulus ratio of deflection to more accurately reflect the material's mechanical properties. TOKUYAMA elastic modulus and Nisshin, Heraeus, ShangHai were significantly different (P <0. 05), Nisshin, Heraeus, ShangHai had no significant difference (P> 0. 05). TOKUYAMA modulus minimum. Four kinds of curing at room temperature elastic modulus of PMMA order: Nisshin≈ShangHai≈Heraeus> TOKUYAMA. Best reflect the impact strength of soft and rigid materials, has gradually been recognized as denture base materials, one of the most important mechanical property.Impact test specimen size 60 mm×5 mm×4 mm, each of 10 specimen materials. In the Charpy impact test machine for testing. TOKUYAMA impact strength and Nisshin, Heraeus, ShangHai were significantly different (P <0. 05), Nisshin, Heraeus, ShangHai had no significant difference (P> 0. 05). TOKUYAMA the lowest impact strength. Four kinds of curing at room temperature impact strength of PMMA material order: Nisshin≈ShangHai≈Heraeus> TOKUYAMA.Experimental results show that four kinds of elastic modulus and impact strength of the order are: Nisshin≈ShangHai≈Heraeus> TOKUYAMA. That: elastic modulus and impact strength are relevant.Surface hardness of the material to resist deformation and fracture surface of regional capacity. Some scholars of hardness and wear have relevance, methods and materials, wear different complexity, draw conclusions inconsistent.Surface hardness test specimen size 60 mm×20 mm×5 mm, each sample materials 6. Cloth wheel with conventional polishing the specimen surface, in the HB-3000 Brinell Rockwell & Vickers hardness test on each sample measured three points, results were the mean value. TOKUYAMA Surface hardness and Nisshin, ShangHai were significantly different (P <0. 05), Nisshin and TOKUYAMA, Heraeus significant difference (P <0. 05), Heraeus and Nisshin, ShangHai were significantly different (P <0. 05); TOKUYAMA with Heraeus and Nisshin and ShangHai was no significant difference between (P> 0. 05). Four kinds of room temperature curing PMMA material hardness of the order: Nisshin≈ShangHai > Heraeus≈TOKUYAMA.As the oral environment is complex, diverse way of occlusal movement, artificial mouth simulator also can only simulate one or more of them, and the design was expensive to maintain and wear conditions are complicated, difficult to directly compare the experimental results, therefore more inclined scholars wear and tear on the use of simple machines, simulation of one or two wear mechanisms observed wear mechanism of materials under specific wear characteristics.Currently, the wear volume measurement methods are: weight loss and dimensional change method. PMMA material as residual monomer curing at room temperature over recent years, room temperature curing a lot of modification of PMMA: chemical composition of adjustment, adding other material matrix. The modification of an impact on the material density measurement, thus affecting the wear weight loss method for the determination of accuracy, so changes in the size selection method for the determination of wear. Wear test specimens with a diameter of 5 mm, 5 mm high cylindrical specimens of each materials 5. Room temperature under 20℃, the MG-2000 friction and wear testing machine to test. Nisshin wear and Heraeus, ShangHai were significantly different (P <0. 05), Nisshin and ShangHai, Heraeus significant difference (P <0. 05), Heraeus and Nisshin, ShangHai were significantly different (P <0. 05). 3 kinds of room temperature curing PMMA material wear of the order: ShangHai > Heraeus> Nisshin.TOKUYAMA specimens were cracked in the wear experiments, failed to complete the test, no test results. The reason may be: TOKUYAMA hard liner-type room temperature curing PMMA material, fragmentation of specimens with low bending strength and impact strength of the wear experiment, the vertical bending strength to strength and direction of the force imposed by the same, mainly positive pressure; strength and impact strength of lateral direction of the force imposed by the same main shear. The outcomes and Yap scholars same view: wear volume and hardness of no relevance.Confocal laser scanning microscope (CLSM) appeared in the late 80s of this century, because of its high resolution, sample preparation is simple, three-dimensional reconstruction by CT scanning and three-dimensional image observation of the sample, and samples of the observed object in space and orientation advantages of sample preparation to avoid changes in the course of human factors, such as spray gold. Electron microscopy in vitro wear test is usually subtle changes on the surface of the