Nikolaos Nikitas Giannakopoulos

Anxiety and depression in patients with chronic temporomandibular pain and in controls

OBJECTIVES The purpose of this study was to assess the prevalence of anxiety and depression in temporomandibular disorders (TMD) patient subgroups and in controls with or without chronic facial pain (CFP). METHODS Our sample consisted of 61 men and 161 women. All TMD patients had suffered from pain for at least 6 months and were divided into two subgroups-an exclusively myofascial pain group and an exclusively joint pain group. Subjects without signs or symptoms of TMD but with and without CFP served as controls. All subjects were examined by calibrated examiners in accordance with the Research Diagnostic Criteria for Temporomandibular Disorders. The German version of the Hospital Anxiety and Depression Scale was used for assessment of anxiety and depression. Analysis of covariance was used to determine the effects of sex, age, and subgroup on anxiety and depression scores. Additional t-tests were performed and the subgroups were then compared with those from a general population sample. RESULTS Females from the exclusively myofascial pain group were significantly more depressed than those from the general population or from the exclusively joint pain group. Male controls with CFP were significantly more depressed than female CFP controls. For anxiety, no significant effect of sex or subgroup was found. CONCLUSIONS Depression may play an important role in women with chronic myofascial pain whereas anxiety does not seem to be relevant for either females or males. Further anxiety screening of patients with temporomandibular pain could not be justified.

Long-term training effects on masticatory muscles.

Neuromuscular adaptations during skill acquisition have been extensively investigated for skeletal muscles. Motor rehabilitation is the main target for application of motor training. Such measures are also relevant for the musculature of the jaw, but few data are available for motor adaptation of the masticatory system. The objective of this study was to evaluate and compare long-term training effects of different motor tasks on masseter and temporal muscles. In 20 healthy subjects, the electromyographic response to unilateral and bilateral maximum voluntary tooth clenching, balancing the mandible on a hydrostatic system under force-feedback-controlled conditions, and unilateral chewing was investigated in an initial session and then in two follow-up sessions separated by 2 and 10 weeks from baseline. Motor tasks were repeated three times for chewing, nine times for maximum biting (MB) and 24 times for the coordination tasks (CT). The sequences of the various motor tasks were applied once in the first session and twice in the second and third sessions. No effects of training were observed for MB tasks except for MB in intercuspation, for which significant yet transient avoidance behaviour occurred in the second session. No significant effects were found for chewing tests. For the CT, however, a robust significant long-term training effect was detected which reduced the electric muscle activity in session 2 by approximately 20% and in session 3 by approximately 40% compared with the initial measurements. The study showed that the masticatory muscles are remarkably prone to motor adaptation if demanding CT must be accomplished.

Neuromuscular Interaction of Jaw and Neck Muscles During Jaw Clenching

AIMS To test the hypothesis that jaw muscles and specific neck muscles, ie, levator scapulae, trapezius, sternocleidomastoideus, and splenius capitis, co-contract at the different submaximum bite forces usually generated during jaw clenching and tooth grinding, and for different bite force directions. METHODS Bite-force transducers that measured all three spatial force components were incorporated in 11 healthy subjects. The test persons developed feedback-controlled submaximum bite forces in a variety of bite-force directions. The electromyographic (EMG) activity of the levator scapulae, splenius capitis, and trapezius muscles was recorded, at the level of the fifth cervical vertebra, by use of intramuscular wire electrodes. The activity of the sternocleidomastoideus and masseter muscles was recorded by surface electrodes. For normalization of the EMG data, maximum-effort tasks of the neck muscles were conducted in eight different loading directions by means of a special force-transducer system. Differences between neck-muscle activity during chewing, maximum biting in intercuspation, and the force-controlled motor tasks were compared with the baseline activity of the various muscles by one-way repeated-measures analysis of variance. RESULTS The results confirmed the hypothesis. Co-contractions of the neck muscles in the range of 3% to 10% of maximum voluntary contraction were observed. Significant (P < .05) activity differences were recorded as a result of the different force levels and force directions exerted by the jaw muscles. Long-lasting action potential trains of single motor units triggered by jaw clenching tasks were also detected. CONCLUSION The findings support the assumption of a relationship between jaw clenching and the neck muscle activity investigated. The low level of co-contraction activity, however, requires further study to elucidate possible pathophysiological interactions at the level of single motor units.

