小臼歯の萌出停止の分類と後遺症

Classification and sequelae of arrested eruption of primary molars.

抄録

目的:

本研究の目的は、小臼歯の早期無発達萌出を分類し、周囲の歯槽骨および後続小臼歯の後遺症を分析・説明することである。

AIM: The aim of this study was to classify early arrested eruption of primary molars and to analyse and explain the sequelae for the surrounding alveolar bone and the succeeding premolar.

デザイン:

29名の小児のX線写真から、下顎における停止した小臼歯の位置、周囲の歯槽骨の高さ、および後続小臼歯の形態と位置を評価した。

DESIGN: The position of the arrested primary molars in the mandible, the height of the local alveolar bone, and the morphology and location of the succeeding premolar were evaluated on radiographs from 29 children.

結果:

下顎の位置が軽度から重度の4群に分類された（I～IV群）。紹介時の平均年齢は、I群（8歳10ヵ月）からIV群（5歳9ヵ月）へと減少した。後遺症：(i)歯槽骨の高さの減少(I～III群)、(ii)後継小臼歯の成熟遅延(3分の2の症例)、(iii)後継小臼歯の奇形(主にIII群とIV群)、(iv)保定大臼歯の咬合側に異所性小臼歯が存在する(IV群)。

RESULTS: Four groups of arrest from mild to severe with regards to infra-position were categorized (Groups I-IV). Mean ages at the time of referral decreased from Groups I (8 years, 10 months) to Group IV (5 years, 9 months). SEQUELAE: (i) Reduction of alveolar bone height (Groups I-III); (ii) delayed maturity of the succeeding premolar (two-thirds of the cases); (iii) malformation of the succeeding premolar (mainly Groups III and IV); and (iv) ectopically located premolar occlusal to the retained molar (Group IV).

結論:

第一大臼歯が歯槽突起の深い位置で保定されるほど、萌出障害が早期に発生し、永久歯胚の奇形や位置異常のリスクが高くなる。乳臼歯の萌出停止が最も早く起こるのは3歳以前と推定されている。

CONCLUSIONS: The deeper in the alveolar process a primary molar is retained, the earlier the disturbance in the eruption has occurred, and the greater is the risk of the permanent tooth germ being malformed and malpositioned. It is estimated that the earliest occurrences of arrested eruption of primary molars supposedly occur before the age of 3.