Angle Orthod. 2024 Mar 1;94(2):240-246. doi: 10.2319/040223-233.1.
To determine the effect of orthodontic pressure on periodontal ligament (PDL) compression in rats and assess correlation between PDL compression and orthodontically induced root resorption (OIRR).
Eight female Wistar rats aged 10 weeks underwent surgery to place 2 mini-screws at the center of the palatal plate. 25 cN coil springs connecting the maxillary first molars and mini-screws were applied bilaterally to generate mesial force. Maxillary first molars were assigned to undergo either bodily or tipping movements. Micro-computed tomography (μCT) scans were taken on days 0, 3, 7, and 14, and histological sections were taken on day 14. OIRR was measured from histological sections, and the corresponding PDL compression ratio was quantified using μCT images.
The PDL was compressed by approximately 76% in tipping movement and 55% in bodily movement after 3 days, and by approximately 47% in bodily and tipping movements after 7 days of orthodontic force application. The extent of OIRR in tipping movement was significantly greater than that in bodily movement. A strong positive correlation between OIRR and PDL compression ratio was observed on day 3; however, no correlation was observed on day 7.
A strong correlation between PDL compression ratio and OIRR was observed at an early stage after the application of orthodontic force regardless of the tooth movement type (bodily or tipping), implying the importance of early stage PDL compression in the induction of OIRR.
确定正畸压力对牙周韧带（PDL）压缩的影响，并评估 PDL 压缩与正畸诱导根吸收（OIRR）之间的相关性。
10 周龄的 8 只雌性 Wistar 大鼠接受手术，在腭板中心放置 2 个微型螺钉。25cN 螺旋弹簧将上颌第一磨牙和微型螺钉连接起来，在双侧产生近中力。上颌第一磨牙被分配进行整体或倾斜运动。在第 0、3、7 和 14 天进行微计算机断层扫描（μCT）扫描，并在第 14 天进行组织学切片。从组织学切片测量 OIRR，并使用 μCT 图像定量相应的 PDL 压缩比。
在 3 天后的倾斜运动中，PDL 被压缩了约 76%，在整体运动中被压缩了约 55%；在 7 天后的正畸力应用中，在整体和倾斜运动中分别被压缩了约 47%。倾斜运动中的 OIRR 程度明显大于整体运动。在正畸力应用后第 3 天观察到 OIRR 与 PDL 压缩比之间存在强烈的正相关；然而，在第 7 天没有观察到相关性。
在正畸力应用后的早期阶段，无论牙齿移动类型（整体或倾斜），PDL 压缩比与 OIRR 之间均存在强烈相关性，这表明 PDL 压缩在 OIRR 的诱导中非常重要。
