Postural response of the head to bite opening in adult males

A kinematic analysis on the immediate effects of occlusal splints in gait and running body sway patterns

Objective: This study aims to determine whether changes in dental occlusion are correlated to body posture during walking and running.Methods: Fifteen healthy subjects were assessed by a prosthodontist and deemed asymptomatic. Analyses of gait and running were performed in three conditions, in random order: a) occlusal splint; b) placebo splint; and c) no splint. The occlusal splint used in this study positioned the mandible in a stable position. Kinematic data was collected using a 3D motion capture system.Results: Changes in dental occlusion induced by occlusal splints did not influence body sway during gait or running. No significant differences were found between any of the test conditions.Conclusion: Occlusal splints have no effect on body sway during gait or running. High inter-subject variability in kinematic parameters was found, which should be considered in future studies.

The inconclusiveness of research on functional pathologies of the temporomandibular system and body posture: Paths followed, paths ahead: A critical review

Objective: Literature on the functional pathologies of the temporomandibular system (FPTS) in its relationships with body posture is plagued with inconclusiveness. Despite being sometimes altogether disregarded, the issue is most relevant, due to its clinical implications. This paper aims for a deeper understanding of the origins of the inconclusiveness of research on such relationships by means of a critical analysis of the scientific literature on the subject, in order that clinicians may better treat patients with FPTS.Methods: Analysis of over 100 studies, published from 1918 through March 2018 in the PubMed database, using descriptors temporomandibular joint disorders and posture.Results: The analysis of the paths followed by researchers allowed for pinning down several methodological issues that may have led to the prevailing ambiguity on the matter.Conclusion: This review then proposes certain standardization of procedures in future studies, to be conducted by a proposed consortium of researchers.

Postural evaluation of patients with temporomandibular disorders under use of occlusal splints

Objectives:

Alterations in the temporomandibular complex can reflect in adaptations of the individual's entire muscular system, intervening with the head position and scapular waist, developing postural alterations and modifying all corporal biomechanics. The aim of this study was to evaluate the head position (HP) and head postural alterations before and after installation of occlusal splints.

Material and Methods:

Twenty patients with temporomandibular disorders (TMD) underwent clinical and postural examination, before the installation of an occlusal splint, and after 1 week and 1 month of use.

Results:

There were statistically differences for HP, between the initial values and after 1 week of use of the occlusal device (p= 0.048) and also between 1 week and 1 month of evaluation (p= 0.001). Decrease of the painful symptomatology and maintenance of the rectification were also observed.

Conclusions:

The individual's postural position can suffer biomechanical alterations due to stomatognathic alterations, causing clinically visible changes in dysfunctional individuals and affecting the performance of the involved structures.

Body posture evaluations in subjects with internal temporomandibular joint derangement

The aim of this study was to verify possible relationships between global body posture and temporomandibular joint internal derangement (TMJ-id), by comparing 30 subjects presenting typical TMJ-id signs to 20 healthy subjects. Body posture was assessed using the analysis of muscle chains on several photographs. Results show a higher frequency of lifted shoulders (p=0.04) and of changes in the antero-internal hip chain (p=0.02) in the test group, but no further differences were found significant between the control and test groups. The test group was then divided into three subgroups according to the Helkimo index of temporomandibular disorder severity. Again, no significant differences were found between the subgroups. However, there was a trend noticed in the group with the most severe dysfunction, to present a forward head and shoulders posture. Results are discussed in light of previous studies using the same sample.

Effects of anterior cruciate ligament (ACL) injury on muscle activity of head, neck and trunk muscles: a cross-sectional evaluation

This study evaluated the that effects a pathology of the knee, due to an anterior cruciate ligament (ACL) injury, has on muscular activity of neck, head, and trunk muscles. Twenty-five (25) subjects (mean age 28+/-9 years) with ACL injury of the left knee were compared with a control no-pathology group. Surface electromyography (sEMG) at mandibular rest position and maximal voluntary clenching (MVC) wasused to evaluate muscular activity of the areas: masseter, anterior temporalis, posterior cervicals, sternocleidomastoid (SCM), and upper and lower trapezius. The sEMG activity of each muscle, as well as the asymmetry index between the right and the left sides, were compared between the two groups. Subjects in the study group showed a significant increase in the asymmetry index of the sEMG activity of the anterior temporalis at mandibular rest position (p<0.05). At rest, the areas of anterior temporalis and masseter in the control group showed a significantly lower sEMG activity compared with subjects in the study group, both in the right and the left sides (p<0.05). The same was found for the sEMG activity of the areas of SCM and lower trapezius. At MVC, the right areas of anterior temporalis and masseter in the study subjects showed a significantly lower sEMG activity compared with the control group. The same was observed for the lower trapezius area, both in the right and the left sides. In general, ACL injury appears to provide a change in the sEMG activity of head, neck and trunk muscles.

