第二小臼歯形成不全における乳歯性第二大臼歯の保定状態と年齢との関係

Status of retained deciduous second molars in subjects with agenesis of second premolars in relation to age.

抄録

目的:

永久歯の後継歯を持たない第二小臼歯の保定の有無と状態を年齢との関連で評価すること。

AIM: To evaluate the presence and status of retained DM2 without permanent successors in relation to age.

背景:

先天性第二小臼歯欠如（PM2）の治療には、乳歯性第二大臼歯（DM2）の保存が適用できる。しかし、う蝕や進行する歯根吸収や低位咬合は、DM2の保存に影響を及ぼす可能性がある。

BACKGROUND: Preservation of retained deciduous second molars (DM2) can be applied to treat congenital absence of second premolars (PM2). However, the consequences of caries and progressing root resorption or infraocclusion may affect their survival.

方法:

少なくとも1本のPM2が欠如している10歳以上の患者のパノラマX線写真を評価し、年齢により3群に分けた。残存DM2の有無と位置、う蝕/修復、歯内咬合、歯根吸収を調査した。

METHODS: Panoramic radiographs of individuals >10 years of age with agenesis of at least one PM2 were evaluated and divided into three groups according to age. The presence and location of retained DM2, caries/restorations, infraocclusion and root resorption were investigated.

結果:

131名のPM2欠損症例（平均年齢13歳11ヵ月）が対象となった。PM2が1本または2本欠損している症例が大半を占め、174本のDM2が残存していた（33％）。う蝕・修復は88本（50.6％）、低位咬合は21本（12％）であった。根の吸収は根の長さの1/2がほとんどであった（35％）。

RESULTS: A total of 131 subjects with PM2 agenesis were included (mean age: 13 years 11 months). The majority were missing one or two PM2. In total, 174 retained DM2 were present (33%), and their incidence was higher in the younger age groups. Caries/restorations were found in 88 (50.6%) and infraocclusion in 21 (12%) retained DM2. The roots were resorbed mostly for ½ of the root length (35%).

結論:

永久的な後継歯のない保定DM2の長期予後は、特に若年層では不確実であると思われる。17歳以上の高齢者では、明瞭な歯内咬合や広範な歯根吸収がなければ、健全なDM2の予後は良好である。

CONCLUSION: Long-term prognosis of retained DM2 without permanent successors seems uncertain, especially within the younger age group. In individuals older than 17 years, the prognosis for a healthy DM2 is favorable, if no distinct infraocclusion or extensive root resorption is present.