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Effect of occlusion status on the time required for initiation of recovery in response to external disturbances in the standing position
Abstract
To examine whether occlusion status contributes to improvement of postural balance.
Thirty healthy adolescents (15 males and 15 females; mean age, 20.3; standard deviation (SD) 1.6 years) with no equilibrium or stomatognathic function abnormalities were examined. Occlusion is a term meaning "jaw clenching." Occlusion status was evaluated by measuring masseter activity using the EMG system. Balancing ability was evaluated using the EquiTest system, which measures sway of the center of gravity produced by rapid movement of force plates as an external disturbance (three intensity levels). The time required for initiation of recovery after application of the disturbance was calculated by measuring displacement of the center of foot pressure. Data were compared according to occlusion status.
Little difference in latency was observed following a small disturbances; however, the greater the disturbance the shorter the latency with occlusion, while without occlusion, latency increased with increasing disturbance. A statistically significant interaction (P<0.001) between occlusion and external disturbance was also found.
This study suggested that occlusion contributes to maintenance of postural balance and improvement of stability when unexpected sway occurs in the standing position.
... jaw clenching muscles) are more active during an isokinetic movement of knee flexion/extension [10] . Changes in dental occlusion can have a major repercussion on human body mechanics [17] , for instance, mechanical changes in the temporomandibular joint (TMJ) may affect muscles located in other parts of the body [17] . Moreover, Raadsheer et al. [18] found a significant relationship between the muscle thickness of arm flexors and leg extensors and the muscle thickness of masseter and temporal muscles, suggesting that these muscles are influenced by the same interactions, and/or could play an important role in the same muscles contractions patterns. ...
... jaw clenching muscles) are more active during an isokinetic movement of knee flexion/extension [10] . Changes in dental occlusion can have a major repercussion on human body mechanics [17] , for instance, mechanical changes in the temporomandibular joint (TMJ) may affect muscles located in other parts of the body [17] . Moreover, Raadsheer et al. [18] found a significant relationship between the muscle thickness of arm flexors and leg extensors and the muscle thickness of masseter and temporal muscles, suggesting that these muscles are influenced by the same interactions, and/or could play an important role in the same muscles contractions patterns. ...
... The type of mouthguard used in these studies may explain the outcomes. All of the studies presented an increase in VDO as well as a repositioning of the TMJ, which may explain the results, since changes in TMJ position could have an impact on human body and affect distal areas [17] . However, some studies have presented opposite results [24][25][26] , and did not detect acute changes in force related parameters, while using customized mouthguards. ...
Background
It is widely accepted that mouthguards are effective for injury protection in sports. However, findings on the effects of mouthguards in strength and power production remains controversial. Therefore, the aim of this study was to determine whether controlled-mandible position mouthguards influence strength and power production in well trained athletes.
Methods
Twenty-two male amateur rugby players (25 ± 3.84 yrs; 1.92 ± 0.07 m; 93.91 ± 11.99 kg) volunteered for this study. Every participant performed an 1RM bench press test (113.20 ± 16.83 kg) to determine his maximal strength. In a randomized order, a ballistic bench press using 40% of the obtained 1RM (44.93 ± 6.76 Kg) was performed in a guided bar attached to a linear position transducer (LPT) for the following conditions: a) no mouthguard (CON); b) controlled mouthguard (MCM - jaw in centric relation); c) non-controlled mouthguard (NCM) and d) occlusal splint (OS). Vertical dimension of occlusion was also assessed for each of the testing conditions.
Results
Athletes using a controlled mouthguard demonstrate a significant (p< 0.05) higher peak acceleration and peak force than those using no mouthguard. Additionally, when analysing the results of vertical dimension of occlusion, a significant difference (p< 0.05) was observed between controlled mouthguard and the other tested conditions.
Conclusion
Controlled mouthguards enhance peak force and peak acceleration in the ballistic bench press exercise without negatively affecting any other measure assessed in this study. We speculate that this is possibly due to an increased stability of temporomandibular joint.
... A study made by Baldini et al. also demonstrated that mandibular position is able to influence the pilots' postural stability, analyzed using a static force platform [23]. A study done by Hosoda et al. [24] examined whether dental occlusion contributes to improvement of balance, analyzing the latency measurements of the MCT, representing the time from application of external disturbance to initiation of recovery action. In a sample of healthy subjects, they found that the time required for initiation of recovery in response to external disturbance in the standing position is shortened with jaw occlusion compared to no jaw occlusion. ...
... In the Baldini et al. study [23], static posturography instrumentation was used, and the different results could be related to the use of dynamic posturography. But in the Hosoda et al. study [24], the same equipment (Equitest®) was used to conduct a different test, obtaining variations of their parameter related to dental occlusion. Considering these previous results, it could be assumed that the composite parameter of the SOT is not sensitive in analyzing the influence of the stomatognathic system on the postural balance. ...
... In this study, the SOT composite parameter was recorded in Air Force and civilian pilots who were tested with the mandible positioned in mandibular rest position and mandibular position of centric occlusion. In disagreement with Baldini et al. [23] and Hosoda et al. [24], the postural balance was not influenced by the occlusal condition. It is generally accepted that chronic stressful situations and mental states like anxiety or depression contribute to the development of occlusal parafunctions and temporomandibular disorders without being the only cause. ...
Objective: The aim of this study is to evaluate the influence of the mandibular position on the postural stability in a sample of civilian and military pilots.
Methods: Twenty military pilots (males, mean age 35.15 ± 3.14 years) and 17 civilian pilots (males, mean 34.91 ± 2.15 years) were enrolled in this study and underwent a Sensory Organization Test (SOT) using the EquiTest® (NeuroCom International Inc., Clackamas, OR, USA) computerized dynamic posturography. The composite parameter was recorded and analyzed.
Results: The equilibrium score (ES) recorded in centric occlusion is slightly higher than the ES recorded in mandibular rest position; civilian pilots showed ESs slightly higher than military pilots. The two-way ANOVA analysis shows these differences are not statistically significant.
Discussion: The findings of this study seem to suggest that the composite parameter of the SOT is not sensitive in analyzing the influence of the stomatognathic system on the postural balance of civilian and military pilots.
... There were also several reports that confirmed the oral motor activity relations on postural control, [10][11][12][13][14][15] revealing the superior effect of teeth clenching on body balance control against body sway. However, these pieces of research were subjected to static balance, and there were few reports that investigated the effect of teeth clenching on dynamic balance. ...
... Several studies report the relationship between teeth clenching and static balance. [10][11][12][13][14][15] Fujino et al 11 investigated the effect of voluntary teeth clenching on static balance. They showed that voluntary teeth clenching contributed to stabilization of the postural stance perturbed transiently by electrical stimulation. ...
... [27][28][29][30][31][32] Several recent studies revealed the positive effects of teeth clenching on static balance. [10][11][12][13][14][15] However, it is suggested that teeth clenching during jump-landing may adversely affect dynamic balance control in this study. Previous studies indicate that teeth clenching affects the skeletal muscles of the limb, and contributes to stabilization of body orientation. ...
The aim of this study was to analyze the effect of teeth clenching on dynamic balance at jump-landing. Twenty-five healthy subjects performed jump-landing tasks with or without teeth clenching. The first three trials were performed with no instruction; subsequently, subjects were ordered to clench at the time of landing in the following three trials. We collected the data of masseter muscle activity by electromyogram, the maximum vertical ground reaction force (vGRFmax) and Center of Pressure (CoP) parameters by force plate during jump-landing. According to the clenching status of control jump-landing, all participants were categorized into a spontaneous clenching group and no clenching group, and the CoP data were compared. The masseter muscle activity was correlated with vGRFmax during anterior jump-landing, while it was not correlated with CoP. In comparisons between the spontaneous clenching and the no clenching group during anterior jump-landing, the spontaneous clenching group showed harder landing and the CoP area became larger than the no clenching group. There were no significant differences between pre and post intervention in both spontaneous clenching and no clenching groups. The effect of teeth clenching on dynamic balance during jump-landing was limited.
... Salusvita, Bauru, v. 29, n. 2, p. 57-67, 2010. rante longos períodos de tempo em posições incorretas (NUNES et al., 2007), má formação de algum segmento corporal (VANICOLA et al., 2007), ou mesmo alterações relacionadas à oclusão dentária (HOSODA et al., 2007). A oclusão dentaria é parte integrante do sistema estomatognático, sendo definida como a relação do encaixe da arcada dental superior com a inferior, e qualquer transtorno nesse sistema, seja por má oclusão ou disfunção temporomandibular, pode repercutir sobre todo o corpo humano, possibilitando diversas alterações mecânicas (GON- ZALEZ e MANNS, 1996; VAL et al., 2005; HOSODA et al., 2007). ...
