Shoji Kohno

Bio: Shoji Kohno is an academic researcher from Meirin College. The author has contributed to research in topics: Masticatory force & Medullary cavity. The author has an hindex of 1, co-authored 8 publications receiving 8 citations.

Biting force and chewing ability in removable denture wearers

Abstract: It is important to know that dentures will function properly in patient's daily life. Generally, a convenient method to know chewing performance is to measure biting force that can be achieved. However, the relationship between biting force and the function of dentures has not yet been established. The purpose of this study was to investigate the relationship between biting force and chewing ability in removable denture wearers. Biting force was investigated in 321 subjects (76y) with and without removable dentures in the first molar. Kinds of foods that can be masticated in these subjects were also investigated by means of questionnaires. The findings of the research are summarized below: 1.Subjects with dentures in the upper and/or lower jaw was found to have a biting force of 1/2 of that of subjects with natural teeth in the upper and lower jaws. ; 2. Subjects with dentures in the upper and/or lower jaw could chew fewer kinds of food than subjects with natural teeth in the upper and lower jaws. ; 3. Subjects with dentures in the upper and/or lower jaw could chew softer foods such as rice. Subjects with dentures in both the upper and lower jaw were found to have difficulty in chewing harder foods. In conclusion, it is important to retain the biting ability of natural teeth to enjoy the benefits of a varied diet. 抄録:日常生活において,装着された補綴物が実際に十分に機能しているかどうか評価することは,治療成績の向上 のために重要である。口腔機能のなかで特に咬合機能を評価する簡便な方法として,咬合力の測定が挙げられるが, 可撤性義歯装着者における咬合力の実態と実際に発揮される機能との関連性についてはあまり知られていない。そこ で本研究では,可撤性義歯の装着によって発揮される咬合力と,実際に噛める食品との関連性を明らかにすることを 目的とした。 被検者は76歳321名,評価対象部位は第一大臼歯とした。 咬合力については,両顎天然歯を保っている被検者に比べると,義歯を使用する被検者では半分以下の有意に低い 値を示した。しかし片顎義歯と両顎義歯の間には,有意な差はなかった 噛める食品数においては,両顎天然歯は高い値を示したが,義歯を有する場合は低い値を示した。片顎義歯と両顎 義歯の装着と咬合力および噛める食品との関係 岩 舩 素 子,五十嵐 直 子,河 野 正 司, 清 田 義 和,葭 原 明 弘,宮 崎 秀 夫 新潟大学大学院医歯学総合研究科 摂食機能再建学分野(主任:河野正司教授) 新潟大学大学院医歯学総合研究科 口腔保健推進学分野(主任:宮崎秀夫教授) さかもと歯科医院 Biting force and chewing ability in removable denture wearers Motoko Iwafune,Naoko Igarashi,Shoji Kohno, Yoshikazu Seida,Akihiro Yoshihara, Hideo Miyazaki Division of Removable Prosthodontics, Department of Tissue Regeneration and Reconstruction (Chief: Prof. Shoji Kohno), Division of Preventive Dentistry, Department of Oral Health Science (Chief: Prof. Hideo Miyazaki), Niigata University Graduate School of Medical and Dental Science, Sakamoto Dental Clinic 平成16年10月22日受付 12月9日受理

The Influence of Food Size During Food intake on Mouth Opening and Head Movement

Abstract: 食物取り込み時の開口量は食物の大きさに伴って変化することが報告されている.一方下顎運動には, その運動に協調した頭部運動が存在し, 開口時には頭部は後屈方向に, 閉口時には前屈方向に運動している.そこで, 種々の大きさの食物取り込み時における開口量の変化と共に, 同時に観察される頭部運動の詳細を測定, 分析し, 頭部運動の存在意義についても考察を試みた.被験者は顎口腔系に異常が認められず, 顎機能障害の既往を持たない, 本学大学院生および職員, 女性2名, 男性1名の計3名 (年齢24歳～26歳) とした.被験食品には一辺を6mmから35mmとした10種類の立方体のりんごを, 測定には6自由度顎運動測定装置 (東京歯材社製TRIMET) を使用し, 頭部無拘束状態で, 下顎運動と頭部運動の同時記録を行った.実験結果は以下の通りである.1.食物取り込み時には食品空隙が存在することが明らかとなり, その食品空隙は同じ大きさの食物取り込みの際には, 頭位に関係なくほぼ一定量を示した.2.頭部運動量は頭位がFrankfort平面水平ではCamper平面水平に比較して大きくなる傾向を示し, 下顎機能時にもその運動を補う随伴運動として頭部運動が存在していることが示唆された

Coactivated rhythmical activity in the neck muscles during masticatory movements in the rabbit.

