低位下顎第一乳臼歯の歯列・咬合に与える影響に関する研究

A Study on Dentition and Occlusion in Children with Infraocclusal Lower First Decidous Molars

Kaihara Yasutaka

Ito Naoko

Amano Hideaki

Miura Kazuo

Kozai Katsuyuki

小児歯科学雑誌

低位下顎第一乳臼歯の存在が歯列咬合関係に与える影響を検討した。対象は男児12名, 女児17名, 計29名の日本人乳児である。歯列研究用模型を用いて, 咬合関係, 歯および歯列の大きさ, 下顎歯列の彎曲について, Hellmanの歯齢別に検討を行い, 以下の結果を得た。

1. 咬合関係

前歯の咬合関係では, 反対咬合の割合が最も高かった。ⅡC期の資料のterminal planeはmesial step typeが最も多く, ⅢA期以降の資料の第一大臼歯の咬合関係はAngleのⅢ級が最も多かった。

2. 歯および歯列弓の大きさ

下顎第一乳臼歯が左右とも低位乳歯である歯列は, 上下顎ともに第二乳臼歯間の歯列弓幅径が小さく, 歯列弓長径が大きかった。

3. 下顎歯列弓の彎曲

下顎第一乳臼歯が左右とも低位乳歯である歯列の彎曲は, 左右差はなく, 左右ともに標準値より大きかった。左右どちらか一方が低位乳臼歯の歯列の彎曲は, 患側は標準値に近かったが, 健側は標準値より大きく, 左右非対称であった。また, ⅡC期よりもⅢA期の方が彎曲が大きく, 第一乳臼歯がより低位である傾向が認められた。

以上の結果より, 下顎第一乳臼歯が低位乳歯である歯列の咬合関係は, 反対咬合である割合が高く, 矢状方向からみた下顎歯列弓の彎曲が強い傾向が示された。

The purpose of this study was to examine the effects of lower infraocclusal first deciduous molars on the dental occlusal relationship. The occlusal relationship, length of the dental arch, width of the dental arch, and the occlusal curvature of lower dentition were discussed in accordance with Hell-man's dental age using 29 study casts.

The results of this study were as follows:

1. Concerning the anterior occlusal relationship, the anterior crossbite was found to occur with high frequently.

2. Concerning the occlusal relationship of the first molars in materials of dental age IIIA and dental age IIIB, Angle's class III was the most common.

3. For the dentition with lower infrnocclusal first deciduous molars on both sides, the width of the dental arch between the second deciduous molars was small, and the length of the dental arch was large in both maxilla and mandible.

4. The occlusal curvature of the dentition with lower infraocclusal first deciduous molars on both sides was larger than the standard value of the lower occlusal curvature of the normal occlusion.

5. The occlusal curvature of the dentition when one side has no lower infraocclusal first deciduous molar was close to the standard value. On the other hand, the side with the infraocclusal first deciduous molar was larger than the standard value and dissymmetrical with respect to the side with the infraocclusal first deciduous molar.

6. The subjects of dental age IIIA showed a larger curve than those of dental age IIC, showing a tendency of toward infraocclusal first deciduous molars.

低位乳歯

歯列

咬合

三次元計測

歯列弓彎曲

Infraocclusal decidous teeth

Dentition

Occlusion

Three-demensional measurment

Medical sciences [ 490 ]

jpn

日本小児歯科学会

Copyright (c) 2003 Authors, 日本小児歯科学会

[ISSN] 0583-1199

[NCID] AN00116228