... rante longos períodos de tempo em posições incorretas (NUNES et al., 2007), má formação de algum segmento corporal (VANICOLA et al., 2007), ou mesmo alterações relacionadas à oclusão dentária (HOSODA et al., 2007). A oclusão dentaria é parte integrante do sistema estomatognático, sendo definida como a relação do encaixe da arcada dental superior com a inferior, e qualquer transtorno nesse sistema, seja por má oclusão ou disfunção temporomandibular, pode repercutir sobre todo o corpo humano, possibilitando diversas alterações mecânicas (GON- ZALEZ e MANNS, 1996; VAL et al., 2005; HOSODA et al., 2007). Diante disso, este estudo buscou realizar uma revisão bibliográfica das interações existentes entre o sistema estomatognático com relação à postura e ao equilíbrio corporal, procurando assim, sanar a lacuna literária sobre a temática em questão. ...
... Como estes músculos são importantes na manutenção da posição da cabeça e da horizontalização do olhar, lesões incidentes podem causar conseqüências no sistema de controle do equilíbrio. Com relação ao equilíbrio corporal, existem alguns estudos que analisaram os efeitos da oclusão dentária sobre tal variável (GON- ZALEZ e MANNS, 1996; GANGLOFF et al., 2000; VAL et al., 2005; HOSODA et al., 2007). Um deles trata especificamente sobre o tempo necessário para haver início da recuperação, em resposta às perturbações externas na posição de equilíbrio. ...
RESUMO O sistema estomatognático está intimamente ligado à postura e ao equilíbrio corporal, porém essa relação é pouco enfatizada na litera-tura cientifica. Diante disso, esse estudo buscou analisar as influên-cias e as relações das disfunções do sistema estomatognático com a postura e o equilíbrio corporal dos indivíduos, por meio de uma re-visão de literatura. Para isso, foi realizada uma busca em base de da-dos, livros e demais produções cientificas da área de biomecânica e odontológica. Foi priorizado a inclusão de artigos que tivessem sido publicados nos últimos 10 anos, sendo assim, obteve-se 54 estudos relacionados ao tema, selecionando-se os 36 estudos mais relevantes. Os resultados dessa pesquisa mostram que muitas modificações pos-turais são influenciadas pela articulação temporomandibular e por conseqüência, a postura e o equilíbrio corporal são também altera-dos. Conclui-se que a relação específica do sistema estomatognático com a postura e equilíbrio, é uma abordagem pouco estudada e ne-cessita ainda ser bem desenvolvida.
... The designs of the 21 studies are listed in Table 4. These studies included 12 experimental and nine observational studies classified as follows: 1 CCT with 28 days of follow-up (6), 2 CCT without follow-up (7, 8), 1 NCCT with 1 year of follow-up (5), 8 NCCT without follow-up, (4,(9)(10)(11)(12)(13)(14)(15), 1 case-control study (16) and 8 CS studies (17)(18)(19)(20)(21)(22)(23)(24). No RCTs or meta-analyses were retrieved. ...
... Fourteen studies included only asymptomatic subjects with variable occlusal conditions (5, 6, 20, 23), normal occlusion (9,11,15), unilateral crossbite (8,24) or non-specified occlusal status (4,10,(12)(13)(14). Six studies compared asymptomatic subjects with patients positive for functional disorders of the stomatognathic system (16-19, 21, 22). ...
... Among the studies classified as clinical trials, the treatments were as follows: (i) change of mandibular positions through the use of intra-oral devices (including clench with cotton rolls between the dental arches) (7-9, 11, 14, 15); (ii) wearing of a splint to modify the masticatory muscle hypertonia, as recorded through electromyography analysis (6, 10, 12); (iii) unilateral trigeminal anaesthesia (4); (iv) orthognathic surgery (5) and (v) external disturbance for challenging body equilibrium, using an oscillating platform recorded in combination with different jaw clenching (13). ...
The aim of this systematic review of the literature was to assess the scientific evidence for detectable correlations between the stomatognathic system and whole-body posture and to provide information on the relevance of posturography as a diagnostic aid in dentistry. A literature survey was performed using the Medline database, covering the period from January 1966 to May 2009, and using the medical subject headings. After selection, 21 articles qualified for the final analysis. Only one study was judged to be of medium/high quality, with all of the rest classified as of low quality design. Only two studies included follow-up of 28 days and 1 year. Overall, 14 of the studies reported detectable correlations between the stomatognathic system and body posture in at least one of the parameters used, although in four of these studies the authors suggested caution in the interpretation of their data. After a reappraisal of the data provided in 13 of the studies, a weak correlation that reaches biological, but not clinical, relevance is apparent. With limitations because of the poor methodological quality of the present published studies, conclusions are that a correlation between the stomatognathic system and whole-body posture can be detected, at least under experimental conditions; although posturography has little relevance in the monitoring of body posture responses to changes in the stomatognathic system (including temporomandibular disorders). While more investigations with improved levels of scientific evidence are needed, the current evidence does not support the usefulness of posturography as a diagnostic aid in dentistry.
... The studies comprising the occlusion effects on the balance refer mostly to static occlusion (Bracco et al., 1998;Gangloff et al., 2000;Julià-Sánchez et al., 2015Michelotti et al., 2011;Nowak et al., 2023;Sakaguchi et al., 2007;Tardieu et al., 2009). However, even if it is very rare, the term "occlusion" can also be used as a synonym for "jaw clenching" (Hosoda et al., 2007). In this thesis, the term "jaw clenching" will be preferred over "occlusion" if the term "occlusion" is used to refer to "jaw clenching". ...
... They reported that a functionally more symmetric mandibular position resulted in a more symmetric sternocleidomastoid muscle contraction pattern as well as less body sway. In another study by Hosoda et al. (2007), it was investigated if jaw clenching with 50% of the maximum voluntary contraction (MVC) of the masseter muscle may affect the latency of the center of gravity movement initiation after external perturbations (i.e. dynamic reactive balance). ...
... There is evidence that CMGs do not detract from or influence an athlete's performance, cardiopulmonary parameters, or oxygen uptake (VO 2 ) [7,28,31,32,39]. A few studies have shown that teeth clenching plays an important role in rapid postural stabilization [19,25,33], gait stabilization [18], and balance control [4]. Some investigations [26,40] detected positive correlations between a modified occlusal vertical dimension and the head, as well as a cervical posture in patients affected by craniomandibular disorders, while others failed to demonstrate a relationship between an occlusal change and posture [35]. ...
... These data suggest that there is either no stronger bite force under load with mouthguards, or that athletes do not voluntarily Fig. 6 Performance tests A single-leg stance; B kettlebell swing; C countermovement jump clench their jaws during a load. Several studies have demonstrated that clenching the teeth can improve postural stability or balance control [4,18,19,25,33]. Some authors suspect the presence of ergogenic effects from wearing an mouthguard, especially during dynamic exercises demanding a great deal of force [1,2]. ...
Background
Some studies have suggested that a mouthguard is a performance-enhancing device due to a remote voluntary contraction. The extent to which a mouthguard can induce this phenomenon, e.g., by potentially increasing biting, has not been clarified. This study’s aim was to investigate the muscular activity of the maxillary and peripheral musculature and motor performance during a rest and exercise test.
Methods
Our study comprised 12 active, male, professional young handball players (age 18.83 ± 0.39 years). Their performance, electromyographic (EMG) muscle activity ( Σ ), and lateral deviation ( Δ ) of the masticatory and peripheral musculature were measured during rest in a maximum bite force measurement, one-legged stand, a kettlebell swing exercise and a jump test while wearing a customized mouthguard (CMG) or not wearing one (Co).
Results
Maximum bite force measurements did not differ significantly in their mean values of muscle activity ( Σ ) for the masseter and temporalis muscles (Co 647.6 ± 212.8 µV vs. CMG 724.3 ± 257.1 µV p = 0.08) (Co 457.2 ± 135.5 µV vs. CMG 426.6 ± 169.3 µV p = 0.38) with versus without CMG. We found no differences in the mean activation values during a one-legged stand, the kettlebell swing, and jump test ( Σ ) in any of the muscles tested. Lateral deviations ( Δ ) wearing a CMG were significantly less in the erector spinae during the kettlebell swing (Co 5.33 ± 3.4 µV vs. CMG 2.53 ± 1.8 µV p = 0.01) and countermovement jump (Co 37.90 ± 30.6 µV vs. CMG 17.83 ± 22.3 µV p = 0.03) compared to the performance without a CMG. Jump height, rotation moment, and balance were unchanged with versus without CMG.
