Biomedical subjects

L M Gallo

Publications and source records attributed to L M Gallo.

At least 19 recordsLinked to original sources

PubMed2006

No effect of experimental occlusal interferences on pressure pain thresholds of the masseter and temporalis muscles in healthy women.

It has been suggested that occlusal interferences may lead to pain and tenderness of the masticatory muscles. Tender jaw muscles are more sensitive to pressure pain, as assessed by means of pressure algometry. We tested the effects of occlusal interferences on the pressure pain threshold of the jaw muscles by means of a double-blind randomized crossover experiment carried out on 11 young healthy females. Golden strips were glued either to an occlusal contact area (active interference) or to the vestibular surface of the same tooth (dummy interference) and left for 8 d each. Pressure pain thresholds of the masseter and anterior temporalis muscles were assessed under interference-free, dummy-interference and active-interference conditions. The results indicated that the application of an active occlusal interference, as used in this study, did not influence significantly the pressure pain thresholds of these muscles in healthy individuals.

Adult↗

PubMed2006

Mechanical work during stress-field translation in the human TMJ.

The pathomechanics of degenerative joint disease of the temporomandibular joint (TMJ) may involve fatigue produced by mechanical work on the articulating tissues. This study tested the hypotheses that mechanical work in the TMJ (i) varies with the type of mandibular activity, and (ii) is evenly distributed over TMJ surfaces. Ten healthy human participants were recorded with Magnetic Resonance Imaging (MRI) and jaw tracking. The data were used to reconstruct and animate TMJ activity. Aspect ratios, instantaneous velocities, and distances of stress-fields translation were used to calculate work (mJ). The results were analyzed by least-squares polynomial regression and ANOVA. Work magnitudes were related to peak velocity (R(2) = 0.92) and distance of stress-field translation (R(2) = 0.83), and were distributed over the joint surfaces (p < 0.03). During mandibular laterotrusion, average mechanical work was 1.5 times greater in the contralateral joint. Peak magnitudes of work (> 3000 mJ) were 4 times that previously reported.

Adult↗

PubMed2005

Relevance of mandibular helical axis analysis in functional and dysfunctional TMJs.

The helical axis (HA), or motion screw, yields a comprehensive description of joint motion. The perspective representation of this axis clearly visualizes the regularity of mandibular functional movements (Yatabe et al. 1997. Journal of Dentist Research 76, 714-719 and Gallo et al. 2000. Journal of Dental Research 79, 1566-1572). In this study, the sensitivity of the HA representation was investigated relative to (a) irregularities in pathologic motion of clicking temporomandibular joints (TMJs) for jaw opening/closing and (b) differences in food bolus size and consistency for unilateral mastication in subjects with normal TMJs. Mandibular motion relative to the head was acquired using a jaw tracker with six degrees-of-freedom with a sampling frequency of 70 Hz. The HA was calculated according to an eigenvalue method (Spoor and Veldpaus 1980. Journal of Biomechanics 13, 391-393) and parameters were defined describing its position and orientation relative to the anatomy. We analyzed 39 subjects with unilateral or bilateral reciprocal TMJ clicking during jaw opening/closing and seven asymptomatic subjects during unilateral mastication of five different types of soft and hard food in two different bolus sizes. The results showed a greater variability of the HA parameters in the group of clicking joints than in the asymptomatic group: in particular, the area in which the HA moved was wider in clicking joints than in normal ones and the HA in clicking TMJs had a much greater fluctuation than in normal ones. During unilateral mastication, for more consistent food or a bigger bolus the HA showed a significantly greater excursion of the orientation parameters. Furthermore a significantly greater excursion of the dorsoventral and of the craniocaudal component of the distance vector from the HA to the condyle were found. The helical axis analysis of mandibular movements was sensitive to kinematic irregularities of the mandible due to an internal joint derangement as well as to differences in food bolus size and consistency.

Adult↗

PubMed2005

Effect of occlusal interference on habitual activity of human masseter.

