Destructive bruxism: sleep stage relationship.

Despite apparent similar amounts of bruxism, two groups that had been evaluated polysomnographically differed dramatically in symptomatology. Patients with severe symptoms were referred to as the destructive bruxism group and were compared with (a) a group with sleep disturbance complaints who had bruxism and (b) a group of insomniac depressed patients chosen without regard to bruxism. It was hypothesized that not only the presence of bruxism during sleep but its pattern and sleep stage relationship were factors affecting clinical symptoms. The results indicated that the sleep stage relationship was an important factor. Patients with severe symptoms attributed to nocturnal bruxism were likely to have more bruxism in REM sleep than the other groups. These results if replicated prospectively would help explain some of the discrepancies in the literature concerning sleep stage relationship of bruxism, as well as help explain differences in symptomatology of bruxism patients.

Nocturnal masseter muscle activity and urinary catecholamine levels in bruxers.

Nocturnal electromyographic recordings of masseter muscle activity were performed on 20 bruxist and ten control subjects. Each subject collected two 24-hour urine samples. An analysis of urinary catecholamine content was performed. A positive relationship was found between increased epinephrine content and high levels of nocturnal masseter muscle activity.

Hysteresis in jaw positioning following lateral stretches.

The purpose of this study was to examine hysteresis of the masticatory system following brief, voluntary lateral positioning of the mandible. Hysteresis was studied in ten healthy subjects, as a function of both time and distance that the mandible was held laterally off the midline. So that the effects of distance of lateral stretch on hysteresis could be studied, subjects positioned their jaws to the left or right of the midline distances of 2, 4, 6, 8, and 10 mm for ten s. So that the effects of time could be studied, the distance of lateral stretch was held a constant 8 mm for durations of two, four, six, 12, 16, and 20 s. Following each voluntary lateral stretch, subjects relaxed the muscles using EMG biofeedback and allowed the mandible to reposition itself passively. Hysteresis was defined as the difference in the mandibular resting position between pre- and post-stretch recordings. Mean hysteresis effects ranged from 0.7 mm to 1.8 mm. Hysteresis effects were found to increase with both distance and time; after eight s, however, no additional effect of time was noted.

Association of salivary flow rates with maximal bite force.

Mean salivary secretion and bite force decrease with advancing age. Previous studies have shown that salivary flow rates are influenced by mastication. In the present study, we examined the relationship between salivary flow rates and maximal bite force in a community-based sample of men and women 35 years of age or older. Salivary flow rates for unstimulated whole and unstimulated submandibular/sublingual (SMSL) saliva as well as citrate-stimulated parotid and SMSL saliva were measured in 399 subjects. Bite force was assessed with a bilateral force transducer. Pearson correlation analysis yielded significant positive correlations between bite force and flow rates for unstimulated whole saliva (r = 0.24, p < 0.0001), stimulated parotid saliva (r = 0.13, p < 0.03), unstimulated SMSL (r = 0.14, p < 0.0001), and stimulated SMSL (r = 0.16, p < 0.003). When adjusted for age and gender, the partial correlations between bite force and salivary flow rates remained significant for unstimulated whole saliva (r = 0.10, p < 0.05), stimulated parotid saliva (r = 0.13, p < 0.02), and stimulated SMSL saliva (r = 0.14, p < 0.006). Subjects were divided into four groups based on their maximal bite force score (low, medium low, medium high, and high). For each saliva type, the flow rate of the high-bite-force group was significantly greater than that of the low-bite-force group as well as that of the medium-high-bite-force group. These results confirm an age-related decrease in bite force and salivary flow rates and show that, regardless of age or gender, bite force is correlated with salivary flow.

Oral function and diet quality in a community-based sample.

Overall diet quality indices, such as the Healthy Eating Index (HEI), are preferred for epidemiological studies, yet studies in dentistry have focused on isolated dietary components. This study investigated the influence of socio-demographic and masticatory variables (masticatory performance, bite force, number of posterior functional tooth units, TMJ disorder, and dentition status) on overall diet quality in a community-based sample (n = 731). Cross-sectional data were derived from clinical examinations, bite force recordings, masticatory performance measurements, and two 24-hour dietary recalls. Females, European-Americans, and older subjects had better HEI scores than males, Mexican-Americans, and younger subjects, respectively. Income, education, and the masticatory variables were not related to diet quality. Analyses according to dentition status (good dentition, compromised dentition, partial denture, and complete dentures) showed no inter-group differences for HEI except for the age groups. The results suggest that the chewing-related factors evaluated in this sample are not predictors of overall diet quality across the socio-demographic groups.