Electromyographic activity of masticatory, neck and trunk muscles of subjects with different skeletal facial morphology ? a cross-sectional evaluation

The electromyographic pattern activity of masticatory, neck and trunk muscles was assessed using surface electromyography (sEMG) in 60 Caucasian adult females (20 subjects in skeletal class I, 20 subjects in skeletal class II and 20 subjects in skeletal class III), classified on the base of their skeletal class (ANB angle), corrected on the base of maxillary and mandibular rotations. The sEMG activity was recorded at mandibular rest position and during maximal voluntary clenching. At mandibular rest position, the sEMG activities of masseter and anterior temporal muscles were significantly higher in class III subjects than in class I and class II subjects, that showed no significant difference between them. Then, the sEMG activities of posterior cervicals and upper trapezius were significantly higher in skeletal class III subjects than in the other two groups. During maximal voluntary clenching, no significant difference was observed in the sEMG activity of masticatory muscles among the three considered groups. However, the sEMG activities of posterior cervicals and upper trapezius were significantly higher in skeletal class III subjects than in the other two groups, which showed no significant difference between them. In conclusion, the skeletal class seems to affect the sEMG pattern activity of masticatory, neck and trunk muscles.

Cervical lordosis in patients who underwent anterior cruciate ligament injury: a cross-sectional study

It has been proposed that intraoral devices can influence cervical posture. Cervical posture might also be influenced by stimuli from the lower limbs, such as injury of the knee. The hypothesis to be tested is that intraoral devices are useful during the rehabilitation of orthopedic patients to accelerate the restoration of postural control. This study evaluates cervical posture on lateral skull radiographs in subjects who suffered anterior cruciate ligament (ACL) injury of the left knee. Twenty adult Caucasian males (mean age 30.6+/-9.2 yrs.) with ACL injury of the left knee were compared with 40 control subjects (mean age 27.9+/-7.2) who did not show any ACL injury. Lateral skull radiographs, made in natural head position (mirror position), were obtained for all subiects. Various postural and morphological variables were individualized on each radiograph. To assess errors due to landmark identification, duplicate measurements were made of 15 radiographs and compared using the Dahlberg formula. The method error from both sources was less than 0.5 degrees for all angular measurements and less than 0.5 mm for all linear measurements. No difference was observed between the two groups in any of the morphological variables of face or in the cervical lordosis angle (CVT/EVT). However, subjects in the study group showed significantly higher craniocervical angulations (SN/OPT, SN/CVT, SN/EVT, pns-ans/OPT, pns-ans/CVT, pns-ans/EVT, GoGn/OPT, GoGn/CVT, GoGn/EVT) compared with the control subjects (p<0.001). The subjects with ACL injury had significant head extension compared with the control subjects.

Electromyographic Activity of Masticatory, Neck and Trunk Muscles of Subjects with Different Mandibular Divergence

OBJECTIVE

To record and compare the surface electromyographic (sEMG) activity of masticatory, neck, and trunk muscles at different functional requirements of the stomatognathic system in an adult sample classified according to the mandibular divergence angle (SN-GoGn angle).

MATERIALS AND METHODS

60 Caucasian adult subjects were classified on the basis of SN-GoGn angle: 20 subjects with normal mandibular divergence, 20 subjects with lower angles, and 20 subjects with higher angles. Their sEMG activity was recorded at mandibular rest position and during maximal voluntary clenching.

RESULTS

sEMG activity of subjects with a lower angle was significantly higher than that of subjects in the other two groups at mandibular rest position for the masseter, the anterior temporal, the upper trapezius, and the posterior cervical muscles. During maximal voluntary clenching, no significant difference was observed in the sEMG activity of the masticatory muscles among the three groups. However, the sEMG activity of the posterior cervicals and that of the upper trapezius were significantly higher in subjects with a lower angle than in the other two groups.

CONCLUSION

Skeletal class does seem to affect the sEMG pattern activity of the masticatory, neck, and trunk muscles.

Effects of anterior cruciate ligament (ACL) injury on postural control and muscle activity of head, neck and trunk muscles

The aim of the study was to evaluate the effects that an anterior cruciate ligament injury of the knee has on postural control and activity of neck, head and trunk muscles to investigate the existence of connections between the masticatory system and body posture. Surface electromyographic activity of the muscles at mandibular rest position, and during maximal voluntary clenching and posturometric and stabilometric measurements of 25 adult patients having pathology on the left knee were compared with a control non-pathological group. At rest, the patients showed a higher muscular activity of anterior temporalis, masseter, sternocleidomastoid and lower trapezius, compared with the control subjects (P < 0.05). At maximal voluntary clenching, the patients showed a lower muscular activity of the right anterior temporalis and masseter and a higher muscular activity of the lower trapezius, compared with the control subjects. For the stabilometric measurements, all the subjects showed a significant reduction in the postural centre of pressure path length during the test with eyes open and cotton rolls, compared with the test with eyes closed and mandibular rest position (P < 0.05). In addition, the patients showed a significant displacement of the postural centre of pressure in a forward direction (P < 0.05) and into the right side (P < 0.05), compared with the control subjects. Anterior cruciate ligament injury appears to be associated to a change in the activity of head, neck and trunk muscles and to a change in the position of the postural centre of pressure. Cotton rolls seem to improve the stability of the subject.

