• Restorative Dentistry and Endodontics
• /
• v.28 no.6
• /
• pp.457-466
• /
• 2003

The aim of study was to investigate the effect of flow, specimen geometry and adhesion on the measurement of linear polymerization shrinkage of light cured composite resins using linear shrinkage measuring device. Four commercially available composites - an anterior posterior hybrid composite Z100, a posterior packable composite P60 and two flowable composites, Filtek flow and Tetric flow-were studied. The linear polymerization shrinkage of composites was determined using 'bonded disc method' and 'non-bond-ed' free shrinkage method at varying C-factor in the range of 1∼8 by changing specimen geometry. These measured linear shrinkage values were compared with free volumetric shrinkage values. The viscosity and flow of composites were determined and compared by measuring the dropping speed of metal rod under constant load. In non-bonded method, the linear shrinkage approximated one third of true volumetric shrink-age by isotropic contraction. However, in bonded disc method, as the bonded surface increased the linear shrinkage increased up to volumetric shrinkage value by anisotropic contraction. The linear shrinkage value increased with increasing C-factor and approximated true volumetric shrinkage and reached plateau at about C-factor 5∼6. The more flow the composite was, reduced linear shrinkage was measured by compensation radial flow.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.2
• /
• pp.322-329
• /
• 1995

Series of experimental work was performed to mold tensile specimens by using the injection molding machine Mold temperature, melt temperature and packing time were chosen as processing parameters for studying the effects of those conditions on the linear shrinkage of final product. Here, each processing variable was decided from the numerical simulation and resin manufacturer's suggested value. The effects of molding conditions on the linear shrinkage in flow direction of the resin were analyzed by measuring the parts 2, 10, 30 and 60 days after molding. As a result, the linear shrinkage increased with the higher mold and melt temperature, and the change of mold temperature has shown more influence. The linear shrinkage of polypropylene has been found to progress up to 30 day with the lapse of the time, and the amount of the linear shrinkage has shown to be between 2.14% and 2.75%. In addition, the effects of packing pressure on the weight has shown to be extremely significant up to freezing time, and proper packing time of the tensile specimen has been found to be 2.0 seconds.

• The Journal of Advanced Prosthodontics
• /
• v.2 no.3
• /
• pp.81-87
• /
• 2010

PURPOSE. The purpose of this study was to compare the linear sintering behavior of presintered zirconia blocks of various densities. The mechanical properties of the resulting sintered zirconia blocks were then analyzed. MATERIALS AND METHODS. Three experimental groups of dental zirconia blocks, with a different presintering density each, were designed in the present study. Kavo $Everest^{(R)}$ ZS blanks (Kavo, Biberach, Germany) were used as a control group. The experimental group blocks were fabricated from commercial yttria-stabilized tetragonal zirconia powder (KZ-3YF (SD) Type A, KCM. Corporation, Nagoya, Japan). The biaxial flexural strengths, microhardnesses, and microstructures of the sintered blocks were then investigated. The linear sintering shrinkages of blocks were calculated and compared. RESULTS. Despite their different presintered densities, the sintered blocks of the control and experimental groups showed similar mechanical properties. However, the sintered block had different linear sintering shrinkage rate depending on the density of the presintered block. As the density of the presintered block increased, the linear sintering shrinkage decreased. In the experimental blocks, the three sectioned pieces of each block showed the different linear shrinkage depending on the area. The tops of the experimental blocks showed the lowest linear sintering shrinkage, whereas the bottoms of the experimental blocks showed the highest linear sintering shrinkage. CONCLUSION. Within the limitations of this study, the density difference of the presintered zirconia block did not affect the mechanical properties of the sintered zirconia block, but affected the linear sintering shrinkage of the zirconia block.

• Journal of the Korean Ceramic Society
• /
• v.33 no.12
• /
• pp.1373-1379
• /
• 1996

Change of sintering shrinkage in alumina-based multilayer ceramics was observed in various lamination condi-tions and binder burnout (BBO) temperatures. It was found that the linear shrinkages in X and Y directions were nearly the same with the BBO temperatures but a large shrinkage difference in Z direction was observed. However this phenomenon was diminished when BBO temperature was increased. A linear relationship between the laminated density and the sintering shrinkage was found and the slope was independant on the BBO temperature but dependant on the shrinkage direction.

• Restorative Dentistry and Endodontics
• /
• v.28 no.4
• /
• pp.348-353
• /
• 2003

The purpose of present study was to evaluate the polymerization shrinkage stress and amount of linear shrinkage of composites and compomers for posterior restoration. For this purpose, linear polymerization shrinkage and polymerization stress were measured. For linear polymerization shrinklage and polymerization stress measurement, custom made Linometer (R&B, Daejon, Korea) and Stress measuring machine was used (R&B, Daejon, Korea). Compositers and compomers were evaluated: Dyract AP (Dentsply Detrey, Gumbh. German) Z100 (3M Dental Products, St. Paul. USA) Surefil (Dentsply Caulk, Milford, USA) Pyramid (Bisco, Schaumburg, USA) Synergy Compact (Coltene, Altstatten, Switzerland), Heliomolar (Vivadent/Ivoclar, Liechtenstein), and Compoglass (Vivadent Ivoclar/Liechtenstein) were used. 15 measurements were made for each material. Linear polymerization shrinkage or polymerization stress for each material was compared with one way ANOVA with Tukey at 95% levels of confidence. For linear shrinkage: Heliomolar, Surefil

