M. Koutris

Effects of Intense Chewing Exercises on the Masticatory Sensory-Motor System

Nociceptive substances, injected into the masseter muscle, induce pain and facilitate the jaw-stretch reflex. It is hypothesized that intense chewing would provoke similar effects. Fourteen men performed 20 bouts of 5-minute chewing. After each bout, 20 min and 24 hrs after the exercise, muscle fatigue and pain scores and the normalized reflex amplitude from the left masseter muscle were recorded. Before, 20 min, and 24 hrs after the exercise, signs of temporomandibular disorders and pressure-pain thresholds of the masticatory muscles were also recorded. Fatigue and pain scores had increased during the exercise (P < 0.001), but the reflex amplitude did not (P = 0.123). Twenty minutes after the exercises, 12 participants showed signs of myofascial pain or arthralgia. Pressure-pain thresholds were decreased after 20 min (P = 0.009) and 24 hrs (P = 0.049). Intense chewing can induce fatigue, pain, and decreased pressure-pain thresholds in the masticatory muscles, without concomitant changes in the jaw-stretch reflex amplitude.

Is myofascial pain in temporomandibular disorder patients a manifestation of delayed-onset muscle soreness?

Objective:In a study to the possible role of overuse of the jaw muscles in the pathogenesis of jaw muscle pain, we used a protocol involving concentric and eccentric muscle contractions to provoke a state of delayed-onset muscle soreness (DOMS) in the jaw muscles of healthy individuals. We tested whether the accompanying signs and symptoms would yield the temporary diagnosis of myofascial pain according to the research diagnostic criteria for temporomandibular disorders (RDC/TMD) in these individuals. Methods:Forty persons (mean age±SD=27.7±7.5 y) performed six, 5-minute bouts of eccentric and concentric jaw muscle contractions. Before and immediately after the exercise, and 24 hours, 48 hours, and 1 week later, self-reported muscle fatigue and pain, pain-free maximum mouth opening, pressure-pain thresholds, and the number of painful jaw muscle palpation sites were recorded. Results:Significant signs and symptoms of DOMS in the jaw muscles were found, which all had resolved after 1 week. In 31 (77.5%) of the participants, these signs and symptoms also gave rise to a temporary diagnosis of myofascial pain according to the RDC/TMD. Conclusions:The results of this study demonstrate that an experimental protocol involving concentric and eccentric muscle contractions can provoke DOMS in the jaw muscles and the temporary diagnosis of myofascial pain according to the RDC/TMD. The results observed strengthen the supposition that the myofascial pain in TMD patients may be a manifestation of DOMS in the jaw muscles.

Comorbidity negatively influences the outcomes of diagnostic tests for musculoskeletal pain in the orofacial region

&NA; Diagnostic tests for musculoskeletal pain are negatively influenced by the presence of comorbidity. This influence decreases when the presence of familiar pain is used as outcome measure. &NA; The aim of this study was to investigate whether diagnostic tests for musculoskeletal pain in the orofacial region [temporomandibular disorder (TMD) pain] are influenced by the presence of comorbid conditions, and to determine whether this influence decreases when the presence of “familiar pain” is used as outcome measure. In total, 117 patients (35 men, 82 women; 75 TMD‐pain patients, 42 pain‐free patients; mean age ± SD = 42.94 ± 14.17 years) were examined with palpation tests and dynamic/static tests. After each test, they were asked whether any pain was provoked and whether this pain response was familiar or not. For four clinical outcome measures (pain on palpation, familiar pain on palpation, pain on dynamic/static tests, and familiar pain on dynamic/static tests), multiple logistic regression analyses were performed with the presence of TMD pain as the primary predictor and regional (neck/shoulder) pain, widespread pain, depression, and somatization as comorbid factors. Pain on palpation was not associated with the primary predictor but with regional pain [P = 0.02, odds ratio (OR) = 4.59] and somatization (P = 0.011, OR = 8.47), whereas familiar pain on palpation was associated with the primary predictor (P = 0.003, OR = 5.23), but also with widespread pain (P = 0.001, OR = 2.02). Pain on dynamic/static tests was associated with the primary predictor (P < 0.001, OR = 11.08), but also with somatization (P = 0.037, OR = 4.5), whereas familiar pain on dynamic/static tests was only associated with the primary predictor (P < 0.001, OR = 32.37). In conclusion, diagnostic tests are negatively influenced by the presence of comorbidity. This influence decreases when the presence of familiar pain is used as outcome measure.

