Department of Orthodontics and Oral Facial Genetics, Indiana University School of Dentistry, Indianapolis 46202, USA.
Eur J Orthod. 2010 Aug;32(4):371-80. doi: 10.1093/ejo/cjp103. Epub 2010 Jan 6.
While both intermittent and continuous forces are commonly used to expand sutures, it remains unclear which force is most effective. Using nickel-titanium (NiTi) open coil springs (50 g) and 3 mm long miniscrew implants (MSIs) for skeletal anchorage, intermittent and continuous forces were used to expand the midsagittal sutures in 18 New Zealand white juvenile male rabbits, 11 weeks of age, for 29 days. In the intermittent group, expansion forces of 50 g were delivered for 5 days (on) and paused for 1 day (off); the on/off cycles were repeated five times. Expansion forces of 50 g were delivered for 29 consecutive days in the continuous group. Longitudinal biometric and histomorphometric analyses were performed to evaluate sutural separation and bone formation using implanted tantalum bone markers and fluorescent bone labelling, respectively. Multilevel modelling procedures were undertaken to compare the groups and time intervals. Continuous forces produced significantly greater overall sutural separation (1.3 mm) than intermittent forces (0.8 mm). Although they were delivered over a period of time 86 per cent as long, intermittent forces produced only 61 per cent of the sutural separation of continuous forces. Between days 7 and 17, continuous forces resulted in significantly greater mineral apposition and bone formation rates than intermittent forces. Intermittent forces produced approximately 59 per cent as much mineral apposition and 61 per cent as much bone formation as continuous forces. Due to greater sutural separation and bone formation, continuous forces provide a more effective approach for separating sutures than intermittent forces.
虽然间歇力和连续力常用于扩张缝线，但哪种力最有效仍不清楚。本研究使用镍钛（NiTi）开环弹簧（50 g）和 3 mm 长微型螺钉植入物（MSIs）作为骨骼锚固，通过间歇性和连续性力量在 18 只 11 周龄新西兰白兔的中矢状缝中扩张 29 天。在间歇组中，每天（ON）施加 50 g 的扩张力 5 天，然后暂停 1 天（OFF）；ON/OFF 循环重复 5 次。在连续组中，每天连续 29 天施加 50 g 的扩张力。使用植入的钽骨标记和荧光骨标记分别进行纵向生物计量和组织形态计量分析，以评估缝线分离和骨形成。采用多水平模型程序比较组间和时间间隔。连续力产生的总缝线分离（1.3 mm）明显大于间歇力（0.8 mm）。尽管连续力的施加时间是间歇力的 86%，但间歇力仅产生了连续力的 61%的缝线分离。在第 7 天至第 17 天期间，连续力导致的矿化附着和骨形成率明显高于间歇力。间歇力产生的矿化附着量约为连续力的 59%，骨形成量约为连续力的 61%。由于更大的缝线分离和骨形成，连续力比间歇力更有效地分离缝线。
