• Journal of Dental Rehabilitation and Applied Science
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• v.40 no.1
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• pp.24-30
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• 2024

Complicated crown fractures of maxillary anterior teeth caused by trauma in adolescence can cause functional and aesthetic problems. For crown fractures with pulp exposure, various restorative methods can be considered depending on the amount of remaining tooth structure. Direct resin restorations are the most traditional and effective method, but they are likely to discolor and break over time. Fixed prosthesis have a high possibility of re-restoration due to marginal disharmony due to tooth movement during the growth period, and restorations using post which are mainly performed for extensive crown fractures increase the risk of root perforation and root fracture. However, endocrown is an integrated structure that gains retention force from the pulp space, enabling effective reconstruction from a biomechanical perspective and providing advantages in restoring function and aesthetics. Therefore, endocrown can be considered as a restoration method for complicated crown fractures caused by trauma in adolescence.

• Korean Journal of Agricultural Science
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• v.30 no.2
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• pp.175-183
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• 2003

Fruit and vegetables are subjected to complex dynamic stresses in the transportation environment. During a long journey from the production area to markets, there is always some degree of vibration present. Vibration inputs are transmitted from the vehicle through the packaging to the fruit. Inside, these cause sustained bouncing of fruits against each other and container wall. These steady state vibration input may cause serious fruit injury, and this damage is particularly severe whenever the fruit inside the package is free to bounce, and is vibrated at its resonance frequency. The determination of the resonance frequencies of the fruit and vegetables may help the packaging designer to determine the proper packaging system providing adequate protection for the fruit, and to understand the complex interaction between the components of fruit when they relate to expected transportation vibration inputs. Instrumentation and technologies are described for determining the vibration response characteristics of the fruits with frequency range 3 to 150 Hz. The computer program for controlling the vibration exciter and the function generator and for measuring the vibration response characteristics of the fruits was developed. The resonance frequency of the pear ranged from 64.5 to 72.2 Hz and the amplitude at resonance was between 1.78 and 2.21 G-rms. The resonance frequency and amplitude at resonance decreased with the increase of the sample mass, and they were slightly affected by mechanical properties such as bioyield deformation and rupture deformation. Regression analysis was performed among the relatively high correlated parameters from the results of correlation coefficient analysis.

• Restorative Dentistry and Endodontics
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• v.33 no.1
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• pp.28-38
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• 2008

This study was to investigate the influence of composite resins with different elastic modulus, cavity modification and occlusal loading condition on the stress distribution of restored notch-shaped noncarious cervical lesion using 3-dimensional (3D) finite element (FE) analysis. The extracted maxillary second premolar was scanned serially with Micro-CT. The 3D images were processed by 3D-DOCTOR. ANSYS was used to mesh and analyze 3D FE model. A notch-shaped cavity and a modified cavity with a rounded apex were modeled. Unmodified and modified cavities were filled with hybrid or flowable resin. After restoration, a static load of 500N was applied in a point-load condition at buccal cusp and palatal cusp. The stress data were analyzed using analysis of principal stress. The results were as follows: 1. In the unrestored cavity, the stresses were highly concentrated at mesial CEJ and lesion apex and the peak stress was observed at the mesial point angle under both loading conditions. 2. After restoration of the cavity, stresses were significantly reduced at the lesion apex, however cervical cavosurface margin, stresses were more increased than before restoration under both loading conditions. 3. When restoring the notch-shaped lesion, material with high elastic modulus worked well at the lesion apex and material with low elastic modulus worked well at the cervical cavosurface margin. 4. Cavity modification the rounding apex did not reduce compressive stress, but tensile stress was reduced.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.4
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• pp.245-251
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• 2017

Since light curing composite resin was introduced in the 1960s, light curing process has been considered as an essential process. Herein, various light sources became available for the process. Quartz-tungsten-halogen (QTH) light curing units (LCUs) dominated the market until the 1990s, before the LED LCUs started replacing them in the 2000s. The LED, developed approximately 50 years ago, came into use in the dentistry field from the late 1990s, and the LED LCUs, with the 2000s. Since then, the LED LCUs have gone through many advancements to its current fourth generation. In accordance to such advancements of the LED light curing unit, the majority of light curing unit used today are LED LCUs. As much as its usage has increased, it is necessary that dental clinicians understand the characteristics of the device. The objective of this review report is to provide the history of the scientific development and describe the characteristics of the LED LCUs.

