Saddle Angle and Maxillary Prognathism: A Radiological Analysis of the Association between the NSAr and SNA Angles
Saddle Angle and Maxillary Prognathism: A Radiological Analysis of the Association between the NSAr and SNA Angles
复制标题
鞍角和上颌前突：NSAr 和 SNA 角之间关联的放射学分析
DOI：
10.1179/bjo.11.4.209
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发表时间：
1984
影响因子：
1.3
通讯作者：
S. Järvinen
中科院分区：
文献类型：
--
作者：
S. Järvinen
在头颅x线摄影中，常用两种角度，鞍角（NSAr）和SNA角。前者被认为是颅底角，后者被认为是上颌骨与颅底前后关系的一个指标。在这项研究中，我们分析了138例未经治疗的7-15岁正畸患者的侧颅骨x线片。样本包括Angle的I类、II类和III类错牙合病例。估计不同错颌组的nsna和SNA角以及S-N和S-Ar线的均值和标准差，并对每个错颌组计算SNA和NSAr角之间的线性回归模型（y=bx+a）。ⅱ类错颌组的NSAr角均值明显大于ⅲ类错颌组（p< 0.05）。计算回归表明，不同错颌组中SNA角的变化约占14 - 40%，整个样本中约24%的变化可由NSAr角的变化来解释。由于NSAr和SNA角之间的相关性至少有一部分与地形有关，这种地形相关的主要原因可能是S-N平面的旋转，因此SNA角被认为是一个不可靠的指标，使用SNA角会导致相当大的误差。
In cephalometric radiography, two angles have been commonly used, the saddle angle (NSAr) and the SNA angle. The former has been regarded as the cranial base angle, the latter as an indicator of the antero-posterior relation of the maxilla to the cranial base. In this study, a sample of 138 lateral skull radiographs of untreated orthodontic patients aged 7–15 years was analysed. The sample consisted of Angle's Class I, Class II, and Class III malocclusion cases. Means and standard deviations of the NSAr and SNA angles and the S—N and S—Ar lines for different malocclusion groups were estimated, and for each malocclusion group, the model of linear regression (y=bx+a) between the SNA and NSAr angles was computed. The mean of the NSAr angle was significantly larger in the Class II malocclusion group than in the Class III malocclusion group (p<0·05). The computed regressions indicated that about 14–40 per cent of the variation of the SNA angle in different malocclusion groups and about 24 per cent in the whole sample could be explained by the variation of the NSAr angle. Because at least a part of the correlation between the NSAr and SNA angles had a topographical causation, the main cause of this topographical correlation probably being the rotation of the S-N plane, the SNA angle was regarded as an unreliable indicator, the use of which can lead to considerable errors.