Nocturnal bruxism and temporomandibular disorders.

This chapter has discussed the important aspects of nocturnal bruxism and its relation to disorders of the masticatory system and headaches. Bruxism is believed to be a stress-related sleep disorder, occurring in both men and women, in children, and in adults. In most patients, bruxism results only in minor tooth wear; however, it can become extremely severe with damage occurring in essentially every part of the masticatory apparatus. Nocturnal bruxism should not be overlooked as an etiologic factor in muscular headaches. Short-term acute therapy may involve physical therapy, nocturnal electromyographic biofeedback, and medication to relieve anxiety and improve sleep. Long-term management usually includes some form of stress reduction, change in lifestyle, and an occlusal splint or nightguard to protect the teeth and masticatory system.

Temporal analysis of nocturnal bruxism during EMG feedback.

Several studies have demonstrated that nocturnal bruxism and related symptoms can be relieved through nocturnal electromyogram (EMG) feedback. The effects, however, are not always long lasting and the mechanism of suppression is not understood. It was the object of this study to examine more closely the manner in which nocturnal feedback works in suppressing bruxism. Chart recordings were made of nocturnal masseter EMG activity in five bruxism subjects. Baseline recordings were made in the subject's home followed by 10 or more nights of feedback treatment. Treatment involved sounding a 300 mW tone when EMG activity exceeded about 20 micro V for more than 1 second. All subjects showed a decrease in the duration of bruxism. The decrease in bruxism was due to a reduction in the duration of bruxism episodes rather than a change in the number of episodes, i.e. rather than reducing the probability of an event starting, nocturnal feedback appears to simply suppress the activity once it is initiated. This provides little evidence of learning.

Determinants of masticatory performance in dentate adults.

Masticatory performance results from a complex interplay of direct and indirect effects, yet most studies employ univariate models. This study tested a multivariate model of masticatory performance for dentate subjects. Explanatory variables included number of functional tooth units, bite force, sex, age, masseter cross-sectional area, presence of temporomandibular disorders, and presence of diabetes mellitus. The population-based sample consisted of 631 dentate subjects aged 37-80 years. Covariance structure analysis showed that 68% of the variability in masticatory performance could be explained by the combined effects of the explanatory variables. Age and sex did not show a strong effect on masticatory performance, either directly or indirectly through masseter cross-sectional area, temporomandibular disorders, and bite force. Number of functional tooth units and bite force were confirmed as the key determinants of masticatory performance, which suggests that their maintenance may be of major importance for promoting healthful functional status.

Effect of experimental stress on masseter and temporalis muscle activity in human subjects with temporomandibular disorders.

Temporomandibular (TM) disorders have an uncertain aetiology. The purpose of this study was to replicate and extend the work of Yemm (1969) (Archs oral Biol. 14, 873-878, 1437-1439; Br. dent. J. 127, 508-510), who reported a lack of habituation to experimentally induced stress in subjects with TM disorders. In this study, 20 TM disorder patients and 20 controls, matched for age and sex, performed a timed psychomotor task while bilateral masseter and anterior temporalis electromyographic (EMG) activity, finger temperature and skin admittance were monitored. These data were sampled, stored every 4s and averaged by an Apple II Plus/ISAAC interface. A significant trials effect for finger temperature (F[4/152] = 34.99, p less than 0.001) and skin admittance (F[4/152] = 41.90, p less than 0.001) was found, suggesting that the independent variable (stress) had been successfully manipulated. A significant trials by groups effect was found for right temporalis EMG activity (F[3/144] = 3.94, p less than 0.05); the left temporalis showed a similar, but not significant, trend. The masseter muscles did not show differences or trends between groups. No significant differences were found in resting EMG levels or in the initial magnitude of EMG responses during baseline. These results provide support for the hypothesis that TM disorder and control groups respond differently to stress in terms of habituation to stressful stimuli.

