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At least 1,153 records · Page 64Linked to original sources
PubMed1999

Proximal segment position after distraction with the MD-DOS device.

We investigated cephalometrically the movement of the proximal segment in the sagittal plane in patients treated with distraction (MD-DOS device) for mandibular lengthening. The proximal segment was anteriorly rotated, whilst the distal segment was posteriorly rotated after the lengthening procedure. Thus the angle of the jaw was advanced half the distance of the advancement of the distal segment. One possible reason for the anterior rotation of 3.3 degrees on average is the repositioning of the proximal segment during application of the anterior fixation unit in the cases where mobilization was complete. Another more plausible reason is the anterior pull by the masticatory muscles and elastic bands being greater than the reactive distraction vector component in concert with a flexible telescopic distraction module and a single posterior screw anchorage. The positional movements of both distal and proximal segments were similar to those observed after mandibular advancement with bilateral sagittal split osteotomies.

Adolescent↗
PubMed1996

Temporomandibular disorders in the adult population of Okayama City, Japan.

In order to discover the prevalence of signs and symptoms of temporomandibular disorders (TMD) in Japan, and the difference in the prevalence among various sex and age groups in the Japanese population, 672 individuals (304 males and 368 females, age range 20-92 years) were selected randomly in Okayama City, Japan, and were investigated by means of questionnaires and clinical examinations. The reported frequency of symptoms was: TMJ sounds 24%, facial-TMJ-jaw pain 11%, headache 27%, teeth clenching 30%, and grinding 34%. The percent frequency of the following signs was: impaired mouth opening 5%, clicking 46%, reciprocal clicking 20%, crepitus 19%, TMJ tenderness 6%, and masticatory muscle tenderness 21%. The subjects with TMJ clicking were more frequently females than males. TMD signs and symptoms were found to be common in all age groups, but they were fewer in the older than in the younger age group. The younger-aged subjects with clicking appeared with significant frequency, whereas crepitus was populated with significant frequency by the oldest age group.

Adult↗
PubMedDate not supplied

[Specifics of mastication with complete dentures].

INTRODUCTION: Mastication is a process characterized by alternating phases of physiological inactivity, food intake, initial food crumbling, mouthful formation and deglutition. Although there is a so called human type of mastication, this process is individual for variety of reasons. Mastication is not an innate characteristic and it must be learned, but once it is learned, it gets a reflexive function, demanding maximal involvement of the highest nervous system centers. DISCUSSION: Specificities of mastication in complete denture wearers are caused by specificities connected to changes of the oral cavity due to teeth loss, technical features of complete dentures and quality of their manufacture. Loss of teeth causes loss of periodontal receptors consequently damaging the source of information which, as long as teeth are present, travels from the oral cavity towards the central nervous system and regulates the masticatory muscles activity. As one of the consequences of periodontal receptors' loss, interocclusal perception decreases, because the number of receptors within the masticatory mucosa is negligible. Another problem is that loss of teeth causes loss of the occlusal surface. Occlusal surface is considered to be the only reference coordinate of the zero intermaxillary separation with precise spatial representation within the someostatic field cortex. Permanent loss of antagonistic contact causes disappearance of the memory pattern of the occlusal surface. Therefore completely edentulous mouths are characterized by disintegration of the free interocclusal space. Masticatory forces' value directly depends on the: size of muscles creating the forces, their position in the mandibula, shape of the edentulous alveolar ridge, type of chewing, the relationship between the height of the branch, length of the mandibular body, gonial angle, mandibular angle in relation to the anterior cranial base and posterior facial height and the degree of intermaxillary separation. Bite forces in complete denture wearers are significantly decreased in relation to persons with natural teeth. There is a fundamental difference in the distribution of the functional energy in complete denture wearers and subjects with intact teeth. Persons with natural teeth tend to generate energy through bolus, whereas in complete denture wearers most of the chewing energy is distributed outside bolus, directly through the denture base on the supporting tissues. RESULTS: As the result of this specific dynamics stress of supporting tissues often occurs with consequential mucosal inflammation and rapid alveolar bone resorption. Reduction of masticatory efficacy in denture wearers may be caused by irregular activity of masticatory musculature or is the consequence of irregular flow of energy during mastication. In comparison with young examinees with healthy teeth, authors have registered that complete denture wearers need about seven times more masticatory movements to achieve equal number of sample parts. CONCLUSION: It has been documented by experience and also scientifically proved, that the satisfaction of complete denture wearers is not often proportional with objective functional denture values. Comparison of subjective parameters with objective test results reveals that the percentage of complete denture wearers who consider their dentures to be good, although they objectively are not such, is significantly higher than the percentage of those who complain about their dentures, although they are functionally proper. Our study comprised patients (average age of 69) who wore complete dentures longer than five years.

