Gianluigi Lodetti

Surface electromyographic assessment of patients with long lasting temporomandibular joint disorder pain

The normalized electromyographic characteristics of masticatory muscles in patients with temporomandibular joint disorders (TMD) and healthy controls were compared. Thirty TMD patients (15 men, 15 women, mean age 23 years) with long lasting pain (more than 6 months), and 20 control subjects matched for sex and age were examined. All patients had arthrogenous TMD according to the Research Diagnostic Criteria for TMD (RDC/TMD). Surface electromyography of masseter and temporal muscles was performed during maximum teeth clenching either on cotton rolls or in intercuspal position. Standardized EMG indices and the median power frequency were obtained, and compared between the two groups and sexes using ANOVAs. During clenching, the TMD patients had larger asymmetry in their temporalis muscles, larger temporalis activity relative to masseter, and reduced mean power frequencies than the control subjects (p<0.05, ANOVA). In both groups, the mean power frequencies of the temporalis muscles were larger than those of the masseter muscles (p<0.001). No sex related differences, and no sex × group interactions were found. In conclusion, young adult patients with long lasting TMD have an increased and more asymmetric standardized activity of their temporalis anterior muscle, and reduced mean power frequencies, relative to healthy controls.

EMG spectral characteristics of masticatory muscles and upper trapezius during maximum voluntary teeth clenching.

To assess the surface electromyographic spectral characteristics of masticatory and neck muscles during the performance of maximum voluntary clench (MVC) tasks, 29 healthy young adults (15 men, 14 women, mean age 22years) were examined. Electromyography of masseter, temporalis and upper trapezius muscles was performed during 5-s MVCs either on cotton rolls or in intercuspal position. Using a fast Fourier transform, the median power frequency (MPF) was obtained for the first and last seconds of clench, and compared between sexes, muscles, sides, tests and time intervals using ANOVAs. On average, the MPFs did not differ between sexes or sides (p>0.05), but significant effects of muscle (MPF temporalis larger than masseter, larger than trapezius muscles), test (larger MPFs when clenching in intercuspal position than when clenching on cotton rolls) and time (larger MPFs in the first than in the fifth second of clench) were found. In conclusion, a set of data to characterize the sEMG spectral characteristics of jaw and neck muscles in young adult subjects performing MVC tasks currently in use within the dental field was obtained. Reference values may assist in the assessment of patients with alterations in the cranio-cervical-mandibular system.

Morphometry of the Orbital Region Soft Tissues in Down Syndrome

Abstract The orbital region of subjects with Down syndrome (DS) has been scanty described so far. We wanted to detail the morphologic characteristics of the soft tissue orbital region in Italian and North Sudanese subjects with DS. The three-dimensional coordinates of 10 landmarks on the orbital soft tissues were obtained using computerized anthropometry in 53 Italian and 64 North Sudanese subjects with DS aged 4 to 52 years, and in 461 (Italian) and 682 (North Sudanese) sex- and age-matched controls. From the landmarks, linear distances, ratios, areas, and angles were calculated, z scores computed, and compared by t-tests and analyses of covariance. In North Sudanese DS subjects, intercanthal width and height-to-length ratio were increased; biorbital width, eye height, length, and area were reduced. Eye fissure and orbital inclinations relative to Frankfort plane were reduced, whereas orbital inclinations versus the true horizontal were increased. In Italian DS men, orbital height and height-to-length ratio were increased, eye length was decreased; orbital inclination versus the true horizontal was increased. For almost all measurements, a significant effect of age was found. No effects of sex were found. Ethnic group influenced orbital height, area, and orbital inclination versus Frankfort plane. All paired measurements had similar discrepancies on both sides. The orbital soft tissues of North Sudanese DS subjects differed from those of their reference subjects, but this was only partially true for Italian subjects. The 2 ethnic groups had different alterations in their soft tissue orbital regions that were influenced by age, but not by sex.

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.

