永久歯の埋伏と不正咬合の関係に関する病因論的研究

[Etiological study of relationship between impacted permanent teeth and malocclusion].

抄録

この調査は、永久歯の咬耗が歯列、咬合および骨格パターンに及ぼす影響を明らかにするために行われた。使用した材料は、愛知学院大学歯学部矯正学教室で1964年から1985年までの3979症例（男性1215例、女性2764例）のうち、永久歯の埋伏が認められた194症例（男性51例、女性143例）のデンタルX線写真、咬合デンタルX線写真、パノラマX線写真、セファログラムおよび歯列模型である。得られた結果は以下の通りである：1.永久歯の埋伏率は矯正患者全体の4.9％であった．男女間に有意差はなかった。2.2.永久歯の埋伏歯数による発生率は以下の通りであった：埋伏歯1本：74.8％、埋伏歯2本：21.1％、埋伏歯3本：3.6％、埋伏歯4本：0.5％。左右対称に2本の永久歯が埋伏している割合は61.5％であった。3.3.動揺歯の種類では、上顎中切歯の頻度が最も高く33.7％、次いで3本（25.0％）、5本（22.2％）、5本（11.9％）、2本（4.4％）、3本（1.2％）、4本（0.8％）、4本（0.4％）、7本（0.4％）であった。しかし、1,2,6,6,7,7の部位では埋伏歯は認められなかった。4.4.有歯咬合と不正咬合の種類では、前歯部の有歯咬合が最も多く、次いで叢生、開咬、側方交叉咬合であった。最も発生率の低い不正咬合は交叉咬合と上方突出であった。両顎前突よりも有歯顎弓の方が有歯咬合率が高かった。後方領域（臼歯部）では、側方交叉咬合、開咬、上方突出が最も多く、叢生が2番目、交叉咬合が最も少なかった。5.長軸方向では、水平方向の埋伏歯が最も多く（35.2％）、次いで多い順に逆方向（32.7％）、唇側または内側傾斜（22.0％）、舌側または遠位傾斜（5.7％）、直角方向（4.4％）であった。さらに、上顎中切歯が逆向き、上顎犬歯が内側に傾いていることが最も多かった。歯根が曲がっている上顎中切歯の頻度は64.7％であり、上顎犬歯（19.0％）よりも高かった。6.前歯部ではスペース不足が最も多く認められ、犬歯の埋伏歯の主な原因であった。前歯部では、上顎犬歯による萌出障害と外傷が特徴的な原因であった。

This investigation was undertaken to determine the causes of impacted permanent teeth and whether they have any influence on dentition, occlusion and skeletal patterns. The materials used were dental X-rays, occlusal dental X-rays, panoramic radiograms and cephalograms and dental casts of 194 cases (51 males and 143 females) which revealed impacted permanent teeth among 3979 cases (1215 males and 2764 females) from 1964 to 1985 in the Department of Orthodontics, School of Dentistry, Aichi-Gakuin University. The results obtained were as follows: 1. The incidence of impacted permanent teeth in these samples was 4.9% of the entire number of orthodontic patients. There was no significant difference between sexes. 2. The incidence according to the number of impacted permanent teeth was as follows: one impacted tooth, 74.8%; two impacted teeth; 21.1%, three impacted teeth; 3.6%, four impacted teeth; 0.5%. The incidence of two symmetrically impacted teeth was 61.5%. 3. As to the type of impacted teeth, the frequency of maxillary central incisors was the largest (33.7%), followed by 3 (25.0%), 5 (22.2%), 5 (11.9%), 2 (4.4%), 3 (1.2%), 4 (0.8%), 4 (0.4%), and 7 (0.4%). But no impacted teeth were found in the regions of 1, 2, 6, 6, 7 and 7. 4. As to impacted teeth and the type of malocclusion, the spaced arch in the anterior region had impacted teeth most frequently followed by crowding, open bite and lateral cross bite. Malocclusions with the smallest incidence were cross bite and upper protrusion. The spaced arch had a higher incidence of impacted teeth than bimaxillary protrusion. In the posterior region (impacted molar teeth), the lateral cross bite, spaced arch, and upper protrusion had impacted molars most frequently, crowding was second and cross bite had the least. 5. In the direction of long axis, the impacted tooth with a horizontal direction was found most frequently (35.2%), followed in the order of frequency by inverse direction (32.7%), labial or mesial tipping (22.0%), lingual or distal tipping (5.7%), and right-angled (4.4%). Moreover, the inverse maxillary central incisor and mesially tipped maxillary canine were found most frequently. The frequency of maxillary central incisors with crooked roots was 64.7%, which was higher than that of maxillary canines (19.0%). 6. Lack of space is the most frequently found cause of impacted teeth, and in the anterior region this was the main cause of canine impacted teeth. Eruption impediment by supernumerary teeth and trauma were found to be characteristic causes of anterior impacted teeth.