Dysgnathia, orthognathic surgery and spinal posture

The aim of this study was to evaluate the spine by video rasterstereography before and after orthognathic surgery. Twenty-nine patients (17 patients with a skeletal class III, 7 patients with a skeletal class II, and 5 patients with mandibular asymmetry) were evaluated preoperatively and 1 year postoperatively. Video rasterstereography is a method of back surface measurement and shape analysis using the moire topography. Orthognathic surgery in cases of class III and asymmetry did not lead to significant changes in body posture. In class II patients it led to some changes in body posture, but without orthopaedic consequences. It is concluded that orthognathic surgery causes minimal or no change in body posture.

Relationship between head posture and hyoid position in adult females and males

AIM

The aim of this study was to investigate head posture and hyoid bone position using cephalometric radiographs of adults.

MATERIAL AND METHODS

The material consisted of 76 cephalometric films (38 each male/female) taken at the natural head posture. The individuals were over 18 years of age, had parents of Turkish origin, an acceptable face structure, ideal dental occlusion, and an ANB angle of 1-5 degrees; the dentitions were complete except the third molars and there were no visual, hearing, breathing or swallowing disorders. In addition, the subjects had not undergone orthodontic treatment or orthognathic surgery, had no burns, injuries, or scars in the head and neck regions. In order to determine the natural head position, the subjects were asked to stand in a relaxed manner (the self-balance position), and this position was transferred to the cephalostat by means of a fluid level device. The differences among sexes were investigated by means of Student's t-test, carried out using SPSS (Windows 7.5).

RESULTS

It was found that there were no sex variations in head position. The linear measurements regarding the position of hyoid bone showed statistically significant differences with respect to sex. However, hyoid bone position was higher and more posterior in females, while natural head position was not affected by sex.

Changes in natural head position observed immediately and one year after rapid maxillary expansion

Rapid maxillary expansion (RME) has been shown to increase nasal permeability and reduce nasal airway resistance. A number of studies have examined the relationship between RME and the change in airway resistance, or the relationship between airway resistance and natural head position (NHP). Few studies, to date, have examined the relationship between RME and the change in NHP resulting from the consequent change in airway resistance. A sample of 43 adolescent patients with uni- or bilateral crossbite in the permanent dentition underwent RME as part of normal orthodontic treatment. Cephalograms in NHP were taken before, immediately after expansion, and one year after RME. No significant changes in the craniofacial angles were observed immediately after expansion. One year post-expansion, however, NSL/VER had reduced by 3.14 degrees (P < 0.01), OPT/HOR by 2.13 degrees (P < 0.05), and CVT/HOR by 2.55 degrees (P < 0.05). The results of this study suggest an ongoing change in head posture possibly due to a change in the mode of breathing from oral to nasal as a result of RME, thereby contributing to a change in craniofacial development, supporting and adding to the soft tissue stretching hypothesis.

Induced oral breathing and craniocervical postural relations: an experimental study in healthy young adults

The influence of induced oral breathing on head and craniocervical posture was studied in ten healthy young adults. After a baseline recording, oral respiration was induced by using a swimmer's type nose clip. The subjects were filmed 15 and 90 minutes after wearing the nose clip, immediately and 15 minutes after taking it off. The angles C7-tragion versus the true vertical, nasion-tragion versus the vertical, and C7-tragion-nasion were calculated, and the difference between the baseline and the four experimental recordings was computed. During the experiment, head and neck positions were modified in all subjects, but with a large variability for both the direction (flexion or extension) and the extent of the modification. Overall, the mean differences were minimal with large standard deviations. Differences between baseline and the experimental recordings were significant only for the C7-tragion versus the vertical angle (analysis of variance, p=0.0083). In conclusion, induced oral respiration may have a significant role in the alteration of head and craniocervical posture, but the effect was highly variable.

Changes in weight distribution at the feet due to occlusal supporting zone loss during clenching

To establish the relationship between the condition of the stomatognathic system and body posture, changes in the weight distribution at the feet using the four-quadrant weight scale were investigated when the occlusal supporting zone was lost unilaterally and bilaterally. The results were as follows: 1. Regardless of occlusal conditions, the weight distribution was changed during clenching; 2. The weight distribution was shifted anteriorly during clenching regardless of the condition of the occlusal supporting zone. Additionally, weight distribution shifted more laterally to the opposite side of the lost occlusal supporting zone during clenching with the occlusal supporting zone lost more unilaterally than bilaterally. From the present findings, it is suggested that the body posture may be affected and changed to an unusual position causing neck or shoulder pain, especially when the occlusal supporting zone is lost both unilaterally and bilaterally.

