Do miniscrews remain stationary under orthodontic forces?
Miniscrews have been used in recent years for anchorage in orthodontic treatment. However, it is not clear whether the
miniscrews are absolutely stationary or move when force is applied. (miniscrew雖然使用在矯正力的拉動上多年,但是,對於其是否不動如山這件事,尚是一個謎!)
Sixteen adult patients with miniscrews (diameter = 2 mm, length = 17 mm) as the maxillary anchorage were included in this study. Miniscrews were inserted on the maxillary zygomatic buttress as a direct anchorage for en masse anterior retraction.
(這是長庚的報告,使用16個病人,口徑2mm,長度17mm,給前牙做整體後退的錨定源)
Nickel-titanium closed-coil springs were placed for the retraction 2 weeks after insertion of the miniscrews. Cephalometric radiographs were taken immediately before force application (T1) and 9 months later (T2). The cephalometric tracings at T1 and T2 were superimposed for the overall best fit on the structures of the maxilla, cranial base, and cranial vault to determine any movement of the miniscrews. (使用niti的封閉型彈簧來拉動牙齒,當放上2周後,照x光比對其在特定位置的移動量)
The miniscrews were also evaluated clinically for their mobility (0: no movement,1: < or =0.5 mm, 2: 0.5-1.0 mm, 3: >1.0 mm). The mobility of all miniscrews was 0 at T1 and T2. On average, the miniscrewstipped forward significantly, by 0.4 mm at the screw head. The miniscrews were extruded and tipped forward (-1.0 to 1.5 mm) in 7 of the 16 patients.(測定後,還是可以看到骨釘會有些許的向前傾斜,,,,)
Miniscrews are a stable anchorage but do not remain absolutely stationary throughout orthodontic loading. They might move according to the orthodontic loading in some patients. To prevent miniscrews hitting any vital organs because of displacement, it is recommended that they be placed in a non-tooth-bearing area that has no foramen, major nerves, or
blood vessel pathways, or in a tooth-bearing area allowing 2 mm of safety clearance between the miniscrew and dental root.
(最後這段話就是重點,骨釘的放置位置很重要,也就是不可以對組織產生干擾,或是傷到,必需保持與牙根2mm的安全距離,,,)
Am J Orthod Dentofacial Orthop, 126(1): 42-7 2004 (這是長庚劉人文dr,等的報告)
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