混合歯列におけるII級不正咬合の横断面歯骨格的特徴の形態分析

Morphometric analysis of the transverse dentoskeletal features of class II malocclusion in the mixed dentition.

抄録

本研究の目的は、形態分析（薄板スプライン分析[TPS]）を前歯部セファログラムに適用することにより、II級不正咬合の横断面における歯骨格系の特徴を評価することである。II級1号不正咬合の被験者49例（男性24例、女性25例、平均年齢7歳9±5ヵ月）を、I級咬合の対照群50例（男性17例、女性33例、平均年齢8歳4±3ヵ月）と比較した。両群とも混合歯列で、矯正治療歴はなかった。平均的な頭蓋顔面形状をTPS分析に供し、両群間の形状の違いを比較した。本研究の結果、II級不正咬合の被験者は、正常咬合の被験者と比較して、前頭面における頭蓋顎顔面形態に有意な形状の相違を示した。これらの相違は主に、骨格レベルおよび歯槽骨レベルの両方における上顎骨の収縮と鼻底の狭小化から構成されていた。上顎の歯骨格幅の縮小は、上顎の垂直高さの増加と関連していた。

The aim of the present study was to evaluate the dentoskeletal features of Class II malocclusion in the transverse plane by means of a morphometric analysis (thin-plate spline analysis [TPS]) applied to posteroanterior cephalograms. A sample of 49 subjects (24 males, 25 females; mean age 7 years, 9 +/- 5 months) with Class II Division 1 malocclusion was compared with a control group of 50 subjects (17 males, 33 females; mean age 8 years, 4 +/- 3 months) with Class I occlusion. Subjects of both groups were in the mixed dentition and had no history of orthodontic treatment. Average craniofacial configurations were subjected to TPS analysis to compare the differences in shape between the two groups. The results of the present study showed that subjects with Class II malocclusion exhibited significant shape differences in craniofacial configuration in the frontal plane when compared with subjects with normal occlusion; these differences mainly consisted of a contraction of the maxilla at both the skeletal and the dentoalveolar levels and a narrowing of the base of the nose. The reduction in maxillary dentoskeletal width was associated with an increase in the vertical height of the maxilla.