Preliminary approach for the surface electromyographical evaluation of the oral phase of swallowing.

Swallowing is a muscular activity that occurs both after mastication and spontaneously as a result of saliva accumulation. Spontaneous saliva swallowing occurs about every 2 minutes. Comprehension of its functional mechanisms is relevant to assess their modification in clinical situations. A standardised surface electromyographical (ssEMG) protocol for the evaluation of this muscle activity is lacking. Aims of the present study are: (i) to determine the reproducibility of a ssEMG protocol for the evaluation of the oral phase of saliva swallowing and (ii) to evaluate the activity of masseter (MM), anterior temporalis (TA), submental muscles (SM) to draw a reference model of swallowing. Standardised surface electromyographical activity of MM, TA and SM during swallowing of saliva spontaneously accumulated was recorded in 20 healthy participants. Functional indexes including symmetry (POC), recruitment (Impact), duration of activation of each couple of muscles and of the whole exercise, position, intensity of the spike were computed. Inter- and intra-appointment reliabilities were assessed and method errors calculated. Descriptive statistics, sex- and muscles-related comparisons were carried out. Standardised surface electromyographical assessment of MM, TA and SM muscles was reliable. A high inter-individual variability was found. Percentage overlapping coefficient (POC) values were close to 80% for TA and SM, higher than for MM (P < .001). Impact values ranged between 16.4% and 30.7%, and differences were found between muscles (P < .001). The global muscle activity during swallowing lasted between 1.5 and 1.8 seconds. For each couple of muscles, the duration of activation ranged between 0.7 and 1.6 seconds and muscles-related differences were found (P < .001). The spike of activation for each couple of muscle ranged between 35.7% and 44.2% of the duration. The protocol was reliable and intra-participants repeatable measures can be carried out. Due to the high inter-participants variability, further analyses are needed to draw a model of muscular activity.

Electromyographic assessment of jaw muscles in patients with All-on-Four fixed implant-supported prostheses.

This study evaluated the electromyographic (EMG) characteristics of masticatory muscles in patients with fixed implant-supported prostheses according to All-on-Four(®) principles and in control healthy dentate subjects. Twenty-six subjects aged 50-74 years were examined. Eighteen were edentulous and had been successfully rehabilitated with (i) mandibular All-on-Four(®) implant-supported fixed prostheses and maxillary complete dentures (10 patients) and (ii) mandibular and maxillary All-on-Four(®) implant-supported fixed prostheses (eight patients). Eight reference subjects had natural dentition. Surface EMG recordings of the masseter and temporalis muscles were performed during maximum voluntary teeth clenching and during unilateral gum chewing. All values were standardised as percentage of a maximum clenching on cotton rolls. During clenching, a good global neuromuscular equilibrium was found in all participants. During chewing, all groups had similar values of working-side muscle activities and of chewing frequency. No significant differences in the analysed EMG parameters were found between the patients with mandibular and maxillary All-on-Four(®) implant-supported prostheses and the reference subjects. In contrast, standardised pooled muscle activities and standardised muscular activities per cycle were larger in patients with a maxillary removable prosthesis than in control subjects (Kruskal-Wallis test, P < 0·01). Also, patients wearing a complete maxillary denture showed a poor neuromuscular coordination with altered muscular pattern and lower values of the index of masticatory symmetry than dentate control subjects (P < 0·01). EMG outcomes suggest that All-on-Four(®) implant-supported prostheses may be considered a functionally efficient treatment option for the rehabilitation of edentulous patients with reduced residual bone volume.

Three-dimensional analysis of dentolabial relationships: effect of age and sex in healthy dentition.

Morphological changes in three-dimensional (3D) dentolabial relationships during ageing were assessed in healthy individuals. 38 subjects with healthy dentition were analysed. They were divided into a youthful group (21-34 years, mean 26 years, SD 4) and an older group (45-65 years, mean 53 years, SD 5). Stone labial and dental models were made, digitized and 3D virtual reproductions of dentolabial morphology were obtained. From the digital reconstructions, the relative positions of the labial commissure and of the maxillary dental clinical crowns in the vertical direction were obtained. Sex and age effects were compared using two-way analysis of variance. Lip position relative to the teeth was significantly different in youthful and older subjects (P<0.01). No statistically significant effects of sex in dentolabial relationship were demonstrated, but a sex×age effect was found in the anterior labial segments (P<0.05). The perioral soft tissues drop down in older subjects and the soft tissue descends on the entire labial arch. These differences may help the clinician when estimating, planning and evaluating surgical, orthodontic and prosthetic treatments.