The effect of various jaw motor tasks on body sway.

Alterations of body sway caused by isometric contractions of the jaw muscles have been reported previously. The objective of this study was to test if motor tasks of the masticatory system with different control demands affect body posture differently during quiet stance. Position and sway displacements of the center of foot pressure (COP) were measured for 20 healthy subjects who either kept the mandible at rest or performed unilateral and bilateral maximum voluntary teeth clenching, feedback-controlled biting tasks at submaximum bite forces, or unilateral chewing. Two weeks later the measurements were repeated. Compared with quiet stance, the COP results revealed significant changes during the feedback-controlled biting tasks. Robust sway reduction and anterior displacement of the COP were observed under these conditions. Body oscillations were not significantly affected by maximum bites or by unilateral chewing. For most of the variables investigated there were no significant differences between unilateral and bilateral biting. Robust sway reduction during feedback-controlled biting tasks in healthy subjects involved a stiffening phenomenon that was attributed to the common physiological repertoire of posture control, and might optimize the stability of posture under these conditions.

How strong is the evidence for the need to restore posterior bounded edentulous spaces in adults? Grading the quality of evidence and the strength of recommendations

BACKGROUND It is unclear whether or not untreated bounded edentulous spaces (BES) can cause patients problems because of migration of unopposed and adjacent teeth. OBJECTIVES To quantitatively assess BES-related occlusal changes and the level of evidence available. MATERIAL AND METHODS A systematic search of the literature was conducted in triplicate in the PubMed and Cochrane Register of Controlled Trials (CENTRAL) databases up to and including February 2010 to assess studies related to the topic. The LILACS database also was searched by one of the authors (CMF). Quantitative mesio-distal changes and overeruption were the outcome measures. Manual searching of the reference lists of studies retrieved from the electronic databases was also conducted. Google Scholar in English, French, German, Greek, Italian, Portuguese, and Spanish was also searched to retrieve potential studies. Grey literature was searched in OpenSIGLE (System for Information on Grey Literature in Europe) for more potential papers. The quality of the retrieved literature and the strength of recommendations were assessed by use of the GRADE system. A decision-tree-like scheme was produced to depict treatment options. RESULTS The available evidence demonstrated that for most cases occlusal changes in BES after tooth loss might be limited (on average up to 2mm). The quality of evidence was regarded as very low, however. CONCLUSIONS Tooth replacement should not necessarily be regarded as the mainstay of therapy for posterior BES, although more robust studies are necessary to clarify the long-term effects of non-treatment. The GRADE approach may be useful for enhancing the transparency of the decision-making process in dentistry, especially when evidence of only limited quality is available.

Comparison of particle-size distributions determined by optical scanning and by sieving in the assessment of masticatory performance.

Aim of this study was to introduce a feasible and valid technique for the assessment of masticatory performance that is comparable to the standard sieving method. Twenty-one chewing samples (Optosil) comminuted by healthy dentate adults were analysed with a sieving and scanning method. Scanning was performed using a conventional flatbed scanner (1200dpi). All scanned images underwent image analysis (ImageJ), which yielded descriptive parameters such as area, best-fitting ellipse for each particle. Of the 2D-image, a volume was estimated for each particle, which was converted into a weight. To receive a discrete distribution of particle sizes comparable to sieving, five chewing samples were used to calculate a size-dependent area-volume-conversion factor. The sieving procedure was carried out with a stack of 10 sieves, and the retained particles per sieve were weighed. The cumulated weights yielded by either method were curve-fitted with the Rosin-Rammler distribution to determine the median particle size x(50) . The Rosin-Rammler distributions for sieving and scanning resemble each other. The distributions show a high correlation (0·919-1·0, n= 21, P<0·01, Pearsons correlation coefficient). The median particle sizes vary between 3·83 and 4·77mm (mean: 4·31) for scanning and 3·53 and 4·55mm (mean: 4·21) for sieving. On average, scanning overestimates the x(50) values by 2·4%. A modified Bland-Altman plot reveals that 95% of the x(50) values fall within 10% of the average x(50) . The scanning method is a valid, simple and feasible method to determine masticatory performance.