Assessment of the progression of tooth wear on dental casts.

Many methods are available for the grading of tooth wear, but their ability to assess the progression of wear over time has not been studied frequently. The aim was to assess whether the occlusal/incisal grading scale of the Tooth Wear Evaluation System (TWES) was sensitive enough for the detection of tooth wear progression from 14 to 23 years of age. A total of 120 sets of dental casts were gathered from 40 people, of whom impressions were made at 14, 18 and 23 years. The TWES was used to assess loss of clinical crown height throughout the entire dentition. There was a significant difference in the TWES scores between the three age groups on all teeth (Friedman tests; P < 0.005 in all cases). Post hoc Wilcoxon tests revealed that the difference between the scores between 14 and 18 years and between 18 and 23 was significant for most teeth. It was concluded that the TWES is sensitive enough to detect changes in tooth wear over time.

Assessment of the amount of tooth wear on dental casts and intra-oral photographs

Tooth wear is a multifactorial condition, leading to the loss of dental hard tissues. Many grading scales are available to assess the amount of tooth wear, one of which is the tooth wear evaluation system (TWES). A grading scale can be used chairside, on casts and on photographs. The aim was to test whether the grading scales of the TWES, used on casts and on photographs, resulted in comparable scores. In addition, it was tested whether these scales can be used to assess tooth wear reliably on photographs. Of 75 tooth wear patients, sets of casts and series of photographs were obtained and graded. Comparison of the grading on casts and on photographs revealed equal median values and percentiles for both occlusal/incisal grading and non-occlusal/non-incisal grading. The grading on casts and on photographs showed a high correlation for the occlusal/incisal grading and a low correlation for the non-occlusal/non-incisal grading (Spearmans rho = 0·74 and rho = 0·47; P < 0·001). Concerning the grading on photographs, the interexaminer reliability was fair-to-good (ICC = 0·41 to ICC = 0·55) while the intra-examiner reliability was fair-to-good to excellent (ICC = 0·68 to ICC = 0·86) for the occlusal/incisal grading. For the non-occlusal/non-incisal grading, the interexaminer reliability was poor to fair-to-good (ICC = 0·22 to ICC = 0·59), while the intra-examiner reliability was fair-to-good to excellent (ICC = 0·64 to ICC = 0·82). It was concluded that the scores obtained with the grading scales of the TWES on casts and on photographs are comparable. The grading scales can be used in a reliable way on photographs, which is especially the case for occlusal/incisal grading.

Long-term variability of sleep bruxism and psychological stress in patients with jaw-muscle pain: Report of two longitudinal clinical cases

Sleep bruxism (SB) and psychological stress are commonly considered as contributing factors in the aetiology of temporomandibular disorder (TMD) pain. However, the lack of longitudinal studies and fluctuating nature of SB, psychological stress and TMD pain have led to contradictory results regarding the association between the possible aetiological factors and TMD pain. In the present study we investigated the contribution of SB and psychological stress to TMD pain in a longitudinal study of 2 clinical TMD pain cases during a 6-week study protocol. Two female volunteers with clinically diagnosed myalgia based on the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) participated in the study. Questionnaires were used to record jaw-muscle pain and psychological stress experience, and an ambulatory polysomnography technique was used to record SB intensity. Visual analysis of the data revealed that the intensity of TMD pain was not hardwired, neither with psychological stress experience nor with increased SB activity. Within the limitations of single-patient clinical cases design, our study suggested that the presence of TMD pain cannot be explained by a simple linear model which takes psychological stress or SB into account. It also seems that psychological stress was a more important predictor factor for TMD pain than SB.

Two different analyzing methods for inhibitory reflexes: Do they yield comparable outcomes?