Facial mimicry after conservative parotidectomy: a three-dimensional optoelectronic study.

Facial nerve paralysis is one of several possible complications following conservative parotidectomy. To assess three-dimensional facial movements non-invasively in patients with unilateral facial palsy following parotidectomy for benign tumours, the three-dimensional coordinates of 21 soft-tissue facial landmarks were recorded in 32 patients (21 HB I, 5 HB II, 6 HB III-IV; 3 months post-surgery follow-up), and 40 control subjects, during the performance of facial movements (smile, 'surprise', eye closure, single eye closure). For all symmetric animations, control subjects had larger total mobility than patients; mobility progressively decreased in patients with larger clinical grades. For asymmetric eye closures, HB I patients and control subjects had similar total movements, while HB II patients had smaller movements, especially for the paretic side eye closure; smaller total movements were found in HB III-IV patients. The method allowed the quantitative detection of alterations in facial movements. Significant differences between patients and control subjects in the magnitude and asymmetry of movements were found.

The effect of age and sex on facial mimicry: a three-dimensional study in healthy adults.

To assess sex- and age-related characteristics in standardized facial movements, 40 healthy adults (20 men, 20 women; aged 20-50 years) performed seven standardized facial movements (maximum smile; free smile; "surprise" with closed mouth; "surprise" with open mouth; eye closure; right- and left-side eye closures). The three-dimensional coordinates of 21 soft tissue facial landmarks were recorded by a motion analyser, their movements computed, and asymmetry indices calculated. Within each movement, total facial mobility was independent from sex and age (analysis of variance, p>0.05). Asymmetry indices of the eyes and mouth were similar in both sexes (p>0.05). Age significantly influenced eye and mouth asymmetries of the right-side eye closure, and eye asymmetry of the surprise movement. On average, the asymmetry indices of the symmetric movements were always lower than 8%, and most did not deviate from the expected value of 0 (Student's t). Larger asymmetries were found for the asymmetric eye closures (eyes, up to 50%, p<0.05; mouth, up to 30%, p<0.05 only in the 20-30-year-old subjects). In conclusion, sex and age had a limited influence on total facial motion and asymmetry in normal adult men and women.

Relationship between facial morphology and cervical vertebral shape: a radiographic investigation.

AIM: The aim of this study was to investigate the relationships between the characteristics of cervical vertebrae and craniofacial morphology using a global mathematical method. METHODS: Several cephalometric measurements and the outlines of the second (C2) and fourth (C4) cervical vertebrae were obtained from 45 head films (32 females aged 20-40 years; 13 males aged 21-37 years). Vertebral outlines were mathematically obtained by Fourier series, and the morphological distance between each outline and a reference one was computed. Linear correlations were run between cephalometric variables and morphological distances. RESULTS: Significant correlations (P<0.05) were found between anterior cranial base length (sella-nasion) and the morphological distance of C4 (subjects with a longer cranial base differ more from the reference vertebral outline), and between maxillary length and the morphological distance of C2 (subjects with a shorter maxilla differ more from the reference vertebral outline). The relationship between mandibular base length (Go-Me) and the morphological distance of C2 (subjects with a shorter mandible differ more from the reference vertebral outline) was nearly significant. Within each subject, the two analyzed vertebrae had independent relationships with the reference outlines. CONCLUSION: A significant but limited relationship between craniofacial structures and vertebral morphology was found: at the best, 10% of the differences between the individual vertebral morphology and the reference one may be explained by craniofacial cephalometric measurements. The differences found between C2 and C4 morphologies may show a different effect of suboccipital muscles and of neck muscles within the theories of the functional matrix hypothesis.

Palate morphology of bruxist children with mixed dentition. A pilot study.

