骨格性III級不正咬合に対する矯正治療後の下切歯の歯根吸収をコーンビームCTを用いた3次元体積計測により評価した

Evaluation of root resorption in the lower incisors after orthodontic treatment of skeletal Class III malocclusion by three-dimensional volumetric measurement with cone-beam computed tomography.

抄録

目的:

前方交叉咬合を有する骨格性III級不正咬合患者において、小臼歯抜歯治療後の下切歯根の容積変化を検討する。

OBJECTIVES: To investigate the volumetric changes of the lower incisor roots in skeletal Class III orthodontic patients with anterior crossbite after premolar extraction therapy.

材料と方法:

18歳～28歳の成人36名に4回小臼歯抜歯治療を行った。治療前後のコーンビームCT（CBCT）画像を用いて、歯槽骨の厚みと高さ、歯根の体積、長さを評価した。治療前後の歯根体積と長さの変化を検出するために，paired t-testを使用した．ピアソンの相関分析により、歯根体積と歯骨格の形態との相関を推定した。

MATERIALS AND METHODS: Thirty-six adults, aged 18-28 years, had four-premolar extraction treatment. Pre- and posttreatment cone-beam computed tomography (CBCT) images were used to assess the thickness and height of alveolar bone, root volume, and length. A paired t-test was used to detect changes in root volume and length before and after treatment. Pearson's correlation analysis was applied to estimate the correlation between root volume and dentoskeletal morphology.

結果:

中切歯、側切歯ともに治療後、侵入、転倒運動が見られた。治療前と比較して，歯根長が有意に減少していた．歯頸部，根尖部3分の1の舌側根量，根尖部3分の1の唇側根量は有意に減少し（P < .05），その中でも先端部の歯体積の減少率が最も高かった．治療前の歯槽堤の高さ，歯槽骨の厚さ，切歯の移動の種類は，容積と長さの減少に関連していた．

RESULTS: Both the central and lateral incisors had intrusion and tipping movement after treatment. Compared with pretreatment data, root length decreased significantly. The lingual root volume of root cervical, apical third, and the labial root volume of the root apical third decreased significantly (P < .05), among which the percentage of tooth loss at the tip volume was the highest. The pretreatment height of the alveolar ridge crest, thickness of the alveolar bone, and type of incisor movement were related to the volume and length loss.

結論:

骨格性III級小臼歯抜歯パターンにおいて、下切歯根の先端3分の1の体積と長さの損失は一般的である。治療前の歯槽堤の高さ、歯槽骨の厚さ、歯の移動の種類は、損失に関連している。

CONCLUSIONS: Volume and length loss in the apical third of the lower incisor roots in skeletal Class III patients treated with a Class III bicuspid extraction pattern is common. The pretreatment height of the alveolar ridge crest, thickness of the alveolar bone, and type of tooth movement are related to the loss.