Conclusion
Our results at rest and during specific motor stress show no differences with or without a CMG. The improved peripheral muscular balance while wearing a CMG indicates improved muscular stabilization.
... hand grip) (Ebben, 2006;Hiroshi, 2003;Cherry et al., 2010). It has also been reported that dental occlusion status contributes to the maintenance of postural balance (Milani et al., 2000;Hosoda et al., 2007). Previous studies allow us to infer that the jaw and neck systems are functionally related. ...
... It is possible that occlusal changes are involved in the decline of balance ability in the elderly. Indeed, in the absence of proper occlusion, the ability of the body to adjust its COG becomes impaired (Hosoda et al., 2007). It has been reported that wearing an occlusal splint may allow patients to alter their postural attitude (Milani et al., 2000) and occlusal therapy has been shown to induce a re-equilibrium of masticatory muscles via a descending action resulting in an improved body posture (Bracco et al., 2004). ...
Studies in the literature show that jaw and neck regions are linked anatomically, biomechanically and neurologically. Voluntary clenching has been shown to improve muscle strength and performance of various motor tasks. Information from the neck sensory-motor system is reported to be important for posture. Hence it is reasonable to believe that activation of the jaw sensorymotor system has the potential to modulate posture. In a sample of 116 healthy subjects, we compared center of gravity (COG) velocity during quiet standing on a foam surface during three test positions: i) resting jaw, ii) open jaw, and iii) clenching; these were tested in two conditions: with eyes open and with eyes closed. The COG velocity decreased significantly during clenching in comparison to both open and resting jaw positions (p<0.0001). This suggests that the jaw sensory-motor system can modulate postural mechanisms. We conclude that jaw clenching can enhance postural stability during standing on an unstable surface in both the presence and absence of visual input in healthy adults and suggest that this should be taken into consideration in treatment and rehabilitation planning for patients with postural instability.
... On this basis, the following concepts should be considered when interpreting such data: (i) The different populations, recording conditions, treatments and methods of monitoring. For instance, comparisons of results from studies focused either on mandibular position mainly in normocclusion subjects (23,(25)(26)(27)(28)(29) or on skeletal ⁄ dental malocclusion (3,8,12,14,15) need to be carried out cautiously; (ii) in most of the previous studies that have reported statistically significant correlations, the corresponding clinical significance of the outcomes were Diff. P = 0AE171; NS P = 0AE000; S P = 0AE000; S Diff., significance of the difference among the groups; NS, not statistically significant; S, statistically significant. ...
... ª 2010 Blackwell Publishing Ltd of the studies mentioned earlier were performed using static postural recordings. To date, very few studies have been performed using the Fukuda test (23) or other dynamic postural tests (26)(27)(28)35). Interestingly, all of these studies have reported significant correlations between the stomatognathic system and body posture, although concerns have been raised about the clinical significance of these findings (2). ...
Whether there are correlations between the stomatognathic system and body posture remains controversial. Here, we have investigated whether malocclusal traits and having a Helkimo Index ≥ 5 show detectable correlations with body-posture alterations in children and young adults. A total of 1178 11- to 19-year-old subjects were divided into four groups: (i) controls; (ii) malocclusion; (iii) Helkimo Index ≥ 5 and (iv) malocclusion + Helkimo Index ≥ 5. Dental occlusion assessment included the following: overbite, overjet, posterior crossbite, scissorbite, mandibular crowding and dental class. Subsequently, body-posture assessments were performed through static analyses of body inclination and trunk asymmetry, and according to the dynamic Fukuda stepping test. Univariate and multivariate statistical analyses were performed. Although at the univariate level both the trunk asymmetry and Fukuda stepping test showed significant differences among the groups, the multivariate level revealed that age and gender were mostly responsible for this. The only significant correlation that was seen was for the malocclusion + Helkimo Index ≥ 5 group: these subjects had a positive (worse) trunk asymmetry and a negative (better) Fukuda stepping test performance. At the further multivariate analyses of each single malocclusal trait ⁄Helkimo Index ≥ 5 (irrespective of the groups), only an increased overbite showed a statistically significant association with a slightly better Fukuda stepping test performance. Given the small number of significant associations seen and their limited entities, this study does not support the existence of clinically relevant correlations for malocclusal traits and Helkimo Index ≥ 5 with body posture in children and young adults.
... When combined, these vari ables provide a more comprehensive analysis of muscle activity during complex movements. [13][14][15][16] Since 1950s, this technology has been used to analyse jaw muscle activity. 11,12 In 2017, a systematic review analysing this topic was published. ...
Background:
Adequate muscle activity is important for the success of oral rehabilitation: it maintains the integrity of the stomatognathic system and is responsible for chewing movements needed to break, crush and grind food.
Objective:
To compare muscle activity using electromyography (EMG) while clenching or chewing soft and/or hard foods among individuals with natural dentition (ND) and edentulous patients rehabilitated with dental prostheses.
Methods:
This review was conducted until March, 2023, and the research question was "Is the muscle activity of edentulous patients rehabilitated with dental prostheses similar to that of dentate individuals?" A search strategy was conducted in PubMed/MEDLINE, The Cochrane Library, Web of Science, Lilacs, Embase and manual journal searches.
Results:
Ten studies were included in the analysis. Most of them reported that individuals with ND had significant higher muscle activity (clenching or chewing) than complete dentures (CD) users. However, no difference was observed between patients with full mouth implant-supported fixed dental prosthesis (ISFDP) and ND. Additionally, two studies compared patients with mandibular ISFDP with maxillary CD and individuals with ND and found no differences; however, one study concluded that patients with ISFDP with CD (maxillary or mandibular) had lower muscle activity than individuals with ND. Only one study reported a higher muscle activity in patients with full-mouth ISFDP than in individuals with ND.
Conclusions:
Bimaxillary CD users had lower muscle activity than individuals with ND. During rehabilitation, the muscle activity of patients with full-mouth ISFDP and mandibular ISFDP with maxillary CD is similar to individuals with ND.
... In previous studies, postural control has generally been assessed by measuring postural sway. The effect of jaw clenching to increase postural stability has been demonstrated in some studies (Alghadir et al., 2015;Hosoda et al., 2007). However, there are also studies stating that jaw clenching did not increase postural stability (Tomita et al., 2021). ...
The jaw sensorimotor system has functional relationships with other parts of the body through neuroanatomical and biomechanical interactions. The aim of this study was to examine the effects of different jaw positions on upper extremity performance, core endurance, and postural stability. This cross-sectional study included 49 healthy young adults aged 18-28 years. Upper extremity performance was evaluated using the push-up test, core endurance was evaluated using the McGill’s Trunk Flexion and Extension Test and postural stability was evaluated using the Balance Error Scoring System. All assessments were made with resting jaw and clenching jaw positions. There was no significant difference in the Push-up test and Balance Error Scoring System scores in different jaw positions (p>0.05). The Mcgill trunk flexion test and extension test performance were found to be better in the clenched jaw position (p=0.017, p=0.035, respectively). The results of this study showed that jaw clenching increases core endurance time. This result should be taken into account when planning an evaluation and rehabilitation program for the core area.
... In fact, previous experiments examining the remote facilitation from maximum effort (high-intensity) occlusion demonstrated effective results in static standing balance stability. [20][21][22][23][24] However, previous studies assessing motor function with teeth occlusion have only examined high-intensity conditions, more detailed studies including low-intensity occlusion would thus be required. ...
Background
Remote facilitation refers to teeth occlusion‐activated spinal cord activity resulting in increased trunk and limb muscle strength. Facilitation depends on dentition‐related pressure during occlusion and masticatory muscle contraction strength.
Aims
This study aimed to clarify the neurophysiological phenomenon and mechanisms by which occlusal strength and balance affect leg muscle activity and smooth joint movement execution.
Materials & Methods
To examine occlusal strength, three conditions were set: no contact between teeth and Moderate‐ and Maximum‐strength occlusion (No‐bite, Moderate, and Max conditions, respectively). To assess occlusal balance, we measured occlusal forces and calculated the left‐right force ratio. We designated the sides with higher and lower occlusal pressure as hypertonic and hypotonic, respectively. We assessed ankle dorsiflexion movements with joint movement and isometric tasks.
