Brain ; physiology ; Humans ; Magnetic Resonance Imaging ; Mastication ; physiology

Chewing-side preference is one of the risk factors for temporomandibular disorders (TMD), and people with chewing-side preference is more prone to have short and displaced condyles, increased articular eminence inclination and glenoid fossa depth. The proportion of TMD patients with chewing-side preference is often higher than that of the normal subjects. Clinical studies have shown a strong correlation between chewing-side preference and TMD symptoms and signs; and animal studies have shown that chewing-side preference can affect the growth, development, damage and repair of the mandible. After long-term unilateral mastication, changes in the stress within the joint cause the imbalance of temporomandibular joint (TMJ) structural reconstruction, the transformation and even destruction of the fiber structure of masticatory muscle, resulting in uncoordinated movement of bilateral muscles. The joint neurogenic diseases caused by the increase of neuropeptide substance P and calcitonin-gene-related-peptide (CGRP) released locally by TMJ may be the mechanism of TMD. This article reviews the research progress of the influence of chewing-side preference on the structure of TMJ, the relationship between chewing-side preference and TMD, and the related mechanisms.
Humans ; Mastication/physiology* ; Temporomandibular Joint/physiology* ; Temporomandibular Joint Disorders/etiology* ; Mandible/physiology*

OBJECTIVETo observe neuronal activities related to right-sided mastication in cortex and to explore the effect of mastication on brain function.

METHODSNeuronal activities related to right-sided mastication were detected with functional magnetic resonance imaging in 10 healthy volunteers. Image data was analyzed by SPM99 software with the use of t test.

RESULTSLocalization of activation in brain was different among subjects. Brain activation during mastication included left basal ganglion, Broca's area, angular gyrus and right supramarginal gyrus.

CONCLUSIONSThe functional areas related to right-sided mastication and speech were closely connected, which indicated close relationship between mastication and speech. The central control of mastication might share part of common neural mechanism with that of speech. The roles of activated brain regions in mastication still remained to be elucidated.

Adult ; Brain ; physiology ; Female ; Humans ; Magnetic Resonance Imaging ; Male ; Mastication ; physiology

OBJECTIVETo investigate the activities of head, neck and upper trunk muscles with mandibular movement in normal adults.

METHODSThe integral data of surface electromyography (EMG) had been recorded to analyze the activities of anterior temporal (Ta), posterior temporal (Tp), sternocleidomastoid (SCM) and trapezius (TRAP) muscles with mandibular movement in ten normal adults.

RESULTSThe former mentioned muscles acted constantly when the mandible was in the rest position. The activities of Ta, Tp and SCM muscles increased with protrusion of mandible, mouth opening, tapping, maximum clenching, and chewing movements. The amplitudes of the increased activity of these muscles were correlated significantly with each other. When the activities of Ta and Tp muscles increased to 56 times and 25 times respectively, the activity of SCM muscle increased to 5 - 6 times. The activity of trapezius muscle increased with protrusion of mandible and opening movement, but tended to stop with the maximum clenching and chewing movement. The correlations of left and right sides of the same muscles had been found.

CONCLUSIONSThe muscles of head, neck and upper trunk can act as contributors to keep the mandibular positions and take part in the mandibular movements.

Adult ; Electromyography ; Female ; Head Movements ; physiology ; Humans ; Male ; Mandible ; physiology ; Mastication ; physiology ; Movement ; Muscle, Skeletal ; physiology ; Neck Muscles ; physiology ; Range of Motion, Articular ; Shoulder ; physiology ; Temporomandibular Joint ; physiology

OBJECTIVETo calculate the delay times and embedding dimensions of surface electromyogragh (sEMG) signal of the masseter and temporal muscle during clenching at intercuspal position (ICP), and to reconstruct the space phase of sEMG signal with method of nonlinear dynamics.

