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 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

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 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

Colorimetry ; Coloring Agents ; Evaluation Studies as Topic ; Filtration ; methods ; Food ; Humans ; Image Interpretation, Computer-Assisted ; Mastication ; physiology ; Particle Size ; Time Factors

OBJECTIVETo compare the masticatory efficiency and the character of mandibular movement trace of the patients with complete denture (CD), complete overdenture (COD) and implant-supported overdenture (IOD).

METHODSA total of 42 subjects were rehabilitated with CD, COD and IOD respectively and wore the dentures at least half a year. Each study group was composed of 14 subjects. The masticatory function of patients were investigated by means of masticatory efficiency and mandibular movement trace. The characters of mandibular movement trace were evaluated from four aspects: the regulation of chewing cycle, centralization of end traces, the type of the contact slides and the type of the trace on the frontal plane.

RESULTSThe average chewing efficiency of almond and jujube in the IOD patients was higher than that in the CD group (P < 0.01), and the chewing efficiency of almond in COD group was higher than that in the CD group (P < 0.01). In the IOD group, there were more patients with regular chewing cycle (P < 0.05) and centralized end traces (P < 0.01) in mandibular movement than those in the CD group and COD group.

CONCLUSIONSIOD and COD benefit the fully or partially edentulous patients with a relatively good masticatory function. The patients with IOD have more regular mandibular movement than those with CD.

Adult ; Aged ; Aged, 80 and over ; Dental Prosthesis, Implant-Supported ; Denture, Complete ; Denture, Overlay ; Female ; Humans ; Male ; Mandible ; physiology ; Mastication ; physiology ; Middle Aged

OBJECTIVEThe purpose of the present study was to investigate effects of developmental lateral jaw deformity (DLJD) on masticatory movement.

METHODSThree coordinates of mandibular movement signals were recorded in 35 young healthy adults with normal occlusion and 28 patients with DLJD by means of a Sirognathography System during gum chewing movement. Paired and unpaired t-tests were used to compare significant difference of intra-group and inter-groups in displacement and speed. P < 0.05 was chosen as significance level.

RESULTS(1) The rhythm and directional sequence of chewing trajectory in both frontal and sagittal planes were normal in control group, while anomalies of rhythm and distribution (n = 9) and reversed sequencing (n = 7) were found in DLJD group. (2) The maximum magnitude of jaw retrusion and average speed were significant higher in DLJD group than those in control group (P < 0.01). The spatial displacement and average speed in horizontal plane and in chewing phase were also higher in DLJD group compared with control group (P < 0.05).

CONCLUSIONSDLJD patients showed anomalies in chewing pattern as well as chewing speed and displacement in horizontal plane.

Adult ; Case-Control Studies ; Dentition, Permanent ; Female ; Humans ; Jaw Abnormalities ; physiopathology ; Jaw Relation Record ; Male ; Mandible ; physiology ; Mastication ; physiology ; Young Adult