The functional relationship between the craniomandibular system, cervical spine, and the sacroiliac joint: a preliminary investigation

The hypothesis of a functional coupling between the muscles of the craniomandibular system and the muscles of other body areas is still controversial. The purpose of this pilot study was to examine whether there is a relationship between the craniomandibular system, the craniocervical system and the sacropelvic region. To test this hypothesis, the prevalence and localization of dysfunction of the cervical spine and the sacroiliac joint were examined in a prospective, experimental trial. Twenty healthy students underwent an artificial occlusal interference, which caused an occlusal interference. The upper cervical spine (CO-C3) and the sacroiliac joint were examined before, during and after this experimental test. The primary outcome with these experimental conditions was the occurrence of hypomobile functional abnormalities. In the presence of occlusal interference, functional abnormalities were detected in both regions examined and these changes were statistically significant. The clinical implications of these findings may be that a complementary examination of these areas in CMD patients could be useful.

Effects of laterotrusive occlusal scheme and body position on bilateral sternocleidomastoid EMG activity

This study was conducted to determine the effects of laterotrusive occlusal scheme and body position on bilateral sternocleidomastoid electromyographic (EMG) activity. The study was performed on 20 healthy subjects with natural dentition and bilateral molar support. During laterotrusive occlusal excursion (working side), each individual had to present canine guidance on one side and group function on the opposite side, without balancing-side contacts. Integrated EMG (IEMG) recordings were performed by placing bipolar surface electrodes on the right and left sternocleidomastoid muscles. IEMG activity was recorded seated upright with the head unsupported and in the right and the left lateral decubitus body positions (head, neck and body horizontally aligned), under the following experimental conditions: 1. Maximal voluntary clenching in the intercuspal position; 2. Laterotrusive occlusal excursion with canine guidance; 3. Laterotrusive occlusal excursion with group function. Bilateral sternocleidomastoid IEMG activity with canine guidance or group function was significantly lower than the intercuspal position in both body positions. In the seated upright position, significantly lower activity was observed with canine guidance than in group function. In the lateral decubitus position activity was similar with both laterotrusive occlusal schemes and significantly higher than seated upright. Results suggest that both laterotrusive occlusal scheme and body position have significant influence on sternocleidomastoid IEMG activity. The clinical relevance of both factors is discussed.

Changes in head position due to occlusal supporting zone loss during clenching

To establish the relationship between the condition of the stomatognathic system and body posture, changes in the head position during clenching were observed and investigated when the occlusal supporting zone was lost unilaterally and bilaterally. The results were as follows: 1. Regardless of the occlusal conditions, the head position was changed by clenching; 2. The occlusal conditions did not affect the changed distance of the head position; 3. The head position was changed forward and down by clenching regardless of the condition of the occlusal supporting zone. The head position changed more laterally to the opposite side of the lost occlusal supporting zone by clenching with the occlusal supporting zone lost unilaterally rather than bilaterally. Based on this study, it is suggested that unilateral loss of the occlusal supporting zone may cause the neck muscles to become inharmonious and thus affect body posture.

Measurement of the profile angle and the aesthetic analysis of the facial profile

Cephalometric measurement of the face in terms of aesthetics can be difficult and misleading due to the variability of the intra-cranial reference lines. Extra-cranial references are more accurate, but can be time-consuming to apply. The Aesthetic Horizontal is an intuitive datum line related to the 'photographic position' of the head, which is expedient in use and clinically relevant. A new and straightforward technique is presented for transferring the Aesthetic Horizontal directly from the patient to any recent radiograph, which can then be used as the reference line for an aesthetic analysis of the facial profile. The instrument used for measuring the profile angle and the transfer is readily constructed from a protractor and small weight. The technique can also be used to transfer any other orientation (e.g. Natural Head Position or Natural Head Posture) from the patient to a recent radiograph.

Effects of the antigravitary modification of the myotension of asset (MAGMA) therapy on myogenic cranio-cervical-mandibular dysfunction: a longitudinal surface electromyography analysis

This study was aimed at evaluating the effects of a novel physiotherapy machine called MAGMA (AntiGravitary Modification of the Myotensions of Asset) on postural and masticatory muscles of subjects with myogenic cranio-cervical-mandibular dysfunction (CMD), by using surface electromyography (sEMG). Fifteen subjects, nine males and six females (mean age 27.6 years), with CMD were included in the study. The bilaterally monitored muscles were: masseter, anterior and posterior temporalis, digastric, posterior cervical, sternocleidomastoid, and upper and lower trapezius. All muscles were monitored at rest, with a second record of maximal voluntary clenching (MVC) for both the masseter and anterior temporalis. Patients were subjected to MAGMA therapy for one session/week of 30 min over ten weeks. The surface EMG activity was recorded twice, at the baseline and at the end of the therapy. After MAGMA therapy, the sEMG activity at rest of the monitored muscles was significantly better when compared to the baseline; the only exception was the anterior and posterior temporalis muscles which did not improve. On the contrary, with the MVC, all the monitored muscles (masseter and anterior temporalis) significantly improved their sEMG activity. Although more investigations are needed, these results indicate that the use of such antigravitary therapy can provide a tool for resolving myogenic CMD.