It has been suggested that occlusal interference may increase habitual activity in the jaw muscles and may lead to temporomandibular disorders (TMD). We tested these hypotheses by means of a double-blind randomized crossover experiment carried out on 11 young healthy females. Strips of gold foil were glued either on a selected occlusal contact area (active interference) or on the vestibular surface of the same tooth (dummy interference) and left for 8 days each. Electromyographic masseter activity was recorded in the natural environment by portable recorders under interference-free, dummy-interference, and active-interference conditions. The active occlusal interference caused a significant reduction in the number of activity periods per hour and in their mean amplitude. The EMG activity did not change significantly during the dummy-interference condition. None of the subjects developed signs and/or symptoms of TMD throughout the whole study, and most of them adapted fairly well to the occlusal disturbance.

Adaptation, Physiological↗

PubMed2004

Analysis of human mandibular mechanics based on screw theory and in vivo data.

In this paper the mechanics of human mandibular function is described in terms of the associated screws. The two distinct, yet related features of jaw mechanics, involving the motion itself as well as the forces, are both functions of the anatomical constraints, namely the contact areas that exist within the temporomandibular joint, and the forces of the muscles and tendons that allow motion to occur. The relationships that exist between these two aspects of jaw-motion are identified in this paper showing that muscle forces can be uniquely represented in terms of the action screw. This new approach to analyzing the mechanics of jaw-motion also incorporates the previously studied motion screw or helical axis. A consistent dynamic model is formulated where the action screw is used to represent the action of the closing muscle forces while the moment arms of the muscle forces are determined about the motion screw representing mandibular kinematics. The action screw formulation is verified using in vivo motion data and MR image information for a single asymptomatic subject. The results confirm the feasibility of the method and its application in dental research. A general increase in the mechanical advantage of most muscles, in the distance between action and motion screws as well as in the expended energy towards the end of the jaw-closing phase was observed. Asymmetries in the distribution of muscle force magnitudes appeared to influence the resultant force and moment of the action screw but had little effect on its spatial location. The method presented is intended to facilitate understanding of mandibular function and dysfunction.

Biomechanical Phenomena↗

PubMed2004

Dynamic intra-articular space variation in clicking TMJs.

During mandibular movement, the geometric relationships of the articular surfaces in the temporomandibular joint (TMJ) change, so that the disc undergoes different stress concentrations with respect to time and position. In this study, we compared the intra-articular space variations of 13 clicking and 15 asymptomatic TMJs for jaw opening/closing. Magnetic resonance imaging and jaw tracking were combined to display the motion of the whole condyle within the fossa. In clicking TMJs, the mediolateral spread s of the stress-field trajectories was 2.4 +/- 1.0 mm (s(max) = 4.9 +/- 2.1 mm) with an aspect ratio a/h of 2.5 +/- 1.6, both significantly greater than in controls (p < 0.05). The stress-field trajectories of the controls coincided during opening/closing (s = 0.9 +/- 0.2 mm, s(max) = 1.8 +/- 0.8 mm, a/h = 1.6 +/- 0.3). Clicking TMJs showed much less coincident stress-field paths and much "flatter" stress-fields than controls during jaw opening/closing.

Adolescent↗

PubMed2004

Cortical activation resulting from painless vibrotactile dental stimulation measured by functional magnetic resonance imaging (FMRI).

There have been few investigations on hemodynamic responses in the human cortex resulting from dental stimulation. Identification of cortical areas involved in stimulus perception may offer new targets for pain treatment. This initial study aimed at establishing a cortical map of dental representation, based on non-invasive fMRI measurements. Five right-handed subjects were studied. Eight maxillary and 8 mandibular teeth were stimulated after the vibratory perception threshold was determined for each tooth. Suprathreshold stimulation was repeated thrice per session, in a total of three sessions performed on three consecutive days. Statistical inference on cluster level identified increased blood-oxygen-level-dependent signal during vibratory dental stimulation, primarily in the insular cortex bilaterally and in the supplementary motor cortex. No significant brain activation was observed in the somatosensory cortex with this stimulation protocol. These results agree with previous findings obtained from invasive direct electrical cortical stimulation of the human insula.

