Assessment of electromyographic activity in patients with temporomandibular disorders and natural mediotrusive occlusal contact during chewing and tooth grinding.

OBJECTIVES: The aim of this study was to investigate whether the presence of a natural mediotrusive contact influences electromyographic (EMG) pattern activity in patients with temporomandibular disorders (TMDs). METHOD: Bilateral surface EMG activity of the anterior temporalis (AT), masseter (MM), and sternocleidomastoid (SCM) muscles was recorded in 43 subjects during unilateral chewing and tooth grinding. Thirteen patients had TMD and a natural mediotrusive contact (Group 1), 15 had TMD without a natural mediotrusive contact (Group 2), and 15 were healthy subjects without mediotrusive contacts (Group 3). All subjects were examined according to the Research Diagnostic Criteria for TMD (RDC/TMD). All EMG values were standardized as the percentage of EMG activity recorded during maximum isometric contraction on cotton rolls. RESULTS: EMG activity from all muscles measured showed no significant differences between groups during chewing and grinding. Overall, in all groups, the EMG activity during chewing was higher in the working side than the non-working side in AT and MM muscles. During grinding, these differences were only found in masseter muscles (mainly in eccentric grinding). SCM EMG activity did not show significant differences during chewing and grinding tasks. Symmetry, muscular balance, and absence of lateral jaw displacement were common findings in all groups. DISCUSSION: EMG results suggest that the contribution of a natural mediotrusive occlusal contact to EMG patterns in TMD patients is minor. Therefore, the elimination of this occlusal feature for therapeutic purposes could be not indicated.

Validity of three screening questions (3Q/TMD) in relation to the DC/TMD.

Temporomandibular disorders (TMD) are common but seem to be largely undetected within general dental care. To improve dentists' awareness of these symptoms, three screening questions (3Q/TMD) have been introduced. Our aim was to validate 3Q/TMD in relation to the diagnostic criteria for TMD (DC/TMD), while taking into account the severity level of the symptoms. The study population consisted of 7831 individuals 20-69 years old, who had their routine dental check-up at the Public Dental Health Service in Västerbotten, Sweden. All patients answered a health declaration, including the 3Q/TMD regarding frequent temporomandibular pain, pain on movement and catching/locking of the jaw. All 3Q-positives (at least one affirmative) were invited for examination in randomised order. For each 3Q-positive, a matched 3Q-negative was invited. In total, 152 3Q-positives and 148 3Q-negatives participated. At examination, participants answered 3Q/TMD a second time, before they were examined and diagnosed according to DC/TMD. To determine symptom's severity, the Graded Chronic Pain Scale and Jaw Functional Limitation Scale-20 (JFLS-20) were used. In total, 74% of 3Q-positives and 16% of 3Q-negatives met the criteria for DC/TMD pain or dysfunction (disc displacements with reduction and degenerative joint disorder were excluded). Fifty-five per cent of 3Q-positives had a TMD diagnosis and CPI score ≥3 or a JFLS-20 score ≥5, compared to 4% of 3Q-negatives. The results show that the 3Q/TMD is an applicable, cost-effective and valid tool for screening a general adult population to recognise patients in need of further TMD examination and management.

Assessment of the effect of two occlusal concepts for implant-supported fixed prostheses by finite element analysis in patients with bruxism.

The aim of this study was to evaluate the effects of bruxing forces on implants configured under 2 different occlusal schemes by dynamic finite element analysis. A main model consisting of a 5-unit fixed partial denture supported by 3 implants was simulated with bone, implants, and superstructures. All calculations were made individually for each component, namely porcelain crowns, abutments, abutment screws, implants, and bone. Maximum stresses were found in the group-function occlusion. Group-function loading may result excess stresses on the components compared with canine-guidance loading. According to the results of this study, use of canine guidance is encouraged in bruxers with implant-supported prostheses.

Profiling the clinical presentation of diagnostic characteristics of a sample of symptomatic TMD patients.