Denture, Complete↗
PubMed2002

Sagittal occlusal relationships and asymmetry in prematurely born children.

The aim of this investigation was to examine the effect of pre-term birth on sagittal occlusal relationships. The subjects were 328 prematurely born white and black children and 1804 control children who participated in the cross-sectional study of the Collaborative Perinatal Project (USA) in the early 1960s and 1970s. Dental examinations, including dental casts and photographs, were performed at the age of 6-12 years. The sagittal occlusion of the permanent molars and the canine relationship was recorded by examining and measuring the hard stone casts. The pre-term and comparison groups were divided by sex and race. A significantly greater prevalence of pre-normal canine relationships was found in the pre-term group than in the controls (P < 0.001). The incidence of a bilateral symmetrical canine relationship was 60.3 per cent in both the pre-term and control groups, but in the pre-term group the girls had better symmetry than the boys. Asymmetry occurred significantly more often on the left side (P < 0.001), especially in the control boys, but this was not so clear in the pre-term group. The prevalence of mesial molar occlusion was greater in the pre-term group. These results suggest that premature birth and the consequent exceptional adaptation from intra- to extra-uterine nutrition may influence dental occlusal development. This emphasizes the importance of early functional activity and differences in masticatory muscle activity and the largely unknown phenomenon of early catch-up growth. Individual differences in neonatal factors, in the need for intubation and other medical care are also of importance. Pre-term birth may also interfere with the development of symmetry and lateralization.

Black People↗
PubMed1999

Regeneration ad integrum of the condyle head in a patient with temporomandibular disorders.

A 14-year-old who had suffered from a beta-hemolytic streptococcus infection presented with serious temporomandibular disorders, including a reabsorption of the condyle head on the right side, and reabsorption in the cavern of the left side. Her masticatory muscles were electronically deprogramed, achieving a mandibular position supported by a relaxed musculature. The patient's signs and symptoms subsequently disappeared. Study of the magnetic resonance image a year later clearly showed a regeneration ad integrum of the condyle head and a spontaneous reinsertion of the articular disk. The results suggest the need for use of electronic elements in order to treat patients with temporomandibular disorders effectively.

Adolescent↗
PubMed2001

Oral motor parafunctions among heavy drug addicts and their effects on signs and symptoms of temporomandibular disorders.

AIMS: To investigate the prevalence of temporomandibular disorders (TMD), bruxism, and other oral habits among drug addicts compared to a normal, non-addicted, matched control population, and to assess the detrimental effect of long-term drug abuse on the parameters studied. METHODS: Subjects included 55 drug-addicted patients (51 males and 4 females) randomly selected from long-term addicts using "hard" narcotics and attending a methadone maintenance center and a control group of 52 normal non-addicted individuals (48 males and 4 females) matched to the addicts for age, gender, and socioeconomic status. A clinical examination and a questionnaire were used. One examiner determined that all questions were correctly understood and answered, and a second examiner performed the clinical examinations and was unaware of the results of the questionnaire. RESULTS: The addicted group had a high prevalence of orofacial motor behavior (bruxing, clenching) as well as signs and symptoms of TMD (morning headache, joint noises, joint and masticatory muscle tenderness to palpation, and tooth wear) compared to the controls. Active (voluntary) jaw opening was significantly smaller, although within an acceptable range when compared to the controls. CONCLUSION: Long-term drug abuse detrimentally affects the stomatognathic system, as expressed in a high prevalence of oral motor behavior and signs and symptoms of TMD.