Abstract: ヒトにおいて, 咀嚼時には頭部は下顎運動と協調してリズミカルに動いていることが報告されている.この咀嚼時の頭部運動のメカニズムを調べる目的で, 覚醒無拘束のウサギを用いて, 性状の異なる2種の試料 (パン, 生米) を咀嚼している際の頭部運動と頸筋 (胸骨乳突筋, 頭板状筋) のEMGを記録した.また, ウレタン麻酔を施したウサギを用いて, 皮質誘発性咀嚼様運動時に頸筋 (胸骨乳突筋, 頭半棘筋) のEMGを記録した.覚醒咀嚼時には, 頭部が下顎運動と同じ周期でリズミカルに動いており, その垂直的な運動方向は下顎運動と反対であった.同時に, 胸骨乳突筋には試料に応じて異なるリズミカルな活動が観察された.パン咀嚼時には開口時と閉口時の二相性に活動し, 生米咀嚼時には閉口時のみに活動した.頭板状筋は持続的に活動しており, 活動に明瞭なリズム性は認められなかった.麻酔下の皮質誘発性咀嚼様運動時には, 胸骨乳突筋は閉口時にのみ活動を示し, 臼歯で木片を咬合させると活動が増強した.頭半棘筋は持続的に活動しており, 活動にリズム性は見られなかった.覚醒咀嚼時に観察されたリズミカルな頭部運動が, ヒトと同様な様相を呈したことから, ウサギは咀嚼時頭部運動の実験モデルとして有用であることが示された.また, 咀嚼リズムに同期してリズミカルに活動した胸骨乳突筋は, 咀嚼筋や頸部の固有感覚受容器あるいは歯根膜などからの末梢性入力によって活動が増強され, 反射性に活動することが示唆された.一方, 頭板状筋, 頭半棘筋活動の咀嚼運動時におけるリズム性は明瞭でなく, 頭部運動との関連は明らかでなかった.

Study on the relationship between lateral facial morphology andbite force in orthodontic patients with temporomandibular disorder.

Abstract: 顎関節症患者の側面顎顔面形態と咬合力の相関関係を調べるために咬合力感圧シート (Dental Prescale 50HR type) を用いて, 矯正女性患者42名 (顎機能正常者23名, 顎関節症患者19名) の咬合力, 側面顎顔面形態を調べ, 以下の結論を得た.1.側面頭部X線規格写真の計測では, 側面顎顔面形態は顎機能正常者と顎関節症患者の間に有意差は見られなかった.2.歯列全体の咬合力は顎機能正常者では768.8±525.8N, 顎関節症患者では438.1±380.1N, 咬合接触面積は顎機能正常者では12.9±11.9mm2, 顎関節症患者では6.4±2.8mm2, 平均咬合圧は顎機能正常者59.8±13.4kg/mm2, 顎関節症患者68.9±9.Okg/mm2で両群間に有意差を示した.3.各歯の咬合力, 咬合接触面積, 平均咬合圧は後方歯にいくにしたがい増加した.臼歯部では咬合力, 咬合接触面積, 平均咬合圧に顎機能正常者と顎関節症患者で有意差を示した.4.側面顎顔面形態と咬合力は歯列全体ではMandibular plane angle, Gonial angleと負の相関, L1 tomandibular plane angleと正の相関を示し, 臼歯部ではMandibular plane angle, Gonial angle, Occlusal planetoFHと負の相関, LI to mandibular plane angle, U1-SNと正の相関を示し, 小臼歯部ではMandibular planeangle, Gonialangleと負の相関を示した.5.顎関節症患者では咬合力と側面顎顔面形態は相関を示さなかった.以上から, 顎機能正常者では咬合力と側面顎顔面形態が関連し, 顎機能異常者では咬合力と側面顎顔面形態が関連しないことが示された.