The objective of the study was to analyse quantitatively palatal morphology in bruxist and non-bruxist children with mixed dentition. Twenty-three children with mixed dentition were classified as bruxist according to their anxiety level, audible occlusal sounds related by the parents and signs of temporomandibular disorders; 23 children were control subjects matched for gender, age, and dental formula. The maxillary dental arches of all subjects were reproduced from alginate impressions cast in dental stone with a standardized technique. The casts were digitalized and mathematical equations were used to obtain the form of the palate in the sagittal, frontal and horizontal planes. Bruxist children had a statistically significant longer palate in the sagittal plane than control children; palatal shape differed especially in correspondence of the third, fourth and fifth teeth, bruxist children showing a relatively higher palate than control children. In this pilot study, sagittal plane differences in the palate between bruxist and non-bruxist children matched for age and gender were found. Further investigations are needed to understand better the clinical implications of the findings. Results should be taken into account in the diagnosis of the occlusal development in children with parafunctions to prevent future abnormalities: a bruxist child may have bigger dental arches than a normal child.

Anatomy of emotion: a 3D study of facial mimicry.

Alterations in facial motion severely impair the quality of life and social interaction of patients, and an objective grading of facial function is necessary. A method for the non-invasive detection of 3D facial movements was developed. Sequences of six standardized facial movements (maximum smile; free smile; surprise with closed mouth; surprise with open mouth; right side eye closure; left side eye closure) were recorded in 20 healthy young adults (10 men, 10 women) using an optoelectronic motion analyzer. For each subject, 21 cutaneous landmarks were identified by 2-mm reflective markers, and their 3D movements during each facial animation were computed. Three repetitions of each expression were recorded (within-session error), and four separate sessions were used (between-session error). To assess the within-session error, the technical error of the measurement (random error, TEM) was computed separately for each sex, movement and landmark. To assess the between-session repeatability, the standard deviation among the mean displacements of each landmark (four independent sessions) was computed for each movement. TEM for the single landmarks ranged between 0.3 and 9.42 mm (intrasession error). The sex- and movement-related differences were statistically significant (two-way analysis of variance, p=0.003 for sex comparison, p=0.009 for the six movements, p<0.001 for the sex x movement interaction). Among four different (independent) sessions, the left eye closure had the worst repeatability, the right eye closure had the best one; the differences among various movements were statistically significant (one-way analysis of variance, p=0.041). In conclusion, the current protocol demonstrated a sufficient repeatability for a future clinical application. Great care should be taken to assure a consistent marker positioning in all the subjects.

Two-dimensional vs three-dimensional assessment of soft tissue facial profile: a non invasive study in 6-year-old healthy children.

AIM: In medical practice, the analysis of facial soft tissues often complement (or even supplement) the evaluation of the hard-tissue relationships. Current technology provides reference data in three dimensions, but clinical practice still uses two-dimensional photographs. In the current study, two-dimensional photographic and computerized, three-dimensional angles measured on the facial profile of children were compared. METHODS: Two-dimensional angular measurements (facial convexity including/excluding the nose; maxillary prominence; nasal prominence; nasolabial; mentolabial; maxillo-labio-mandibular; interlabial) were obtained on the facial profile photographs of 55 boys and 31 girls aged 6; measurements were compared to three-dimensional computerized data collected on 27 boys and 28 girls of the same age and ethnic group. RESULTS: On average, in boys, only the angles of facial convexity including the nose, interlabial, nasolabial and maxillo-labio-mandibular showed differences between the means larger than 2 degrees (up to 2.5 degrees). Statistically significant differences (P<0.05, Watson-Williams' test) were found for the angle of facial convexity including the nose and the maxillary prominence angle. In girls, differences between the two methods larger than 2 degrees were found for the interlabial, maxillo-labio-mandibular (statistically significant), and mentolabial angles (differences up to 7 degrees, corresponding to 4% of the relevant mean). CONCLUSION: The two-dimensional photographic and the three-dimensional computerized data compared in the current study, even not superimposable, seemed sufficiently interchangeable, at least from a clinical point of view. A particular attention should be given to the recording of lip position.

The influence of occlusion on jaw and neck muscle activity: a surface EMG study in healthy young adults.