Adult↗

PubMed2003

Dynamic stereometry of the temporomandibular joint.

Studies on jaw kinematics have provided a good understanding of the motion of the mandible in space, but are of little biomechanical relevance because they could not relate the movements to anatomic structures. This is possible by the combination of three-dimensional reconstructions of the temporomandibular joint (TMJ) anatomy with jaw motion recordings. This technique allows us to analyze the variation of the relationship between the articular surfaces, providing indirect insight into disk deformation during function and parafunction as well as TMJ loading. As far as the variation of the condyle-fossa distance is concerned, data indicated that during chewing the distance was smaller 1) on closing than on opening; 2) on the balancing than on the working side; and 3) during chewing of hard than soft food. Moreover, during a forceful static biting, the condyle-fossa distance decreased more on the contralateral, i.e. on the balancing side than on the working side. The decrease was related to the degree of clenching force. These results support the content that both condyles are loaded during chewing and the balancing side joint more than the working one. Biomechanically, the development of osteoarthrosis is more likely related to the magnitude and frequency of stresses applied on the cartilage. Joint movements produce tractional forces that may cause shear stresses contributing to cartilage wear and fatigue. Tractional forces are the result of frictional forces caused by the cartilage surface rubbing and of plowing forces caused by the translation of a stress-field through the cartilage matrix, as the intra-articular space changes during motion. Translation of the stress-field in mediolateral direction seems to be particularly important for the integrity of the TMJ disk because of its anisotropic properties. Dynamic stereometry showed that stress-fields translate in mediolateral direction during opening/closing, protrusion and laterotrusion, and that their translatory velocity varies intraindividually and with the rate of the condylar movement. Furthermore, the results seem to indicate that the lateral area of the TMJ disk is more often exposed to shear stresses caused by stress-field translation than the medial one. In conclusion, dynamic stereometry provides a good visualization of the movement of the condyles in the respective fossae. This helps improving our understanding for the complexity of condylar movements. The technique may also contribute to ameliorate our knowledge of TMJ biomechanics and therefore of the etiology of degenerative joint diseases and possibly also of internal derangement.

Biomechanical Phenomena↗

PubMed2000

Mandibular helical axis pathways during mastication.

Condylar and incisor trajectories are often used for the study of mandibular movements. Condylar trajectories, however, depend on the location of the reference point and can be interpreted erroneously. In contrast, the helical axis analysis yields an unequivocal description of rigid body kinematics. The aim of this study was to analyze the mandibular helical axis during mastication. Seven subjects without signs and symptoms of craniomandibular disorders and with class I occlusion were recorded by means of the opto-electronic system Jaws-3D during unilateral mastication of bread cubes (2-cm side). The helical axis was computed every 14 ms with a rotation threshold of 1 . Parameters describing its spatial orientation and position relative to the condyles were calculated. The helical axis changed orientation and position more pronouncedly during the closing than during the opening phases of mastication. The orientation varied significantly from beginning to end of closing but not of opening, indicating less fluctuation of the helical axis on opening than on closing. Also, the distance dCP between helical axis and reference condylar point varied more significantly (p < 0.05) on the working than on the balancing side: On the working side, dCP decreased during both opening and closing, whereas on the balancing side, dCP increased only for closing. Furthermore, the helical axis pathway often showed a bowing ventrally to the balancing condyle, indicating that, during closing, the balancing condyle still translated backward while essentially only rotation occurred around the working condyle. Thus, the helical axis changed its position and orientation continuously during mastication.

Adult↗

PubMed2000

Stress-field translation in the healthy human temporomandibular joint.

