骨性Ⅲ类错牙弓、基骨弓宽度及协调性分析

Dental arch, basal arch width and coordination analysis in skeletal Class Ⅲ malocclusion

目的 探讨骨性Ⅲ类错（牙合）患者牙弓、基骨弓宽度及二者协调性,为临床诊断和治疗提供理论依据.方法 选择骨性Ⅲ类错（牙合）患者33例为实验组,47例个别正常（牙合）为对照组,利用锥形束CT扫描颌面部,将扫描后图像导入Mimics10.01图像处理软件分别测量牙弓宽度、基骨弓宽度,并计算上下颌对应宽度之差,对测量结果进行独立样本t检验.结果 骨性Ⅲ类错（牙合）组上颌牙弓宽度与个别正常（牙合）组比较无显著性差异,但下颌牙弓宽度大于正常（牙合）,其中下颌第一磨牙处平均宽度正常（牙合）为（56.26±3.09）mm,骨型Ⅲ类患者为（57.78±3.22）mm,差异有统计学意义（P＜0.05）；骨性Ⅲ类错（（牙合）上颌基骨弓宽度测量值均小于对照组,其中在上颌第二前磨牙处正常（骀）为（59.11±5.97）mm,骨型Ⅲ类患者为（56.23±5.28）mm,有统计学差异（P＜0.05）,下颌基骨弓宽度均大于对照组,其中在前磨牙及第一磨牙处分别为（47.44±2.96）mm、（59.81±3.87）mm和（76.20±4.20）mm,与正常（牙合）相比差异显著（P＜0.05）.骨性Ⅲ类错（牙合）上下颌基骨弓宽度差值均小于正常（牙合）（P＜0.01）,而牙弓宽度差值仅在尖牙处差异显著（P＜0.05）,其余牙位测量项目无统计学差异.结论 ①骨性Ⅲ类错（牙合）组上颌基骨宽度发育不足,下颌基骨宽度发育过度.②骨性Ⅲ类错（牙合）的宽度不协调表现在基骨水平,牙弓对基骨弓宽度不调有代偿.

Objective To provide references for diagnosis andtreatment plan of skeletal Class Ⅲ malocclusion based on the study of dental arch widths, basal bone widths and their coordination. Methods Experimental groupconsists of 33 skeletal Class Ill malocclusion cases and control groupconsists of 47 individual normal occlusion cases. The data samples of thetwo groups were derived from Cone Beam Computed Tomography （CBCT） scans, and were used to measure dental arch widths and basalbone arch widths. The differences between the paired maxilla and mandible measurements were calculated. All the measurements and calculations were done in Mimics 10. 01. Independentsample t-testwas used to compare the two groups. Results Differences between the maxillary dental arch widths were unapparent; skeletal Class Ⅲ malocclusion had a tendency of larger mandibular dental arch widths. Maxillary basalbone archwidths of Class UI malocclusion groupwere narrower compared with normal occlusion samples. The second premolar segment was significantly narrower. Moreover, mandibular premolar and molarbasalbone arch widths of the skeletal Class Ⅲ malocclusion were significantly larger than the normal occlusion groups. Difference between maxillary and mandibular basal bone arch widths was larger in skeletal Class Ⅲ malocclusion. Difference between maxillary and mandibular dental arch widths in canine area was smaller while other dental segment width difference showed no statistical differences. Conelusions （1） In transverse dimension, maxillary basal bone arch grows insufficiently, while the mandibular basal bone archgrows excessively in skeletal class Ⅲ patients. （2） Widthdiscrepancy inskeletal class Ⅲ is at basal bonelevel. Dental arch showssome extent of compensation.