Results
The rate of joint development and peak ankle dorsiflexion torque were significantly higher under occlusion (moderate and max compared to No‐bite conditions), and the joint movement performance time was significantly shorter under Moderate compared to No‐bite conditions. The joint movement execution time change rate from No‐bite to Moderate condition was significantly lower on the Hypertonic side. Joint movement function was most improved under Moderate conditions.
Discussion
While remote facilitation improves with higher occlusal strength, leading to increased muscle strength, there is optimal occlusion intensity in joint movement. Moreover, an occlusal balance‐dependent imbalance exists in remote facilitation between the Hyper‐ and Hypotonic sides.
Conclusion
Thus, low‐intensity occlusion is optimal for smooth joint movement, and unbalanced occlusion results in asymmetrical motor function facilitation.
... Ohlendorf et al. [8] placed silicon panels between the subjects' teeth, and it is reasonable to assume they had to bite to keep them in place. Masseter muscle contraction during clenching has been correlated with posture [30] via functional coupling with the trigeminal nerve [31]. This relationship between masseter muscles and trigeminal nerves is dynamic and can be mutually activated or inhibited [32]. ...
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.
... Abb. 1; s. dazu auch [24,25] [41,47,39] beeinträchtigt, wenn die Mandibula fixiert wird. Diese Beobachtung stützt sowohl die Hypothese der passiven Verlagerung als auch die der Lageinformation über die Zahnkontakte. ...
In Forschung und Praxis werden Haltungs- und Bewegungsveränderungen bei oraler Schienenapplikation beobachtet. Dieser Effekt wird bislang dem stomatognathen System zugeschrieben und als kausal abhängig von der Okklusion vermutet. Dies hat seinen Niederschlag in Diagnostik und Therapie gefunden, obgleich die Untersuchungsergebnisse dazu fortlaufend divergieren. Hypothesen. Wahrscheinlicher ist die Haltungsänderung als Reaktion des posturalen Systems, das bei Schienenapplikation auf die Veränderung einer seiner elementarsten Größen reagiert: Die Oberkieferzahnlänge trägt zu einer Ebene bei, die dem posturalen System als Referenz für die Orientierung im Raum dient – Folge ist eine körperstatische Neuorganisation. Dies lässt vermuten, dass sowohl die Funktion des stomatognathen Systems als auch ein entscheidender
Aspekt der Reizverarbeitung des posturalen Systems auf den somatischen Strukturen des Kieferbereichs basiert und dass beide Systeme dort parallel, aber unabhängig voneinander arbeiten. Ergebnisse. Die zahnärztliche Diagnostik wäre um den räumlichen Aspekt durch Einbeziehen der Lage von Kiefer und anderen Körperstrukturen zur Schwerkraft sinnvoll zu erweitern, um ungünstigen Haltungsveränderungen vorzubeugen. Zeitlich vor der Fokussierung der Okklusion als stomatognathe Größe sollte therapeutisch der posturale Aspekt durch die Festlegung einer optimal im Schädel positionierten Referenzebene berücksichtigt werden.
Schlüsselwörter Kraniomandibuläre Dysfunktion · Stomatognathes System · Okklusion · Körperhaltung · Kieferorthopädie
Influence of stomatognathic alterations on posture. Effect of spatial orientation
Abstract Background. Alterations in body posture as well as in functional movements have been observed after application of oral devices. This effect has been attributed to the stomatognathic system and is thought to be causally dependent on occlusion. In consequence, occlusion has become the dominant target in dental diagnostics and therapy, although conclusions of investigations have remained controversial for decades. Hypotheses. However, it is more likely that the alterations in body posture develop from the postural system: the alterations have to be considered as a static restructuring of body posture as a reaction to shifting of a basic indicator of the postural system. This seems to be a reference layer which is elementarily needed for the spatial orientation of the postural system. The length of upper jaw teeth contributes to this reference layer and changes in tooth length will therefore cause an adaptation of body posture. This
leads to the assumption that the structures located in the area of the jaws and teeth form the basis not only for stomatognathic function but also for postural function where they are basically needed in processing information for spatial orientation and body posture. Application of oral wafers can also cause the shifting of this postural reference layer and lead to an alteration of body posture. Results. Dental diagnostics and therapy should benefit from considering the spatial position of the jaw and other body structures in order to prevent unfavorable alterations in posture. Before focusing on occlusion dentists should first aim at finding the optimal position of the postural reference layer in the skull.
Keywords Craniomandibular disorders · Stomatognathic system · Occlusion · Posture · Orthodontics
... Variation in activation pattern of the jaw sensory-motor system while maximum biting, sub-maximum biting, clenching or chewing has been shown to modulate strategies of central postural motor control mechanisms differently (Alghadir et al., 2014;Hellmann et al., 2011;Kushiro & Goto, 2011). These include improvement in sports performance, distal muscle strength, and postural balance (Cherry, Brown, Coburn, & Noffal, 2010;Hosoda et al., 2007). Instant reduction of body sway after using dental splints in patients with whiplash-associated disorders in comparison with healthy subjects further supports the conspicuous role of jaw sensory-motor system (Eriksson, Zafar, & Backén, 2018). ...
Background:
Jaw sensory-motor system has been shown to affect static balance of the body. It would be interesting to know whether it can influence dynamic balance as well. The objective of this study is to examine the influence of different jaw positions on dynamic balance using the Y-balance test.
Methods:
Eighty healthy male participants aged 20-35 years were invited to participate in this study. Dynamic balance was measured by the Y-balance test in three directions (anterior, posteromedial, and posterolateral) for each leg separately in three jaw positions: resting jaw (control), open-jaw, and clenched jaw.
Results:
There were no significant differences in reach distances between the different jaw positions except in the posterolateral direction. In comparison with resting jaw position, reach distance was significantly higher in open-jaw position for the right leg and in clenched and open-jaw positions for the left leg in the posterolateral direction.
Conclusions:
Although various studies have shown direct or indirect influence of jaw sensory-motor system on static postural control, results of this study point to limited relation with dynamic postural control among healthy subjects. However, it supports the potential of the jaw sensory-motor system to affect motor control during functional tasks in patients with postural instability or similar disorders.
... The mandibular proprioception, assisted by the trigeminal nerve and mediated by the masticatory muscles and periodontal ligament, contributes to head posture control via the sternocleidomastoid muscles [9]. Several studies showed that teeth clenching may play an important role in rapid body posture stabilization [10][11][12], gait stabilization [2], posture stability, and balance control [13]. The stomatognathic system may influence the muscle functions in other parts of the body, e. g., the range of hip movement [5], the visual stabilization quality [14], and the head posture [9]. ...
Dental occlusion may affect static and dynamic balance. The effects of a mouthguard on pinpoint accuracy in volleyball were investigated in 28 players who completed a volleyball specific test. Also, masticatory electromyographic tests were performed. The mean pinpoint accuracy was significantly higher with a mouthguard (68.6±9.3 vs. 64.0±7.0 points from 100; p< 0.006). However, differential mouthguard effects were seen, and three subgroups were classified: Group 1 (markedly improved pinpoint accuracy), Group 2 (improved pinpoint accuracy), and Group 3 (reduced pinpoint accuracy). Group 1 had a high masseter resting tone, the masseter activity was low in MVC (maximum voluntary clench) and increased in BOC (maximum bite on cotton rolls; p< 0.04). This indicates a masseter weakness, which would be compensated by a mouthguard. In Group 2, the masseter activity in MVC was high-normal with an imbalance which was improved in BOC (p< 0.01), indicating a possible mouthguard benefit. In Group 3, MVC and BOC were in a high-normal range and showed no relevant deficits. In these subjects the mouthguard had adverse effects. Overall, subjects with masticatory deficits had a benefit from the mouthguard in pinpoint accuracy. Positive or negative mouthguard responders may be detectible from electromyographic tests.
... occlusion on balance was strengthened on unstable platform, thus indicating that the afferent signals from dental occlusion may most effectively contribute to balance control with more pronounced instability conditions 10 . In addition, an interaction between dental occlusion and external disturbances on the balancing ability has been recently described using dynamic posturography (EquiTest system) 95 Recently, the influence of dental occlusion on balance control was suggested to become stronger under fatigue conditions, indicating that even when muscle fatigue is present, dental occlusion in CR allows a better body balance. This reinforces the hypothesis that the sensory information linked to the dental occlusion for balance control becomes especially important when more difficult conditions are present, i.e. unstable condition, fatigue 11 . ...