BACKGROUND For the analysis of inhibitory reflexes, no consensus exists regarding the methodology that should be used. The most commonly used methods are the cumulative sum (CUSUM) error box and the t-test. The aim of this study was to assess the interexaminer reliability of those two analyzing methods and to test whether both methods: yield similar results. METHODS Inhibitory jaw reflexes were recorded from the right masseter muscle of 11 participants (6 males, 5 females). Electrical stimuli were applied at the hairy skin of the upper lip on the right side. In total, 16 stimuli were applied while the participants maintained their clenching level at 10% of their maximum voluntary EMG activity. Two different examiners analyzed the reflex data with two different methods: the CUSUM error box and the t-test. The outcome variables were the number of reflex parts, the reflex area size, and the reflex onset. Comparability between examiners and between the two analyzing methods: was assessed with the use of the intraclass correlation coefficient (ICC). RESULTS The interexaminer reliability was fair-to-good to excellent for both the CUSUM error box and the t-test analyses and for all the variables tested. The comparability of the two analyzing methods: was fair-to-good. COMPARISON WITH EXISTING METHODS/CONCLUSION When analyzing the inhibitory reflex data, both the CUSUM error box and the t-test can be used.

Human jaw joint hypermobility: Diagnosis and biomechanical modelling

Patients with hypermobility disorders of the jaw joint experience joint sounds and jerky movements of the jaw. In severe cases, a subluxation or luxation can occur. Clinically, hypermobility disorders should be differentiated from disc displacements. With biomechanical modelling, we previously identified the anterior slope angle of the eminence and the orientation of the jaw closers to potentially contribute to hypermobility disorders. Using cone-beam computed tomography (CBCT), we constructed patient-specific models of the masticatory system to incorporate these aspects. It is not known whether the clinical diagnosis of hypermobility disorders is associated with the prediction of hypermobility by a patient-specific biomechanical model. Fifteen patients and eleven controls, matched for gender and age, were enrolled in the study. Clinical diagnosis was performed according to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) and additional testing to differentiate hypermobility from disc displacements. Forward simulations with patient-specific biomechanical models were performed for maximum opening and subsequent closing of the jaw. This predicted a hypermobility disorder (luxation) or a control (normal closing). We found no association between the clinical diagnosis and predictions of hypermobility disorders. The biomechanical models overestimated the number of patients, yielding a low specificity. The role of the collagenous structures remains unclear; therefore, the articular disc and the ligaments should be modelled in greater detail. This also holds for the fanned shape of the temporalis muscle. However, for the osseous structures, we determined post hoc that the anterior slope angle of the articular eminence is steeper in patients than in controls.

Bruxism in dentists’ families

Bruxism is defined as a repetitive jawmuscle activity that is characterised by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible. It is indicated as either sleep bruxism or awake bruxism, depending on its circadian phenotype.1 While the jawmuscle activity as such does not justify extensive diagnosis and treatment,2 sleep bruxism that goes with severe (especially anterior) tooth wear, highintensity pain in the masticatory muscles and temporomandibular joints, or penetrating grinding noises does urge bruxists to seek dental help for their condition. During the consultation with the dentist, the oral history often touches upon the common observation that other family members grind their teeth as well, leading to the question whether or not bruxism runs in families. A recent, quasisystematic review of the literature now enables an evidencebased answer to the frequently asked question whether bruxism is hereditary: based on four family studies, five twin studies, and one DNA study, bruxism appears to be partly genetically determined.3

Parkinson's disease, temporomandibular disorders and bruxism: A pilot study

BACKGROUND Even though bruxism and Parkinsons disease (PD) share common characteristics, their relation is still not clear. Both bruxism and PD are movement disorders in addition, patients with bruxism as well as those with PD complain about musculoskeletal pain, including temporomandibular disorders (TMD) pain. OBJECTIVES Therefore, the aim of this pilot study was to gain more insight into the possible relation between bruxism and TMD on one hand and PD on the other. METHODS In total, 801 persons gave their written informed consent and agreed to participate in the study filling in a questionnaire. Complete data were collected from 708 persons (368 with PD or Parkinsonism [PR] and 340 controls) and were included in the analysis. The questionnaire included the graded chronic pain scale, the DC/TMD oral behaviour checklist, the DC/TMD symptom questionnaire and the TMD pain screener. In addition, a question about self-reported tooth wear was included. The chi-square test and independent samples t test were used for the data analysis. RESULTS Patients with PD/PR reported significantly more often bruxism during sleep and wakefulness than controls. Also, patients with PD/PR had more often possible TMD and reported a significantly higher mean pain intensity in the orofacial region than controls. There was no significant difference in complaints of jaw locking between the patient group and the control group. A tendency towards a significant association was found between PD/PR and tooth wear. CONCLUSION There is a relation between PD/PR and bruxism. Furthermore, a relation of PD/PR with TMD pain is suggested to be present.