Browsing by Author "Oshida, Yoshiki"

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    A Frictional Evaluation of a New Surface-Modified Titanium Orthodontic Bracket
    (2000) Olsen, Marc E.; Oshida, Yoshiki; Andres, Carl J.; Katona, Thomas R.; Moore, B. Keith; Roberts, W. Eugene; Shanks, James C.
    Sliding mechanics is a popular method of moving teeth orthodontically. Sliding mechanics refers to the guiding of a tooth by means of the bracket slot along an archwire in response to some applied force. This concept of tooth movement is subject to both static and kinetic friction. An accurate evaluation of an appliance's frictional properties enables a clinician to identify applications where the utilization of a new appliance may be advantageous. The aim of this study was to evaluate the frictional properties of this new surface-modified titanium orthodontic bracket compared with a traditional stainless steel orthodontic bracket and a currently available non-surface modified titanium bracket. Fifteen brackets (5 Stainless steel, 5 Titanium, 5 Coated Titanium) were combined with five archwires from each material type (SS, NiTi, βTi). Frictional evaluation was completed on each bracket material utilizing .021" x .028" size archwire materials in a specially designed apparatus under wet conditions. The frictional resistance was measured on an Instron Universal Testing machine (Instron Corp, Canton, Mass). The brackets/archwire samples were tested one at a time individually. In addition, a single bracket/ archwire sample from each group was repeatedly tested five times. Measurements were made at every 0.1mm for 30mm via a computer attached to the testing machine. An ANOV A was used to determine differences between groups. The results indicate that stainless steel brackets exhibited significantly better static and kinetic frictional properties than the titanium brackets. Stainless steel wires possessed superior frictional properties to NiTi and β-Ti wires. NiTi wires were generally superior than β-Ti wires. As brackets and archwires were reused, the overall frictional values showed a distinct trend to increase.
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    Comparison of Frictional Forces Between Three Grades of Low Friction "Colors" TMA
    (2001) Rosenthall, Mark R.; Oshida, Yoshiki; Baldwin, James; Hohlt, William; Katona, Thomas; Shanks, James
    Frictional forces between archwires and brackets play a significant role in the efficiency of orthodontic tooth movement. The purpose of this investigation were to (1) compare the wet static frictional forces of low friction "Colors" TMA ™ arch wires with arch wires of other materials (stainless steel, NiTi, and uncoated TMA ™) and (2) test the effects of repetitive sliding. Testing was accomplished by using a cantilever testing device, which held the archwire in place between two 303 stainless steel test flats. The test flats were used to simulate an orthodontic bracket. A saliva substitute (Ringer's solution) was used to simulate the oral environment. Six wire types (stainless steel, NiTi, TMA ™, and three types of "Colors" TMA ™ wires [purple, aqua and honeydew]). For each said wire type, 15 archwires were tested. Each archwire type was run five times at three different weights (normal forces) and each wire was subjected to five repetitions. In total, 450 runs were established. The effects of wire type (6 types), normal force (1267g, 2153g, 2533g) and repetition (5 per wire) on wet static frictional were examined using three-way analysis of variance (ANOVA). Pairwise comparisons between treatment combinations were made using Sidak method to control the overall significance level. After wire testing, a sample of untested (0 runs) and tested (1 run, 5 runs) wires were viewed under a light microscope at 160X magnification. The results indicated uncoated TMA ™ wires produced the highest wet static frictional forces. In general, NiTi produced the next highest force levels followed by the three "Colors" TMA ™ wires, and then stainless steel. Repetition was observed to affect only NiTi and uncoated TMA TM wires. NiTi wires showed a decrease in force values between runs 1 and 5 at p < 0.05. Uncoated TMA ™ showed an increase in force values between runs 1 and 2. The cause for these findings could not be validated by light microscope evaluation.
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    Comparison of Tensile Bond Strengths of Glass Ionomer Cements Using Hydroxyapatite Coated and Uncoated Orthodontic Brackets
    (1993) Ng, Richard I. Cheng Hin; Hohlt, William F.; Moore, B. Keith; Oshida, Yoshiki; Garetto, Lawrence P.; Roberts, W. Eugene; Shanks, James C.
