Nitinol wires are now widely used in the orthodontic field because of their unique shape memory effect and superelasticity. But sometimes Nitinol wires are deformed in clinical use. Fatigue load is possible cause of Nitinol deformation. To determine the effect of fatigue load to the mechanical properties of Nitinol, various fatigue cycle(1X10(4), 2X10(4), 3X10(4), 4X10(4), 5X10(4), 1X10(5)) were applied to 0.017 X 0.025 inch Nitinol. The results obtained were as follows; 1. Applied load increased as fatigue cycle increased in three point bending test. 2. Maximum tensile strength and elongation decreased as fatigue cycle increased. 3. In SEM, brittle fracture pattern was increased when fatigue cycle increased.
Fatigue* ; Memory ; Tensile Strength

The purpose of this study is to evaluate biomechanical stability of Korean Ilizarov fixator before clinical application. We measured the ultimate tensile load and stiffness of Ilizarov smooth wire and olive wire, bending stiffness of half-pin, ultimate compressive load and stiffness of Ilizarov ring using Instron 1331. Four types of Ilizarov assembly were tested for measuring stiffness of axial compression, anteroposterior bending, and lateral bending. There were group I fixed with only smooth wires; group II with only olive wires; group III with wires and half-pins; and group IV with only half-pins. The results of Korean Ilizarov apparatus were compared to those of American Ilizarov apparatus using unpaired t-test. The ultimate tensile strength of Korean smooth wire was greater than that of American wire. The ultimate tensile strength of Korean olive wire was lower than that of American wire. There was no significant difference of stiffness of axial compression, anteroposterior bending, and lateral bending between American and Korean apparatus. There was no significant difference of axial compression stiffness and bending stiffness between group III and group IV. In conclusion, Korean Ilizarov apparatus can be used with good stability for treatment of fracture, internal bone transport, and limb lengthening according to this biomechanical study.
Extremities ; Olea ; Tensile Strength

This report describes the elongation and rupture pattern studied on 42 tissue slices of the fibrous coats (Cornea, Sclera and Limbus) of the fresh rabbit eye. The size of slices was 1.OOO +/- O.667 long by 0.900 +/- 0.667mm. wide. For each slice elongation was measured under the microscope in a magnitude of 30 X. The elongation, micron per each 10 gram load added, was taken as an elongation ratio. The results were as follows: 1. The shapes of elongation curve of all slices showed two different patterns between 1st limit (20~30gm.) and 2nd limit (150-180gm.), that was markedly greater elongation ratio in 1st limit than that in 2nd limit. 2. Elongation curves showed increased magnitude from central portion toward limbus in the cornea and from limbus to posterior pole in sclera. 3. Mean elongation ratio was greater in latitudinal than meridional of all slices. 4. Mean elongation ratio of the macular area was similar to that of the posterior portion of sclera. 5. The range of weight required to make rupturing of each slice was 150~230gm., though the slices were taken in same portion.
Cornea ; Rupture ; Sclera ; Tensile Strength*

PURPOSE: The mechanical and interfacial characterization of laser welded Co-Cr alloy with two different joint designs. MATERIALS AND METHODS: Dumbbell cast specimens (n=30) were divided into 3 groups (R, I, K, n=10). Group R consisted of intact specimens, group I of specimens sectioned with a straight cut, and group K of specimens with a 45degrees bevel made at the one welding edge. The microstructure and the elemental distributions of alloy and welding regions were examined by an SEM/EDX analysis and then specimens were loaded in tension up to fracture. The tensile strength (TS) and elongation (epsilon) were determined and statistically compared among groups employing 1-way ANOVA, SNK multiple comparison test (alpha=.05) and Weibull analysis where Weibull modulus m and characteristic strength sigmaomicron were identified. Fractured surfaces were imaged by a SEM. RESULTS: SEM/EDX analysis showed that cast alloy consists of two phases with differences in mean atomic number contrast, while no mean atomic number was identified for welded regions. EDX analysis revealed an increased Cr and Mo content at the alloy-joint interface. All mechanical properties of group I (TS, epsilon, m and sigmaomicron) were found inferior to R while group K showed intermediated values without significant differences to R and I, apart from elongation with group R. The fractured surfaces of all groups showed extensive dendritic pattern although with a finer structure in the case of welded groups. CONCLUSION: The K shape joint configuration should be preferred over the I, as it demonstrates improved mechanical strength and survival probability.
Alloys* ; Joints* ; Tensile Strength ; Welding