The effect of stepwise increases in vertical dimension of occlusion on isometric strength of cervical flexors and deltoid muscles in nonsymptomatic females

This mixed, single-double blind study examined the effect of a stepwise increase in vertical dimension of occlusion (VDO) on the isometric strength of cervical flexor and deltoid muscles in 20 asymptomatic females with deep bite (age range 20-40 years). Vertical dimension of occlusion was increased by mandibular acrylic bite plates, 2, 4, 6 and 12 mm. Subjects were instructed to bite while resisting: 1. an increasing horizontal force was applied to the forehead; and 2. an increasing vertical downward force to the wrist of each extended arm. Forces were applied by a hand-held strain gauge until resistance yielded. The force applied at the point of yielding was recorded as isometric peak strength of that trial. The peak strength for each muscle group was measured twice and averaged to produce a mean peak strength measure. This procedure was repeated in the subject's habitual occlusion and for the four increased VDOs. Mean strength of cervical flexors with increased VDO (12.0 kg) was significantly greater than that for existing vertical dimension occlusion (9.6 kg). With the exception of pre-experimental existing VD of occlusion, strength for right and left deltoids did not differ, but mean deltoid strength in the increased condition (8.6 kg) was significantly greater than biting in without a bite plate (6.6 kg). In the peak condition, cervical flexor strength increased 24% and deltoid strength increased an average of 29% from that of biting without an increase. As VDO increased further, strength in all sites was found to diminish. Repeating the strength test without a bite plate, after all trials were administered, did not show differences from pre-experimental levels, indicating that fatigue was not an important factor. The findings demonstrate that isometric strength of the cervical flexors and deltoids increases significantly from habitual occlusion as the VDO is increased, then diminishes as VDO is increased further. The strength of both cervical flexors and deltoids varied in concert with changes of VDO.

Vertical dimension. Part 2: the changes in electrical activity of the cervical muscles upon varying the vertical dimension

This study was conducted in order to determine the effect of vertical dimension variation on the electromyographic (EMG) activity of the sternocleidomastoid and trapezius muscles. The study was performed on 15 healthy subjects. Basal tonic electromyographic (BT-EMG) recordings were performed by placing surface electrodes on the left sternocleidomastoid and trapezius muscles. BT EMG activity was recorded upon varying the vertical dimension every five millimeters from vertical dimension of occlusion to 45 millimeters of jaw opening (series 1), following the habitual opening path. Afterward, BT-EMG activity was recorded every millimeter from vertical dimension of occlusion to 4 mm, and then every two millimeters from four to ten millimeters (series 2). In series 1, a significant increase of BT-EMG activity was observed in both muscles (simple logarithmic regression analysis). In series 2, a significant increase was observed in the sternocleidomastoid muscle whereas trapezius muscle did not present a significant change. BT-EMG behavior of the sternocleidomastoid muscle in series 2 could be relevant when dentists increase vertical dimension by means of intermaxillary appliances during a short-term period. Moreover, these results add further information to the concept of the interrelatedness between the different components of the cranio cervical-mandibular system.

Head posture and deprivation of visual stimuli

INTRODUCTION

Natural head position (NHP) has been defined as the cranial position that is attained when individuals stand with their visual axes in the true horizontal plane. The visual axis is considered to be a key component in establishing, and maintaining NHP so that, in the absence of visual stimuli, gravitation and muscular proprioception chiefly control head position.

SUBJECTS AND METHODS

In this study, the natural head positions of a group of normal sighted subjects were measured in a well-lighted room. The findings were compared to similar observations made in the same subjects when they were placed in a completely dark environment. Measurements of cranio-cervical angulation were made on adults (N = 30, males = 17, females = 13) by means of an electronic inclinometer. Sitting Head Position (SIHP), Standing Head Position (STHP), and Orthoposition (OP) were determined for each subject in a well-lighted room, and subsequently, in a completely dark room.

RESULTS

The data indicate that there were statistically significant differences between Standing Head Position, and Orthoposition, measured in the light and in the dark. There were no statistically significant differences between Sitting Head Position measured in the light and in the dark.

CONCLUSION

The results indicate that craniocervical angulation is more extended in the dark than it is in the light. This finding suggests that head position responds to visual stimuli, and that when this sensory input is not present, there is a tendency for subjects to extend their heads.

Fifteen-year reproducibility of natural head posture: A longitudinal study

Natural head posture continues to be widely used as the logical reference position for the evaluation of craniofacial morphology. The basic underlying premise is that the long-term clinical reproducibility (variability) of natural head posture is significantly less than the variability of conventional reference planes with respect to the vertical. This study reports the 15-year longitudinal reproducibility of natural head posture. Twenty Chinese adults in Hong Kong, who had initial natural head posture radiographs at age 12 years, were followed up and had repeated cephalograms after 15 years. The method error (reproducibility) after 15 years was 2.2 degrees, which compared favorably with the 5-year reproducibility (method error = 3.0 degrees ) and the 5 to 10 minutes reproducibility (method error = 1.9 degrees ). The individual variability of natural head posture reproducibility increased slightly over time. After 15 years the variance of natural head posture (4.8 degrees [= 2.2(2)]) remains significantly less than the variance of intracranial reference planes to the vertical (25 degrees to 36 degrees ). Cephalometric analyses based on natural head posture therefore remain valid over time.