Background
In the past few years, growing interest was given to the relationship between the dental occlusion and the body balance. While most research focused on this relationship at static conditions, it is evident that the contribution of the sensory information for balance control is different depending on the environmental constraints.
Research question
The aim of the present paper was to elucidate whether the stomatognathic system (SS) contributes differently on body balance regulation according to the presence of external disturbances.
Methods
Literature regarding the different sources involved in the proprioceptive information to the SS was reviewed. The influence of dental occlusion on balance control at different external environments was then explored.
Results
The main findings are: (i) a plausible evidence between the masticatory and cervical muscles can be described; (ii) a reciprocal connection between the trigeminal and vestibular nuclei supports the influence of the SS on body balance; (iii) traditionally, research involving the relationship between the SS and balance control has focused on strictly controlled situations, thus ignoring the sensory reweighting which occurs depending on the external disturbances; and (iv) the afferences of dental occlusion for balance control seem strengthened when more difficult conditions are present.
Conclusion
Results of the present review suggest that afferent signals from dental occlusion effectively contribute to balance control when more external perturbations are present, i.e. unstable support surface, fatigue, tasks being performed. However, more studies are needed to elucidate the mechanisms by which dental occlusion may influence balance control focusing on different external environments.
This article is protected by copyright. All rights reserved.
... E-mail contact of the corresponding author: amandio30@gmail.com Introduction: The relationship between dental occlusion and static body posture has been well researched and debated in several publications (1,2,3). Far less attention has been spent on studying the same relationship, but with regards to human locomotion, with only a scarce number of studies addressing the matter. ...
This presentation focus on the effects of occlusal splints on the gait and running kinematics
... Muscle proprioceptive messages provide the main information necessary for coding postural configurations and body movements as well as for exerting both reflex and automatic controls on these configurations and movements 48 . Voluntary jaw clenching has been known to improve distal muscle strength, sports performance and postural balance instantly 49,50 . However, current study did not find any significant difference in head-neck relocation error during different movements while jaw clenching. ...
Objectives:
To investigate the effect of different induced head-neck-jaw postures on head-neck relocation error among healthy subjects.
Methods:
30 healthy adult male subjects participated in this study. Cervicocephalic kinesthetic sense was measured while standing, habitual sitting, habitual sitting with clenched jaw and habitual sitting with forward head posture during right rotation, left rotation, flexion and extension using kinesthetic sensibility test.
Results:
Head-neck relocation error was least while standing, followed by habitual sitting, habitual sitting with forward head posture and habitual sitting with jaw clenched. However, there was no significant difference in error between different tested postures during all the movements.
Conclusions:
To the best of our knowledge, this is the first study to see the effect of different induced head-neck-jaw postures on head-neck position sense among healthy subjects. Assuming a posture for a short duration of time doesn't affect head-neck relocation error in normal healthy subjects.
... Neck trauma is also shown to derange integrated jaw and neck behavior showing the functional coupling between the jaw and neck motor systems Haggman-Henrikson and Eriksson 2004). It has also been shown that dental occlusion status contributes to the maintenance of standing postural balance (Hosoda et al. 2007;Milani et al. 2000). Chewing co-activates jaw and neck muscles leading to coordinated jaw and head-neck movements (Eriksson et al. 2000). ...
Background and aims:
There is an important role of the neck sensory motor system in control of body posture and balance, and it is reasonable to believe that the jaw sensory motor system can directly and indirectly influence the modulation of the postural control system. The purpose of this study was to evaluate possible effects of dynamic jaw position while chewing on the postural control system.
Materials and methods:
We compared the mean center of gravity (COG) velocity during quite standing on a foam surface with eyes closed during three test conditions: (i) with resting jaw position, (ii) with open jaw position, and (iii) while chewing standard bolus of chewing gum. One hundred and sixteen normal healthy male subjects (average age 31.56 ± 8.51 years; height 170.86 ± 7.26 cm) were recruited for the study. Their COG velocity (deg/s) was measured using the NeuroCom® Balance Master Version 8.5.0 (Clackamas, OR, USA).
Statistical analysis:
Data was tested by the Friedman test.
Results and conclusions:
The results show that COG velocity decreased significantly while chewing in comparison to both open and resting jaw position (p < 0.0001). Our finding corroborates previous studies and suggests that the jaw sensory motor system can modulate postural control mechanisms. Gum chewing activity can enhance the postural stability during upright standing on an unstable surface and in the absence of visual input in healthy young adults. Our results should be taken into consideration in treatment and rehabilitation planning for patients with postural instability.
... Furthermore, dynamic body balance-associated functions, such as quickness or recovery action of the body, appeared to have deteriorated in the absence of dental occlusion. 19,20 In such conditions, muscle strength factors can be more important to balancing ability than static body balance, as examined in this study. An earlier report suggested that voluntary teeth clenching, in which the ankle extensors and flexors co-contract to fix the ankle joint, may contribute to the stabilization of postural stance. ...
Since tooth loss may be considered to affect postural control, the aim of this study was to compare body balance control among samples of edentulous and dentate community-dwelling elderly subjects.
A case control study was conducted using test and control groups matched by age, gender, body fat, and muscle composition. The test group included all participants of the 2006 Kyoto Health Seminar who wore a full denture in either or both arches. The control group was blindly selected from the same population, but only included individuals who retained all of their dentition with either natural teeth or crown prostheses. The results of physical fitness examinations and stabilometer tests were compared between these two groups.
The test and control groups both included 12 male and 23 female subjects. Body balance ability, measured by time spent standing on one leg with eyes open (P = .013) and functional reach (P = .037), was significantly less in the test group when compared to the control, as shown by analysis done using the Mann-Whitney Utest. The stabilometer examination also indicated that sway area (an accurate indicator of postural balance) and body sway (evidence of energy consumption for postural control) while standing with eyes closed were both significantly higher in the test group (P = .035 and .048, respectively; Wilcoxon signed ranks test) than the control.
It is suggested that tooth loss is a risk factor for postural instability. This further suggests that proprioceptive sensation from the periodontal ligament receptor may play a role in body balance control.
O centro de gravidade está intimamente ligado ao equilíbrio corporal, porém algumas vezes essa relação é pouco enfatizada. Diante disso, esse estudo buscou analisar as influências e relações do CG com o equilíbrio corporal dos indivíduos, por meio de uma revisão de literatura. Para isso, realizou-se uma busca em base de dados, livros e demais produções cientificas da área de biomecânica. Os resultados dessa pesquisa mostram que muitas variáveis influenciam na posição do CG e por conseqüência no equilíbrio corporal. Conclui-se que a relação específica da altura do centro de gravidade com o equilíbrio, é uma abordagem pouco estudada e pode ainda ser bem desenvolvida, relacionando diversos tipos de indivíduos como obesos, idosos, atletas, entre outros.
Räumliche Orientierung, Körperhaltung und Zähne scheinen durch eine Schnittstelle verbunden zu sein: ein rechtwinkliger Raum, der der Kaufläche der Oberkieferzähne aufsitzt. Er verarbeitet und berechnet Vektoren des eigenen Körpers und der Umwelt. Nur diese synoptische Sichtweise ermöglicht es Lebewesen, mit ihrer Umwelt umzugehen, sich zurechtzufinden und Vektoren von Umweltobjekten zu antizipieren. Unvorstellbar wird hier hypothetisiert, dass dieser Vektorraum sich nach den (äußeren) Raumdimensionen ausrichtet. Er bleibt auch bei der automatischen Fortbewegung identisch zu ihnen. Seine Position relativ zum Kopf hängt jedoch von der Position der Kauebene relativ zum Kopf ab. Wir stellen ein neues Modell der räumlichen Orientierung vor, mit dem sich Verarbeitung und die hohe Geschwindigkeit der posturalen Reaktionen erklären lassen: Im Vektorraum berechnet, erfolgt die Übertragung in den Körper durch den Schlauch der Dura mater (harte Hirnhaut), und zwar durch ihre 16 Längssegmente. Entscheidend für den "Setup" ihres Tonus und Verlaufs ist die Region C0-C2, bereits als "Schlüsselregion" bekannt. Ein Abknicken, Verkürzen oder Verdrehen des Dura-Schlauches zwischen C0-C2 verändert Tonus und Verlauf des gesamten Längssegments - und damit auch des entsprechenden Körpersegments. Hypothetisch wird der auf der Kaufläche der Oberkieferzähne liegende Vektorraum durch zu flache oder zu hohe Füllungen, Brücken oder Prothesen an den oberen Zähnen schräggestellt (relativ zum Kopf). Dennoch wird dieser Raum identisch zu den Raumdimensionen ausgerichtet - das geschieht durch ausgleichende Schrägstellung des Kopfes sowie Kippungen und Drehungen des Körpers und ist ganz offensichtlich lebenswichtig. Die daraus resultierende Haltung ist schmerzhaft und hat eine hohe Prävalenz ("Haltungsschwäche", "Fehlhaltung"). Dank einiger Probebehandlungen scheint dieses Krankheitsbild heilbar zu sein, indem die ursprüngliche Position der Oberkieferkaufläche relativ zum Kopf wiederhergestellt wird.