• Journal of the Korean Wood Science and Technology
• /
• v.45 no.3
• /
• pp.335-342
• /
• 2017

This study was carried out to explore a new application of the by-products sawdust, formed during sawing and mandarin peels which are agricultural by-products. The boards were manufactured by mixing the sawdust and mandarin peels at different mixing ratio and density. The boards were then converted to ceramics by various percentage of resin impregnation and at different carbonization temperatures. As the percentage of resin impregnation increased, the weight loss was decreased; on the other hand, density, linear shrinkage and thickness shrinkage increased. As the carbonization temperature increased, the weight loss was increased and linear thickness shrinkage increased to $1000^{\circ}C$ and the subsequent increase was insufficient. As the percentage of mandarin peels addition increased, the weight loss, linear shrinkage and thickness shrinkage was decreased.

• Journal of the Korean Wood Science and Technology
• /
• v.42 no.3
• /
• pp.251-257
• /
• 2014

For new use development of miscanthus sinensis var. purpurascens, which investigated properties of ceramics made from different carbonization temperature ($600{\sim}1,200^{\circ}C$) and percentage of resin impregnation(30~60%) using a mincanthus board. As the carbonization temperature increased, the density, thickness shrinkage, linear shrinkage, weight loss were increased. As the percentage of resin impregnation increased, the density, linear shrinkage and weight loss were increased. On the other hand, thickness shrinkage decreased.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.2
• /
• pp.729-737
• /
• 2013

The environmental load of concrete pavement can be categorized by temperature and moisture loads, which mean temperature distribution, and drying shrinkage and creep in the concrete slab. In this study, a method calculating the environmental load essential to mechanistic design of airport concrete pavement was developed. First, target area and design slab thickness were determined. And, the concrete temperature distribution with slab depth was predicted by a pavement temperature prediction program to calculate equivalent linear temperature difference. The concrete drying shrinkage was predicted by improving an existing model to calculate differential shrinkage equivalent linear temperature difference considering regional relative humidity. In addition, the stress relaxation was considered in the drying shrinkage. Eventually, the equivalent linear temperature difference due to temperature and the differential shrinkage equivalent linear temperature difference due to moisture were combined into the total equivalent linear temperature difference as terminal environmental load. The environmental load of eight civilian and two military airports which represent domestic regional weather conditions were calculated and compared by the method developed in this study to show its application.

• Restorative Dentistry and Endodontics
• /
• v.34 no.4
• /
• pp.364-370
• /
• 2009

The aim of this study was to evaluate the effect of fiber direction on the polymerization shrinkage of fiber-reinforced composite. The disc-shaped flowable composite specimens (d = 10 mm, h = 2 mm, Aeliteflo A2, Bisco, Inc., IL, USA) with or without glass fiber bundle (X-80821P Glass Fiber, Bisco, Inc., IL, USA) inside were prepared, and the longitudinal and transversal polymerization shrinkage of the specimens on radial plane were measured with strain gages (Linear S-series 350${\Omega}$, CAS, Seoul, Korea). In order to measure the free polymerization shrinkage of the flowable composite itself, the disc-shaped specimens (d = 7 mm, h = 1 mm) without fiber were prepared, and the axial shrinkage was measured with an LVDT (linear variable differential transformer) displacement sensor. The cross-section of the polymerized specimens was observed with a scanning electron microscope to examine the arrangement of the fiber bundle in composite. The mean polymerization shrinkage value of each specimen group was analyzed with ANOVA and Scheffe post-hoc test (${\alpha}$=0.05). The radial polymerization shrinkage of fiber-reinforced composite was decreased in the longitudinal direction of fiber, but increased in the transversal direction of fiber (p<0.05). We can conclude that the polymerization shrinkage of fiber-reinforced composite splint or restoratives is dependent on the direction of fiber.

• Restorative Dentistry and Endodontics
• /
• v.35 no.3
• /
• pp.180-187
• /
• 2010

Since the introduction of restorative dental composites, their physical properties have been significantly improved. However, polymerization shrinkage is still a major drawback. Many efforts have been made to develop a low shrinking composite, and silorane-based composites have recently been introduced into the market. In addition, many different methods have been developed to measure the polymerization shrinkage. In this study, we developed a new method to measure the linear polymerization shrinkage of composites without direct contact to a specimen using a particle tracking method with computer vision. The shrinkage kinetics of a commercial silorane-based composite (P90) and two conventional methacrylate-based composites (Z250 and Z350) were investigated and compared. The results were as follows: 1. The linear shrinkage of composites was 0.33-1.41%. Shrinkage was lowest for the silorane-based (P90) composite, and highest for the flowable Z350 composite. 2. The new instrument was able to measure the true linear shrinkage of composites in real time without sensitivity to the specimen preparation and geometry.