• Archives of Plastic Surgery
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• v.40 no.4
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• pp.335-340
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• 2013

Background In patients with medial orbital wall fracture, predicting the correlation between the degree of enophthalmos and the extent of fracture is essential for deciding on surgical treatment. We conducted this retrospective study to identify the correlation between the two parameters. Methods We quantitatively analyzed the correlation between the area of the bone defect and the degree of enophthalmos on computed tomography scans in 81 patients with medial orbital wall fracture who had been left untreated for more than six months. Results There was a significant linear positive correlation between the area of the medial orbital wall fracture and the degree of enophthalmos with a formula of E=0.705A+0.061 (E, the degree of enophthalmos; A, the area of bone defect) (Pearson's correlation coefficient, 0.812) (P<0.05). In addition, that there were no cases in which the degree of enophthalmos was greater than 2 mm when the area of the medial orbital wall fracture was smaller than $1.90cm^2$. Conclusions Our results indicate not only that 2 mm of enophthalmos corresponds to a bone defect area of approximately $2.75cm^2$ in patients with medial orbital wall fracture but also that the degree of enophthalmos could be quantitatively predicted based on the area of the bone defect even more than six months after trauma.

• Restorative Dentistry and Endodontics
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• v.15 no.2
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• pp.17-33
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• 1990

The purpose of this study was to evaluate the fracture toughness of dental composite resins and to investigate the filler factor affecting the fracture behaviour on which the degree of fracture toughness depends. Six kinds of commercially available composite resin;, including two of each macrofilled, microfilled, and hybrid type were used for this study, The plane strain fracture toughness ($K_{10}$) was determined by three-point bending test using the single edge notch specimen according to the ASTM-E399. The specimens were fabricated with visible light curing or self curing of each composite resin previously inserted into a metal mold, and three-point bending test was conducted with cross-head speed of 0.1mm/min following a day's storage of the specimens in $37^{\circ}C$ distilled water. The filler volume fractions were determined by the standard ashing test according to the ISO-4049. Acoustic Emission(AE), a nondestructive testing method detecting the elastic wave released from the localized sources In material under a certain stress, was detected during three-point bending test and its analyzed data was compared with, canning electron fractographs of each specimen. The results were as follows : 1. The filler content of composite resin material was found to be highest in the hybrid type followed by the macrofilled type, and the microfilled type. 2. It was found that the value of plane strain fracture toughness of composite resin material was in the range from 0.69 MPa$\sqrt{m}$ to 1 46 MPa$\sqrt{m}$ and highest In the macrofilled type followed by the hybrid type, and the microfilled type. 3. The consequence of Acoustic Emission analysis revealed that the plane strain fracture toughness increased according as the count of Acoustic Emission events increased. 4. The higher the plane strain fracture toughness became, the higher degree of surface roughness and irregularity the fractographs demonstrated.

• The Journal of Advanced Prosthodontics
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• v.12 no.4
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• pp.181-188
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• 2020

PURPOSE. The effect of core design on the fracture resistance of zirconia-lithium disilicate (LS2) bilayered crowns for anterior teeth is evaluated by comparing with that of metal-ceramic crowns. MATERIALS AND METHODS. Forty customized titanium abutments for maxillary central incisor were prepared. Each group of 10 units was constructed using the same veneer form of designs A and B, which covered labial surface to approximately one third of the incisal and cervical palatal surface, respectively. LS2 pressed-on-zirconia (POZ) and porcelain-fused-to-metal (PFM) crowns were divided into "POZ_A," "POZ_B," "PFM_A," and "PFM_B" groups, and 6000 thermal cycles (5/55 ℃) were performed after 24 h storage in distilled water at 37 ℃. All specimens were prepared using a single type of self-adhesive resin cement. The fracture resistance was measured using a universal testing machine. Failure mode and elemental analyses of the bonding interface were performed. The data were analyzed using Welch's t-test and the Games-Howell exact test. RESULTS. The PFM_B (1376. 8 ± 93.3 N) group demonstrated significantly higher fracture strength than the PFM_A (915.8 ± 206.3 N) and POZ_B (963.8 ± 316.2 N) groups (P<.05). There was no statistically significant difference in fracture resistance between the POZ_A (1184.4 ± 319.6 N) and POZ_B groups (P>.05). Regardless of the design differences of the zirconia cores, fractures involving cores occurred in all specimens of the POZ groups. CONCLUSION. The bilayered anterior POZ crowns showed different fracture resistance and fracture pattern according to the core design compared to PFM.

