目的 探讨改良Nance弓前方牵引矫治器对替牙期骨性Ⅲ类错ND03F的矫治效果。方法 选择21例替牙期骨性Ⅲ类错ND03F畸形患儿,应用改良Nance弓前方牵引矫治器进行治疗,通过其X线头颅侧位片和石膏模型进行测量,比较治疗前后软硬组织的变化及PAR指数评价。结果 SNA、ANB、NA-PA、Ptm-A、ANS-Ptm、Wits值均增大,A点前移2.15 mm,差异有统计学意义(P＜0.05)。 PAR指数评价,治疗后加权PAR减少百分率为86.67%,治疗后覆盖、覆ND03F、后牙咬合改善程度较大,所有患儿前牙反ND03F解除,但牙齿排列及中线改善程度不明显。6～7岁组平均疗程5.4个月,8～10岁组平均疗程8.9个月。结论 应用改良Nacne弓前方牵引治疗替牙期骨性Ⅲ类错ND03F十分有效,有利于Ⅲ类骨骼的调整。较小年龄组对矫治力更加敏感,平均疗程较短。但还需固定矫治器进一步调整后牙咬合、牙齿排列及中线问题。

Objective To evaluate the dental, skeletal and profile changes in the patients with skeletal class III malocclusion after using maxillary protraction appliance combined with modified Nance arch. Methods 21 patients with skeletal class Ⅲ malocclusion in mixed dentition were treated by maxillary protraction combined with modified Nance arch. Cephalometric radiographs and plaster model were analyzed to evaluate skeletodental and profile changes and Peer Assessment Rating (PAR) index before and after treatment. Results SNA and ANB angle, NA-PA, Ptm-A, ANS-Ptm, Wits values were increased and subspinale was protracted by 2.15 mm. All of the changes were statistically significant (P<0.05).PAR index indicated that the weighted PAR reduction percentage was 86.67%. The anterior overjet and overbite, posterior occlusion were effectively improved. All the patients’ anterior crossbites were corrected after treatment, but there was no significant change in teeth alignment and midline correction. Conclusions The maxillary protraction combined with modified Nance arch are obviously effective for skeletal class III malocclusion in mixed dentition, but posterior occlusion, teeth alignment and midline need to be adjusted with fixed appliance in the further treatment.