The purpose of this study was to evaluate the bond strength of orthodontic brackets bonded to metal bar with chemically cured adhesive (Ortho-one, Bisco Co, USA) in various types and directions of force application. Three types of metal bracket with different bracket base configurations; Micro-Loc base(Tomy Co, Japan), Chessboard base(Daesung Co, Korea), Non-etched Foil-Mesh base(Dentaurum, Germany); were used in this study. Peel, shear, tensile bond strengths were measured by universal testing machine and compared each other. The peel force directions applied were 0degrees, 15degrees, 30degrees, 45degrees, 60degrees, 75degrees, 90degrees. And then, in consideration of the different surface area of the bracket bases, the bond strength per unit area were calculated and compared. The results obtained were summarized as follows : 1. The bond strengths according to the types and the directions of the forces were greatest at the shear forces in all three bracket base configuration groups(p < 0.01). 2. As the peel force direction grew higher in degree, peel bond strength decreased. The patterns of peel bond strength change according to force direction was similar in all three bracket base configurations. The minimum bond strength was 60 degree-peel bond strengths in all three bracket base configurations. 3. In Micro-Loc base group, minimum peel bond strength(60PBS) was in 29% level of shear bond strength and 52% level of tensile bond strength. In Chessboard base group, 60PBS was in 34% level of shear bond strength and 61% level of tensile bond strength. In Non-etched Foil-Mesh base group, 60PBS was in 34% level of shear bond strength and 55% level of tensile bond strength. 4. The bond strengths per unit area were lowest in Non-etched Foil-Mesh base group and highest in Chessboard base group(p < 0.05). However, there were no differences in shear bond strength, tensile bond strength, 75PBS and 90PBS per unit area between Micro-Loc and Chessboard base groups.
Adhesives ; Orthodontic Brackets ; Tensile Strength

PURPOSE: The objective of this study was to compare the bonding strength between cement and an implant according to the cementing time. MATERIALS AND METHODS: The two types of cement used were CMW(R) 1 and 3 (Depuy Ltd., Blackpool, UK). Plastic molds containing CMW(R) 1 were pressed onto metal blocks at 2, 4, 5 or 6 minutes after mixing the cement, while molds containing CMW(R) 3 were pressed onto blocks at 3, 5, 6 or 7 minutes after mixing the cement. Tensile strength was tested with using an Instron Model 8874 (Instron Corp., Canton, MA, USA). Tensile strengths were compared using the Kruskal-Wallis test and the Mann-Whitney U test. RESULTS: The strongest bonding strengths for the tensile load were at 2 minutes post-mixing for CMW(R) 1, and at 3 minutes post-mixing for CMW(R) 3. The strength rapidly decreased after 5 minutes for CMW(R) 1 and after 6 minutes for CMW(R) 3. CONCLUSION: This study suggests that the risk of loosening between cement and an implant is likely to be minimized by the surgical technique that considers the bonding strength according to time.
Arthroplasty ; Fungi ; Plastics ; Tensile Strength

Surgical suture is a common medical device made extensive use of hold body tissues together after an injury or surgery. Suture sizes are associated with the requirement of diameter and tensile strength in standard. They correspond with one by one. Suture sizes should be unified, standardized and correctly marked for correct and convenient selection in surgery. Using the average diameter of single suture is more scientific and reasonable than that of multiple sutures in marking.
Suture Techniques ; Sutures ; Tensile Strength