material characteristics of the observation, description of wear law, material properties.Laser confocal microscope and fractured surfaces of the wear surface. With×5,×10,×20 objective lens to observe the end-user×200,×400 magnification,×20 objective lens with a pre-established access to confocal observation zone map, and monitor use of the image introduced by the software were measured and analyzed. In this study, experiments using CLSM on the bending fracture surface ofspecimens were observed in the bending test, the most obvious micro-cracks. By the tension of the bottom samples, but slow loading, micro-cracks can be fully generated. From the CLSM Figure 1.1, Figure 2.1, Figure 3.1, Figure 4.1 can be observed micro-cracks and the number of complete order: Figure 2.1> Figure 3.1≈Figure 4.1> Figure 1.1. By CLSM three-dimensional reconstruction of the fracture surface that: bending strength of the material, the fracture surface micro-cracks produced complete and a small number of higher strength material.This study selected CLSM specimen wear surface on the three dimensional reconstruction of observation can be seen. Nisshin visible on Figure 5.1-5.2 wear into the smooth surface, thin and shallow furrows;From Figure 6.1-6.2 Heraeus the worn surface showed a clear furrow phenomenon, showing a more typical abrasive wear; from Figure 7.1-7.2 visible wear ShangHai surface is rough, wide and deep furrows. The three-dimensional reconstruction image shows: The result of this research into the wear on the teeth was significantly better than the results consistent. The wear ShangHai surface is rough, showing signs of falling filler, the wear mechanism may be to fatigue wear.According to our experimental results, analysis of indicators, we believe that practical clinical applications in the process: 1.day suitable for the attachment into the negative parts of cement on the surface of base tissue and orthodontic appliances, maxillofacial plates and other long-term fix, the various aspects of performance are high, and wide application. Heraeus and the day the price, elastic modulus, impact strength and wear resistance of close attachment can also be used to cement the negative components in the base surface of the long-term tissue repair.2.TOKUYAMA only oral conditions for poor denture re-lining, which has a certain degree of flexibility and plasticity.3.in addition to special requirements of re-lining material TOKUYAMA, the date forward, Heraeus, the teeth can be applied to temporary production base and individual trays.ShangHai more suited to a temporary base and individual trays made for tworeasons:①cheap;②because two of the bending, impact strength and wear resistance requirements are lower. Based on this study the following results:1. Four kinds of curing at room temperature flexural strength of PMMA order: Nisshin≥ShangHai≈Heraeus> TOKUYAMA. TOKUYAMA lowest flexural strength, Nisshin flexural strength into the approximate date is the highest.2. Four kinds of PMMA curing at room temperature elastic modulus of the order: Nisshin≈ShangHai≈Heraeus> TOKUYAMA. TOKUYAMA modulus minimum.3. Four kinds of curing at room temperature impact strength of PMMA material of the order: Nisshin≈ShangHai≈Heraeus> TOKUYAMA. TOKUYAMA the lowest impact strength. elastic modulus and impact strength of relevant.4. Four kinds of room temperature curing PMMA material surface hardness of the order: Nisshin≈ShangHai > Heraeus≈TOKUYAMA. Nisshin of hardness higher than the Heraeus and TOKUYAMA. 5. 3 kinds of room temperature curing PMMA material wear of the order: ShangHai > Heraeus> Nisshin. TOKUYAMA specimens were cracked in the wear experiments, failed to complete the test, no test results. wear and hardness of no relevance.6. CLSM through research on the fracture surface and wear surface analysis of the three-dimensional reconstruction of images:①Bending strength of the material, the fracture surface micro-cracks produced complete high and quantity.②Heraeus showing the worn surface of a clear furrow phenomenon; Nisshin wear into the smooth surface, thin and shallow furrows; on the ShangHai rough surface abrasion, wide and deep furrows. Show: The results of this study, the wear resistance results are consistent.7. For the clinical application: TOKUYAMA only oral conditions for poor denture re-lining. ShangHai more suited to a temporary base and production of individual trays. Nisshin used for the various performance requirements of oral and high repair. Heraeus is suitable for the attachment of the negative parts of cement in the base surface of the long-term tissue repair and production of basic repair.