Nordeen Katherine A, Kharouf John G, Mabry Tad R, Dahlke William O, Beiraghi Soraya, Tasca Amy W
Pediatric dentist and orthodontist in private practice, Apple Valley, Minn.
Department of Orthodontics, University of Colorado Anschutz Medical Campus, Aurora, Colo., USA.
Pediatr Dent. 2022 Mar 15;44(2):123-130.
The purpose of this study was to investigate pre-extraction variables associated with spontaneous space closure of the perma- nent second molar (PSM) following early extraction of the permanent first molar (PFM), and test an existing prediction model for the mandibular arch as the rates of spontaneous space closure are significantly lower in the mandible compared to the maxilla.
Pre-extraction panoramic radiographs of 162 patients (138 maxillary and 168 mandibular quadrants) between five and 15 years old at the time of PFM extraction were evaluated. The prediction model was applied to the mandibular quadrants. Postextraction radiographic evaluation was used for outcome assessment, with success defined as the presence of a visible contact between the second premolar and PSM without marginal ridge discrepancy.
Success was observed in 82 percent of maxillary quadrants and 51 percent of mandibular quadrants. Maxillary PFM extraction between eight and 10 years or PSM Demirjian stage D or E demonstrated over 90 percent predictive probability for success. Mandibular PFM extraction at age eight years or PSM Demirjian stage D demonstrated 80 percent success. The prediction model did not add a more predictive value than chronological age or PSM Demirjian stage.
The prediction model was not validated in this study population. Chronological age and permanent second molar developmental stage were the primary predictors for successful substitution with the permanent second molar.
本研究旨在调查在恒牙第一磨牙（PFM）早期拔除后，与恒牙第二磨牙（PSM）自发间隙关闭相关的拔牙前变量，并测试一种现有的下颌弓预测模型，因为下颌骨的自发间隙关闭率明显低于上颌骨。
对162例患者（138个上颌象限和168个下颌象限）在拔除PFM时年龄在5至15岁之间的拔牙前全景X线片进行评估。将预测模型应用于下颌象限。拔牙后的影像学评估用于结果评估，成功定义为第二前磨牙与PSM之间存在可见接触且无边缘嵴差异。
上颌象限成功率为82%，下颌象限成功率为51%。8至10岁之间拔除上颌PFM或PSM处于Demirjian D期或E期，成功预测概率超过90%。8岁时拔除下颌PFM或PSM处于Demirjian D期，成功率为80%。该预测模型并未比年龄或PSM Demirjian分期增加更多的预测价值。
本研究人群未验证该预测模型。年龄和恒牙第二磨牙发育阶段是恒牙第二磨牙成功替代的主要预测因素。