Spatial Orientation, posture and teeth seem to be linked through an interface: this is a rectangular space built up upon the maxillary chewing surface. It processes the vectors of the own body and those of the environment to compute them. Only this synoptic view enables creatures to deal with their environment and to anticipate vectors of environmental objects. Unimaginably, the vector space is aligned to the (external) spatial dimensions. It remains identic with the spatial dimensions even during automatic locomotion. However, its position relative to the head depends on the position of the maxillary chewing plane relative to the head. We are presenting a new model of spatial orientation, allowing to explain the procession and the high speed of postural reactions. Calculated within the vector space, the transfer into the body is performed through the tube of the dura mater (hard meninges), namely by its 16 longitudinal segments. Crucial region for the setup of tone and course of the longitudinal segments is the region C0-C2, already known as "key region". Buckling, shortening or twisting of the dural tube between C0-C2 will change tone and course of the whole longitudinal segment and the corresponding body segment. Resting on the maxillary chewing surface, the vector space may be dislocated through applying too flat or too high fillings, bridges or denture to the upper teeth. Nevertheless, it will be aligned to the spatial dimensions - through a head tilt and tilts and rotations of the body. The resulting posture is painful and may be seen very often („postural weakness“, „misaligned posture“). Due to some trial treatments, this clinical picture seems to be curable by restoring the original position of the maxillary chewing surface relative to the head.
Purpose:
Centric Relation (CR) is a universally recognized term and an acceptable reference position with a long history of success. The problem is that there is little consensus as to its definition or the method of recording it, and this has created an uprising to abolish it.
Methods:
A review of pertinent literature related to its definition, method of recording, anatomic considerations and long-standing principles was conducted.
Results:
CR is an established term but there are valid concerns over its definition and method of recording. There is consensus on using it as a restorative position in a patient in need of full arch reconstruction and there is no substantive clinical research to contradict this. If a clinician decides to use a different position, it should have a different name.
Conclusions:
CR is a reproducible reference position that can be utilized for diagnostic and restorative dental procedures with substantial scientific evidence to support that premise. There are numerous well documented techniques, all of which are intermaxillary, that can replicate the position. There is little scientific evidence to support a premise as to where the exact position of the condyle should be in relation to the fossa. This article is protected by copyright. All rights reserved.
Introduction: The relationship between dental occlusion and static body posture has been researched and debated in some publications [1–3 Baldini A, Nota A, Tripodi D, et al. Evaluation of the correlation between dental occlusion and posture using a force platform. Clinics. 2013;68(1):45–49. doi:10.6061/clinics/2013(01)OA07
Hosoda M, Masuda T, Isozaki K, et al. Effect of occlusion status on the time required for initiation of recovery in response to external disturbances in the standing position. Clinical Biomechanics. 2007;22(3):369–373. doi:10.1016/j.clinbiomech.2006.11.001
Julià-Sanchez S, Álvarez-Herms J, Gatterer H, et al. Dental Occlusion Influences the Standing Balance on an Unstable Platform. Motor Control. 2015;19(4):341–354. doi:10.1123/mc.2014-0018 ]. Far less attention has been spent on studying the same relationship, but with regards to human locomotion, with only a scarce number of studies addressing the matter. Therefore, the aim of this study was to determine if changes in dental occlusion are correlated to body posture while walking and running.
Materials and methods: This study enrolled fifteen healthy subjects (age: 21.13 ± 2.53 yrs), assessed by an expert dentist and deemed asymptomatic for temporomandibular disorders. Gait and running analysis was randomly performed on a treadmill in three different conditions: a) Occlusal splint; b) Placebo splint and c) No splint (control). The occlusal splint used in this study positioned the temporomandibular joint in a centric relation position. Kinematic data were collected using a 3D motion capture, consisting five high speed cameras system, for body horizontal sway (shoulders, anterior and posterior superior iliac spine) and vertical sway (spine). This research was approved by the ethics committee of the Faculdade de Motricidade Humana for use of human research (6/2016).
Results: The use of occlusal splints did not influence the body sway during gait and running since no differences were found in the mean values for both horizontal and vertical body sway, for all the test conditions
Discussion and conclusions: Dental occlusion, achieved through the use of occlusal splints, that change the temporomandibular joint into a centric relation position, appears to have no effect on body horizontal and vertical sway, for gait and running in healthy male subjects. High inter-subject variability in the kinematic parameters was found, mainly during gait. Due to this, intra-subject variability should be considered in future studies in order to understand the occlusal splints influence among subjects.
Introduction: The biggest challenge in the area of Temporomandibular Dysfunction and pain is the establishment of a classification system that is internationally valid and reliable. The RDC/TMD [1 Le Resche L, Fricton J, Nd M. Research diagnostic criteria, A. Axis I;: Clinical TMD conditions. In Le Resche L, Dworkin S. (eds). Research diagnostic criteria for temporomandibular disorders: Review, criteria, examinations and especifications. J Craniomandib Disord Facial Oral Pain. 1992;6:327–30. [Google Scholar]] is used worldwide allowing to typify populations. Using the RDC/TMD, the aim of the study was to: a) establish prevalence of Orofacial Pain and Temporomandibular Disorders; b) establish the prevalence of group I, II-A, II B, IIIA, III.b, III.c disorders according with axis I; c) quantify and assess the severity of chronic pain in the population according with axis II; d) compare the prevalence of temporomandibular disorders with the results obtained in other population groups studied.
Materials and methods: After the approval by the ethics committee of Egas Moniz we obtained a sample of 50 individuals who attended an appointment of occupational health at SAMS/PICS company in the region of Greater Lisbon and the South of the Tagus. The individuals were subjected to the RDC/TMD protocol from Dworkin and Leresche, consisting of a questionnaire on the psychological and emotional characteristics. Next, a clinical examination consisting of an examination of the mandibular mobility and of the muscular and articular palpation was made. Data was analyzed using a biaxial system of evaluation. After the analysis of the collected data we divided and classified the individuals in specific subgroups in terms of statistical analysis we have used descriptive statistics and considered significant significant differences when the confidence intervals of the results of the two groups did not overlap (p ≤ 0.05).
Results: With the RDC/TMD protocol - Axis I - it was possible to quantify the number of individuals diagnosed with Temporomandibular Dysfunction: Group I - 14% II.a - 26%, II.b - 0% III.a - 6% III.b - 0% and III.c - 12%, considering a confidence interval of 95%.
Discussion and conclusions: These results are different from many of the published studies but very similar to the very few studies with similar design [2 Rantala M, Ahlberg J, A S, M K nen. Symptoms, signs, and clinical diagnoses according to Research Diagnostic Criteria for Temporomandibular Disorders Among Finnish Multiprofessional Media Personnel. J Orofac Pain J Orofac Pain. 2003;17:21–28.[PubMed], [Web of Science ®] , [Google Scholar]]. The RDC/TMD protocol allowed to know the characteristics of pain and Temporomandibular Dysfunction contributing this way to typify the studied population.
Occlusal support may influence muscular function during complex motor tasks. This study evaluated the duration and sequence of muscular activation of masticatory (temporal, masseter), postural head/neck (sternocleidomastoid, trapezius), postural trunk (rectus abdominis, paravertebrals), and low extremity strength (rectus femoris, gastrocnemius) muscles during simulation of activities of daily living (ADL) in edentulous women wearing complete dentures (n = 10) and in dentate women (n = 10). Electromyographic activity was recorded during tests of stand‐up/sit down in the Chair, sit up/lie down in the Bed and lift/lower Bags. Occlusal support (dentures) had a significant effect on duration of muscular activation in the Chair Test: the masseter muscle activated longer with dentures during the standing movement. The masseter and sternocleidomastoid muscles showed significant alteration in their order of activation in non‐denture‐wearing women. For the Bed Test, dentures had significant effect for the gastrocnemius during the sitting‐up phase and for the rectus abdominis during the lying‐down movement. For the Bag Test, head/neck muscles were activated in a different order as a function of occlusal support. Anticipation of activation of the paravertebral muscles, rectus abdominis, and gastrocnemius was observed in dentate women compared with denture wearers. These findings suggest that occlusal support influences electromyographic activity of some muscles during simulation of ADL.