The temporomandibular joint: from classical anatomy to modern functional assessments

The temporomandibular joint (TMJ) is a complex synovial articulation, made by the mandibular condyles and the squamous surface of temporal bones. The skeletal surfaces are highly incongruent and are separated by a fibrous disc, that reduces joint incongruence, increases joint stability, and allows mandibular movements with six degrees-of-freedom. In mammals, TMJ characteristics are so unique that are used to define the class Mammalia. TMJ development is strictly related to that of the middle ear, and it represents a complex modification of a phylogenetically older articulation found in non-mammalian vertebrates [1]. In particular, human TMJ possesses several differences from that of the other mammals, and animal models cannot be easily used to investigate its dynamic and kinematic characteristics. Several hypotheses have been proposed to describe TMJ movements and intra-articular force, but a major limitation lies in the difficulty in the actual assessment of condylar movements. Indeed, no current imaging system can provide a complete three-dimensional evaluation of TMJ motion: conventional radiographic images lack the third dimension and cannot inform about the behaviour of soft tissues; CT provides all three spatial planes but still cannot image the disc and related structures; magnetic resonance (MR), while providing adequate details of soft tissue structures, lacks the necessary dynamic information. Therefore, most of these studies are based on biomechanical models, where TMJ motion is recorded with three-dimensional motion analyzers, and mathematical and geometrical calculations provide the necessary background for the hypotheses about joint mechanical behaviour [2].

The face in Down’s syndrome: indices of overall size and harmony in Sudanese vs Italian subjects

The study aimed to provide quantitative information about the facial soft-tissues of Italian and Northern Sudanese subjects with Down’s syndrome (DS) by using summary anthropometric measurements representative of facial size and harmony. The 3D coordinates of soft-tissue facial landmarks were obtained by a computerized digitizer in 54 Italian subjects with DS (20 females, 34 males, aged 13-52 years), in 64 Northern Sudanese subjects with DS (18 females, 46 males, aged 5-34 years), in 578 healthy Italian, and 653 healthy Northern Sudanese reference subjects, matched for sex and age. From the landmarks, 16 facial dimensions were calculated. Data from subjects with DS were compared to those collected in reference individuals by computing z-scores. Two summary anthropometric measurements for quantifying craniofacial variations were obtained: the mean z-score (an index of overall facial size), and its standard deviation, or the craniofacial variability index (an index of facial harmony) [1]. In subjects with DS, facial size was significantly smaller, and craniofacial variability was significantly larger than in normal individuals; 93% of Italian and 81% of Northern Sudanese subjects with DS had one or both values outside the normal interval. Overall, Italian subjects with DS differed more from the norm than Northern Sudanese ones. In the Northern Sudanese subjects, the mean z-scores and the CVI decreased significantly with age. The facial soft-tissue structures of subjects with DS differed from those of normal controls of the same age, sex and ethnic group: a reduced facial size was coupled with a global anomalous relationship between individual measurements. The alterations in soft-tissue facial dimensions were different in the two ethnic groups and partially influenced by age.

Morphological and functional facial asymmetry in patients with mild temporomandibular disorders: a pilot study

Facial asymmetry is normal in humans[1]. Authors indicated that facial asymmetry could influence the shape and function of the temporomandibular joints and vice versa[2]. In this study we collected preliminary reference values for facial asymmetry in adults with temporomandibular disorders (TMD), compared to a control group, using a 3D stereophotogrammetric imaging system and electromyographic (EMG) indices. Forty subjects (22 TMD; 18 control; paired for age: 21±2y) were recruited. Five linear measurements for each hemiface and asymmetry index (AI%) were computed from stereophotogrammetric scans. Standardized EMG indices for masseter and temporal muscles were obtained during clenching and gum chewing. Means of control and TMD groups were compared by t-test. For both groups, the AI for all linear measurements ranged from -10% to +10%; there was a great variability, especially for TMD group, who showed the higher values. For EMG indices, TMD group demonstrated a tendency to a more asymmetric muscular recruitment in static activities (masseter & temporal symmetry, C 87.5±1.76%; TMD 84.6±6.2%; p=0.06) and reduced symmetry during gum chewing (C 67.1± 20.9%; TMD 55.0±18.1%; p=0.06). The presence of higher asymmetry for stereophotogrammetry and EMG analyses, as well as the presence of alterations of masticatory function for the TMD group, suggest that this relationship should be further investigated. An analysis with a larger sample and with more severe TMD patients, together with a longitudinal study, is required to understand these possible relationships between morphology and function.

