Browsing by Author "Baldwin, James"

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    An Analysis of the Fatigue Resistance of Beta Titanium and the Effect of Spot-Welding Upon the Fatigue Resistance of this Alloy
    (1984) Wong, Michael B.; Garner, LaForrest; Baldwin, James; Moore, Keith; Barton, Paul; Shanks, James
    This investigation was designed to establish a fatigue curve for beta titanium, determine the effect of spot-welding upon the fatigue resistance of this alloy, and provide qualitative observations about surface characteristics of different batches of TMA in relation to their fatigue lives. Rectangular .016" x .022" 1MA was evaluated. Twelve specimens in each group were tested, making the total sample size 108. The wire samples were evaluated using a cantilever bend test in which specimens were stressed cyclically at varying deflections. Two welded groups were also tested. An auxiliary .016" x .022" TMA was welded to a main test segment of TMA with the .016" side against the opposing .016" side. The weld overlap varied at 25% for one group and 50% for the other. These specimens were stressed at the area adjacent to the weld. One specimen from each group was viewed under the scanning electron microscope to evaluate the fractured area. Specimens from three different batches of 1MA were tested and their fatigue lives compared at .625 inch deflection. One specimen from each batch was viewed under the scanning electron microscope to evaluate its surface structure. A fatigue curve for TMA was plotted from the data. At .625 inch deflection, welding an auxiliary onto the main segment significantly decreased the fatigue resistance of the wire. However, both welded groups had comparable fatigue lives. These wire specimens fractured at some point adjacent to the welded site. Fatigue resistance differed significantly between one batch of TMA and the other two. The scanning electron micrographs of representative specimens from each batch seemed to indicate that the fatigue resistance of each batch was inversely related to its surface roughness.
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    Assessment of Dental Asymmetry Utilizing Orthodontic Study Casts Comparing Tooth Positions to the Midpalatal Raphe and Tooth Size Among Antimeres
    (2002) Sprowls, Matthew W.; Hartsfield, James K., Jr.; Baldwin, James; Everett, Eric T.; Hathaway, Ronald; Shanks, James C.; Ward, Richard E.
    Several studies have been conducted in relation to the treatment and etiologies of craniofacial and dental asymmetries in the orthodontic scientific literature. However, limited research has attempted to correlate asymmetry in dental traits to each other. The purpose of this research study was to develop a better understanding of the correlations between dental arch asymmetry and dental tooth size asymmetry and their underlying causes. Understanding asymmetries is essential in orthodontic diagnosis and treatment planning. An orthodontist cannot obtain an optimal occlusal and functional result without properly balancing skeletal and dental relationships. Pretreatment dental study casts of 86 sequential patients from the postgraduate orthodontic clinic at the Indiana University School of Dentistry were used for the analysis. Each patient was analyzed in a single blind fashion to minimize bias. The Adobe Photoshop® ruler and Chicago® brand electronic digital calipers accurate to the nearest tenth of a millimeter were used for digital measurements. Measurements were made to determine the amount and direction of asymmetry along the dental midlines relative to the median palatine raphe. Transverse and sagittal measurements were made to record asymmetries in canine and molar positioning. Furthermore, three sets of antimeric maxillary teeth were measured for length and width. These included the central incisors, the canines, and the first molars. Fluctuating asymmetry was present in all measurements, except molar distance to median palatal raphe. This was found to be directional to the left in the entire sample group. Statistical analysis was subsequently performed and the results showed significant correlations in the individuals in the subsample dentition group. Subjects belonging to this group with a measurable degree of fluctuating asymmetry had a greater tendency toward transverse maxillary discrepancies as measured from the canines and first maxillary molars relative to the median palatal raphe. Moreover, individuals in the subsample group with above average total weighted fluctuating asymmetry values according to the parameters analyzed in this study appeared more likely to have decreased developmental stability leading to the clinical expression of more severe malocclusions.
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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.