Movement over the surface of the temporomandibular joint (TMJ) disc produces tractional forces. These forces potentially increase the magnitude of shear stresses and contribute to wear and fatigue of the disc. Theoretically, tractional forces in all synovial joints are the result of frictional forces, due to rubbing of the cartilage surfaces, and plowing forces, due to translation of the stress-field through the cartilage matrix as the joint surface congruency changes during motion. For plowing forces to occur in the TMJ, there must be mediolateral translation of the stress-field as the condyle moves dorsoventrally during jaw function. To test whether mediolateral stress-field translation occurs in the intact TMJ, we measured stress-field position and translation velocities in ten normal individuals during rhythmic jaw opening and closing. Magnetic resonance imaging and jaw tracking were combined to animate the three-dimensional position of the stress-field between the articulating surfaces. This allowed for mediolateral translation velocity measurements of the centroid of the stress-field. The results showed that during jaw opening and closing at 0.5 Hz, the average peak mediolateral translation velocity was 35 +/- 17 mm/sec. When opening and closing increased to 1.0 Hz, the average peak velocity was 40 +/- 19 mm/sec. Theoretical model estimates of the work done during such translation ranged from 6 to 709 mJ between the individual joints studied. The potential clinical importance of this measure is that long-term exposure of the TMJ disc to high work may result in fatigue failure of the TMJ disc.

Adult↗

PubMed2000

Dynamic magnetic resonance imaging technique for the study of the temporomandibular joint.

AIMS: Echo planar imaging (EPI) is an ultrafast magnetic resonance imaging (MRI) technique that can scan a single frame in less than a second. The aim of this study was to use the EPI technique to develop a new dynamic MRI protocol for the temporomandibular joint (TMJ). METHODS: Basic fast-field echo and EPI pulse sequences were used for dynamic studies of the TMJ. The subjects were instructed to perform spontaneous, continuous, slow opening/closing movements without visual or audio feedback. Different scanning parameter settings were explored to optimize the results. RESULTS: With an opening/closing movement of approximately 6 to 7 seconds per cycle, the proposed protocol yielded a good insight into the relative motion between condyle and disc. It was also possible to see the deformation of the disc during movement. CONCLUSION: The EPI technique is a non-invasive technique that can be used for dynamic imaging study of a slow but continuous, uninterrupted jaw movement.

Adult↗

PubMed2000

Individualized oblique-axial magnetic resonance imaging for improved visualization of mediolateral TMJ disc displacement.

AIMS: A new individualized oblique-axial orientation of magnetic resonance imaging scans of the temporomandibular joint (TMJ), corrected to be perpendicular to the tangent of the posterior slope of the articular eminence, has been proposed to improve the representation of the disc. The aim of this study was to evaluate the quality of the images obtained with this new type of scanning plane and to assess the factors that can affect the scans. METHODS: Twenty-nine TMJs were scanned by the use of sagittal, conventional coronal, and individualized oblique-axial scanning planes. On the sagittal images, the angle alpha between the tangent of the posterior slope of the articular eminence and the vertical was measured, and the disc position was evaluated. For both imaging planes, 2 examiners, blind to the scanning techniques, counted the number of conventional coronal and oblique-axial scans in which the disc was visible and in which the medial and lateral disc borders were well demarcated and evaluated the mediolateral disc position. RESULTS: The individualized oblique-axial technique was superior to the conventional coronal technique in depicting the disc and its medial and lateral demarcations (paired t test, P < 0.05). The possibility of correct diagnosis of the mediolateral disc position and the agreement between the observers in this evaluation were better with the oblique-axial technique than with the conventional technique (P < 0.05). This was particularly evident when the disc was anteriorly displaced. CONCLUSION: The individualized oblique-axial scanning planes should be used for a better representation of the disc/condyle complex mediolaterally if the disc is anteriorly displaced.

Adolescent↗

PubMed2000

Reproducibility of temporomandibular joint clicking.