The effect of vertical dimension and mandibular position on isometric strength of the cervical flexors

This study compared the peak isometric strength of the cervical flexors in deep bite temporomandibular dysfunction (TMD) patients while biting in four bite positions: habitual occlusion, edge-to-edge, lateral shift and retruded. These values were then compared to those of the same subjects' bite positions elevated to a functional criterion (maximum isometric strength of the deltoid muscles). The mean height increase was 2.4 mm with a range of 1.5-3.8 mm. Fifteen of eighteen deep bite subjects met an inclusionary criterion, at least 13.3 Newtons (N) stronger cervical muscle strength with mandible relaxed open than habitual bite. Peak strength biting edge-to-edge was significantly greater than biting in habitual occlusion. Strength was found to increase significantly when biting in each of four mandibular positions when the bite was elevated to the functional criterion. The greatest strength was obtained from elevated habitual and edge-to-edge positions. The findings are of clinical significance, suggesting that cervical muscle isometric strength is affected by bite position and vertical dimension of occlusion. The results suggest that when biting, individuals with deep bite may be functioning at about 60% of their potential cervical flexor, isometric strength. The interaction between occlusal position, vertical dimension and cervical muscle function suggests a craniomandibular-cervical masticatory system.

Body position effects on sternocleidomastoid and masseter EMG pattern activity in patients undergoing occlusal splint therapy

This study was conducted in order to determine the effects of body position on electromyographic (EMG) activity of sternocleidomastoid and masseter muscles, in 15 patients with myogenic cranio-cervical-mandibular dysfunction undergoing occlusal splint therapy. EMG activity was recorded by placing surface electrodes on the sternocleidomastoid and masseter muscles (contralateral to the habitual sleeping side of each patient). EMG activity at rest and during swallowing of saliva and maximal voluntary clenching was recorded in the following body positions: standing, supine and lateral decubitus. In the sternocleidomastoid muscle significant higher EMG activities at rest and during swallowing were recorded in the lateral decubitus position, whereas during maximal voluntary clenching EMG activity did not change. In the masseter muscle significant higher EMG activity during maximal voluntary clenching in a standing position was observed, whereas EMG activity at rest and during swallowing did not change. The opposite pattern of EMG activity supports the idea that there may exist a differential modulation of the motor neuron pools of the sternocleidomastoid and masseter muscles, of peripheral and/or central origin. This suggests that the presence of parafunctional habits and body position could be closely correlated with the clinical symptomatology in these muscles in patients with myogenic craniomandibular dysfunction.

Increase of the vertical occlusal dimension by means of a removable orthodontic appliance and its effect on craniocervical relationships and position of the cervical spine in children

The aim of this study was to determine the effect of the increase in the occlusal vertical dimension by means of an orthodontic appliance on craniocervical relationships and position of the cervical spine. Thirty children presenting malocclusion were divided into two groups of 15 (a study and a control group). Those in the study group wore an orthodontic appliance to correct cross-bite. The children in the control group had no treatment during the experimental period. Two lateral craniocervical radiographs were taken for each child. The first one was taken in the intercuspal position in both groups. The second radiograph was taken of the study group after four months of wearing the appliance and also of the control group after four months. Cephalometric analysis in the study group showed a significant forward cervical spine position. There were no significant changes in the control group. The changes found in the study group suggest that when there are signs and symptoms of cervical dysfunction in children undergoing long-term orthodontic treatment, it is necessary to make an evaluation of the cervical column position after the insertion of any orthodontic appliance which increases the occlusal vertical dimension.

The relationship between ortho head posture and head posture measured during walking

Murphy, Preston, and Evans recognized the dynamic nature of head posture and developed instrumentation capable of measuring and recording this posture in a continuous manner. The aim of the current project was to use the newly developed instrumentation to determine whether the difference is statistically significant between the mean natural head ortho posture, measured in a controlled manner, and the mean dynamic head posture obtained during 5 minutes of walking activity in an experimental situation. The mean ortho head posture and the mean walking head posture were measured in each of 30 men. The differences between these two sets of mean head postures were statistically significant (p < or = 0.05). In 23 persons, the mean walking head posture was tipped backward relative to the mean natural head ortho position.

Snoring and obstructive sleep apnea: does head posture play a role?

The aim of this article is to present scientific and clinical evidence to support the role of proper head and neck posture in the management of snoring and obstructive sleep apnea. Obstruction of the upper-airway during sleep is a serious medical condition often associated with severe daytime somnolence, morning headache, and a host of cardiopulmonary complications, including but not limited to systemic and pulmonary hypertension, nocturnal cardiac dysrhythmias, myocardial infarction, and stroke. Though anti-snoring pillows are occasionally mentioned in the literature, the role of proper head-neck support during sleep has been largely neglected. In this article the effect of head-neck position on upper-airway obstruction during sleep is discussed from the perspective of both causation and treatment. Based on the evidence presented by the author, it is recommended that the use of cervical-support pillows be considered as an adjunctive treatment modality in patients suffering from snoring and obstructive sleep apnea.

Occlusion and center of foot pressure variation: is there a relationship?

