Kunihisa Nakajima

Masticatory path pattern during mastication of chewing gum with regard to gender difference

PURPOSE To clarify the masticatory path patterns of the mandibular incisal point during mastication of softened chewing gum with regard to gender difference. METHODS One hundred healthy subjects (50 males and 50 females) were asked to chew softened chewing gum on one side at a time (right side and left side) and the movement of the mandibular incisal point was recorded using MKG K6I. After a catalog of path patterns was made, the movement path was classified into one of the pattern groups, and then the frequency of each pattern was investigated. RESULTS A catalog of path patterns consisting of the three types of opening path (op1, linear or concave path; op2, path toward the chewing side after toward the non-working side; op3, convex path) and two types of closing path (cl1, convex path; cl2, concave path) was made. The movement path was classified into one of seven patterns, with six patterns being from the catalog and a final extra pattern in which the opening and closing paths crossed. The most common pattern among the subjects was Pattern I, followed by Patterns III, II, IV, V, VII, and VI, in that order. The majority of cases, 149 (74.5%) of 200 cases, showed either Pattern I (op1 and cl1) or Pattern III (op2 and cl1). There was no significant difference between the two genders in the frequency of each pattern. CONCLUSION The movement path could be classified into seven patterns and no gender-related difference was found in the frequency of each pattern.

Differences in masticatory function of subjects with different closing path

PURPOSE The purpose of this study was to clarify whether there was a difference in the masticatory function between two masticatory path patterns: a convex closing path and a concave closing path. METHODS For 80 healthy subjects, the masticatory function (masticatory muscular activity, mandibular movement, and masticatory performance) when chewing a gummy jelly was recorded. Out of the 160 chewing cases (80 subjects chewing on either side), 65 cases (Group I) in which the incisal point opened in a linear or concave manner toward the working side and closed in a convex manner, and 15 cases (Group II) in which the opening path was the same as that in Group I, but the closing followed a concave path, were selected. For the masticatory function, the integral values per unit time of masseter and temporal muscular activities, the gape and masticatory width, the indicators representing the stability of movement path, and the glucose extraction from chewing gummy jelly were measured and compared between the two groups. RESULTS The integral values of muscular activities and the amount of glucose extraction were significantly greater in Group I. The gape and masticatory width were not significantly different between the groups. The values of the indicators representing the stability of path were smaller in Group I than in Group II. CONCLUSION From these results, it was suggested that there was a functional difference between Group I (with a convex closing path) and Group II (with a concave closing path), and that Group I had a superior masticatory function to Group II.

Influence of two masticating conditions on assessment of movement path stability

PURPOSE The purpose of this study was to clarify whether differences in masticating conditions affected masticatory path stabilities of healthy subjects and TMD patients. METHODS Twenty healthy female subjects as the healthy group, and 20 female Temporomandibular Disorders (TMD) patients as the TMD group, were selected. Incisal point movement of during mastication of both masticating condition 1 (mc1; crispy bread chewed until swallowing on the free side) and masticating condition 2 (mc2; softened chewing-gum chewed for 20s on the habitual side) were recorded by MKG. As for mc1, out of all cycles during mastication only those cycles on the habitual chewing side were analyzed. As for mc2, the ten cycles from the fifth cycle were analyzed. For these analyzed sections, the indicators representing movement path stability were calculated and compared between the two groups. RESULTS As for mc1, though the values of the indicators representing path stability were larger for the TMD group, there were cases where no significant differences were found between the two groups. As for mc2, the values were significantly larger for the TMD group (SDs; P<0.05, SD/ODs; P<0.01). CONCLUSIONS From these results, it was suggested that the differences in masticating conditions affected the assessment of masticatory path stabilities of healthy subjects and TMD patients and the conditions should be considered for analyzing masticatory movement.

Relationship between masticatory performance using a gummy jelly and food intake ability in Japanese complete denture wearers

Twenty patients wearing complete dentures were asked to chew a gummy jelly, and their glucose extraction was measured. Two types of masticatory scores (MS1 and MS2) were calculated using a food intake questionnaire. The relationship between masticatory scores and glucose extraction was investigated. The values of masticatory scores were large when the amount of glucose extraction was also large, and there were significantly positive correlations between the two. There was also a positive correlation between MS1 and MS2. It was suggested that the food intake ability was high when the masticatory performance using a gummy jelly was high.

