歯科用コーンビームCTを用いた下顎第2大臼歯の歯根および根管形態の観察

Observation of mandibular second molar roots and root canal morphology using dental cone-beam computed tomography.

抄録

下顎第2大臼歯は，根および根管に様々な形態を示し，中根と遠心根の癒合による樋状根（GSR）が高頻度に観察される．本研究では，歯科用コーンビームCT（CBCT）を用いて下顎第2大臼歯の歯根の数を観察した．GSRを有するものについては、根の形態と根管分類の判定を行った。日本人下顎第2大臼歯173本のCBCT画像データを入手した．スライスした画像を用いて，根の数と根の形態を決定した．GSRが認められた症例では，融合根の比率を求め，根管形状の特徴を分類した．GSRは61例（35.3%）に認められ，女性に多くみられた．また、GSRを有する者の根の太さに対する融合部の比率は全体で48.7％であり、性別による有意差はなかった。さらに，C 型根管形態は GSR を有する男女に共通して観察された．日本人を対象とした今回のコホートでは、下顎第二大臼歯のほとんどが2根であり、35.5％にGSRが認められた。GSRは女性に多く認められたが、根管形態は男女ともにC型が最も多かった。下顎第2大臼歯の根管形態とGSRの有無を正確に判断するためには、CBCT所見を用いた評価が有用であると考えられる。

The mandibular second molars show various morphological features in the roots and root canal, and a guttershaped root (GSR) caused by fusion of the mesial and distal roots is frequently encountered. In this study the number of the roots associated with mandibular second molars were observed using dental cone-beam computed tomography (CBCT). For those with a GSR, determination of root morphology and root canal classification were performed. CBCT image data from 173 Japanese mandibular second molars were obtained. Using sliced images, the number of the roots and root morphology were determined. In cases with a GSR, the ratio for the fused roots was determined and root canal morphology features were classified. A GSR was found in 61 (35.3%), with greater prevalence in females. In addition, the overall ratio of the fused part to root thickness in those with a GSR was 48.7%, with no significant difference related to sex. Furthermore, a C-shaped root canal morphology was commonly observed in both males and females with a GSR. In the present cohort examined in Japanese, most of the mandibular second molar were found to have two roots, with a GSR noted in 35.5%. While a GSR was more often observed in females, a C-shaped root canal was the most common root canal morphology in both sexs. It is considered that assessment using CBCT findings is helpful for precise determination of root canal morphology and presence of a GSR in mandibular second molars.