The influences of head and body posture on the mandibular rest position, the range of functional movements, and the initial tooth contact have been documented. In this investigation, the modifications of the position of the center of foot pressure during natural standing were studied in 30 women. The subjects were divided into three groups: healthy women (control), women with an asymmetric (unilateral) Angle class II malocclusion, and women with temporomandibular disorders. Data were acquired in 30-second trials by use of a force plate that allowed a separate assessment of each foot while the subjects maintained different dental positions: rest position; centric occlusion; maximum clench; occlusion on two cotton rolls placed on the mandibular teeth distal to the canines; and maximum clench on two cotton rolls. Bivariate analysis was used to compute the mean values and relevant variability for the center of foot pressure location during each trial. The results demonstrated that the modifications of foot center of pressure were not influenced by temporomandibular disorders and asymmetric malocclusion or by different dental positions.

Body position effects on EMG activity of sternocleidomastoid and masseter muscles in patients with myogenic cranio-cervical-mandibular dysfunction

This study was conducted in order to determine the effects of body position on integrated electromyographic (IEMG) activity of sternocleidomastoid and masseter muscles in 17 patients with myogenic cranio-cervical-mandibular dysfunction. EMG recordings at rest and during swallowing of saliva and maximal voluntary clenching were performed by placing surface electrodes on the sternocleidomastoid and masseter muscles (contralateral to the habitual side of sleeping of each patient), in the following body positions: standing, seated, supine, and lateral decubitus position. Significant higher EMG activities were recorded in the sternocleidomastoid muscle in the lateral decubitus position and in the supine position (except during swallowing), whereas a significant higher EMG activity was recorded in the masseter muscle during maximal voluntary clenching in standing and seated positions. The EMG pattern observed suggests that the presence of parafunctional habits and body position could be closely correlated with the clinical symptomatology in the sternocleidomastoid and masseter muscles at wakening and during waking hours, respectively, in patients with myogenic cranio-cervical-mandibular dysfunction.

Forward head posture: its structural and functional influence on the stomatognathic system, a conceptual study

An extensive conceptual analysis to establish the primary role a forward head posture plays in the appearance of some craniomandibular dysfunctions and internal derangements of the temporomandibular joints, associated to craniocervical postural disturbances. The analysis is based on findings contributed by scientific investigations in the field of dentofacial orthopedics and dysfunction. Special emphasis has been put on the influence of forward head posture on the craniofacial growth as it can determine a morphoskeletal and neuromuscular pattern leading to a dysfunctional condition. A correlation is established between Class II Occlusion, forward head posture, and craniomandibular dysfunction. The concept of craniocervical postural position is defined, as well as its close relation to the mandibular postural position.

Influence of variation in jaw posture on sternocleidomastoid and trapezius electromyographic activity

This study was conducted in order to determine the influence of variation in the occlusal contacts on electromyographic (EMG) cervical activity in 20 patients with myogenic cranio-cervical-mandibular dysfunction. EMG recordings during maximal voluntary clenching were performed by placing surface electrodes on the left sternocleidomastoid and upper trapezius muscles in the following conditions: intercuspal position; edge to edge left laterotrusive contacts (ipsilateral); edge to edge right laterotrusive contacts (contralateral); edge to edge protrusive contacts; and retrusive occlusal contacts. A significant higher EMG activity was recorded in both muscles during maximal voluntary clenching in retrusive occlusal contact position, whereas no significant differences in EMG activity were observed between intercuspal position, ipsilateral, contralateral and protrusive contact positions. The EMG pattern observed suggests that a more frequent intensity and duration of tooth clenching in retrusive occlusal contact position could result in more clinical symptomatology in these cervical muscles in patients with myogenic cranio-cervical-mandibular dysfunction.

Effect of masticatory muscle fatigue on cranio-vertical head posture and rest position of the mandible

The aim of this study was to investigate whether induced fatigue of the masticatory muscles had any influence on the head posture, and whether this influence is related to the rest position and the movement characteristics of the mandible. The sample consisted of 13 female individuals, aged 23-34 yr. For the evaluation of possible changes in the natural cranio-vertical head posture, standardized facial profile photographs were used. Photographs were also used for the study of the facial characteristics. The freeway space and the opening and closing velocity of the mandibular displacement, as well as the duration of the masticatory cycles, were monitored with an optoelectronic method. A controlled dynamic fatigue was induced by a specially constructed spring-loaded device placed in the premolar region. No significant changes in the mean cranio-vertical postural position of the head were found during the various recording stages, while the freeway space was found to increase significantly after the fatigue test. No significant differences were observed concerning the average values of the mandibular movement characteristics. The analysis of the association between the individual changes showed an increase in the freeway space after the fatigue test in the subjects which exhibited an increase in the duration of the masticatory cycle in that period. No significant associations could be found between the changes in the head posture and the mandibular movement characteristics. Also, no significant correlation could be found between the facial type of the subjects and the variables studied.