    The use of glass ionomer cements (GIC) in orthodontics as a bonding agent has been receiving considerable attention due to its favorable properties, ie., physico-chemical adhesion to enamel, fluoride leaching capabilities and less traumatic bonding procedure to tooth structure. GIC ability to bond to the hydroxyapatite (HA) in the tooth enamel was tested utilizing an HA coated bracket developed by American Orthodontics. This study compared in vitro tensile bond strengths of four dental adhesives: Ketac-cem™ (KC), Vitrebond™ (VB), Transbond™ (TB) or Unite™ (UN), when used to bond to HA coated brackets and non-HA coated brackets. Bovine incisors were divided into eight groups of 20 specimens each. Each group included either an HA coated or non-HA coated bracket and one of the four adhesives. The brackets are manufactured with a Tricalcium Phosphate (TPC) coating, which is converted to an HA coating by the addition of -OH during autoclaving. The coated and non-coated brackets were bonded to the bovine teeth, which were embedded in epoxy resin blocks to fabricate the testing specimen. All of the specimens were stored in distilled water at room temperature for two weeks. This was followed by thermocycling after which the specimens were returned to water storage for an additional two weeks. The specimens were tested in tension on an lnstron Testing Machine until bond failure occurred. Mode of bond failure was determined visually by light microscope. The mean tensile bond strengths for KC and VB were each significantly less (p< 0.05) than the other three materials, while UN and TB were not significantly different. KC was the weakest at 0.68± 0.31 MPa, while UN was the strongest, 4.38±0.84 MPa. When comparing the GIG alone, there was a significant difference (p<0.0001) between the VB and the KC. The resins were not significantly different from each other. Differences between coated and non-coated were significant at p<0.05 with the noncoated brackets having the higher strength. Adhesive failure at the bracket interface for the two bracket types showed no difference for KC. TB and UN showed this type of failure significantly more with the coated brackets (p<0.05), and VB showed the opposite and more failure with non-coated brackets (p<0.01). The tensile bond strength of GIG continues to be significantly less than those of existing resins. The bond failure also revealed a high degree of within group variability. Trends relating failure mode to tensile bond strength could not be established. Greater bond strengths with the coated brackets and the GIG were not shown; however in the case of VB, the tendency for the coated brackets to fail less frequently at the bracket adhesive interface shows some promise. Further studies of these coated brackets are still warranted.
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    The Effects of Mechanical Cyclic Loading on the Bond Strength of Orthodontic Brackets
    (1995) Varallo, Daniel C.; Katona, Thomas R.; Arbuckle, Gordon R.; Moore, B. Keith; Oshida, Yoshiki; Shanks, James C.
    During treatment, orthodontic brackets are exposed to repeated loads that are below their ultimate bond strengths (UBS) and therefore do not cause bond failure. However, these loads may cause fatigue damage and thus decrease the UBS. The objective of this study was to accelerate fatigue damage and to determine its effect on UBS. Ormco's Ormesh ™ central incisor brackets were bonded to bovine teeth with Ormco's System 1 + TM adhesive. Each test group contained 17-20 specimens. An unfatigued group was used to determine the control shear-peel UBS (216N). The four experimental groups were defined by the applied shear-peel load (30% or 50% of UBS) and the number of sinusoidally applied load cycles (10,000 or 20,000). Group L1C1 was loaded at 30% of UBS for 10,000 cycles, L2C1 at 50% of UBS for 10,000 cycles, L1C2 at 30% of UBS for 20,000 cycles, and L2C2 at 50% of UBS for 20,000 cycles. The results suggest that there was no significant amount of fatigue damage occurring at the tested loads and cycles.
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    The Oxidative Response of Human Monocytes to Surface Modified Commercially Pure Titanium
    (Frontiers Media, 2021-06-02) De Poi, Robert P.; Kowolik, Michael; Oshida, Yoshiki; El Kholy, Karim; Periodontology, School of Dentistry
    Cellular responses to implanted biomaterials are key to understanding osseointegration. The aim of this investigation was to determine the in vitro priming and activation of the respiratory burst activity of monocytes in response to surface-modified titanium. Human peripheral blood monocytes of healthy blood donors were separated, then incubated with surface-modified grade 2 commercially pure titanium (CPT) disks with a range of known surface energies and surface roughness for 30- or 60-min. Secondary stimulation by phorbol 12-myrisate 13-acetate (PMA) following the priming phase, and luminol-enhanced-chemiluminescence (LCL) was used to monitor oxygen-dependent activity. Comparison among groups was made by incubation time using one-way ANOVA. One sample from each group for each phase of the experiment was viewed under scanning electron microscopy (SEM) and qualitative comparisons made. The results indicate that titanium is capable of priming peripheral blood monocytes following 60-min incubation. In contrast, 30 min incubation time lead to reduced LCL on secondary stimulation as compared to cells alone. At both time intervals, the disk with the lowest surface energy produced significantly less LCL compared to other samples. SEM examination revealed differences in surface morphology at different time points but not between differently surface-modified disks. These results are consistent with the hypothesis that the titanium surface characteristics influenced the monocyte activity, which may be important in regulating the healing response to these materials.