BACKGROUND: Temporomandibular disorder (TMD) patients might present a number of concurrent clinical diagnoses that may be clustered according to their similarity. Profiling patients' clinical presentations can be useful for better understanding the behavior of TMD and for providing appropriate treatment planning. The aim of this study was to simultaneously classify symptomatic patients diagnosed with a variety of subtypes of TMD into homogenous groups based on their clinical presentation and occurrence of comorbidities. METHODS: Clinical records of 357 consecutive TMD patients seeking treatment in a private specialized clinic were included in the study sample. Patients presenting multiple subtypes of TMD diagnosed simultaneously were categorized according to the AAOP criteria. Descriptive statistics and two-step cluster analysis were used to characterize the clinical presentation of these patients based on the primary and secondary clinical diagnoses. RESULTS: The most common diagnoses were localized masticatory muscle pain (n = 125) and disc displacement without reduction (n = 104). Comorbidity was identified in 288 patients. The automatic selection of an optimal number of clusters included 100% of cases, generating an initial 6-cluster solution and a final 4-cluster solution. The interpretation of within-group ranking of the importance of variables in the clustering solutions resulted in the following characterization of clusters: chronic facial pain (n = 36), acute muscle pain (n = 125), acute articular pain (n = 75) and chronic articular impairment (n = 121). CONCLUSION: Subgroups of acute and chronic TMD patients seeking treatment can be identified using clustering methods to provide a better understanding of the clinical presentation of TMD when multiple diagnosis are present. Classifying patients into identifiable symptomatic profiles would help clinicians to estimate how common a disorder is within a population of TMD patients and understand the probability of certain pattern of clinical complaints.

Prosthetic complications in fixed endosseous implant-borne reconstructions after an observations period of at least 40 months.

One hundred and seventy-two fixed reconstructions (317 prosthetic units), made on 283 ITI implants in 105 patients (age range 25-86 years) with a minimum follow-up period of 40 months, were taken into the study to analyse technical complication rate, complication type and costs for repair. The mean evaluation time was 62.5 +/- 25.3 months. Eighty were single crowns and 92 different types of fixed partial dentures (FPDs). In 45 cases the construction was screw retained and in 127 cases cemented with zinc phosphate cement or an acrylic-based cement. Complications occurred after a minimum period of 2 months and a maximum period of 100 months (mean: 35.9 +/- 21.4 months). Fifty-five prosthetic interventions were needed on 44 constructions (25%) of which 88% in the molar/premolar region. The lowest percentage of complications occurred in single crowns (25%), the highest in 3-4 unit FPDs (35%) and in FPDs with an extension (44%). Of the necessary clinical repair, 36% was recementing and 38% tightening the screws. Of all interventions, 14% were classified as minor (no treatment or <10 min chair time), 70% as moderate (>10 min but <60 min chair time) and 14% as major interventions (>60 min and additional costs for replacement of parts and/or laboratory). For seven patients the additional costs ranged from euro 28 to euro 840. Bruxing seemed to play a significant role in the frequency of complications. Longer constructions seemed to be more prone to complications. The relatively high occurrence of technical complications should be discussed with the patient before the start of the treatment.

Prediction of demand for treatment of temporomandibular disorders.

Baseline (BL) data on signs and symptoms characteristic of temporomandibular disorders (TMDs) were analysed in 67 young non-patients participating as controls in a clinical trial. Data on the incidence of demand for treatment of TMD were collected during the 4-year follow-up period, and, by means of a mailed questionnaire, during an additional 2 years. The variables analysed included palpation and auscultation of the joints, palpation of the muscles of mastication, experience of joint sounds, of pain on jaw movements, of ear symptoms, awareness of a clenching habit, and frequency of headache. A present-absent dichotomy was applied throughout. Palpation tenderness of masticatory muscles was significantly (P=0.02) more often present at BL in those who subsequently requested treatment than in those who did not. The same was true of the combination of palpatory tenderness and clenching habit (P=0.007), whereas the clenching habit alone failed to show a significant difference (P=0.06). However, the predictive values remained too low to be clinically useful, with a possible exception of the negative predictive value of muscle tenderness. The findings indicate that the variables conventionally used to describe the functional status of the masticatory system are at best of modest value in the estimation of individual risk of TMD in healthy young subjects.

Dynamic assessment of abnormalities in central pain transmission and modulation in tension-type headache sufferers.