• Archives of Craniofacial Surgery
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• v.20 no.5
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• pp.284-288
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• 2019

Background: Closed reduction of nasal fracture with various instrument is performed to treat nasal fracture. Depending on the type of nasal fracture and the situation in which it is being operated, the surgeon will determine the surgical tool. The objective of this study was to investigate whether a periosteal elevator (PE) was a proper device to perform closed reduction for patients with simple nasal fractures. Methods: From March 2018 to December 2018, 50 cases of simple nasal bone fracture underwent closed reduction performed by a single surgeon. These patients were divided into two groups randomly: nasal bone reduction was performed using only PE (freer) and nasal bone reduction was performed using Walsham, Asch forcep, and Boies elevator (non-freer, non-PE). Results: The paranasal sinus computed tomography was performed on patients before and after operation to carry out an accurate measurement of reduction distance at the same level. According to the results, the interaction between instruments and fracture types had a significant influence on reduction distance (p = 0.021). To be specific, reduction distance was significantly (p= 0.004) increased by 2.157 mm when PE was used to treat patients with partial displacement compared to that when non-PEs were used. Conclusion: Closed reduction using PE and other elevator is generally an effective treatment for nasal fracture. In partial-displacement type of simple nasal fracture, closed reduction using PE can have considerable success in comparison with using classic instruments.

• Journal of Trauma and Injury
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• v.27 no.4
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• pp.186-191
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• 2014

Purpose: The objectives of this study were to assess pain relief according to the time after kyphoplasty and to evaluate the factors affecting pain relief after kyphoplasty in the treatment of a single-level osteoporotic vertebral compression fracture. Methods: A retrospective review of 34 kyphoplasties for single-level osteoporotic vertebral compression fractures was performed. Pain relief was assessed by using the visual analogue scale (VAS) at preoperatively and postoperatively at 6 weeks, 3 months, and 6 months. Associated factors, including age, sex, pain duration, bone mineral density, and cement leakage, were evaluated using the patients' medical records. Statistical analyses were conducted using the paired t-test to assess pain relief and using the independent t-test and Pearson's correlation coefficient to evaluate the relationship between those factors and pain relief. Results: Preoperatively, the mean VAS score was 7.06. Postoperatively, it declined to 3.66 (p=0.001), 2.81 (p=0.001) and 2.24 (p=0.001) at 6 weeks, 3 months and 6 months, respectively. Also, statistically significant pain relief was observed during the periods from 6 weeks to 3 months (p=0.001) and from 3 months to 6 months (p=0.001). However, reduction of the VAS score showed no significant correlation with age, sex, pain duration, bone mineral density, or cement leakage (p>0.05). Conclusion: Our study suggests that a kyphoplasty may be effective in osteoporotic vertebral compression fracture patients with acute pain and that after the kyphoplasty, pain is reduced remarkably for 6 weeks and then continuously for 6 months.

• Archives of Craniofacial Surgery
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• v.12 no.1
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• pp.12-16
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• 2011

Purpose: This study examined the biomechanical stability of four different plating techniques in the experimental model of mandibular subcondyle fracture. Methods: Twenty standardized bovine tibia bone samples ($7{\times}1.5{\times}1.0cm$) were used for this study. Each of the four sets of tibia bone was cut to mimic a perpendicular subcondyle fracture in the center area. The osteotomized tibia bone was fixed using one of four different fixation groups (A,B,C,D). The fixation systems included single 2.0 mm 4 hole mini adaption plate (A), single 2.0 mm 4 hole dynamic compression miniplate (B), double fixation with 2.0 mm 4 hole mini adaption plate (C), double fixation with a 2.0 mm 4 hole mini adaption plate and 2.0 mm 4 hole dynamic compression miniplate (D). A bending force was applied to the experimental model using a pressure machine (858 table top system, $MTS^{(R)}$) until failure occurred. The load for permanent deformation, maximum load of failure were measured in the load displacement curve with the chart recorder. Results: Double fixation with a 2.0 mm 4 hole mini adaption plate and a 2.0 mm 4 hole dynamic compression miniplate (D) applied to the anterior and posterior regions of the subcondyle experimental model showed the highest load to failure. Conclusion: From this study, double fixation with an adaption plate and dynamic compression miniplate fixation technique produced the greatest biomechanical stability. This technique may be considered a useful means of fixation to reduce the postoperative internal maxillary fixation period and achieve early mobility of the jaw.