Changes in head and cervical-spine postures and EMG activities of masticatory muscles following treatment with complete upper and partial lower denture

A clinical stomatognathic, cephalometric and electromyographic (EMG) study was performed in relation to 14 subjects (10 women, 4 men), each with an edentulous maxilla and residual mandibular dentition before and six months after treatment with complete upper and partial lower dentures. The mean age of the subjects was 54.4 years (range 43-64 years). The mean period of edentulousness and age of dentures were 22.5 years (range 15-33 years) and 14.1 (range 1.5-30 years), respectively. Natural head position was recorded (using a fluid-level method) and measured from cephalograms. EMG activity was measured in relation to masseter and temporal muscles. A decrease in clinical dysfunction index was noted in 12 of 14 subjects (86%). There was no change in cervical inclination, but a slight extension of the head was noted after treatment. Rapid recovery of the masticatory muscles was reflected in increased EMG activity, especially when biting in the maximal intercuspal position. In cases of edentulous maxilla and residual mandibular anterior dentition, treatment with a complete upper and lower partial denture had a favorable effect on craniomandibular disorders and masticatory-muscle function.

Influence of stabilization occlusal splint on craniocervical relationships. Part I: Cephalometric analysis

This study was conducted in order to determine the effect of an occlusal splint on craniocervical relationships, in subjects with muscle spasms in the sternocleidomastoid and trapezius muscles. A full-arch maxillary stabilization occlusal splint was made for each of the 15 subjects. Two lateral craniocervical radiographs were taken for each subject, with and without an occlusal splint. Cephalometric analysis showed that the splint caused a significant extension of the head on the cervical spine. There was also a significant decrease in the cervical spine lordosis in the first, second and third cervical segment. These cervical changes could be a compensation mechanism caused by the extension of the cranium on the upper cervical spine. The change in the curvature implies that it is necessary to periodically evaluate the changes occurring in the craniocervical relationships after the occlusal splint has been inserted.

Natural cervical inclination and craniofacial structure

The purpose of this study was to search for the statistical associations between postural and morphologic variables of the head. Interpretation of the facial structure was made by using both intracranial and the extracranial reference lines. The sample comprised natural head posture (NHP) cephalograms of 106 dental students, aged 19 to 29 years. Results showed that, when the facial structure was evaluated by using a NHP analysis based on extracranial reference lines, it was associated with the inclination of the cervical column to the true horizontal. In addition, in the natural position of the head, inclination of the NSL reference was found to be associated with the vertical localization of sella turcica (r = -724, p < or = 0.001), rather than the "extension" or "flexion" of the head. It was concluded that associations between posture and structure of the head are merely caused by the functional factors related to "forward cervical posture" and "vertical cervical posture".

Head and cervical spine postures in complete denture wearers

Signs and symptoms in the stomatognathic system and head and cervical spine postures were evaluated in 10 edentulous patients prior to renewal of their dentures, as well as immediately and six months after insertion of new dentures. Natural head posture was recorded using the fluid-level method and measured from the roentgen cephalograms. It was shown that the variables duration of edentulousness and free-way space displayed positive correlations with the dysfunction symptoms. In addition, the patients who needed oral rehabilitation the most, who received the greatest reduction in their free-way space, were seen to have raised their heads more than average. There was also an inverse correlation between the reduction of clinical dysfunction index score and cervical spine postures.

Head posture and cervicovertebral and craniofacial morphology in patients with craniomandibular dysfunction

A relationship between particular characteristics of dental occlusion and craniomandibular disorders (CMD) has been reported, while less attention has been focused on the possible effect of dysfunction of the masticatory system on head posture or cervicovertebral and craniofacial morphology. Natural head position roentgen-cephalograms of 16 young adults with complete dentition taken before and after stomatognathic treatment displayed an extended head posture, smaller size of the uppermost cervical vertebrae, decreased posterior to anterior face height ratio, and a flattened cranial base as compared with age- and sex-matched healthy controls. The lordosis of the cervical spine straightened after stomatognathic treatment. The results are an indication of the close interrelationship between the masticatory muscle system and the muscles supporting the head, and lead to speculation on the principles of treating craniomandibular disorders.

The development of instrumentation for the dynamic measurement of changing head posture

Cranial posture and its possible relationship to the morphology of the skull has been studied in some detail, as have the relationships between cranial posture and such functions as respiration and jaw movements. To date, cranial posture has been assessed mainly with techniques that give static interpretations of the angular relationships between intracranial and extracranial reference lines. The present project was undertaken to develop a system of instruments capable of the continuous measurement and recording of cranial posture for extended periods of time. A number of aspects of this system were tested. The results indicate that the experimental array of instruments measures head posture accurately over a defined range of cranial movement. This new technique should make it possible to measure cranial posture in a more dynamic and physiologic manner.

Alteration of vertical dimension and its effect on head and neck posture

Previous research has shown a relationship between head posture and rest position of the mandible. Should this relationship really be an interrelationship? Does a change in mandibular posture alone also alter head and neck posture? The purpose of this article is to demonstrate how a change in mandibular posture, specifically an increase in vertical dimension, contributes to craniovertical extension leading to suboccipital compression and upsetting the postural balance between the head and neck. A model of physiologic equilibrium is presented for the craniomandibular articulation.