METHODSTen male and 10 female young volunteers with normal masticatory system were included in the study, the signals of surface sEMG of bilateral masseter and temporal muscles in the position of ICP were collected, and the delay times and embedding dimensions of the sEMG signals were calculated using C-C method, the space phase of the sEMG signals was reconstructed.

RESULTSA program of nonlinear dynamic analysis of mastication muscles sEMG signals was developed base on the platform of Matlab. The signals of the sEMG of the masseters and temporals were analyzed with nonlinear dynamic methods, the delay times and embedding dimensions of each muscles sEMG signals were obtained, and the space phase of each sEMG signals were reconstructed. The graphs of the space phase indicated the typical characteristic of chaotic attractor.

CONCLUSIONSThe signals of the masseter and temporal muscles of surface sEMG during clenching at ICP of normal masticatory system show the typical characters of chaos, the methods of nonlinear dynamics are effective to analyze the sEMG signals of mastication system.

Adult ; Bite Force ; Electromyography ; Female ; Humans ; Male ; Masseter Muscle ; physiology ; Mastication ; physiology ; Nonlinear Dynamics ; Temporal Muscle ; physiology ; Young Adult

OBJECTIVEThe purpose of this study was to evaluate the changes of masticatory performance of the cases wearing dentures and relative factors.

METHODSThe changes of masticatory performance of the cases wearing dentures were studied before and after wearing by using the light absorption method and peanuts as test food.

RESULTSThe mastication performance of the experimental groups was predominantly lower than that of the control groups. The masticatory performance was gradually improved with wearing denture period increasing. Factors relating to the masticatory performance were age, number of occlusal units lost and the kind of denture, and the number of chewing etc.

CONCLUSIONThe mastication performance of the experimental groups was dominantly lower than that of the control groups, but gradually improved with wearing denture period increasing. Varied factors affect the masticatory performance of experimental groups.

Adult ; Denture, Partial, Removable ; Female ; Humans ; Male ; Mastication ; physiology ; Middle Aged ; Tooth Loss ; complications ; physiopathology

OBJECTIVETo investigate the influence of mandibular curved osteotomy on masticatory function by analyzing the bite force before and after operation.

METHODSFrom Jan. to Oct. 2008, 20 female cases underwent mandibular curved osteotomy. The maximal bite force in incisor area, bilateral premolar area and molar area was measured before operation and 6 months after operation.

RESULTSThe maximal bite force in incisor area, right premolar area, left premolar area, right molar area, left molar area was (11.7 +/- 3.9) kg, (23.2 +/- 1.6) kg, (30.9 +/- 2.3) kg, (35.6 +/- 4.2) kg, (38.5 +/- 3.1) kg, respectively before operation; and was (11.9 +/- 2.1) kg, (23.0 +/- 4.5) kg (31.0 +/- 1.8) kg,(35.9 +/- 3. 5) kg. (38.5 +/- 2.7) kg, respectively 6 months after operation. The postoperative maximal bite force reached the preoperative level, and even slightly above it. There was no significant difference between the measured data before operation and 6 months afterward (P > 0.05).

CONCLUSIONSThe curved osteotomy of prominent mandibular angle has no long-term effect on masticatory function.

Adolescent ; Adult ; Bite Force ; Female ; Humans ; Mandible ; surgery ; Mastication ; physiology ; Osteotomy ; methods ; Young Adult

OBJECTIVETo explore effects of chewing-side preference (CSP) on cerebral cortical response during clenching task with functional magnetic resonance imaging (fMRI).

METHODSSeven patients with left CSP and 7 patients with right CSP were selected to perform the maximum voluntary clenching in intercuspal position, and block designed blood oxygenation level-dependent (BOLD) fMRI scan covering the whole brain was carried out.

RESULTSThere was activation in the parahippocampal gyrus in the four patients among seven with left CSP. But there was no activation in the parahippocampal gyrus among the patients with right CSP.

