| Budget Amount *help |
¥3,460,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥60,000)
Fiscal Year 2007: ¥260,000 (Direct Cost: ¥200,000、Indirect Cost: ¥60,000)
Fiscal Year 2006: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2005: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Research Abstract |
The ratchet bracket that was designed in this research project has a ratchet mechanism, where interrupted orthodontic force induces by a ratchet mechanism built into the bracket. The operation of the bracket is to push the ratchet rod into the tube, tooth movement of 0.25mm in one the operation, every 4 days. The character of the force induced is moving distance-dependent, and the compressed periodontal ligament (PDL) does not degenerate during tooth movement, because of a slight tooth movement within 0.25mm does not prevent the blood circulation. In this project, the bracket was improved and designed compactly, 3.3×4.6mm in size, as same as the standard size, with thought to be less discomfort.
In the experiment using rat upper molars, the interrupted force that defined as one third of the PDL width was used in 4days interval during tooth movement. No degenerating tissue was seen in the compressed PDL, and pathological root resorption was rarely seen during tooth movement. In addition marked bone formation was seen in the tension side.
In practical use for patients, the following results were obtained : 1) No patient claimed about pain or discomfort during tooth movement by the bracket. 2) The tooth movement occurred smoothly, except the case that the bracket did not function by operation error or the failure of the ratchet spring. 3) Root resorption was not seen in patients, while a slight resorption was seen the apexes of upper incisors in one patient.
From these results, a method of tooth movement by repeating the interrupted force that induced by the moving distance within PDL width preserve PDL tissue without compressive degeneration, and it is suggested that the ratchet bracket is a style of optimal tooth movement with a biological safe.
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