目的　比较昼夜不同时段戴用功能矫治器后 ,髁突软骨增殖细胞核抗原 (PCNA)表达的昼夜变化 ,为探讨功能矫治昼夜最佳介入时段 ,提供直接实验依据。方法　采用免疫组织化学法 ,检测不同时段前伸大鼠下颌后 ,髁突软骨PCNA表达的昼夜变化。结果　戴用功能矫治器后 ,PCNA表达强度增加 ;白天戴用组明显高于夜晚组。结论　功能矫治器可以刺激髁突软骨增生 ;在髁突软骨昼夜自发性生长最旺盛时段戴用矫治器 ,效果最佳 Objective To compare the diurnal changes of proliferating cell nuclear antigen (PCNA) expression in condylar cartilage after functional appliance at different times of day and night, and to provide a direct experimental basis for exploring the best daytime and nighttime functional interventional period. Methods Immunohistochemical method was used to detect the diurnal changes of PCNA expression in condylar cartilage after mandibular extension at different time points. Results After wearing functional appliance, the expression of PCNA increased; Day wear group was significantly higher than night group. Conclusion The functional appliance can stimulate condylar cartilage hyperplasia. The best effect is achieved when condylar cartilage is worn during the most vigorous day and night spontaneous growth