MRI of the TMJ and sEMG of masticatory muscles in patients with arthrogenous temporomandibular disorders: a correlation analysis

The aim of this study was to verify if patients with arthrogenous temporomandibular disorders (TMD) with different Magnetic Resonance Imaging (MRI) diagnoses had some objective differences in the surface electromyography (sEMG) characteristics of their masticatory muscles. Twenty-four TMD patients were categorized according to the RDC/TMD [1]; MRI classified patients with disk displacement (DD, mean age 22 years, SD 5; M/F: 3/6), and osteoarthrosis and/or disk displacement (OA, mean age 37 years, SD 10; M/F: 4/11). sEMG of the right and left masseter and anterior temporalis muscles was performed according to a standardized protocol, recording teeth clenching on either cotton rolls or occlusal surfaces [2]. EMG data were compared to those collected in control subjects of similar age and sex, and EMG z-scores were computed. The comparison of EMG z-scores and MRI scores between the 2 patient groups using the Mann-Whitney test was statistically significant (P < 0.05): the patients with OA had larger scores than the patients with only DD. The linear correlation analysis run between the EMG and the MRI scores found significant correlations in both patient groups. The EMG characteristics allowed to well differentiate patients with MRI diagnosis of DD or OA. The objective recording of the masticatory muscle function and dysfunction through sEMG can be a first simple and low cost diagnostic approach to TMD patients.

Three-dimensional analysis of jaw movements during unilateral gum chewing in healthy subjects and patients with temporomandibular disorders

In our laboratory, we are currently analyzing three-dimensional mandibular movements during the performance of physiological movements. The aim of the current investigation was to quantitatively compare the three-dimensional jaw movement of healthy subjects and patients with temporomandibular disorders (TMD) performing standardized unilateral gum chewing. Mandibular movements were non-invasively detected and recorded using an optoelectronic motion analyzer, with a 60 Hz sampling rate. Ten healthy subjects (mean age 32 y, SD 16 y) and ten subjects with mild or moderate TMD signs and symptoms (mean age 27 y, SD 8 y) chewed a gum alternatively on the right (R) and left (L) side of the mouth. Nine passive markers (diameter 5 mm) were used: three created a cranial reference system; three positioned on a stainless steel extraoral frame fixed on the mandibular anterior gingival, provided the mandibular reference system; two individualized the cutaneous projections of the R and L condyles, and one corresponded to the interincisal point. For both the healthy and TMD groups, the three-dimensional pathway of the interincisal reference point was evaluated in 16 chewing cycles on each side of the mouth. On average, the area covered by the interincisal point was similar (2-way ANOVA, p > 0.05) during R and L chewing in both healthy (frontal plane, 21.1±13.5 vs. 22±11.1 mm 2 ; sagittal plane, 9.4±4.8 vs. 9.4±3.8 mm 2 ) and TMD groups (frontal plane, 15.7±9.3 vs. 19.6±10.2 mm 2 ; sagittal plane, 11.3±6.1 vs. 9.3±5.9 mm 2 ). The interincisal point velocity during the closing phase was greater than during the opening phase (3-way ANOVA, p < 0.001), regardless of side in both healthy and TMD groups (respectively: R chewing opening, 3.3±1.1 vs. 3.4±0.6 cm/s; R chewing closing 4.5±1.6 vs. 4.6±0.9 cm/s; L chewing opening, 3.5±0.8 vs. 3.5±0.7 cm/s; L chewing closing, 5.0±1.6 vs. 4.5±1.2 cm/s). The morphological analysis of the frontal plane chewing patterns revealed a higher frequency of altered patterns 1 in the TMD group than in the control subjects (Chi-square, p < 0.01). These findings showed that, in TMD patients, the chewing-cycle kinematics is not different from the normal subjects. Anyway the presence of a higher frequency of altered cycles suggests that TMD can influence the masticatory pattern, even in mild or moderate TMD patients. 1. Takeda et al. J Oral Maxillofac Surg. 2009;67:1844-9.