The electromyographic (EMG) characteristics of masseter, temporalis and sternocleidomastoid (SCM) muscles during maximum voluntary teeth clench were assessed in 27 male and 35 female healthy young adults. Subjects were divided into two groups: (i) 'complete' Angle Class I (bilateral, symmetric canine and molar Class I relationships), and (ii) 'partial' Angle Class I (one to three canine/molar Class I relationships, the remaining relationships were Class II or Class III). On average, standardized muscular symmetry ranged 80.7-87.9%. During maximum voluntary teeth clench, average co-contraction of SCM muscle was 13.7-23.5% of its maximum contraction. On average, all torque coefficients (potential lateral displacing component) were >90%, while all antero-posterior coefficients (relative activities of masseter and temporalis muscles) were >85%. The average integrated areas of the masseter and temporalis EMG potentials over time ranged 87.4-106.8 muV/muV s%. Standardized contractile muscular activities did not differ between 'complete' and 'partial' Angle Class I, and between sexes (two-way analysis of variance). A trend toward a larger intragroup variability in EMG indices was observed in the subjects with 'partial' Angle Class I than in those with 'complete' Angle Class I (significant difference for the temporalis muscle symmetry, P = 0.013, analysis of variance). In conclusion, the presence of a complete or partial Angle occlusal Class I did not seem to influence the standardized contractile activities of masseter, temporalis and SCM muscles during a maximum voluntary clench. Subjects with a 'complete' Angle Class I were somewhat a more homogenous group than subjects with 'partial' Angle Class I.

Facial changes in adult uremic patients on chronic dialysis: possible role of hyperparathyroidism.

BACKGROUND: Uremic patients on regular dialytic treatment (RDT) are often affected by a complex metabolic syndrome leading to osteodystrophy. Bone changes are primarily due to high bone turnover, often combined with a mineralization defect leading to increased bone fractures and bone deformities. Although rarely considered, the craniofacial skeleton represents one of the peculiar targets of this complex metabolic disease whose more dramatic pattern is a form of leontiasis ossea. This complication, although described, has never been evaluated in depth nor quantitatively assessed. In order to assess facial deformities in uremic conditions and to understand the possible relation with hyperparathyroidism, we undertook a quantitative evaluation of soft facial structures in a cohort of uremic patients undergoing RDT. METHODS: The three-dimensional coordinates of 50 soft-tissue facial landmarks were obtained by an electromagnetic digitizer in 10 male and 10 female patients with chronic renal insufficiency aged 53-81 years, and in 34 healthy individuals of the same age, ethnicity and sex. Uremic patients were enrolled according to hyperparathyroid status (PTH < 300 pg/mL and PTH > 500 pg/mL). From the landmarks, facial distances, angles and volumes were calculated according to a geometrical face model. RESULTS: Overall, the uremic patients had significantly larger facial volumes than the reference subjects. The effect was particularly evident in the facial middle third (maxilla), leading to an inversion of the mandibular-maxillary ratio. Facial dimensions were increased in all three spatial directions: width (skull base, mandible, nose), length (nose, mandible), and depth (mid face, mandible). The larger maxilla was accompanied by a tendency to more prominent lips (reduced interlabial angle). Some of the facial modifications (nose, lips, mandible) were significantly related to the clinical characteristics of the patients (age, duration of renal insufficiency and PTH levels). CONCLUSIONS: This report, the first in the literature, shows that facial structures of uremic patients are enlarged in comparison with matched normal subjects and that increased bone turnover could be responsible--at least in part--for facial bone changes.

Morphometry of the ear in Down's syndrome subjects. A three-dimensional computerized assessment.

The three-dimensional coordinates of 13 soft-tissue landmarks on the ears were obtained by a computerized digitizer in 28 subjects with Down's syndrome aged 12-45 years, and in 449 sex, age and ethnic group matched controls. From the landmarks, left and right linear distances (ear width and length), ratios (ear width-to-ear length), areas (ear area), angles (angle of the auricle versus the facial midplane) and the three-dimensional symmetry index were calculated. For both males and females, all linear dimensions and areas were significantly (Analysis of Variance, P < 0.001) larger in the reference subjects than in the subjects with Down's syndrome. All values significantly increased as a function of age (P < 0.05); the increment was larger in the reference subjects than in the subjects with Down's syndrome. On both sides of the face, the subjects with Down's syndrome had larger ear width-to-ear length ratios, and larger angles of the auricle versus the facial midplane than the reference subjects. The three-dimensional symmetry index was significantly larger in the reference subjects and in the older persons. In conclusion, ear dimensions, position and shape significantly differed in subjects with Down's syndrome when compared to sex, age and ethnic group matched controls. Some of the differences were sex and age related.