• Korean Journal of Materials Research
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• v.31 no.9
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• pp.519-524
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• 2021

The impact properties of two austenitic Fe-23Mn-0.4C steels with different Al contents for cryogenic applications are investigated in this study. The 4Al steel consists mostly of austenite single-phase microstructure, while the 5Al steel exhibits a two-phase microstructure of austenite and delta-ferrite with coarse and elongated grains. Charpy impact test results reveal that the 5Al steel with duplex phases of austenite and delta-ferrite exhibits a ductile-to-brittle transition behavior, while the 4Al steel with only single-phase austenite has higher absorbed energy over 100 J at -196 ℃. The SEM fractographs of Charpy impact specimens show that the 4Al steel has a ductile dimple fracture regardless of test temperature, whereas the 5Al steel fractured at -100 ℃ and -196 ℃ exhibits a mixed fracture mode of both ductile and brittle fractures. Additionally, quasi-cleavage fracture caused by crack propagation of delta-ferrite phase is found in some regions of the brittle fracture surface of the 5Al steel. Based on these results, the delta-ferrite phase hardly has a significant effect on absorbed energy at room-temperature, but it significantly deteriorates low-temperature toughness by acting as the main site of the propagation of brittle cracks at cryogenic-temperatures.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.32 no.3
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• pp.207-217
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• 2010

The purpose of this study was to evaluate the effects of the stress distribution and displacement in mandible according to treatment modalities of mandibular angle fractures, using a three dimensional finite element analysis. A mechanical model of an edentulous mandible was generated from 3D scan. A 100-N axial load and four masticatory muscular supporting system were applied to this model. According to the number, location and materials of titanium and biodegradable polymer plates, the experimental groups were divided into five types. Type I had a single titanium plate in the superior border of mandibular angle, type II had two titanium plates in the superior tension border and in the inferior compression border of mandibular angle, type III had a single titanium plate in the ventral area of mandibular angle, type IV had a single biodegradable polymer plate in the superior border of mandibular angle, type V had a single biodegradable polymer plate in the ventral area of mandibular angle. The results obtained from this study were follows: 1. Stress was concentrated on the condylar neck of the fractured side except Type III. 2. The values of von-Mises stress of the screws were the highest in the just-posterior screw of the fracture line, and in the just-anterior screw of Type III. 3. The displacement of mandible in Type III was 0.04 mm, and in Type I, II, IV, and V were 0.10 mm. 4. The plates were the most stable in the ventral area of mandibular angle (Type III, V). In conclusion, the ventral area of mandibular angle is the most stable location in the fixation of mandibular angle fractures, and the just- posterior and/or the just-anterior screws of the fracture line must be longer than the other, and surgeons have to fix accurately these screws, and the biodegradable polymer plate also was suitable for the treatment of mandible angle fracture.

• Tunnel and Underground Space
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• v.31 no.4
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• pp.270-288
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• 2021

We proposed a numerical method to simulate the hydro-mechanical behavior of rock fracture using a grain-based distinct element model (GBDEM) in the paper. As a part of DECOVALEX-2023 Task G, we verified the method via benchmarks with analytical solutions. DECOVALEX-2023 Task G aims to develop a numerical method to estimate the coupled thermo-hydro-mechanical processes within the crystalline rock fracture network. We represented the rock sample as a group of tetrahedral grains and calculated the interaction of the grains and their interfaces using 3DEC. The micro-parameters of the grains and interfaces were determined by a new methodology based on an equivalent continuum approach. In benchmark modeling, a single fracture embedded in the rock was examined for the effects of fracture inclination and roughness, the boundary stress condition and the applied pressure. The simulation results showed that the developed numerical model reasonably reproduced the fracture slip induced by boundary stress condition, the fracture opening induced by fluid injection, the stress distribution variation with fracture inclination, and the fracture roughness effect. In addition, the fracture displacements associated with the opening and slip showed good agreement with the analytical solutions. We expect the numerical model to be enhanced by continuing collaboration and interaction with other research teams of DECOVALEX-2023 Task G and validated in further study experiments.

• Structural Engineering and Mechanics
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• v.14 no.5
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• pp.565-574
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• 2002

This paper presents a method for predicting premature separation of carbon fiber reinforced plastic (CFRP) plates from strengthened steel beams. The fracture criterion based on material-induced singularity is formulated in terms of a singular intensity factor. Static test on double strap joints was selected to provide the critical stress intensity factor in the criterion because good degree of accuracy and consistency of experimental data can be expected compared with the unsymmetrically loaded single lap joints. The debond/separation loads of steel beams with different CFRP lengths were measured and compared with those predicted from the criterion. Good agreement between the test results and the prediction was found.