AIMS: To investigate the stability of temporomandibular joint (TMJ) clicking over a 10-day period and the effect of different open/close velocities on sound amplitude and power spectra in a group of subjects with subjectively stable unilateral clicking during the 3 months preceding the recordings. METHODS: Ten volunteers were recorded with a self-developed microcomputer-based system used in a previous study on asymptomatic subjects. The recordings were performed during 4 different sessions at 3 different open/close rates in each session. The subjective sound intensity was measured with a 100-mm visual analog scale (VAS). The VAS scores, the maximum amplitudes, and the power spectra of the signals were tested for statistical differences among the different open/close rates and over the sessions. The reliability of measurements was also calculated. RESULTS: The maximum amplitude and the power spectra of the TMJ clicking varied between subjects in a broad range that differed from those reported for asymptomatic subjects. No statistically significant differences were found within subjects for the subjective VAS scores for the maximum signal amplitudes or for the power spectrum parameters among the open/close rates and over the 4 sessions. For all 3 open/close rates and for the 4 sessions, a good to excellent reliability of measurements was determined, the values of r being mostly over 0.75. CONCLUSION: Within the limits of the experiment, TMJ clicking was subjectively and objectively stable over a period of 10 days. Therefore, the constant subjective perception of sound intensity was supported by the objective measurements.

Adult↗

PubMed1999

Nocturnal masseter EMG activity of healthy subjects in a natural environment.

Facial pain of patients with craniomandibular disorders might be caused by muscle overload. However, the activity of masticatory muscles of healthy individuals is still unknown. The aim of this study was therefore a first attempt to clarify this question by recording the masseter muscle activity of healthy subjects during sleep by means of portable recorders. The study was performed on 21 healthy subjects selected after telephone and questionnaire screenings and clinical examination from among randomly selected inhabitants of Zürich. The masseter EMG was recorded during seven nights in each subject's natural environment with the electrodes in reproducible position. The signal was analyzed for number, amplitude, and duration of contraction periods defined as signal portions above a threshold which could contain sub-threshold signal portions shorter than the standby time of 5 sec. The signal amplitude was expressed in percent of the amplitude recorded during maximum voluntary clenches (%MVC). An average of 71.9 +/- 28.7 contraction episodes per night (men, 74.7 +/- 30.1; women, 65.0 +/- 23.8; p = 0.043), i.e., of 10.5 +/- 3.8 per hour (men, 11.0 +/- 4.0; women, 9.3 +/- 3.0; p = 0.005), was found. The average mean amplitude was 26.2 +/- 6.4% MVC (men, 27.0 +/- 6.8; women, 24.4 +/- 4.5; p = 0.009). The duration of the episodes had a mode of 0.5 sec, and the group mean of the integral of the amplitude over time was 123.7 +/- 157.9% MVC (men, 138.9 +/- 184.0; women, 85.9 +/- 28.2; p = 0.005). Healthy subjects showed intermittent periods of masseter activity during sleep which, on average, were of rather low intensity and short duration.

Adult↗

PubMed1998

Automatic on-line one-channel recognition of masseter activity.

The etiology of myoarthropathies of the masticatory system (MAP) is not fully understood. For the hypothetical association between the myogenous pain of MAP patients and masticatory muscle overuse to be proved, functional and parafunctional behavior of the masticatory muscles should be analyzed in normal and diseased subjects. The aim of this study was to test on-line the validity and reliability of an algorithm, applied to the electromyographic signal, to recognize various oral activities. The surface electromyogram of the masseter muscle was recorded in 12 subjects (seven females and five males, from 18 to 32 years old) who performed a series of functional and parafunctional activities (chewing soft food, chewing hard food, swallowing, laughing, speaking, and tooth grinding and clenching), as well as no activity. During the computer training phase, intra-individual classification functions of a multivariate discriminant analysis were calculated while each subject performed the described activities. During the test phase, each subject repeated the same activities, and the computer continuously classified them on-line. The percentage of correctly recognized activities was calculated for each activity and for each subject. No activity, chewing hard food, swallowing, laughing, grinding, and clenching were recognized correctly > 99% of the time. Chewing soft food was recognized correctly 97% and speaking 86% of the time. The sensitivity values for the recognition rates of the complete oral activities were, with one exception, > 0.82; the specificity values were > 0.95, and the kappa-values > 0.80. These results show that the algorithm had high sensitivity, specificity, and reliability in the classification of different oral activities under laboratory conditions.

