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*

To investigate the role of p38MAPK signal pathway in spinal cord and dorsal root ganglion (DRG) in rats with phantom limb pain and the effects of specific inhibitors.
 Methods: Healthy adult male SD rats (n=48) were cut off one side of the sciatic under anesthesia to establish a model of phantom limb pain. In addition, the healthy rats were taken as a sham group (group S, n=24). The animals were scored by observing the action of chewing (0=no chewing, 13=the worst chewing) after the operation and were sacrificed on the following day after the operation. The successful model of phantom limb pain were randomly divided into 2 groups: a phantom limb pain group (group P, n=24) and a phantom limb pain plus inhibitor group (group P+I, n=24). SB203580 was given to the rat at 0.8 mg/kg on every Monday until the rats were sacrificed, the rest of the rats received an equal amount of saline. Eight rats from each group were randomly taken for the determination of levels of P-p38MAPK in spinal cord and DRG before administration and on the 4th, 6th, 8th weekend following the administration, respectively.
 Results: In the sham group, no animal developed chewing. Meanwhile, rats in successful model of phantom limb pain group began chewing from the 2nd day after operation with scores at eight to eleven. The chewing scores in the P+I group were reduced after the treatment. Compared with group S, P-p38MAPK levels were elevated in groups of P and P+I (P<0.05 or P<0.01). Compared with group P, P-p38MAPK level was decreased in the group P+I (P<0.05 or P<0.01).
 Conclusion: P38MAPK signal pathway involves in the development of phantom limb pain.
Animals ; Disease Models, Animal ; Enzyme Inhibitors ; pharmacology ; Ganglia, Spinal ; enzymology ; Imidazoles ; pharmacology ; Male ; Mastication ; physiology ; Phantom Limb ; enzymology ; etiology ; physiopathology ; Pyridines ; pharmacology ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Sciatic Nerve ; injuries ; Self Mutilation ; enzymology ; physiopathology ; Signal Transduction ; Spinal Cord ; enzymology ; p38 Mitogen-Activated Protein Kinases ; antagonists & inhibitors ; metabolism

BACKGROUNDThe pain caused by orthodontic treatment has been considered as tough problems in orthodontic practice. Danggui-shaoyao-san (DSS) is a traditional Chinese medicine (TCM) prescription which has long been used for pain treatment and possesses antioxidative, cognitive enhancing and antidepressant effects. We raise the hypothesis that DSS exerts analgesic effect for orthodontic pain via inhibiting the activations of neuron and microglia.

METHODSDSS was given twice a day from day 5 prior to experimental tooth movement (ETM). Directed face grooming and vacuous chewing movements (VCM) were evaluated. Immunofluorescent histochemistry and Western blot analysis were used to quantify the Iba-1 (microglia activation) and Fos (neuronal activation) expression levels in the trigeminal spinal nucleus caudalis (Vc).

RESULTSETM significantly increased directed face grooming and VCM which reached the peak at post-operative day (POD) 1 and gradually decreased to the baseline at POD 7. However, a drastic peak increase of Fos expression in Vc was observed at 4 hours and gradually decreased to baseline at POD 7; while the increased Iba-1 level reached the peak at POD 1 and gradually decreased to baseline at POD 7. Furthermore, pre-treatment with DSS significantly attenuated the ETM induced directed face grooming and VCM as well as the Fos and Iba-1 levels at POD 1.

CONCLUSIONTreatment with DSS had significant analgesic effects on ETM-induced pain, which was accompanied with inhibition of both neuronal and microglial activation.

Animals ; Drugs, Chinese Herbal ; therapeutic use ; Face ; physiology ; Male ; Mastication ; physiology ; Medicine, Chinese Traditional ; methods ; Microglia ; drug effects ; physiology ; Neurons ; drug effects ; physiology ; Pain ; drug therapy ; Pain Management ; methods ; Postoperative Period ; Rats ; Rats, Sprague-Dawley ; Tooth Movement Techniques ; adverse effects

AIMThe aim of this survey was to compare Chinese natives and foreign inhabitants in Chengdu, China, with respect to: (1) attitudes towards dental appearance, (2) subjective orthodontic treatment need, and (3) the main factors influencing orthodontic treatment need.

METHODOLOGYA total of 522 subjects, including 227 foreign inhabitants and 295 Chinese natives in Chengdu participated in the survey. A simple random sampling method was adopted and a face-to-face interview was conducted at some public sites using a questionnaire. Data was entered by two persons synchronously using Epidata 3.0, and SPSS 13.0 was used to analyze these data.

RESULTS89.0% of foreign inhabitants were satisfied with their teeth compared to only 46.8% of Chinese natives. Females were more dissatisfied with their teeth than males. Chinese natives put improving appearance as the top priority (55.9%) for seeking orthodontic treatment; however, in foreign inhabitants, the main reason for seeking treatment was to improve masticatory function (44.1%), followed by "to be pretty" (35.2%). The importance of well-aligned teeth and self-perception of psychosocial impact of malocclusion were the same two main factors influencing subjective orthodontic treatment need (P < 0.05) in foreign inhabitants and Chinese natives. Subjective orthodontic treatment need between the two target groups was significantly different (P < 0.05).

CONCLUSION(1) It was very common that Chinese natives were dissatisfied with their dental appearance, and their subjective orthodontic treatment needs were high. (2) There were some differences in orthodontic treatment motives between the two target groups. (3) There were differences in subjective orthodontic treatment needs between foreign inhabitants and Chinese natives. However, the prominent influential factors were almost the same. There may be benefit to understanding subjective orthodontic needs of different races.

Adolescent ; Adult ; Asian Continental Ancestry Group ; psychology ; Attitude to Health ; ethnology ; China ; Culture ; Emigrants and Immigrants ; psychology ; Esthetics, Dental ; Female ; Humans ; Interpersonal Relations ; Male ; Malocclusion ; psychology ; Mastication ; physiology ; Middle Aged ; Motivation ; Needs Assessment ; Orthodontics, Corrective ; psychology ; Patient Acceptance of Health Care ; Personal Satisfaction ; Self Concept ; Sex Factors ; Young Adult

OBJECTIVETo investigate the changes in cerebral blood flow in patients with maxillary defect treated with prosthesis insertion.

METHODSThirty patients with maxillary defect receiving obturator prosthesis insertion were enrolled with another 30 subjects without dentition defect as the control. The cerebral blood flow rate was recorded before and at 5 and 10 min during mastication, and the results were analyzed statistically.

RESULTSThere was no significant difference in Vs, Vd or Vm between the two groups at the time points for measurement.

CONCLUSIONThe blood supply by the middle cerebral artery is similar between the patients receiving obturator prosthesis insertion for maxillary defect and the subjects with full denture.

Adult ; Aged ; Case-Control Studies ; Cerebrovascular Circulation ; Denture, Complete ; Female ; Humans ; Male ; Mastication ; physiology ; Maxilla ; injuries ; Maxillofacial Prosthesis ; Middle Aged ; Middle Cerebral Artery

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

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 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

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