PURPOSE: The purpose of this study was to evaluate the effect of the zirconia surface architecturing technique (ZSAT) on the bond strength between veneering porcelain and zirconia ceramic. MATERIALS AND METHODS: 20 sintered zirconia ceramic specimens were used to determine the optimal surface treatment time, and were randomly divided into 4 groups based on treatment times of 0, 1, 2, and 3 hours. After etching with a special solution, the surface was observed under scanning electron microscope, and then the porcelain was veneered for scratch testing. Sixty 3 mol% yttria-stabilized tetragonal zirconia polycrystal ceramic blocks were used for tensile strength testing; 30 of these blocks were surface treated and the rest were not. Statistical analysis was performed using ANOVA, the Tukey post-hoc test, and independent t-test, and the level of significance was set at α=.05. RESULTS: The surface treatment of the zirconia using ZSAT increased the surface roughness, and tensile strength test results showed that the ZSAT group significantly increased the bond strength between zirconia and veneering porcelain compared to the untreated group (36 MPa vs. 30 MPa). Optimal etching time was determined to be 2 hours based on the scratch test results. CONCLUSION: ZSAT increases the surface roughness of zirconia, and this might contribute to the increased interfacial bond strength between zirconia and veneering porcelain.
Ceramics ; Dental Porcelain ; Tensile Strength

PURPOSE: The author performed this experimental study to investigate the changes in the tensile strength of a new insertion following a superior rectus recession in a rabbit's eye. METHODS: Conventional superior rectus muscle recession procedures with the hang-back suture technique were performed on New Zealand white rabbits (body weight 2~3kg), after which the disinsertional force was measured using a digital tension gauge on the 3rd, 5th, and 7th days, and then weekly for up to 8 weeks postoperatively. RESULTS: The postoperative disinsertional forces were as follows: 38.25 +/- 2.75, 165 +/- 31.27, and 167.25 +/- 26.99 g at the 3rd , 5th and 7th days, and 211.00 +/- 25.66, 222.75 +/- 26.66, 255.25 +/- 24.51, 271.50 +/- 38.25, 429.50 +/- 21.14 g at the 2nd, 3rd, 4th, 6th and 8th weeks respectively. The disinsertional forces linearly increased with the postoperative time period and there was a strong correlation with correlation coefficient being 0.903. CONCLUSIONS: We concluded that musculoscleral adhesion with hang-back suture maintained enough strength in early postoperative time period.
Rabbits ; Suture Techniques ; Sutures ; Tensile Strength*

PURPOSE: The purpose of this study was to assess the impact of the core materials, thickness and fabrication methods of veneering porcelain on prosthesis fracture in the porcelain fused to metal and the porcelain veneered zirconia. MATERIALS AND METHODS: Forty nickel-chrome alloy cores and 40 zirconia cores were made. Half of each core group was 0.5 mm-in thickness and the other half was 1.0 mm-in thickness. Thus, there were four groups with 20 cores/group. Each group was divided into two subgroups with two different veneering methods (conventional powder/liquid layering technique and the heat-pressing technique). Tensile strength was measured using the biaxial flexural strength test based on the ISO standard 6872:2008 and Weibull analysis was conducted. Factors influencing fracture strength were analyzed through three-way ANOVA (alpha< or =.05) and the influence of core thickness and veneering method in each core materials was assessed using two-way ANOVA (alpha< or =.05). RESULTS: The biaxial flexural strength test showed that the fabrication method of veneering porcelain has the largest impact on the fracture strength followed by the core thickness and the core material. In the metal groups, both the core thickness and the fabrication method of the veneering porcelain significantly influenced on the fracture strength, while only the fabrication method affected the fracture strength in the zirconia groups. CONCLUSION: The fabrication method is more influential to the strength of a prosthesis compared to the core character determined by material and thickness of the core.
Alloys ; Dental Porcelain* ; Prostheses and Implants ; Tensile Strength