There appears to be much confusion or misinformation worldwide regarding mouthguards and their use in sports. In an effort to clarify where the international dental community stands on mouthguards and mouthguard research, the workshop looked at some important questions. The goal is to one day formulate consensus statements related to these questions, which will be based on current scientific evidence-based research, to motivate the international community of the importance of dentally fitted laminated mouthguards and the wearing of them by athletes of all sports. There are only five sports in the USA that require the use of mouthguards. If through workshops such as this, the importance of wearing dentally fitted laminated mouthguards can be demonstrated, then more sports may require their athletes to wear them. This article is protected by copyright. All rights reserved.
Purpose:
This study was to determine whether non-habitual (isotonic) bilateral and unilateral mastication with eyes open and eyes closed exerts an influence on static balance in individuals without temporomandibular disorder (TMD).
Method:
An observational, cross-sectional study was conducted involving 20 volunteers aged 20 to 40 years without temporomandibular disorder. Static balance was assessed with the individuals in a quiet standing position on a force plate performing different types of mastication under six separate conditions.
Results:
Significant differences (p < .05) were found in the area of oscillation during bilateral mastication (eyes open) and the right unilateral mastication, significant differences were only found for oscillation area with eyes open and mediolateral center of pressure with eyes closed (p < .05).
Conclusions:
The findings of the present study reveal that the stomatognathic system (bilateral and unilateral mastication) promote changes in some variables of static balance.
This study was performed with the aim of assessing dispositional optimism (DO) in a sample of Parkinson's disease (PD) patients, in order to evaluate its association with clinical outcomes and its impact on rehabilitation. Before entering an outpatient rehabilitation program, 58 participants suffering from idiopathic PD completed the Life Orientation Test-Revised (LOT-R) to evaluate their level of DO, the WHO-5 scale to evaluate their health-related quality of life (HR-QoL), the Hospital Anxiety and De ression Scale (HADS) to identify emotional distress, and the Barthel Index to evaluate their level of disability. All the measures were repeated four months later, at their discharge from the program. Disease stage and severity measures (Unified Parkinson's Disease Rating Scale) were also taken into consideration. Correlations and multivariate regression analyses compared DO with the health-related variables. On admission a high level of DO was found to be associated with less severe disease, a better quality of life (QoL) and lower emotional distress, but not with level of disability (Barthel Index). Consistent results were found at discharge. The level of DO did not change after rehabilitation, while anxiety was significantly reduced, especially in subjects with low LOT-R and high HADS scores. The Barthel Index values significantly improved. At discharge, participants with high DO showed the best improvements in disability and in QoL. Effects of dispositional optimism on quality of life, emotional distress and disability in Parkinson's disease outpatients under rehabilitation In conclusion, a high level of DO was associated with QoL, HADS and UPDRS both on admission and at discharge. The level of DO remained stable after rehabilitation, while disability and anxiety were reduced. Participants with high DO generally had better QoL, and better clinical and psychological performances.
Objectives: Athletes wear mouthguards for their protective value against trauma. Mandibular position has been linked to postural changes and improved athletic performance. This randomized double-blind comparative study aimed to evaluate the postural changes induced by two different mouthguards in athletes.
Methods: Seventy-four volunteer varsity athletes, male and female, from soccer and hockey teams of the Universit de Moncton were fitted with two mouthguards; Indented Midlined Stabilizing (IMS) and Flat (F). Using MatScan® linked to BioEMG®, sway parameters and surface electromyography of postural muscles were assessed for eyes closed static erect posture for three mandibular positions: habitual occlusion and the two mouthguards. The deltoid resistance was also assessed for the three conditions.
Results: There was significant stabilization of sway (p<0.0001) (area, distance, left-right excursion and antero-posterior excursion) by the IMS mouthguard compared to the F mouthguard and habitual occlusion. Those last two did not differ with respect to sway. There was no difference in the surface electromyographic recording under all three conditions. The deltoid resistance was improved only by the IMS mouthguard.
Conclusions: Properly designed mouthguards provided postural stabilization and increased deltoid resistance for athletes. These observed positive changes in posture could potentiate athletic performances, play a role in injury prevention and have an impact in rehabilitation.
Repeated measures design. This study examined recovery of postural equilibrium (centre of pressure (COP) excursion, time to recover balance, and the number of postural adjustments) following unexpected support surface perturbation in healthy participants with and without a rigid lumbar corset to reduce lumbar motion. Lumbar spine movement is thought to aid postural stability, especially when a "hip" (lumbopelvic) strategy is required, such as in response to large and fast perturbations. Delayed onset of lumbar spine movement in association with prolonged postural recovery in chronic low back pain implies reduced spinal motion could underpin balance deficits in this group. However, other explanations such as poor proprioception cannot be excluded, and the relationship between lumbar movement and postural stability remains unclear. We hypothesized restricted lumbar spine movement would impair control of postural recovery following support surface perturbation. Participants regained postural stability following unexpected support surface perturbations in different directions (forward and backward), with different amplitudes (small, medium, and large), with and without restriction of spine motion by a hard lumbar corset. Although the latency of the postural adjustment was unaffected by the corset, the quality of postural recovery was compromised (increased COP range, time taken for postural recovery, and number of postural adjustments) during recovery, especially in response to large perturbation. Restriction of lumbar spine movement adversely affects postural recovery. The results suggest movement of the lumbar spine, although small in amplitude, is critical for efficient recovery of standing balance.
Previous research has shown that mastication reduces shifts in the center of gravity of persons standing still. The present research was conducted to determine whether mastication improves reactive balance in the standing position in response to unanticipated external disturbances. The subjects were 32 healthy male adults (mean age 21.1 years, standard deviation (SD) 0.7 years). Latency data determined with the Motor Control Test of Computerized Dynamic Posturography (CDP) were compared for the three conditions of mastication status, the direction of translation, and the magnitude of translation, using three-way repeated measures ANOVA and lower-order ANOVA with the three conditions separated. Latency was significantly shorter with mastication than with the lower jaw relaxed (P < 0.00001). Mastication alone, however, cannot be considered significant because of the complex interactions involved among the three conditions. Mastication increases not only static balance but also reactive balance in response to unanticipated external disturbances. Gum chewing may therefore reduce falls among elderly persons with impaired balance.
Analysis of correlations of the functional parameters of the stomatognathic and postural systems with sub-, decompensated, and compensated status was carried out. Disorders in the masticatory muscle activity and interactions between the postural and stomatognathic systems were detected in patients with sub- and decompensated functional status. A significant correlation between the studied functional parameters was detected in the patients with the compensated functional status.
Studies on the relationship between dental occlusion and body balance have suggested that occlusion status contributes to the maintenance of postural balance. However, little has been reported about the effects of voluntary teeth clenching on the stabilization of postural stance in novel environments. In the present study we investigated whether teeth clenching influenced adaptation to the perturbation introduced by electrical stimulation of a unilateral lower limb. Subjects (12 adults) stood on a force plate, from which motion data were obtained in the horizontal plane with and without voluntary teeth clenching and were instructed to maintain the position throughout the experiment. We evoked a novel environment by supramaximal percutaneous electrical stimulation of the common peroneal nerve. Electromyograms (EMG) were recorded from the masseter and the peroneus longus (PL) muscles with bipolar surface cup electrodes. When the disturbed postural stance was generated by electrical stimulation, the maximum reaction force in the anterior-posterior (A/P) direction with teeth clenching (CL) was significantly smaller than that without voluntary teeth clenching (control; CO) (p<0.05) and the peak time of the ground reaction force/body mass (GRF/BM) in the A/P direction occurred earlier in the CL condition than CO (p<0.05). There were no significant differences in the peak-to-peak amplitude of GRF/BM and the peak time of GRF/BM, in the M/L direction under both CL and CO conditions. Thus, the present study showed that voluntary teeth clenching contributed to stabilization of the postural stance perturbed transiently by electrical stimulation. We concluded that voluntary teeth clenching plays an important role in rapid postural adaptation to the anterior-posterior perturbation in the upright position.
To test whether changes in occlusal support differentially modulate masseter and anterior temporalis muscle electromyographic (EMG) activity during controlled maximal voluntary clenching.
