目的：研究上颌牙弓反复快速扩缩对大鼠上颌周围骨缝的组织学影响。方法：选择6周龄健康雄性Sprague-Dawley (SD)大鼠22只，随机分成3组：单次扩弓组9只，连续扩弓5 d后处死；反复扩缩组9只，先扩弓5 d，再缩弓5 d，然后再扩弓5 d，如此反复扩3次，缩2次共25 d后处死；对照组4只，不进行任何矫治，分别在第5天和第25天各处死两只。实验动物处死后，立即取腭中缝及与矢状方向改建密切相关的腭颌缝、额颌缝、前颌缝、颧颌缝，制作脱钙骨切片。HE染色观察组织学改变，酒石酸抗酸性磷酸酶（tartrate-resistant acid phosphatase, TRAP）染色破骨细胞，并进行破骨细胞计数。结果：组织学观察发现，单次扩弓组除腭中缝外，其他上颌周围骨缝与对照组类似，无明显组织学变化；而反复扩缩组的腭中缝及其他骨缝的多处区域受到牵拉，缝宽度增加，成骨细胞增多，纤维结缔组织被拉伸、变形，与骨缘分离，排列紊乱，亦有少数区域呈骨受压吸收现象，破骨细胞和骨吸收陷窝增多，成骨细胞减少，纤维结缔组织密集。破骨细胞计数结果表明，与对照组相比，单次扩弓组只有腭中缝的破骨细胞增加差异有统计学意义（P<0.05），而反复扩缩组各骨缝的破骨细胞数均比单次扩弓组和对照组多，且差异有统计学意义（P<0.05）。结论：上颌牙弓反复快速扩缩后，环上颌周围骨缝均有明显的组织学改建，具有更高的细胞活性。

Objective：To investigate changes in the circum-maxillary sutures during alternate maxillary expansions and constrictions in a rat model. Methods: Twentytwo male Sprague-Dawley rats (6 weeks old) were used and divided into three groups. In maxillary expansion (ME) group (n=9), an expander was activated for 5 d, and then sacrificed. In alternate maxillary expansions and constrictions (AltMEC) group (9 animals), an alternate expansion and constriction protocol (5 d expansion and 5 d constriction for one cycle) was conducted for 2.5 cycles (25 d total), and then sacrificed. The control group comprised 4 animals with no appliances used, each of two sacrificed on day 5 and day 25, respectively. Circum-maxillary sutures (mid-palatal, maxillopalatine, premaxillary, zygomaticotemporal, and frontonasal suture) in each group were characterized histologically. Results: Histological findings of circum-maxillary sutures: in control group, the normal sutures were divided into 5 zones, the center was polygon mesenchyme zone, the lateral was mature chondrocyte zone, the next lateral was bone tissue. In ME group, the mid-palatal suture was expanded after ME, the fibre and connective tissue were extracted and invaded into cartilage zone. Osteoblast hyperplasia and new bone formation occurred. The orientation of the new bone trabecula was consistent with force. The osteoclast appeared in some area. Findings of other sutures were similar with those of control group, osteogenesis was active in some area without obvious reconstruction in Alt-MEC group, mid-palatal suture and other sutures in some area were widened after Alt-MEC with much more osteoblast hyperplasia and new bone formation. Fibre and connective tissue were extracted, distorted or even broken. Sutures in some areas were narrowed with osteoblast cytopenia and osteoclast hyperplasia. Fibre and connective tissue compressed because of the different force and orientation. Osteoclast count results showed that compared with the control group, the number of the osteoclast was increased only in the palatal suture in ME group (P<0.05). Other sutures did not show obvious changes (P>0.05). In Alt-MEC group, the numbers of the osteoclast in circum-maxillary sutures were the most, and had statistical significances (P<0.05). Conclusion: These results suggested that circum-maxillary sutures were actively reconstructed after Alt-MEC. while only midpalatal suture had active reaction after ME.