Body movements on the men's competition mushroom: a three dimensional analysis of circular swings.

OBJECTIVES: To develop a method for the three dimensional analysis of body movements and body positions during the performance of circular swings on the competition mushroom, an apparatus used by young gymnasts for pommel horse training. METHODS: Five experienced male gymnasts, all of national level, performed three series of 10 circular swings on the competition mushroom. An optoelectronic instrument was used for the detection of the three dimensional movement of 13 body landmarks. From landmark trajectories, several technical measurements were obtained: diameters of ideal circles of ankles, hips, shoulders; deviation of the ankle diameters from circularity and from the horizontal plane; angle between the shoulder, hip, and ankle. The values were used for a quantitative assessment of performance of the five gymnasts. RESULTS: During the exercise, each ankle should follow a nearly horizontal circular path (deviation from circularity ranged from 3.6% to 6%, deviation from horizontality was 9.4-19.7%), there should be an angle of about 180 degrees at the hips (actual values 146-153 degrees ), and the shoulders should move as little as possible, and only in the lateral plane, without major anteroposterior movements (shoulder movement was 27-31% of ankle movement, hip movement was 16-20%). CONCLUSIONS: The method could help coaches and gymnasts to determine which parts of the body are not repeating a selected movement with sufficient accuracy and to quantify improvements made after a specific training programme.

Spatiotemporal consistency of trajectories in gymnastics: a three-dimensional analysis of flic-flac.

Sport performance during the execution of closed skills combines specific body and limb movements into codified patterns where stability and consistency may be more important than variability. Repeated sport movements can be investigated to assess the consistency of body trajectories. More consistent trajectories will result in more repeatable movements. The present study quantified the short-term consistency of body trajectories during the performance of the backward flic-flac, a technique of floor gymnastics. Nine experienced gymnasts (six men, three women), all of national level, performed 10 repetitions of backward flic-flac. An optoelectronic instrument was used for the detection of the three-dimensional movement of 13 body landmarks. The spatiotemporal consistency of repeated landmark trajectories was measured by the standard deviation between standardized trajectories. The results showed smaller standard deviation (larger consistency between landmark trajectories) in female than in male gymnasts. The analysis of the consistency of landmark trajectories could help gymnasts indicating which parts of the body do not repeat a selected movement with sufficient accuracy.

Single tooth bite forces in healthy young adults.

The assessment of bite forces on healthy single tooth appears essential for a correct quantification of the actual impact of single implant oral rehabilitations. In the present study, a new single tooth strain-gauge bite transducer was used in 52 healthy young adults (36 men, 16 women) with a complete permanent dentition. The influences of tooth position along the dental arch, of side, and of sex, on maximum bite force were assessed by an ANOVA. No significant left-right differences were found. On average, in both sexes the lowest bite force was recorded on the incisors (40-48% of maximum single tooth bite force), the largest force was recorded on the first molar. Bite forces were larger in men than in women (P < 0.002), and increased monotonically along the arch until the first or second permanent molar (P < 0.0001). The present data can be used as reference values for the comparison of dental forces in patients.

Evidence of an influence of asymmetrical occlusal interferences on the activity of the sternocleidomastoid muscle.

To investigate the hypothesis of a functional coupling between occlusion and neck muscles, the immediate effect of asymmetrical occlusal interferences on the pattern of contraction of the sternocleidomastoid muscles (SCM) during maximum voluntary clench (MVC) was analysed in 30 healthy subjects. All subjects had a complete and sound permanent dentition, without temporomandibular joint (TMJ) and craniocervical disorders. A 5-s surface electromyogram (EMG) examination of the SCM was performed during (1) MVC in intercuspal position and (2) MVC with a single 200-microm occlusal interference alternatively positioned on teeth 16, 13, 23, 26. All subjects had a symmetrical EMG activity during MVC in intercuspal position. For each subject, SCM potentials were standardized as percentage of the mean potentials recorded during the MVC on natural dentition and the EMG waves of left- and right-side muscles were compared by computing the relevant percentage overlapping coefficient (POC). For each subject, the best and the worst POCs computed during the four MVC tests with occlusal interferences were found and the percentage difference between them was calculated. In the four MVC tests with occlusal interferences, SCM symmetry was very different from that recorded during MVC on natural dentition. The difference between the best and worst POCs computed within each subject was very variable, ranging from 1.52 to 41.57%. In conclusion, when young healthy subjects with a normal occlusion clench on an asymmetrical occlusal interference, they have an altered left-right side pattern of contraction of their SCM. In almost all subjects, a previously symmetrical pattern became asymmetrical.