Adolescent↗
PubMed1983

Intra- and interobserver variability in the assessment of signs of disorder in the stomatognathic system.

The observer variability in the assessment of signs of disorder in the stomatognathic system within a 3-hour period was investigated in 19 subjects. The clinical examination comprised measurement of maximal mouth opening capacity, sagittal distance between the retruded position (RP) and the intercuspal position (IP), vertical overbite, horizontal overjet and palpation for tenderness of masticatory muscles. The clinical dysfunction score and index (Helkimo 1974) were also calculated. The observer variability in the measurement of maximal mouth opening was quite low, while the relative variability in the measurement of the sagittal distance between RP and IP was high. The intra-observer variability of the nonparametric variables clinical dysfunction score and clinical dysfunction index was within accept able limits, while the interobserver variability was unacceptably high for all the non-parametric variables.

Adult↗
PubMed2001

A three-dimensional mathematical model of temporomandibular joint loading.

OBJECTIVE: A mathematical model of the temporomandibular joint was developed to study the magnitude and direction of the compressive loading experienced at the temporomandibular joint during clenching. DESIGN: The model was based on the principles of static equilibrium in three dimensions. BACKGROUND: Direct measurement of temporomandibular joint loading in humans is extremely difficult. Animal models have provided an alternative in the past. However, evidence suggests that primates are not the most accurate human analogues for temporomandibular joint studies. A mathematical model was used as an alternative to direct measurement. METHODS: The EMG activity of two masticatory muscles was combined with their cross-sectional areas to calculate the force exerted by each muscle. Experimentally determined forces were implemented into a quadratic programming model to solve for the compressive forces on the joint. Two objective functions were chosen and their ability to predict muscle and joint forces was evaluated. RESULTS: The maximum bite forces for normal men, normal women, and women with temporomandibular joint disorders were 300 N (SD 102 N), 210 N (SD 57.7 N), and 120 N (SD 77.1 N), respectively. The calculated joint force for normal males was 260 N (SD 84.1 N). Normal females and female temporomandibular joint disorder patients produced temporomandibular joint forces of 172 N (SD 37.5 N) and 152 N (SD 44.2 N), respectively.

Electromyography↗
PubMed2003

Masticator myopathy.

A 31-year-old woman developed low-grade fever and pain and swelling of the masticatory muscles. A T2-weighted magnetic resonance image showed high signal intensity in these muscles. Coxsackie B3 and echo 30 viruses were detected from a nasopharyngeal swab and feces, respectively. The clinical symptoms accompanied a marked decline in the serum immunoglobulin G level with progressive eosinophilia. Her symptoms disappeared by 8 weeks after onset. She was diagnosed as having masticator myopathy, which has rarely been reported in humans. The present case suggests that masticator myopathy is associated with coxsackie or echo virus infection.

Adult↗
PubMed2003

Evidence that experimentally induced sleep bruxism is a consequence of transient arousal.

Spontaneous rhythmic masticatory muscle activity (RMMA) during sleep occurs more frequently following spontaneous transient micro-arousal in patients with sleep bruxism (SB) and normal controls. Here, we tested the hypothesis that an experimental arousal would be followed by an increase in RMMA. We identified RMMA on polygraphic recordings taken before and after sensory stimulation to induce experimental arousal in eight SB patients and eight matched normal subjects. The rate of experimental arousal and the level of resting electromyographic activity in masseter and suprahyoid muscles during sleep did not differ between the groups. In both, muscle tone and heart rate increased during the experimental arousal. Although post-arousal RMMA occurred in all SB patients, it was seen in only one normal subject. Moreover, tooth-grinding occurred during 71% of the evoked RMMA in SB patients. These results support the hypothesis that SB is an exaggerated form of oromotor activity associated with sleep micro-arousal.

