萌出障害の臨床 : 上顎中切歯と上顎犬歯
| Jazyk: | japonština |
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| Rok vydání: | 2009 |
| Předmět: | |
| Zdroj: | 小児歯科学雑誌. 47(5):673-682 |
| ISSN: | 0583-1199 |
| Popis: | 上顎中切歯の萌出障害は，先行乳歯の重度齲虫や外傷による根尖病巣が原因となって，歯胚の萌出方向が唇舌的に異常をきたすものが多い。時期が遅れると歯根が湾曲して形成されるため抜歯せざるを得ない場合があるので，発見したときには比較的早期の牽引が必要となる。臨床で頻繁に遭遇する永久歯の萌出過剰歯は，必ず歯列不正の原因となるので発見後ただちに抜去した方がよい。また，米粒大程度でエックス線不透過度の低い歯牙腫であっても萌出障害の原因となる。まれに，形成遅延の側切歯歯胚が中切歯の萌出を障害することがある。先行乳歯が癒合歯の場合に多く，前歯部交換期での精査が必要である。上顎犬歯の萌出障害は，特定の局所的原因が認められないものが全体の75%を占める。埋伏犬歯の歯軸は近心傾斜していることがほとんどで，歯冠部尖頭の側切歯歯根や中切歯歯根との重なり程度によって重症度が判別できる。軽症のものでは，先行乳歯の抜去で埋伏犬歯の歯軸改善が期待できるが，重症のものでは牽引が必要となる。側切歯が矯小であったり，先天欠如していたりすると，骨内での犬歯萌出路のガイドが欠落するため，犬歯萌出障害の原因となりうる。犬歯の萌出障害は片側性に発現するものがほとんどのため，乳犬歯の動揺度や犬歯部頬側歯肉の膨隆を両側で比較し，左右差が顕著なときにはエックス線写真による精査がきわめて重要である。 Eruption disturbances of maxillary central incisors are frequently caused by apical lesions of the predecessors after severe dental caries or traumatic injury, and the eruptive direction is often changed labio-palatally. Since the impacted central incisors will need to be extracted if serious root dilacerations occur due to late treatment, early traction is recommended after early detection. The erupted supernumeraries in the maxillary anterior region should be extracted as soon as possible because they inevitably induce the irregular alignment or impaction of the central incisor. Small odontomas the size of rice disturb the eruption of the incisor, even if their degree of radio-opacity is low. The late-developed germs of the lateral incisors sometimes produce eruption disturbances of the neighboring central incisor. As the late development of the lateral incisors may be related to the fusion of the predecessors, a careful examination is needed during the early mixed dentition period when fused primary teeth are detected in the maxillary anterior region. Eruption disturbances of maxillary canines are often induced by unidentified causes (nearly 75 %), and most affected canines incline mesially. The severity of the canine impaction can be estimated by the degree of overlap between the canine tip and the root of the lateral or central incisor. Although extraction of the predecessor will be effective in mild cases, traction will be needed in severe cases. Ectopic eruption of maxillary canines is sometimes caused by peg-shaped or congenitally absent lateral incisors because the affected canines lose the normal eruptive trail formed by the lateral incisor roots. Since most eruption disturbances of the maxillary canines occur unilaterally, it is important to palpate both sides to detect potential differences in the mobility of the primary canines or the labial gingival bulge before the eruption of the canine. When a difference is clearly noticed, it is critical to take radiographs. |
| Databáze: | OpenAIRE |
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