Date of Award
Thesis - Restricted
Master of Science (MS)
Orthodontic sliding mechanics, using preadjusted edgewise brackets, is a commonly used approach to the translation of a tooth or block of teeth. However, guiding a tooth along an archwire results in a counteracting frictional force which must be exceeded clinically to produce tooth movement and also can cause undesirable secondary effects such as loss of posterior anchorage. The purpose of this study was to investigate the frictional forces generated while sliding an orthodontic molar attachment along a cantilever beam versus a fixed beam utilizing different archwire compositions and sizes. The ultimate objective was to provide a means of comparing alternative clinical strategies to minimize friction arising in the buccal segments during space closure with sliding mechanics. In this in-vitro experiment, specially designed and machined aluminum testing fixtures were used to simulate two fixed appliance systems under controlled periodontal resisting forces of 100 g. An Instron universal testing machine was used to measure the mean kinetic frictional forces for nine different archwire compositions and sizes. Three sizes of archwires were utilized: 0.016" x0.022", 0.017" x0.025", 0.019" x0.025 ", and three alloy compositions: stainless steel, nickel titanium (Nitinol) and beta titanium (TMA). For each combination, three samples were tested in a fixed beam experimental setting and three were tested in a cantilever beam experimental setting. Differences between the beam designs were determined for each measurement using two-tailed unpaired student t-test and analysis of variance (ANOVA) was performed to determine if there were statistical differences between the various wire sizes and compositions. When differences were found, a Scheffe multiple comparison procedure was performed to determine where the differences were located. Results indicate that the effect of archwire size markedly differs within the two beam designs. In the fixed beam design, increasing archwire size brought increasing frictional force. The opposite was true in the cantilever beam design with increasing archwire size demonstrating decreased friction. Int agreement with other studies, the highest overall frictional forces were developed by TMA archwires followed by Nitinol and stainless steel. Comparing the two beam designs, there were no statistically significant differences in the overall frictional forces produced. However, there were considerable differences in the interaction of archwire size/alloy combinations within each beam design. From the beginning to the end of each run, the mean frictional values increased in both beam designs. Clinically, in a fixed beam design, the results of this study suggest that it may be advantageous to use small diameter stainless steel archwires if utilizing sliding mechanics in an attempt to decrease friction. In a cantilever beam design, the opposite is true with larger diameter wires being recommended. The exact reason for this latter finding is unclear and demands further study.
Gordon, John H., "Effect of Beam Design on Frictional Forces At Molar Tube-Archwire Interface for Selected Archwire Size and Alloy Combinations" (1998). Master's Theses (1922-2009) Access restricted to Marquette Campus. 5198.