Anterior and posterior neck muscle activation during a variety of biting tasks

Bruxism may be involved in the aetiology of myofascial neck pain. The objective of this study was to test the hypothesis that anterior and posterior neck muscles co-contract during jaw clenching. Ten test subjects developed different feedback-controlled submaximum bite forces in a variety of bite-force directions by means of bite-force transducers. The electromyographic activity of the sternocleidomastoid and supra/infrahyoidal muscles, and of the semispinalis capitis, semispinalis cervicis, and multifidi muscles was recorded by use of surface electrodes and intramuscular wire electrodes, respectively. For normalization of electromyography data, maximum voluntary contraction tasks of the neck muscles were conducted in eight different loading directions. The results confirmed co-contraction of the neck muscles in the range of 2-14% of the maximum voluntary contraction at a bite force ranging from 50 to 300 N. Significant activity differences were observed as a result of the different force levels and force directions exerted by the jaw muscles. Long-lasting tonic activation of specific neck muscles triggered by the jaw-clenching tasks was also detected. These findings support the assumption of a relationship between jaw clenching and the activity of the neck muscles investigated. The low level of co-contraction activity, however, requires further study to elucidate possible pathophysiological interactions at the level of single motor units.

The methodological quality of systematic reviews of animal studies in dentistry

Systematic reviews and meta-analyses of animal studies are important for improving estimates of the effects of treatment and for guiding future clinical studies on humans. The purpose of this systematic review was to assess the methodological quality of systematic reviews and meta-analyses of animal studies in dentistry through using a validated checklist. A literature search was conducted independently and in duplicate in the PubMed and LILACS databases. References in selected systematic reviews were assessed to identify other studies not captured by the electronic searches. The methodological quality of studies was assessed independently and in duplicate by using the AMSTAR checklist; the quality was scored as low, moderate, or high. The reviewers were calibrated before the assessment and agreement between them was assessed using Cohens Kappa statistic. Of 444 studies retrieved, 54 systematic reviews were selected after full-text assessment. Agreement between the reviewers was regarded as excellent. Only two studies were scored as high quality; 17 and 35 studies were scored as medium and low quality, respectively. There is room for improvement of the methodological quality of systematic reviews of animal studies in dentistry. Checklists, such as AMSTAR, can guide researchers in planning and executing systematic reviews and meta-analyses. For determining the need for additional investigations in animals and in order to provide good data for potential application in human, such reviews should be based on animal experiments performed according to sound methodological principles.

Co-activation of jaw and neck muscles during submaximum clenching in the supine position

OBJECTIVE The purpose of this study was to test the hypothesis that jaw clenching induces co-contraction and low-level long-lasting tonic activation (LLTA) of neck muscles in the supine position. DESIGN Ten healthy subjects developed various feedback-controlled submaximum bite forces in different bite-force directions in supine position. The electromyographic (EMG) activity of the semispinalis capitis, semispinalis cervicis, multifidi, splenius capitis, levator scapulae, trapezius, sternocleidomastoideus, masseter and infra/supra-hyoidal muscles was recorded. For normalization of EMG data, maximum-effort tasks of the neck muscles were performed. RESULTS Co-contractions of the posterior neck muscles varied between 2% and 11% of their maximum voluntary contraction. Different bite forces and bite-force directions resulted in significant (p<.05) activity differences between the co-contraction levels of the neck muscles. In addition, LLTA of specific neck muscles, provoked by the jaw clenching tasks, was observed. CONCLUSIONS This study demonstrated for the first time moderate co-contractions of jaw and neck muscles in the supine position under controlled submaximum jaw clenching forces. LLTA of most neck muscles was observed, outlasting clenching episodes and indicating an additional neuromuscular interaction between the two muscle groups.

Chronic stress in myofascial pain patients

Although myofascial pain has often been described as being associated with psychosocial stress, detailed evidence in support of this assumption, either from standardized clinical examination or from validated chronic stress questionnaires, is absent. The hypothesis of the present study was that some stressors lead to higher scores in patients suffering from chronic myofascial pain than in pain-free controls and in patients suffering from chronic facial pain. One hundred and fifty subjects were included in the study, and depending on clinical findings, divided into three groups: exclusively chronic myofascial pain group, controls with chronic facial pain but without temporomandibular disorders (TMD), and controls without pain or TMD. Chronic stress was assessed on nine subscales by use of a validated questionnaire. Myofascial pain patients have a significantly higher stress score for “social isolation” than pain-free controls (t-test, p = 0.003). However, they do not have higher scores than patients suffering from facial pain (t test, p = 0.169). Thus, the hypothesis of this study could not be completely rejected.