Signs of temporomandibular disorders in patients with horizontal mandibular deficiency.

This study assessed the relationship between temporomandibular disorders (TMD) and malocclusion in a group of 102 patients with horizontal mandibular deficiency who had elected mandibular advancement surgery. The prevalence of TMD as reflected by the overall Craniomandibular Index, Dysfunction index, and Muscle index scores was within the range of non TMD populations (mean Craniomandibular Index = 0.14; mean Dysfunction index = 0.12; mean Muscle index = 0.15). Forty-two percent of the patients exhibited essentially no signs of TMD, 7.8% had primarily muscle tenderness to palpation, 36.3% had joint sounds with or without temporomandibular joint tenderness, and 13.7% had combined muscle-joint signs. There were no convincing correlations among any of the cephalometric variables and Craniomandibular Index, Dysfunction index, and Muscle index scores. A subgroup of 30 of this patient population was evaluated both before and during orthodontic treatment just prior to surgery. No statistically significant changes were found in Craniomandibular Index, Dysfunction index, or Muscle index scores. Thus, a period of orthodontic treatment in these patients does not appear to increase the probability of TMD.

Effects of major Class II occlusal corrections on temporomandibular signs and symptoms.

This study explored the relationship between malocclusion and signs and symptoms of temporomandibular disorders (TMD) in 124 patients with severe Class II malocclusion, before and 2 years after bilateral sagittal split osteotomy (BSSO). Patients were evaluated with the Craniomandibular Index (CMI), the Peer Assessment Rating Index (PAR Index, to assess gross changes in the occlusion), and symptom questionnaires. The results showed a significant improvement in occlusion; PAR Index scores dropped from a mean of 18.1 before surgery to a mean of 6.1 at 2 years postsurgery (P < 0.001). The CMI and masticatory index (MI) for muscle pain indicated clinically small but statistically significant improvement (P = 0.0001) from before surgery (mean CMI = 0.14, mean MI = 0.15) to after surgery (mean CMI = 0.10, mean MI = 0.08). The number of patients with clicking upon opening decreased significantly from 33 (26.6%) to 13 (10.5%) (P = 0.001). However, the number of patients with fine crepitus increased from 5 (4.0%) before surgery to 16 (12.9%) at 2 years postsurgery (P = 0.005). Significant reductions in subjective pain and discomfort were also found 2 years after surgery. The magnitude of change in muscular pain was not related to the severity of the pretreatment malocclusion, a finding that suggests that factors other than malocclusion may be responsible for the change in TMD.

Maintenance of soft tissue changes after rigid versus wire fixation for mandibular advancement, with and without genioplasty.

OBJECTIVE: This multisite prospective randomized clinical trial examined 2-year longitudinal soft tissue profile changes after bilateral sagittal split osteotomy for mandibular advancement by using rigid or wire fixation, with and without genioplasty. STUDY DESIGN: The study sample consisted of 127 subjects. The rigid-fixation group (n = 78) received 2-mm bicortical position screws, whereas the wire-fixation group (n = 49) received inferior border wires. In the rigid-fixation group, 35 subjects underwent genioplasty, whereas 24 subjects underwent genioplasty in the wire-fixation group. Soft tissue profile changes of labrale inferius, B-point, and pogonion were obtained from digitized cephalometric films taken immediately before surgery and up to 2 years after surgery. RESULTS: Regardless of fixation technique, subjects who had genioplasty in conjunction with the mandibular advancement had the largest surgical movement and the largest postsurgical change (P <.05). When all variables were constant, fixation technique was associated with maintenance of soft tissue change. Subjects who underwent rigid fixation maintained more soft tissue change than patients who underwent wire fixation. CONCLUSIONS: These findings suggest that subjects undergoing rigid fixation and genioplasty maintained the most soft tissue advancement.

Mandibular range of motion after bilateral sagittal split ramus osteotomy with wire osteosynthesis or rigid fixation.