Immediate effect of a stabilization splint on masticatory muscle activity in temporomandibular disorder patients.

Surface electromyography (EMG) allows the quantification of the occlusal equilibrium in dysfunctional patients, for instance in those with temporomandibular disorders (TMD). Fourteen patients (ten women, four men) with internal derangement type I were selected among the TMD patients referred to a private practice in Milan. A stabilization splint with posterior contacts was made for each patient. To verify the static neuromuscular equilibrium of occlusion, EMG activity of left and right temporal and masseter muscles was recorded in all patients and the activity (ratio between the activities of the temporal and masseter muscles) index was computed over a maximum voluntary clench test of 3 s. Muscular waveforms were also analysed by computing a percentage overlapping coefficient (POC, an index of the symmetric distribution of the muscular activity determined by the occlusion). The total electrical activity was measured by calculating the area under the entire muscular waveforms. In all patients EMG was performed just before and immediately after the insertion of the splint and data were compared by paired Student's t-tests. Overall, the splint reduced the electrical activity of the analysed muscles (P < 0.005) and made it more equilibrated both between the left and right side (larger symmetry in the masseter muscle POC, P < 0.05) and between the temporal and masseter muscles (activity index, P < 0.01).

Comparison of unilateral chewing movements vs. dental guidance through the dental guidance ratio.

STATEMENT OF PROBLEM: Limited knowledge exists about the interaction between dental morphology and mandibular excursive movements. PURPOSE: This study evaluated dental guidance in lateral excursive movement and its relationship to jaw motion in unilateral chewing. MATERIAL AND METHODS: Three-dimensional mandibular movement paths (in lateral guiding movements and in the final part of a monolateral chewing stroke) were collected with automated infrared motion analysis in 22 subjects with complete, permanent dentitions. On 2 traces selected from the recorded movements, the angular values projected in all planes of space obtained from 2 lines tangent to a point at a distance of 2.5 mm from maximum intercuspation were used to calculate a canine and a molar dental guidance ratio (DGR). Descriptive statistics were computed for the DGRs in the 3 spatial planes. RESULTS: Assuming masticatory movements of any given subject are restricted or guided by dental anatomy, a value below 100% of the DGR was expected. This was true for the frontal plane only, with mean values of approximately 80% (working-side movements, canines, and molars) and approximately 60% (nonworking-side movements for both molars and canines). In the horizontal and sagittal planes, mean values between 102% and 137% were found. CONCLUSION: Within the limitations of this study, masticatory movement was within the physical borders dictated by dental anatomy in the frontal plane only.

Three-dimensional hard tissue palatal size and shape in human adolescents and adults.

Hard tissue palatal dimensions and shape in 29 boys and 32 girls (mean age 14 years) and 30 men and 35 women (mean age 20 years), all with a complete permanent dentition including the second molars, and free from respiratory problems, were analyzed. Palatal landmarks were digitized with a computerized 3D instrument, and their coordinates were used to derive a mathematical model of palatal form. Palatal shape (size-independent) was assessed by a four-order polynomial in the sagittal and frontal plane projections. Palatal dimensions in the frontal and sagittal planes were computed, and compared between ages and sexes by two-way factorial analyses of variance. The effect of age on palatal shape was different in the two sexes: while in females the curves in both the frontal and sagittal planes were practically superimposed, in males the youngest subjects had somewhat 'lower' curves than the oldest subjects. Sex had a significant (p<0.05) effect for all variables. Age was significant only for palatal slope in the sagittal plane (p<0.01), and for raphe inclination in the horizontal plane (p<0.05). For all variables but palatal length in the sagittal plane, a significant (p<0.01) sexxage interaction was found: while in males all linear variables were larger in adults than in adolescents, the reverse was found in females. Overall, while in adolescent females palatal form appeared to have already attained adult characteristics, in males some modifications between adolescence and young adulthood were measured. These modifications should be taken into consideration as a possible factor of relapse after orthodontic treatment.