Ren Yijin, Maltha Jaap C, Liem Robert S B, Stokroos Ietse, Kuijpers-Jagtman Anne Marie
Department of Orthodontics, University Medical Centre Groningen, University of Groningen, The Netherlands.
Acta Odontol Scand. 2008 Apr;66(2):93-8. doi: 10.1080/00016350801982522.
To investigate the effect of age on root resorption and distribution along different parts of the root during prolonged light force application.
Orthodontic appliances were placed in two groups of 30 rats (one group 6 weeks old, the other 9-12 months old), with contralateral sides as controls. Groups of animals were killed at 1, 2, 4, 8, and 12 weeks. At the study site, incidence was counted as either 1 (with resorption) or 0 (without); severity was measured as the summed length of all resorption lacunae as a percentage of study total root length.
Young and adult rats had the same incidence of root resorption in the early phase (<4 weeks), and both increased in the late phase (4-12 weeks) to the same level. Severity of resorption increased with prolonged tooth movement only in adult rats. However, there was no age-related difference in either the early or the late phase. In both groups, the middle part of the root had the highest incidence of resorption; the most severe resorption occurred exclusively at this part.
Orthodontic intervention even with light forces increased both the incidence and severity of root resorption, the more so in the middle part of the root. Adult rats had increased incidence and severity with prolonged tooth movement.
研究在长时间施加轻力的情况下年龄对牙根吸收及牙根不同部位吸收分布的影响。
将正畸矫治器置于两组各30只大鼠（一组6周龄，另一组9 - 12月龄）口中，对侧作为对照。分别在1、2、4、8和12周处死动物组。在研究部位，发生率计为1（有吸收）或0（无吸收）；严重程度以所有吸收陷窝的总长度占研究牙根总长度的百分比来衡量。
幼年和成年大鼠在早期阶段（<4周）牙根吸收的发生率相同，且在后期阶段（4 - 12周）均升高至相同水平。仅成年大鼠的吸收严重程度随牙齿移动时间延长而增加。然而，在早期或后期阶段均无年龄相关差异。两组中，牙根中部的吸收发生率最高；最严重的吸收仅发生在该部位。
即使施加轻力进行正畸干预也会增加牙根吸收的发生率和严重程度，在牙根中部更为明显。成年大鼠随着牙齿移动时间延长，吸收的发生率和严重程度增加。
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