Clinical studies on TMJ sound : Quantitative evaluation of TMJ sound in CMD patients

頭蓋下顎機能障害 (CMD) 患者における顎関節音の性状を客観的に評価する目的で, 可聴音を有するCMD患者20名 (A群) , 雑音を自覚し, 術者が触知できる音を有するCMD患者20名 (B群) , 雑音を自覚せず, 術者が触知できる音を有するCMD患者20名 (C群) , 正常者40名 (D群) について, 開閉口運動時の顎関節音をコンタクトマイクロフォンで記録後, 周波数分析を行い, 被験者群間で比較し, 以下の結論を得た.1.CMD患者群のパワースペクトルは, A群, B群では100Hz以上の帯域にも周波数成分の強調がみられたが, C群では100Hz以下に周波数成分の強調がみられる者が多かった.また, A群, B群, C群の川頁に高周波成分の減少が認められた.他方, D群のパワースペクトルは, ほぼ100Hz以下に限定されたパターンを示し, 周波数成分の強調がみられる者が少なかった.2.パワースペクトルの累積100%値と累積80%周波数値は, A群が最も大きく, 以下B群, C群, D群の順に小さくなった.累積100%値では, A群とB群との間, C群とD群との間を除く他のすべての各2群間に, 累積80%周波数値ではすべての各2群間にそれぞれ有意差が認められた.3.以上のことから, 顎関節音のパワースペクトルのパターン, 累積100%値, 累積80%周波数値の分析は, CMD患者の顎関節雑音の性状の違いを定量的に評価できることが示唆された.また, これらの3指標のうち, 累積80%周波数値は, 特に有効な指標となることが示唆された.

The effect of food dimensions on chewing movements. Mandibular movement and masticatory muscles activity.

ヒトの咀嚼運動における食品の大きさの影響を調べる目的で, 咀嚼中に硬さと大きさを保つチューインガムを被験食品として選択し, 正常者10名にチューインガム1枚 (1G) , 2枚 (2G) , 3枚 (3G) , 4枚 (4G) の4種類のガム咀嚼時における咀嚼開始後第5サイクルからの10サイクルの運動経路, 運動リズム, 運動速度, 咀嚼筋筋活動を分析した.結果は, 以下の通りである.1.開口量と咀嚼幅は, 食品の大きさが増大するに従って徐々に大きくなり, 開口量ではすべてのセッション間, 咀嚼幅ではIGと3Gとの間, IGと4Gとの間に有意差が認められた.2.運動リズム咬合相時間は, 食品の大きさが変化してもほぼ同じ値を示し, いずれのセッション間にも有意差が認められなかった.開口相時間, 閉口相時間, サイクルタイムは, 食品の大きさが増大するにつれてわずかに延長し, 1Gと4Gとの間, 2Gと4Gとの間に有意差が認められた.3.運動速度開口時最大速度と閉口時最大速度は, 食品の大きさが増大するに従って大きくなり, 開口時最大速度では1Gと他のセッションとの間, 2Gと4Gとの間, 閉口時最大速度では1Gと他のセッションとの間にそれぞれ有意差が認められた.4.咀嚼筋筋活動咬筋と側頭筋の積分値は, 食品の大きさが増大するに従って大きくなり, 咬筋では1Gと他のセッションとの問, 側頭筋では1Gと3Gとの間, 1Gと4Gとの間にそれぞれ有意差が認められた.5.以上のことから, 咀嚼時の食品の大きさが変化するに従って, 咀嚼運動を定量的に表わす運動経路, 運動リズム, 運動速度, ならびに咀嚼筋筋活動の各指標の一つあるいは総てが変化することが明らかになった.これは, 末梢からの感覚入力の変化が咀嚼運動に影響を及ぼすことを示すものと考えられる.

Masticatory Path and Rhythm in Patients with Osseointegrated Implants Denture

Osseointegrated implants義 歯 応 用 後 に お け る 治 療 評 価 に つ い て 、implantsの 残 存 率1,2)、 implants周 囲 組 織 の 受 圧 感 覚3,4)、 咬 合 力5,6,7) な ど に 関 す る 報 告 は 多 く 認 め ら れ る が 、 咀嚼 運 動 に 関 す る 報 告 が 極 め て 少 な い の が 現 状 で あ る 。 著 者 ら は 、 す で にOsseointegrated implants 義 歯 装 着 後 に お け る 咀嚼 機 能 を 明 ら か に す る 目 的 で 、Osseointegrated implants義 歯 応 用 患 者 の 咀嚼 運 動 経 路 の 安 定 性 に つ い て 、 応 用 前 、 す な わ ち 治 療 用 総 義 歯 装 着1ヵ 月 後 とimplants義 歯 応 用1ヵ 月 後 と の 間 で 比 較 し た 結 果 、 応 用1 ヵ 月 後 で は 、 個 人 差 が あ り 、 応 用 前 よ り も 安 定 す る 場 合 と 不 安 定 に な る 場 合 と が あ る こ と8,9) を 報 告 し た 。 今 回 は 、Osseointegrated implants義 歯 応 用 後 の 咀嚼 機 能 の 回 復 程 度 を 明 ら か に す る 目 的 で 、 咀嚼 運 動 に お け る 経 路 と リ ズ ム に つ い て 、 implants義 歯 応 用 前 と 応 用1ヵ 月 後 、 応 用1年 後 と の 間 で そ れ ぞ れ 比 較 し た 。