OBJECTIVES: An analysis was conducted to compare mandibular range of motion among Class II patients treated with wire osteosynthesis or rigid internal fixation after surgical mandibular advancement. STUDY DESIGN: Patients randomly received wire osteosynthesis and 8 weeks of maxillomandibular fixation (n = 49) or rigid internal fixation (n = 78). Mandibular range of motion was measured 2 weeks before surgery and 8 weeks, 6 months, and 1, 2, and 5 years after surgery. RESULTS: Both groups showed decreased mobility in all movement dimensions that progressively recovered to near presurgical levels over the 5-year follow-up period. The difference in range of motion between treatment groups was not statistically significant. Changes in proximal and distal segment position could not explain decreased mobility. CONCLUSIONS: Similar decreases in mandibular mobility occurred with wire and rigid fixation of a bilateral sagittal split ramus osteotomy after surgery. Long-term changes were statistically, but not clinically, significant.

Technical factors accounting for stability of a bilateral sagittal split osteotomy advancement: wire osteosynthesis versus rigid fixation.

OBJECTIVE: Relapse after bilateral sagittal split osteotomy has been attributed to various technical factors that are inherent in the surgical procedure. The purpose of this article was to analyze technical factors that predispose to relapse when wire or rigid fixation is used. STUDY DESIGN: Patients were randomized to either rigid or wire osteosynthesis. Cephalometric radiographs were obtained and digitized at multiple time periods before and after surgery. Data were analyzed through use of 2-sample t tests and stepwise regression analyses. RESULTS: Multivariate analysis indicated that the following factors correlated with relapse: initial advancement, change in ramus in inclination, change in the mandibular plane, and fixation type. CONCLUSIONS: Relapse increased with the amount of initial advancement and, to a lesser extent, with control of the proximal segment and change in the mandibular plane. These factors are similar for wire osteosynthesis and rigid fixation.

Bilateral sagittal split osteotomy and temporomandibular disorders: rigid fixation versus wire fixation.

OBJECTIVE: The effects of orthognathic surgery on temporomandibular disorders may be related to the surgical method that is used. Specifically, it has been suggested that the choice of stabilization technique may play a major role in the functional outcome of mandibular advancement surgery. The purpose of this study was to prospectively compare long-term (2 years) signs and symptoms of temporomandibular disorders after orthognathic surgery with bilateral sagittal split osteotomy in 127 patients randomized to receive rigid or wire fixation. STUDY DESIGN: Signs and symptoms of temporomandibular disorders were evaluated before and 2 years after surgery by means of the overall craniomandibular index (CMI), dysfunction index (DI), and muscle index (MI). Patients also reported subjective symptoms of temporomandibular disorders by marking areas of pain on a standard drawing of the head and rating the pain in each area on a scale ranging from 1 (very mild) to 7 (very extreme). Subjective pain was also assessed through use of the Oral Health Status Questionnaire and by a rating of the difficulty in opening the mouth because of pain. RESULTS: There were no statistically significant differences in the CMI, MI, or DI change scores between the wire and rigid fixation groups (mean CMI(wire) = 0.05, mean CMI(rigid) = 0.04; mean DI(wire) = 0.02, mean DI(rigid) = 0. 01; mean MI(wire) = 0.08, mean MI(rigid) = 0.08) 2 years after surgery. Temporomandibular joint sounds also demonstrated no significant differences between the two fixation methods. Subjective pain reports were consistent with the clinical examinations. On average, both wire and rigid scores decreased slightly, but the change scores were not significantly different between groups. CONCLUSIONS: These findings suggest that the long-term (2 years) effects of wire and rigid internal fixation methods on the signs and symptoms of temporomandibular disorders do not differ. Earlier concerns about increased risk for temporomandibular disorders with rigid fixation were not supported by these results.

Short-term changes of condylar position after sagittal split osteotomy for mandibular advancement.