Adult↗
PubMed1979

Correlations of electromyographic silent period duration and the Helkimo dysfunction index.

Fifty-eight patients seen for consultation concerning mandibular dysfunction symptoms were examined utilizing the Helkimo index of dysfunction and electromyographic silent period recordings from masticatory muscles. The data collected were analyzed for correlations between the two parameters. Several significant correlations were noted between certain variables of the dysfunction index and the duration of the silent period. The mean duration of the silent period increased with increasing dysfunction index value. However, the clinical significance of this correlation is not established as long as we do not know the validity of neither the dysfunction index nor the the EMG silent period duration.

Adult↗
PubMed1997

The natural course of anterior disc displacement without reduction in the temporomandibular joint: follow-up at 6, 12, and 18 months.

PURPOSE: The purpose of this study was to examine the natural course of anterior disc displacement without reduction in the temporomandibular joint (TMJ). PATIENTS AND METHODS: The subjects were patients who had been diagnosed as having anterior disc displacement without reduction in the TMJ, but who had not undergone any treatment. Forty-four patients were followed for 6 months, 38 for 12 months, and 22 for 18 months. Clinical signs and symptoms were evaluated at each follow-up, and the incidence of successful resolution was determined using the criteria established in 1984 by the American Association of Oral and Maxillofacial Surgeons. RESULTS: The range of motion increased at each time during the follow-up period. Tenderness in the TMJ and the masticatory muscles was alleviated, but the noise in the TMJ remained unchanged at each follow-up time. The incidence of successful resolution was 34.1% at 6 months, 50.0% at 12 months, and 68.2% at 18 months. CONCLUSIONS: The clinical signs and symptoms of anterior disc displacement without reduction tend to be alleviated during the natural course of the condition. This should be taken into consideration when anterior disc displacement without reduction is treated.

Adolescent↗
PubMed2001

Analysis of rhythmical jaw movements produced by taste stimulation in rats.

Taste stimulation of the mouth induces various oral movements. Sucrose or salt solution induces rhythmical jaw movements (RJM) or tongue protrusion as an ingestive behavior. Bitter taste induces a gaping or tongue retraction as an aversive behavior. There is no report that describes the precise pattern of jaw movements induced by taste stimulation. The purpose of the present study is to clarify the pattern of the taste-induced RJM with electromyographic activities of the masticatory muscles in the anesthetized rat. When water was injected into the mouth of the rat, an RJM was induced. In this type of RJM, the lower jaw swung right and left side in each open-close cycle alternately. The anterior digastric muscle was active in every opening phase, while activities of the jaw closing muscles were generally weak. The RJM induced by water was opening-dominant movements. Sucrose or salt solution induced a similar pattern of RJM to water-induced RJM. When acetic acid was injected, amplitude of the alternate lateral jaw movement was significantly larger than that in the water-induced RJM. The activity of the superficial temporalis muscle was large in those closing phases with ipsilateral side movement, while it was small in the closing phases with contralateral movement. The pattern of quinine-induced RJM was characterized by small lateral, large open-close and large antero-posterior movements. Tastes which are reported to induce ingestive behavior such as sweet or salty don't alter the pattern of RJM; however, the tastes which induce aversive behavior make the pattern of RJM different from the water-induced RJM.

Animals↗
PubMed1998

Stress distribution in the mandible with unilateral condylar fracture.