OBJECTIVE: To examine and compare central pain processing and modulation in young tension-type headache sufferers with that of matched healthy controls using an induced headache "challenge" paradigm. BACKGROUND: Recent research has suggested that abnormalities in central pain processing and descending pain modulation may contribute to chronic tension-type headache. These abnormalities, if they contribute to headache pathogenesis, should be present in young adult tension-type headache sufferers. Recent research using static measures of physiological variables, such as muscle tenderness and exteroceptive suppression, has identified chronic muscle tenderness as a characteristic of young tension-type headache sufferers, but other central nervous system functional abnormalities may require a dynamic "challenge" to be observed. METHODS: Twenty-four young women meeting the International Headache Society diagnostic criteria for tension-type headache (headache-prone) and a matched group of 24 healthy women who reported fewer than 10 problem headaches per year (control) participated in a double-blind, placebo-controlled, crossover study. Subjects completed jaw clenching and a placebo condition on different days in counterbalanced order. Pericranial muscle tenderness, pressure-pain thresholds on the temporalis, and exteroceptive suppression periods were assessed before and after each procedure. Head pain was recorded for 12 to16 hours following each condition. RESULTS: Headache-prone subjects were more likely than controls to experience headaches after both the jaw clenching and placebo procedures, but neither group was significantly more likely to experience headaches following jaw clenching than placebo. In pretreatment measurements, headache-prone subjects exhibited greater muscle tenderness than controls, but pressure-pain detection thresholds and exteroceptive suppression periods did not differ in the two groups. Control subjects showed increases in muscle tenderness and exteroceptive suppression periods following both the clenching and placebo procedures, whereas headache-prone subjects exhibited no significant changes in any of the physiological measures following either experimental manipulation. CONCLUSIONS: These results confirm previous findings indicating abnormally high pericranial muscle tenderness in young tension headache sufferers even in the headache-free state. In addition, the results suggest that the development of headaches following noxious stimulation is more strongly related to headache proneness and associated abnormalities in central pain transmission or modulation (indexed by pericranial muscle tenderness and exteroceptive suppression responses) than muscle strain induced by jaw clenching.

Digital assessment of occlusal wear patterns on occlusal stabilization splints: a pilot study.

STATEMENT OF PROBLEM: If masticatory load distribution is task-dependent, then the pattern of wear on an acrylic resin occlusal splint over time may affect clinical outcome. PURPOSE: This pilot study quantitatively assessed posterior wear after 3 months on the occlusal surfaces of maxillary stabilization splints. MATERIAL AND METHODS: Subjects with known history of nocturnal bruxism were given heat-cured full-arch acrylic resin occlusal stabilization splints to be worn nocturnally for 3 months. Splint occlusion was adjusted at appliance delivery and was refined at the baseline session 1 to 2 weeks later. No further adjustment of the splint surface was performed during the 3-month study period. Sequential impressions of the splint occlusal surface provided epoxy resin models that were digitized and analyzed through specialized software. Changes in the digitized splint surface from baseline to 3 months allowed comparison of wear facets between splint sides and among tooth locations. RESULTS: Splint wear was asymmetric between sides and uneven between dental locations. CONCLUSIONS: For full coverage occlusal splints, the appliance wear phenomenon can be site specific and, if left undisturbed, may yield two extremes of high wear and a zone of low wear in-between.

Electromyographic assessment of non-functional masseter muscle in an awake animal model.

Non-functional activities, such as bruxism, have been implicated in the development of temporomandibular disorders (TMD). It would be of value to have an animal model in which to investigate the processes underlying such disorders. The aim of this study was to determine the electromyographic (EMG) characteristics of experimentally induced, non-functional activity in the jaw-closing muscles of awake, behaving rats and how the EMG characteristics differed from those found under normal conditions. In the same animals, chronic EMG recordings were made prior to and following the insertion of an occlusal cap, which induced non-functional activity. A characteristic EMG pattern was found only during non-functional activity. The durations and amplitudes of the EMG bursts during this activity were significantly different statistically from those found in the same animals under normal conditions.

Assessment of buccal separators in the relief of bruxist activity associated with myofascial pain-dysfunction.

The purpose of this study was to evaluate the effectiveness of heavy (S2) Alastik separators in relieving bruxist activity as monitored through masseter muscle area EMG activity, muscle palpation, and self-reporting in 21 Caucasian subjects. The subjects, all of whom suffered from both bruxism and myofascial pain-dysfunction, were randomly assigned to one of three groups: experimental (separator group); placebo (separator placed and removed); and control groups (no separator). The findings from this study indicate that there were no observable differences in either subjective or objective responses to the pretreatment versus posttreatment questionnaire and clinical examination for tooth clenching or grinding, facial pain, and fatigue of the jaws. In addition, no statistical differences were found between pre and posttreatment data. The EMG data did not show any statistical differences between pretreatment and posttreatment evaluations or among the 3 groups.