短縮歯列弓コンセプトを用いたリハビリテーションが咬筋の厚さと咬合力に及ぼす影響：パイロットスタディ

Effect of rehabilitation by using the shortened dental arch concept on the thickness of the masseter muscle and occlusal force: A pilot study.

抄録

問題提起:

短縮歯列弓が咬筋厚および咬合力に及ぼす影響に関する知見は乏しいが、短縮歯列弓が顎口腔系にどのような影響を及ぼすかを臨床家が理解するのに役立つ可能性がある。

STATEMENT OF PROBLEM: Knowledge of the effect of a shortened dental arch on masseter muscle thickness and occlusal force is sparse but could help clinicians understand how a shortened dental arch might affect the stomatognathic system.

目的:

この試験的臨床研究の目的は、短縮歯列弓を用いてリハビリテーションを行った参加者の咬筋厚および咬合力を、マッチさせた完全歯列弓の人と評価・比較することである。

PURPOSE: The purpose of this pilot clinical study was to evaluate and compare the masseter muscle thickness and occlusal force of participants rehabilitated by using a shortened dental arch with matched completely dentate individuals.

材料と方法:

両側1対以上の後方咬合を有する12名の部分的無歯顎者を本研究に登録した。これらの参加者の下顎弓は、1本の下顎後方インプラントクラウンを用いて修復した（S群）。S群の参加者全員の上顎弓は無傷であった。咬筋の厚さ（cm）と咬合力（N）は、各参加者のインプラントリハビリテーション前（T1）と6ヵ月後（T2）に記録した。12名の参加者をコントロールとして選択した（C群）。年齢、性別、身長、体重をS群と一致させ、咬筋厚と咬合力を評価した。咬筋厚は、安静位および最大容積のクレンチング時の超音波検査を用いて評価した。咬合力は咬合力測定装置を用いて測定した。記録はすべて左右の歯列弓について行った。記述分析に続き、paired t test (α=.05)を用いて群間および群内S比較を行った。

MATERIAL AND METHODS: Twelve partially edentulous participants with a minimum of 1 posterior occluding pair on each side of the arch were enrolled in the study. The mandibular arch of these participants was rehabilitated by using a single posterior mandibular implant crown (group S). The maxillary arch of all participants in group S was intact. Masseter muscle thickness (cm) and occlusal force (N) were recorded before (T1) and 6 months after implant rehabilitation (T2) for each participant. Twelve participants were selected as controls (group C). They were matched for age, sex, height, and weight with group S and evaluated for masseter muscle thickness and occlusal force. Masseter muscle thickness was evaluated by using ultrasonography during the rest position and maximum volumetric clenching. Occlusal force was measured with an occlusal force measuring appliance. All recordings were done for the left and right sides of the arch. Descriptive analysis was followed by comparison between groups and within group S by using the paired t test (α=.05).

結果:

C群ではS群に比べ、リハビリテーション前後で咬筋厚の増加と咬合力の増加が観察された。リハビリテーション後のS群では、安静位での咬筋厚と最大容積のクレンチングでの咬筋厚の増加が観察された。リハビリテーション前、S群とC群の咬筋厚の差は、安静位（P=.017）および最大容積食いしばり時（P=.016）において、左側で統計学的に有意であった。リハビリテーション後、S群とC群の咬筋厚の差は、安静位（右側：P=.890、左側：P=.555）および最大容積食いしばり時（右側：P=.109、左側：P=.755）では統計学的に有意ではなかった。S群とC群の咬合力差は、リハビリテーション前では右側と左側で統計学的に有意（P<.001）であったが、リハビリテーション後では統計学的に有意ではなかった（右側でP=.161、左側でP=.134）。

RESULTS: Higher masseter muscle thickness and higher occlusal force were observed in group C than in group S before and after rehabilitation. An increase in masseter muscle thickness in the rest position and in maximum volumetric clenching was observed within group S after rehabilitation. Before rehabilitation, a difference in the masseter muscle thickness between group S and group C was statistically significant for the left side at the rest position (P=.017) and during maximum volumetric clenching (P=.016). After rehabilitation, the difference between group S and group C was not statistically significant for masseter muscle thickness at the rest position (P=.890 for right side and P=.555 for left side) and during maximum volumetric clenching (P=.109 for right side and P=.755 for left side). The difference in occlusal force between group S and group C was statistically significant for the right side and left side (P<.001) before rehabilitation and statistically not significant after rehabilitation (P=.161 for the right side and P=.134 for the left side).

結論:

短縮歯列弓の概念に従ったリハビリテーションは、部分的無歯顎者の咬筋厚および咬合力を増加させ、咬筋厚および咬合力を完全歯列弓の場合と同等にした。

CONCLUSIONS: Rehabilitation following the concept of a shortened dental arch increased masseter muscle thickness and occlusal force in partially edentulous individuals, making the masseter muscle thickness and occlusal force comparable with those of a completely dentate arch.