• Korean Journal of Food Science and Technology
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• v.19 no.3
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• pp.263-272
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• 1987

Lactobacillus bulgaricus (KFCC 35463) and Kluyveromyres fragilis (KFCC 35458) were inoculated together in soymilk, and then growth characteristics, acid production and the conditions suitable for acid production were investigated. L. bulgaricus produced more acid and the rate of acid production was more rapid when this organism was incubated with K. fragilis in soymilk than when it was incubated singly. Studying the conditions suitable for acid production in soymilk, optimum acid production by the mixed cultures of L. bulgaricus and K. fragilis was achieved with a temperature of $35{\sim}37^{\circ}C$, a 1:2 (O.D.660) ratio of L. bulgaricus to K. fragilis at inoculum, a 1.0% level of sucrose fortification or a 1.5% level of skim milk powder fortification and a culture time of 24hr. Under these conditions the amount of acid produced by the single culture of L. bulgaricus and the mixed cultures of L. bulgaricus and K. fragilis were 0.14% and 0.41%, respectively, in soymilk, 0.13% and 0.70%, respectively, in soymilk fortified with 1.0% level of sucrose. These indicate that the amount of acid produced by mixed cultures is about 2.9-fold greater in soymilk and about 5.4-fold greater in soymilk fortified with 1.0% level of sucrose than that produced by the single culture of L. bulgaricus. The amount of acid produced in soymilk fortified with 1.5% level of skim milk powder was 0.84% level for both of the single culture of L. bulgaricus and the mixed cultures of L. bulgaricus and K. fragilis after 24hr incubation. However, the amount of acid produced by the mixed culture with K. fragilis was greater than that produced by the single culture of L. bulgaricus onlv in soymilk fortified with lower levels of skim milk powder than 1.5%.

• Journal of Animal Science and Technology
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• v.52 no.4
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• pp.281-286
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• 2010

In this study, feeding fermented colostrum to Holstein calves was investigated to find out the effects on their growth and inhibition of diarrhea. The results of this study showed that the mixture of L. rhamnosus and E. faecium would be proper bacteria for fermentation of colostrum because of favorable odor, inhibition of coliform bacteria and high number of lactic acid bacterial count. Among the groups of calves fed 0, 5, 10 and 20% of fermented colostrums, average body weight gain for 28 days on feeding fermented colostrum were 16.6, 16.6, 17.4 and 18 kg, respectively showing that calves fed 20% fermented colostrum achieved the highest body weight gain. Occurrence of diarrhea due to feeding various levels of fermented colostrum was also recorded. Three calves out of 5 suffered diarrhea in 0%, 5%, and 20% group, on the other hand, all 5 calves suffered diarrhea in 10% group. Diarrhea persisted for durations were 2.7, 2.4, 4.0, and 2.4 days in 0, 5, 10, and 20% group, respectively. Fermented colostrum did not prevent the occurrence of diarrhea. In overall, addition of fermented colostrum above 10% level showed favorable effects in gaining body weight under the conditions of adding more portions of the fermented colostrum either for 14 days or longer feeding period of the fermented colostrum. On the other hand, fermented colostrum showed no beneficial effect in prevention of diarrhea in this study.

• Microbiology and Biotechnology Letters
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• v.14 no.6
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• pp.487-493
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• 1986

Lactobacillus helveticus YM-1and Streptococcus lactis Ml$_3$ were inoculated together in reconstituted non-fat skim milk medium, and then their proteolytic activity and stimulatory compound for acid production were investigated. Significant difference between Lactobacillus helveticus YM-1 and Streptococcus lactis Ml$_3$was observed in the proteolytic activities. The proteolytic activity of Lactobacillus helveticus YM-1 and Streptococcus lactis Ml$_3$ was 105 $\mu\textrm{g}$/$m{\ell}$ and 30 $\mu\textrm{g}$/$m{\ell}$ when converted the amounts of hydrolysates of milk protein determined by Folin Ciocaleau phenol method into their tyrosine equivalent Stimulatory compounds in cell-free filtrate of Lactobacillus helveticus YM-1were identified as peptide with a molecular weight of approximately 4, 300 for the acid production by Streptococcus lactis Ml$_3$. Some kinds of amino acids, such as histidine, lysine, arginine and glutamic acid, were rich in acid hydrolysates of peptide. Among amino acids, histidine, glutamic acid and phenylalanine stimulated acid production, on the contrary isoleucine inhibited.

