McReynolds D C, Little R M
Department of Orthodontics, School of Dentistry, University of Washington, Seattle 98195.
Angle Orthod. 1991 Summer;61(2):133-44. doi: 10.1043/0003-3219(1991)061<0133:MSPEPE>2.0.CO;2.
The dental casts and cephalometric radiographs of 46 patients, treated with mandibular second premolar extraction and edgewise orthodontic mechanotherapy, were evaluated for changes over a minimum 10-year postretention period. The sample was divided into two groups: early (mixed dentition) extraction of mandibular second premolars and late (permanent dentition) extraction of mandibular second premolars. Results showed no difference in long-term stability between the two groups. Arch length and arch width decreased with time and incisor irregularity increased throughout the postretention period. No predictors or associations could be found to help the clinician in determining the long-term prognosis in terms of stability. The sample was regrouped according to the postretention degree of incisor irregularity. Statistically significant differences in cephalometric measurements were found between the minimally crowded group and the moderately to severely crowded group.
对46例接受下颌第二前磨牙拔除及方丝弓正畸机械治疗的患者的牙模型和头影测量X线片进行评估，观察其在保持期至少10年期间的变化。样本分为两组：下颌第二前磨牙早期（混合牙列期）拔除组和下颌第二前磨牙晚期（恒牙列期）拔除组。结果显示两组在长期稳定性方面无差异。在整个保持期，牙弓长度和宽度随时间减小，切牙不整齐度增加。未发现有助于临床医生确定长期稳定性预后的预测因素或关联因素。根据切牙不整齐的保持程度对样本重新分组。在轻度拥挤组和中度至重度拥挤组之间，头影测量结果存在统计学显著差异。