Adolescent↗

PubMed1997

Reliability of scoring EMG orofacial events: polysomnography compared with ambulatory recordings.

The study of sleep bruxism is usually based on clinical history, signs and symptoms. The recording of electromyographic signals with either ambulatory portable home recorders or with polysomnographic techniques in the laboratory environment allows collection of objective data. The present study showed a 100% agreement with clinical evaluation in the recognition of bruxism episodes from the masseter electromyogram recorded with portable recorders and using the polysomnographic technique. On the contrary, scorers had difficulties in discriminating between different types of episodes (phasic, tonic and mixed), the between-scorers agreement varied between 62% and 63% and the kappa-values between 0.43 and 0.33. The ideal time base at which electromyographic signals should be integrated to allow for a good discrimination of bruxism patterns is 0.06 s. The results indicate that portable electromyography recorders are a valuable complement to polysomnographic recordings of orofacial motor activities as they provide a very good recognition rate with adequate time base data collection.

Adult↗

PubMed1997

Description of mandibular finite helical axis pathways in asymptomatic subjects.

Despite wide use of systems to record jaw motion with six degrees of freedom, most studies have analyzed only the movement of a single mandibular point. The finite helical axis (FHA) is a mathematical model which can be used to describe comprehensively the movements of a rigid body. The aim of this investigation was to describe the FHA of the mandible during habitual jaw movements. Thirty subjects (13 females, 17 males; mean age, 26 years; range, 18 to 34 years) without myoarthropathies of the masticatory system participated in the study. Opening and closing movements, performed at 1-Hz frequency, were recorded with the optoelectronic system Jaws-3D. Three opening and closing movements were recorded from the right side and three from the left side of the jaw. The movement data were low-pass-filtered for noise reduction prior to the computation of the finite helical axis by means of a software program developed in our laboratory. The following parameters were calculated: the rotation of the FHA, its spatial orientation, and the translation along it, as well as its position and distance relative to an intracondylar point. In addition, methodological errors of the model were calculated. During opening and closing, the group mean FHA rotation was 24.3 degrees +/- 4.2 degrees. The group mean of the maximum total translation along the FHA was 0.9 +/- 0.7 mm. The group mean distance between the FHA and the intracondylar point was 48.9 +/- 9.9 mm. The FHA pathways were smooth and varied between individuals. Furthermore, the finite helical axes were never localized within the condyle, and often were located outside of the mandible. The analysis of the FHA pathways yields more information on whole mandibular movements than simply the movements of a single condylar point.

Adolescent↗

PubMed1995

Activity recognition in long-term electromyograms.

Long-term electromyography with portable recorders allows the study of muscle activity in the natural environment to investigate whether muscle overuse or oral habits may contribute to initiate or perpetuate a myoarthropathy of the masticatory system. At present, little is known about the behaviour of masticatory muscles over long time periods. The aim of this preliminary study was to define parameters which allow the automatic recognition of different types of oral activities from the electromyogram form. A programme with functional and parafunctional activities was performed by four volunteers (total of 333 functional and 82 parafunctional recordings). Electromyograms of the masseter and temporal muscles were recorded by means of a self-developed portable intelligent solid state recorder. Signal mean level (mw) and dynamics (dw) within a sliding window were determined. Temporal muscle recordings allowed better discrimination between function and simulated parafunction. The average of mw for clenching was 51.4 +/- 3.5% and for tooth grinding 21.2 +/- 2% of the peak electromyogram value at maximum voluntary clench. At 0.96 s sliding window duration, clenching, tooth grinding and chewing signals had maximum separation, using dw/mw as parameters (average: 0.16 +/- 0.01 for clenching, 0.39 +/- 0.01 for teeth grinding and 0.88 +/- 0.01 for chewing).

Adult↗