Costopoulos G, Nanda R
University of Connecticut, Farmington, USA.
Am J Orthod Dentofacial Orthop. 1996 May;109(5):543-8. doi: 10.1016/s0889-5406(96)70140-3.
A new radiographic method was developed for measuring changes in root length. With this technique, orthodontic intrusion was investigated as a potential cause of apical root resorption of maxillary incisors. The experimental group consisted of 17 patients with excessive overbite who were treated with a Burstone-type intrusion arch, which delivered a low level of force (about 15 gm per tooth). A control group was made up of 17 patients in full-arch fixed appliances who were randomly selected. After a period of approximately 4 months, the intrusion group had only slightly more root resorption than the controls, 0.6 mm versus 0.2 mm (statistically significant difference). Intrusion measured at the center of resistance of the central incisor averaged 1.9 mm. The amount of resorption was not correlated with the amount of intrusion. A weak correlation, r = 0.45, was found between resorption and movement of the apex (i.e., in addition to intrusion, there was often palatal root movement). Results of this study seem to indicate that intrusion with low forces can be effective in reducing overbite while causing only a negligible amount of apical root resorption.
一种用于测量牙根长度变化的新放射照相方法被开发出来。利用这项技术，正畸压低被作为上颌切牙根尖吸收的一个潜在原因进行了研究。实验组由17名深覆牙合患者组成，他们使用Burstone型压低弓进行治疗，该压低弓施加低水平的力（每颗牙约15克）。对照组由17名随机选择的佩戴全牙弓固定矫治器的患者组成。经过大约4个月的时间，压低组的牙根吸收仅略多于对照组，分别为0.6毫米和0.2毫米（具有统计学显著差异）。中切牙阻力中心处的压低平均为1.9毫米。吸收量与压低量无关。在牙根吸收与根尖移动之间发现了较弱的相关性，r = 0.45（即除了压低外，腭根通常也有移动）。这项研究的结果似乎表明，低力压低在减少深覆牙合方面可能有效，同时仅引起可忽略不计的根尖吸收。