EMG Analysis of Masseter and Temporal Muscles in Patients with skeletal Class III

Abstract: The aim of this study was to elucidate the relationship between the craniofacialmorphology and the activity of the masticatory muscles.The samples for this study consisted of 5 patients with mandibular protrusion (skeletal Class III group) and 5 control subjects with normal occlusion (normal group).Electromyographic activities in the masseter and anterior part of temporal muscles were recorded using bi-polar surface electrodes when subjects were instructed to bite in the intercuspal position (ICP) at several levels of bite force.We evaluated the relationship between total. amount of activity on bilateral masseter and temporal muscles and the activity of each muscle, using normalized value relative to maximum voluntary clenching (MVC).Simple linear regression analysis was performed in each subject. The results were as follows:In normal group, slopesof regression line of the masseter muscle were gentler than those of the temporal muscle, while in skeletal Class III group, slopes of regression line of the masseter muscle were steeper than those of the temporal muscle.Therefore, innormal occlusion, the masseter muscle might predominantly be working as a majorpower generator at any clenching level.In contrast, in skeletal Class III group, the temporal muscle appeared to be predominant compared with the masseter muscle in its activity at any clenching level. Further, at high clenching level, the temporal muscle is possibly working as a major power generator, and working as apower generator as well as a jaw positioner at low clenching level.

Change in maximum occlusal force in association with maxillofacial growth

Abstract: Structured Abstract Authors – Usui T, Uematsu S, Kanegae H, Morimoto T, Kurihara S Objective – To clarify the correlation between variations in maximum occlusal force and the maxillofacial skeletal pattern in subjects with malocclusion using a compact device. Design – Three hundred and fifty patients (150 males 200 females) with malocclusion were included. The male and female subjects were divided into five groups each based on chronological age. The maximum occlusal force was measured with a simplified occlusal force meter. The maxillofacial skeletal pattern was analyzed with lateral cephalograms. On the basis of these data, we studied the correlation between the maximum occlusal force and the maxillofacial skeletal pattern in each age group. Results – The maximum occlusal force tended to increase with age, with a tendency to be greater in male than in female subjects. In the male subjects, up to their 20s, the maximum occlusal force continued to increase, while in the female subjects its increase almost terminated in the later teens. In some of the age groups, the maximum occlusal force showed a negative correlation with the mandibular plane angle. Conclusions – Maximum occlusal force tended to increase with age. There was a gender difference in the maximum occlusal force at all age groups, values being larger in the males. In the males, the maximum occlusal force continued to increase until their 20s, while in the females, this increase almost terminated at the age of 17.

Category of functional tooth units in relation to the number of teeth and masticatory ability in Japanese adults.

Abstract: The purposes of this study were (1) to examine differences in dental status among various age groups, particularly, focusing on whether subjects retained 20 or more natural teeth, and (2) to investigate the relationship among dental status, the number and categories of functional tooth units (FTUs), and masticatory ability. A dental examination and self-administered questionnaire were conducted in a total of 2,164 residents aged 40 to 75 years who dwelt in Japan. The percentage of subjects with 20 and more natural teeth and their number of posterior teeth decreased with age. There was not much difference in the mean number of FTUs in subjects with and without 20 or more natural teeth, but those with 20 natural teeth had fewer numbers of FTUs than those with more than 20 natural teeth. The categories of the FTUs were extremely different. Subjects with 20 or more natural teeth had FTUs consisting mostly of natural to natural teeth. Subjects with 19 or fewer natural teeth had many FTUs consisting of removable prosthetic teeth. The subjective chewing ability test was significantly correlated with the number of natural teeth. Subjects could chew the higher number of test foods as the number of natural teeth increased. Not only the number of natural teeth but the categories of FTUs appear to be key factors of chewing ability. It is important to keep as many natural teeth as possible so that the person’s categories of FTUs are mainly composed of natural to natural teeth to maintain better oral function.

Functional-rhythmical coupling of head and mandibular movements.

Abstract: It is known that small head movements accompany the movements of the jaw during mastication; however, it is unknown whether these movements occur rhythmically and synchronously. The objective of this study was to determine whether there exists a functional coupling between the head and mandibular movements. Four healthy male adults (mean age 25.5) with normal occlusion and without TMD history were selected as subjects. Using the Trimet system, we measured tridimensionally both the movement of the head and the mandible by tracking upper and lower incisal points, respectively, during tapping movements with different opening range and frequency, then analysed the vertical component of these movements. The upper incisal point moved in opposite direction to the mandible in all tapping strokes in all subjects, during opening the head moved in a cranial direction and during closing in a caudal direction; the incidence rate for this concomitant movement was 98%, implying that the head moves periodically and rhythmically, as the mandible does. The cycle time of these coincident movements showed a correlation coefficient of 0.94. Moreover, the vertical range of head movement was within 10% of the jaw's movement. From these results we concluded that, at least during teeth tapping, the head moves in rhythmical coordination with mandibular movement.