OBJECTIVE: The goal of this study was to quantify condylar position changes after mandibular advancement surgery with rigid fixation (screws). Radiographic changes in condylar position were determined in all planes (X, Y, and Z). Computed tomography with image reconstruction was used. STUDY DESIGN: A consecutive population of patients who elected to have rigid fixation for surgical stabilization method were studied (n = 21). Computed tomography data were acquired in the axial plane through use of abutting 1.5-mm-thick slices. Data acquisition occurred 1 week preoperatively and 8 weeks postoperatively. Measurements were made from 2-dimensional reconstructions. RESULTS: The averages were as follows: lateral displacement from midline, 1.2 mm (55% of patients); medial displacement from midline, 1.5 mm (45% of patients; range, 3.2 mm); condyle angle increase from coronal plane, 3.5 degrees (60% of patients); condyle angle decrease from coronal, 4.3 degrees (40% of patients; range, 8.5 degrees); superior rotation of proximal segment, 3.2 degrees (39% of patients); inferior rotation of proximal segment, 8.6 degrees (61% of patients; range, 15.6 degrees); superior displacement, 1.2 mm (60% of patients); inferior displacement, 1.0 mm (40% of patients; range, 2.5 mm); anterior displacement, 1.6 mm (33% of patients); posterior displacement, 1.6 mm (67% of patients; range, 2.8 mm). CONCLUSIONS: Changes occurred in all planes, but the most common postoperative condyle position was more lateral; with increased angle, the coronoid process was higher and the condyle was more superior and posterior in the fossa.

Clinical work posture for the dentist: an electromyographic study.

The results of this study suggest that lumbar support is a significant factor in reducing muscle activity of the upper and lower back for the dentist practicing sit-down dentistry. The importance of lumbar support should be emphasized in any criteria listing correct work posture for the dentist. Under the conditions of this study, stool heights did not influence muscle activity significantly, but did suggest a trend in considering problems of the lower back posture--low stool heights (90 degrees and 75 degrees) produced lower activity than a high stool height (105 degrees) if the back was supported. Therefore, in regard to muscle activity, results of this study suggest that the dental operator should sit low with the lumbar support always in contact with the lower back.

Is use of exogenous estrogen associated with temporomandibular signs and symptoms?

BACKGROUND: Studies of historical data suggest a link between exogenous estrogen use and referral for treatment for temporomandibular disorders, or TMDs. The purpose of the authors' study was to determine the association between exogenous estrogen use and signs and symptoms of TMD assessed by direct physical examination in a randomly selected community sample of primarily postmenopausal women. METHODS: A calibrated clinical examiner examined a stratified random sample of 510 women aged 37 to 82 years using the Craniomandibular Index, or CMI. All medications that subjects were taking at the time of the examination were identified by interview and examination of subjects' medication containers on two occasions. One hundred seventy-four subjects were taking medications containing estrogen, and 336 were taking no such medications. RESULTS: The muscle and joint signs and symptoms of women taking and not taking estrogen were not significantly different after the authors controlled for sociocultural, demographic and health care utilization variables. Estrogen use also failed to distinguish women receiving relatively high and low scores on the CMI. CONCLUSION: Estrogen replacement therapy does not place women at increased risk of developing TMDs. CLINICAL IMPLICATIONS: Clinicians need not be concerned that patients taking oral contraceptives or replacement estrogens are at increased risk of developing TMDs.

Comparing prospective and retrospective evaluations of temporomandibular disorders after orthognathic surgery.

The authors conducted a study to document agreement between prospective examinations performed by trained clinical trial examiners and retrospective surgical chart reviews in identifying signs and symptoms of temporomandibular disorders, or TMD. Only a small fraction of the signs and symptoms identified by clinical trial examiners were documented in the surgical charts. Studies relying on retrospective chart reviews may seriously underestimate signs and symptoms of TMD.

Nocturnal electromyographic evaluation of myofascial pain dysfunction in patients undergoing occlusal splint therapy.

Twenty-five patients with symptoms of myofascial pain and abnormal jaw function were treated with use of a full arch maxillary occlusal splint. The level of nocturnal activity of the masseter muscle was monitored as were symptoms before, during, and after occlusal splint therapy. A decreased nocturnal EMG level during treatment was noted for 52% of the patients. A return to pretreatment EMG levels after removal of the splint was noticed in 92% of the patients; in 28% no change was shown and in 20%, an increase was shown in nocturnal EMG levels. The splint was most likely to reduce nocturnal EMG levels in patients with least severe symptoms.