Browsing by Author "Katona, Thomas"

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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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    The Effect of Nicotine on Human Lymphocyte IL-6 Production
    (2001) Zhang, Shaobin; Olson, Byron L.; Gregory, Richard L.; Hathaway, Ronald; Shanks, James; Katona, Thomas
    Studies have suggested that the immune system may play important roles in the regulation of bone remodeling through cytokines secreted by inflammatory cells migrating from periodontal ligament capillaries after orthodontic force application. There is evidence that tobacco usage has profound effects on bone metabolism. The mechanism of nicotine on bone metabolism is not fully understood. One possibility may be related to certain cytokines. Cytokines are hormone-like molecules. They are important in regulating the development of the immune system and mediating immune responses. Interleukin 6 is an important cytokine secreted by activated T cells. IL-6 is a multifunctional interleukin with significant effects on different cell types. IL-6 can regulate the development and function of osteoblasts and osteoclasts, and thus play important roles in bone remodeling during orthodontic tooth movement. Nicotine is the major pharmacological component of tobacco. It can exert effects directly on lymphocytes by signaling through nicotinic acetylcholine receptors. Nicotine has profound effects on cytokine production in the immune system. The effect of nicotine on T cell IL-6 production may have an important impact on bone remodeling. However, the effects of nicotine on human T cell IL-6 production have not been extensively studied. The purpose of this study was to determine whether nicotine affects T cell proliferation and IL-6 production by activated T cells. Also the effect of nicotine on T cell activation was studied. The H9 cell line derived from a human cutaneous T cell lymphoma was used as the human T cells in this study. 2x106/ml T cells cultured with different mitogens were stimulated with nicotine for 24, 48, and 72 hr. The chosen nicotine concentrations were 0; 1; 10; 100; 1,000; 3,000; and 10,000 ug/ml. The effects of nicotine on T cell proliferation, T cell metabolic activity, and IL-6 production were studied. Also, the effects of different mitogens on T cell activation were studied. The results demonstrated that high concentrations of nicotine (1,000; 3,000; and 10,000 ug/ml) significantly decreased T cell proliferation, T cell metabolic activity, and IL-6 production. A medium concentration of nicotine (100 ug/ml) slightly increased IL-6 production. This study also demonstrated that TP A is essential in induction of IL-6 from activated T cells. PHA has synergistic effects on TPA induced IL-6 production. ConA, PHA, PHA+ IL β and nicotine did not induce IL-6 production from T cells. Signal transduction is probably involved in this complex process. The results of this study suggested that nicotine has adverse effects on T cell functions.
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    Understanding mechanical environment changes and biological responses to canine retraction using t-loop
    (2015-05) Jiang, Feifei; Chen, Jie; Bajaj, Anil; El-Mounayri, Hazim; Katona, Thomas; Nauman, Eric
    Predictability of tooth displacement in response to specific orthodontic load system directly links to the quality and effectiveness of the treatment. The key questions are how the tooth’s environment changes in response to the orthodontic load and how the biological tissues respond clinically. The objectives of this study are to determine the mechanical environment (ME) changes and to quantify the biological tissues’ response. Eighteen (18) patients who needed maxillary bilateral canine retractions were involved in the study. A method was developed to quantify the 3D load systems on the canine, which allowed the treatment strategies to be customized in terms of orthodontic loading systems to meet either translation (TR) or controlled tipping (CT) requirement. Dental casts were made before and after each treatment interval, and the Cone Beam Computed Tomography (CBCT) scans were taken prior to and following the entire treatment for control of treatment strategy and post treatment evaluations. Finite element method (FEM) was applied to calculate the location of center of resistance (CRes) for tooth movement control. The location and variation of CRes were recorded and compared with previous studies. A quick CRes assessment method that locates CRes by calculating the centroid of the contact surface (CCS) and the centroid of the projection of root surface (CPCS) in certain direction was also tested and compared with the results from FEM. Customized T-loop spring, a kind of orthodontic appliance, was designed, fabricated, and calibrated on a load measuring system to ensure that the load met the clinician’s prescription. The treatment outcomes in terms of tooth displacement and root resorption characterized by the changes of tooth length and volume as well as the bone mineral density (BMD) represented by the Hounsfield units (HU) change were recorded and analyzed. The ME in terms of stress were also calculated by using FEM. Paired t-test and mixed model ANOVA methods were used to analyze the relationships between the mechanical inputs (quantified and customized load, and corresponding stress) and clinical outcomes (root resorption and BMD change). It was found that the overall root resorption is not significant for canine retraction, but apical root resorption does occur, meaning that orthodontic load is not a sufficient factor. Also, it was observed that HU distribution changed significantly in both root and alveolar bone. The maximum reduction was on the coronal level in the direction perpendicular to the direction of movement in root, and in the direction of the tooth movement at the coronal level in bone. In addition, it was determined that the locations of the CRes in the MD and BL directions were significantly different. The locations of the CRes of a human canine in MD and BL directions can be estimated by finding the CPCSs in the two directions. Finally, it was shown that the stress invariants can be used to characterize how the osteocytes feel when ME changes. The stress invariants in the alveolar bone are not significantly affected by different M/F. The higher bone modeling/remodeling activities along the direction of tooth movement may be related to the initial volumetric increase and decrease in the alveolar bone.