CONCLUSIONSThis research shows that the parahippocampal gyrus, which is associated with human memory and study, is activated during clenching task in the patients with left CSP.

Adult ; Bite Force ; Female ; Functional Laterality ; physiology ; Humans ; Magnetic Resonance Imaging ; Male ; Mastication ; physiology ; Memory ; physiology ; Parahippocampal Gyrus ; physiology ; Young Adult

OBJECTIVETo investigate the characteristics of and relationship between occlusal plane and masticatory path in young adults with individual normal occlusion, and to provide clinical implications on both morphological and functional reference of occlusal plane location.

METHODSForty-three young adults with individual normal occlusion were included. Lateral projections of cephalometric radiographs were taken. The parameters of anatomical landmarks were analyzed. The BioEGN mandibular kinesiography analyzer was used to record the path of incisal edge of mandibular central incisor movement during mastication. The Pearson's linear correlation analysis was performed to analyze the relationship of inclination of occlusal plane and data mentioned above with SPSS13.0 software.

RESULTSThe inclination of occlusal plane (the angle between occlusal plane and Camper's line OP-CP) was (2.1 ± 3.8)° in youth with normal occlusion. Means of maximal distances of 3-dimensional masticatory mandibular movement paths were as follow: the vertical length was (20.22 ± 4.28) mm, the anterior-posterior width was (11.42 ± 2.45) mm, and the lateral width was (8.62 ± 1.52) mm. The inclination of occlusal plane was negatively correlated to the lateral width of masticatory path in frontal plane (r = -0.39, P < 0.05). Occlusal plane was approximately vertical to the opening and closing path in the vicinity of intercuspal position during mastication. The inclination of occlusal plane was positively related to occlusal plane-closing angles in the upper segments of closing path during mastication (P < 0.05). Masticatory axis angle was (66.50 ± 7.98)° with no significant correlation to the inclination of occlusal plane (P > 0.05).

CONCLUSIONSThese results suggest that the sagittal inclination of occlusal plane can influence 3-dimensional morphology of masticatory path.The inclination of occlusal plane has a guiding effect on masticatory movement in the upper segments of closing path.

Adult ; Cephalometry ; Dental Occlusion ; Female ; Humans ; Incisor ; anatomy & histology ; physiology ; Jaw Relation Record ; Male ; Mandible ; anatomy & histology ; physiology ; Mastication ; physiology ; Movement ; Young Adult

OBJECTIVETo evaluate masticatory performance and life quality of children with ectodermal dysplasia (ED) after prosthetic rehabilitation.

METHODSSix children with ED received denture restoration and 18 healthy children were involved in this study. The surface electromyography (EMG) of masseter (MM) and anterior temporalis (TA) during clenching and chewing movement were recorded. The EMG amplitude, area, asymmetry index of total and activity index of MM/TA were compared at each stage. The masticatory efficiency was measured with spectrophotometer. The life quality was assessed using visual analogue scale questionnaire.

RESULTSThe EMG amplitude of MM and TA during chewing in ED Group were 41.7% and 45.6% of the control group respectively, the area were 35.9% and 36.0% respectively. Significant difference in asymmetry index of total during clenching was observed between the two groups (P < 0.05) but not during chewing (P > 0.05). The differences of activity index of MM/TA during clenching and chewing between the two groups were not detected (P > 0.05). The masticatory efficiency of ED group was 67.2% of the control group. The score of chewing function in children with ED after prosthetic rehabilitation was three times higher than before, and no difference was present between the two groups (P > 0.05).

CONCLUSIONSEarly prosthetic rehabilitation can significantly improve the masticatory performance and life quality of children with ED.

Case-Control Studies ; Child ; Dental Prosthesis ; Ectodermal Dysplasia ; physiopathology ; rehabilitation ; Electromyography ; Humans ; Masseter Muscle ; physiology ; Mastication ; physiology ; Quality of Life ; Temporal Muscle ; physiology