OBJECTIVE: The purpose of this study was to investigate the influence of unilateral condylar neck fracture upon the stress distribution in the mandible and the temporomandibular joint (TMJ) to realize primarily the biomechanical mechanism of the temporomandibular joint disorders (TMD) caused by TMJ injury. METHODS: The character of stress distribution in the mandible of a normal human and a patient with TMD induced by unilateral condylar neck fracture followed by malpositioned healing was analyzed quantitatively and compared during centric occlusion by combining spiral computed tomography scanning technology with the three-dimensional finite element method. RESULTS: The patient with unilateral condylar neck fracture followed by malpositioned healing had unbalanced stress distribution in the mandible, such as differing nature and value of stress. The stress in the fractured side was higher than in the nonfractured side, in which the condyle was more evident. The maximum principal stress and minimum principal stress of each region in the fractured mandible were much higher than those in a normal mandible. Stress quality also differed. CONCLUSIONS: The abnormal stress changes after unilateral condylar neck fracture with malpositioned healing may be related to the effect of condylar shape change on masticatory muscle function and occlusion. TMJ injury not only damaged the condylar structure, but also compromised its biomechanic environment. It is preliminarily thought that unbalanced stress distribution, evidently increased stress, and varied stress character are biomechanic mechanisms of TMD. Condylar dislocated fracture should be treated promptly and properly to maintain the proper prognostic stress distribution.

Adult↗
PubMed2005

Evaluation of stomatognathic function in orthodontic treatment.

AIM: To evaluate changes in stomatognathic function related to orthodontic treatment in 4 patients with various types of dysfunction of the stomatognathic system present prior to orthodontic treatment. METHODS: Four patients who visited the Orthodontic Clinic at Tokyo Medical and Dental University Hospital and whose active orthodontic treatment was complete were analyzed both morphologically and functionally. To analyze stomatognathic function, electromyographic activity of the masticatory muscles and mandibular movements was recorded. RESULTS: In all 4 patients, changes in stomatognathic function were observed following improvements in craniofacial structural and interocclusal relationships. Many of these changes consisted of elimination of functional disharmony, although the cause-effect relationship between these functional changes and orthodontic treatment is unclear. CONCLUSION: Functional analysis during orthodontic treatment can provide useful information concerning the relationship between craniofacial structures and stomatognathic function.

Adult↗
PubMed2001

[Imaging of oto-mandibular dysplasias].

The modern imaging opened a possibility of precise exploration of otomandibular dysplasias. The techniques of browsing by IRM and CT Scan and the software of image processing which is associated with these techniques (three-dimensional, superposition and removing of the anatomical structures) allow to carry out a true anatomical dissection of the whole of these malformative syndromes. The study of the skeletal anomalies gains by specifying the disorders of development of the various mandibular segments: temporomandibular joint, ramus and horizontal branch and also, all cranio-maxillar structures: orbital rim, cranial basis. Study of masticatory muscles shows an important damage correlated with skeletal troubles and performs a grading of morphological and functional gravity. This analytical study emphasizes some malformative axis: malar axis in cases of mandibulofacial dystosis, temporomandibular axis in hemifacial microsomia. Modern imaging can appreciate, by development of three-dimensional cephalometry, growth anomalies and quantification of post therapeutical results. At last usefulness of imaging appears in therapeutic modelisation and in the field of Computer-Aided Planning of surgical techniques of osteotomies and overall maxillaries distractions.

Ear↗
PubMed2003

Relation between stress and symptoms of craniomandibular disorders in adolescents.

The psychophysiologic theory proposes that stress can precipitate craniomandibular disorders (CMD) and that stress correlates more strongly to disorders of the masticatory muscles than to temporomandibular joint disorders. Empirical reports show only low correlations between emotional stress and CMD signs and symptoms, and that some of them might be spurious. In the present study this correlation was assessed in 417 adolescents from 11 to 16 years old. Data from the clinical examination were used to construct two indices: 1) The number of muscles sites tender to palpation, and 2) signs from the joint and restricted movement. Results show that global stress was only significantly correlated with the muscle index (r = .20), but not with the other index. Only the multiple regression analyses regarding muscle disorders had a significant beta weight of global stress that remained significant when controlling for the intervening variables age, gender and psychosomatic symptoms. The pattern of the stress-specific and unspecific CMD signs was consistent with the postulated stress model. Since there are positive results with regard to the stress model in patient samples and in this unselected sample of adolescents, further research is indicated, including the concept of somatization more explicitly.

Adolescent↗