• Restorative Dentistry and Endodontics
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• v.33 no.6
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• pp.570-579
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• 2008

The purpose of this study was to investigate the distribution of tensile stress of canal obturated maxillary second premolar with access cavity and notch-shaped class V cavity restored with composite resin using a 3D finite element analysis. The tested groups were classified as 8 situations by only access cavity or access cavity with notch-shaped class V cavity (S or N), loading condition (L1 or L2), and with or without glass ionomer cement base (R1 or R2). A static load of 500 N was applied at buccal and palatal cusps. Notch-shaped cavity and access cavity were filled microhybrid composite resin (Z100) with or without GIC base (Fuji II LC). The tensile stresses presented in the buccal cervical area, palatal cervical area and occlusal surface were analyzed using ANSYS. Tensile stress distributions were similar regardless of base. When the load was applied on the buccal cusp, excessive high tensile stress was concentrated around the loading point and along the central groove of occlusal surface. The tensile stress values of the tooth with class Ⅴ cavity were slightly higher than that of the tooth without class V cavity. When the load was applied the palatal cusp, excessive high tensile stress was concentrated around the loading point and along the central groove of occlusal surface. The tensile stress values of the tooth without class V cavity were slightly higher than that of the tooth with class V cavity.

• Restorative Dentistry and Endodontics
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• v.33 no.2
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• pp.125-132
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• 2008

The purpose of this study is to compare the shear bond strength of repaired composite resin with different bonding agents and evaluate the effect of bonding agents on composite repair strength. Forty composite specimens (Z-250) were prepared and aged for 1 week by thermo cycling between 5 and $55^{\circ}C$ with a dwell time of 30s. After air abrasion with $50\;{\mu}m$ aluminum oxide, following different bonding agents were applied (n = 10); SB group: Scotchbond multipurpose adhesive (3 step Total-Etch system); XE group: Clearfil SE bond (2 step Self-Etch system); XP group: XP bond (2 step Total-Etch system); XE group: Xeno III (1 step Self-Etch system). After bonding procedure was completed, new composite resin (Z-250) was applied to the mold and cured. For control group. 10 specimens were prepared. Seven days after repair, shear bond strength was measured. Data was statistically analyzed using one-way ANOVA and Tukey's test (p<0.05). The means and standard deviations of shear bond strength (MPa ${\pm}$ S.D.) per group were as follows: SB group: 17.06; SE group: 19.10; XP group: 14.44; XE group: 13.57; Control Group: 19.40. No significant difference found in each group. Within the limit of this study, it was concluded that the different type of bonding system was not affect on the shear bond strength of repaired composite resin.

• Restorative Dentistry and Endodontics
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• v.34 no.1
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• pp.1-7
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• 2009

The purpose of this study was to compare the stress distributions of NiTi rotary instruments based on their cross-sectional geometries of triangular shape-based cross-sectional design, S-shaped cross-sectional design and modified rectangular shape-based one using 3D FE models. NiTi rotary files of S-shaped and modified rectangular design of cross-section such as Mtwo or NRT showed larger stress change while file rotation during simulated shaping. The stress of files with rectangular cross-section design such as Mtwo, NRT was distributed as an intermittent pattern along the long axis of file. On the other hand, the stress of files with triangular cross-section design was distributed continuously. When the residual stresses which could increase the risk of file fatigue fracture were analyzed after their withdrawal. the NRT and Mtwo model also presented higher residual stresses. From this result, it can be inferred that S-shaped and modified rectangular shape-based files were more susceptible to file fracture than the files having triangular shape-based one.