Maxillary incisor protrusion is a prevalent dental deformity and is often treated by upper incisor intrusion and retraction. The mechanical loading triggers the resorption and apposition of the bone. Alveolar bone remodeling is expected to follow orthodontic tooth movement in a one-to-one relationship. However, in many cases, the outcomes are different. Alveolar bone might still remain thick causing lip protrusion and other aesthetic problems after treatment. Additional corrective procedures such as alveoloplasty. On the other hand, if the labial bone becomes too thin, periodontal problems like gingival recession might occur. The unpredictability of the treatment result and the risk of requiring corrective procedures pose significant challenges to both the providers and patients. The aim of this study is to determine factors that can help to predict the alveolar bone reaction before maxillary incisor intrusion and retraction. The cohort included 34 female patients (mean age 25.8 years) who were diagnosed with skeletal class II malocclusion with upper incisor protrusion. These patients underwent extraction and orthodontic treatment with upper incisor intrusion and retraction. Lateral cephalograms at pre-treatment and post-treatment were taken. Linear and angular measurements were analyzed to evaluate the alveolar bone changes based on initial conditions. The study found that the relative change, calculated as change in alveolar bone thickness after treatment divided by the initial alveolar thickness, was inversely correlated with the initial thickness. There was a significant increase of labial alveolar bone thickness at 9-mm apical from cementoenamel junction (B3) (P < 0.05) but no statistically significant change in the thickness at other levels. In addition, the change in angulation between the incisor and alveolar bone was inversely correlated with several initial angulations: between the initial palatal plane and upper incisor angle, between the initial palatal plane and upper incisor labial surface angle, and between the initial palatal plane and bone labial surface angle. On the other hand, the change in labial bone thickness was neither significantly correlated with the initial thickness nor significantly correlated to the amount of retraction. The unpredictability of alveolar bone remodeling after upper incisor intrusion and retraction poses significant challenges to treatment planning and patient experience. The study showed that the initial angulation between the incisor and alveolar bone is correlated with the change in angulation after treatment, the initial thickness of the alveolar bone was correlated with the relative change of the alveolar bone thickness (defined as change in thickness after treatment divided by its initial thickness), and the amount of intrusion was correlated with the alveolar bone thickness change at 9-mm apical from the cementoenamel junction after treatment. The results of the present study also revealed that the change in labial alveolar bone thickness was neither significantly correlated with the initial thickness nor significantly correlated to the amount of retraction.

中文翻译：

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上切牙压入和回缩过程中的牙槽骨重塑

上颌切牙突出是一种常见的牙齿畸形，通常通过上切牙压入和回缩来治疗。机械负荷触发骨的再吸收和并置。牙槽骨重塑预计会以一对一的关系跟随正畸牙齿的移动。然而，在许多情况下，结果是不同的。牙槽骨可能仍然很厚，导致治疗后嘴唇突出和其他美学问题。额外的矫正程序，例如肺泡成形术。另一方面，如果唇骨变得太薄，可能会出现牙龈退缩等牙周问题。治疗结果的不可预测性和需要纠正程序的风险对提供者和患者都构成了重大挑战。本研究的目的是确定有助于预测上颌切牙压入和回缩前牙槽骨反应的因素。该队列包括 34 名女性患者（平均年龄 25.8 岁），她们被诊断为骨骼 II 类错牙合并伴有上切牙突出。这些患者接受了上切牙压入和回缩的拔牙和正畸治疗。在治疗前和治疗后进行侧位头影检查。分析线性和角度测量值以评估基于初始条件的牙槽骨变化。研究发现，相对变化，计算为治疗后牙槽骨厚度的变化除以初始牙槽厚度，与初始厚度呈负相关。牙釉质交界处根尖 9 mm 处的唇牙槽骨厚度显着增加（B3）（P < 0.05），但其他水平的厚度变化无统计学意义。此外，切牙和牙槽骨之间的角度变化与几个初始角度呈负相关：初始腭平面和上切牙角之间，初始腭平面和上切牙唇面角之间，以及初始腭平面和上切牙唇面角之间。骨唇面角。另一方面，唇骨厚度的变化既不与初始厚度显着相关，也不与回缩量显着相关。上切牙压入和回缩后牙槽骨重塑的不可预测性对治疗计划和患者体验提出了重大挑战。研究表明，切牙与牙槽骨之间的初始角度与治疗后角度的变化相关，牙槽骨的初始厚度与牙槽骨厚度的相对变化（定义为治疗后的厚度变化除以通过其初始厚度），侵入量与治疗后牙釉质连接处根尖 9 mm 处的牙槽骨厚度变化相关。