Forty-seven healthy subjects (32 M and 15 F, 22.9+/-1.3 years) were recruited. Cotton-rolls were used to modify the occlusal contact relations and were positioned on the right, left, or both sides, and either in the molar or premolar regions, i.e. six different occlusal combinations. Surface EMG activity was recorded bilaterally from the masseter and anterior temporalis area and normalized with respect to maximal voluntary clenching in the intercuspal position. Analysis of variance and the paired t-test were used to test the data.
Normalized EMG activity was influenced by changes in cotton-roll modified occlusal support, and there were differences between muscles (p<0.001). In general, EMG activity decreased in both muscles when occlusal support was moved from the molar to the premolar region. When occlusal support was moved from bilateral to unilateral contacts, EMG activity in the balancing-side anterior temporalis muscle and in bilateral masseter muscles decreased. Unilateral clenching on the molars, but not on the premolars, was associated with lower EMG activity in the balancing-side masseter and always associated with lower EMG activity in the balancing-side anterior temporalis compared to the working side (p<0.05).
Masseter and anterior temporalis muscles respond differently to changes in occlusal support, which may have implications for stability of the mandible during intense clenching.
The maximal bite force and the strength of the finger-thumb grip of 125 Skolt Lapps, aged 15 to 65, was measured with a specially devised apparatus. The bite force was measured with the biting fork placed between the first molars and between the incisors, respectively. The finger-thumb grip was measured by letting the subject press the prongs of the fork between the thumb and forefinger of each hand as hard as possible. The range of inter-individual variation of the maximal bite force and finger-thumb grip was great. The mean values were higher for the males than for the females. In the males the maximal bite force thus measured in the molar region was 39 kg (382 N) and 18 kg (176 N) in the incisor region. The corresponding values for the females were 22 kg (216 N) and 11 kg (108 N). The finger-thumb grip strength for males was, on the average, 10 kg (98 N); that of the females, 7 KG (69 N). The average difference in bite force between the men and the women was larger in the group with natural teeth than in the one with complete dentures. The values found for the bite force decreased with increasing age, especially for the females. Most of this reduction with increasing age was probably due to the age-dependent deterioration of the dentition. In both sexes the bite force was notably smaller among the denture wearers than among the dentate persons. The number of natural teeth varied closely with the bite force, i.e. the greater number of natural teeth the greater the bite force.
The purpose of this study is to investigate the effect of sagittal plane head-neck posture on initial tooth contacts (muscle contact position) using the T-Scan system of occlusal analysis. Thirty-five subjects from 14 to 72 years old were selected. Computerized T-Scan occlusal printouts were obtained on each subject with the head-neck in 45 degrees dorsiflexion and 30 degrees ventroflexion. To quantify the location of the contacts on the upper arch, the dotted lines appearing on the printout were assigned numerical values. Low numbers represent distal contacts and the higher the number, the more mesial the contact. Wilcoxon's Rank Sum Test was used to analyze the data. Results indicated that below the age of 30 years no significant relationship was demonstrated between head posture and muscle contact position. However, over the age of 30 there was an increasingly significant relationship between sagittal plane head-neck posture and initial occlusal contacts. Based on these findings, the authors recommend that management of occlusally related problems, i.e., temporomandibular disorders include an assessment of the craniovertebral region especially in patients over the age of 30 years.
The concept of a generalized aging effect on a generalized balance mechanism is discussed, and an alternative, multicomponent approach to understanding the heterogeneity of postural dyscontrol in the elderly is presented. Neural sensorimotor components of normal postural control mechanisms are identified and discussed. The effects of Parkinson's disease, hemiplegia, cerebellar degeneration, peripheral vestibular loss, and other disorders on the components of postural control are summarized. Quantitative posturography is advocated to detect preclinical manifestation of multiple musculoskeletal and neuromuscular pathologies and reduced compensatory abilities in posturally unstable elderly adults.
We studied the extent to which automatic postural actions in standing human subjects are organized by a limited repertoire of central motor programs. Subjects stood on support surfaces of various lengths, which forced them to adopt different postural movement strategies to compensate for the same external perturbations. We assessed whether a continuum or a limited set of muscle activation patterns was used to produce different movement patterns and the extent to which movement patterns were influenced by prior experience. Exposing subjects standing on a normal support surface to brief forward and backward horizontal surface perturbations elicited relatively stereotyped patterns of leg and trunk muscle activation with 73- to 110-ms latencies. Activity began in the ankle joint muscles and then radiated in sequence to thigh and then trunk muscles on the same dorsal or ventral aspect of the body. This activation pattern exerted compensatory torques about the ankle joints, which restored equilibrium by moving the body center of mass forward or backward. This pattern has been termed the ankle strategy because it restores equilibrium by moving the body primarily around the ankle joints. To successfully maintain balance while standing on a support surface short in relation to foot length, subjects activated leg and trunk muscles at similar latencies but organized the activity differently. The trunk and thigh muscles antagonistic to those used in the ankle strategy were activated in the opposite proximal-to-distal sequence, whereas the ankle muscles were generally unresponsive. This activation pattern produced a compensatory horizontal shear force against the support surface but little, if any, ankle torque. This pattern has been termed the hip strategy, because the resulting motion is focused primarily about the hip joints. Exposing subjects to horizontal surface perturbations while standing on support surfaces intermediate in length between the shortest and longest elicited more complex postural movements and associated muscle activation patterns that resembled ankle and hip strategies combined in different temporal relations. These complex postural movements were executed with combinations of torque and horizontal shear forces and motions of ankle and hip joints. During the first 5-20 practice trials immediately following changes from one support surface length to another, response latencies were unchanged. The activation patterns, however, were complex and resembled the patterns observed during well-practiced stance on surfaces of intermediate lengths.(ABSTRACT TRUNCATED AT 400 WORDS)
Falls and fall-related hip fractures are among the most serious, common, and costly medical problems facing the elderly. Recently, we and others have shown that falls to the side, particularly those that end with impact on the hip, raise the risk of hip fracture from six- to thirty-fold, compared to about threefold increases in risk associated with one SD reduction in BMD at the hip. And yet, despite the apparently crucial importance of sideways falls, little is known about the mechanics of falling to the side. In addition, while previous studies have helped identify those factors that place the elderly at high risk for falling and provided assessment procedures that can be used to identify those at risk for falls, as far as we are aware no previous work has successfully identified subjects at increased risk of falling to the side. Moreover, while rigorous, multifactorial fall prevention efforts have demonstrated moderate reductions in fall incidence, such programs are expensive and potentially inefficient in that they have not consistently demonstrated reductions in the numbers of injurious falls. While trochanteric padding systems show considerable promise for hip fracture prevention by reducing impact force, they involve difficult acceptance and compliance issues and will require large and rigorous clinical trials to demonstrate effectiveness. Finally, while it also appears that osteodynamic agents can be used to increase BMD at the hip and spine, little is known about the local structural consequences of these changes and, in particular, if they are sufficient to prevent hip fracture from a severe fall. The findings reviewed here thus emphasize the continuing need for combined intervention strategies that focus on fall prevention, on reductions in fall severity, and on maintaining or increasing bone mass and strength, either through targeted exercise programs or the use of osteodynamic agents. By developing and refining the factor of risk phi, a property that captures both the contributions of bone density and the confounding influences of body habitus and fall severity, we believe these intervention strategies can be targeted more appropriately. Based on such approaches and an improved understanding of the complex interplay between fall biomechanics and bone fragility in the etiology of hip fracture, there is hope that the growing worldwide epidemic of hip fractures among the elderly can be substantially abated.
Environmental context influences the strategy for executing a motor act 1) by affecting the information content of movement-associated sensations, and 2) by changing the mechanical configuration for which postural support must be provided. This article describes the postural reactions produced by freely standing subjects attempting to compensate for external perturbations and executing simple arm movements, while exposed to unexpectedly different sensory conditions and configurations of postural support. Based upon these observations, two principles are then advanced 1) by which the weighting of individual sensory inputs to posture, and 2) by which the temporal and spatial distribution of muscular contractions expressing postural reactions adapt to the environmental context.
Of 1042 individuals aged 65 years and over who were successfully interviewed in a community survey of health and physical activity, 35% (n=356) reported one or more falls in the preceding year. Although the overall ratio of female fallers to male fallers was 2.7: 1, this ratio approached unity with advancing age. Mobility was significantly impaired in those reporting falls. Asked to provide a reason for their falls, 53% reported tripping, 8% dizziness and 6% reported blackouts. A further 19% were unable to give a reason. There was no association between falls and the use of diuretics, antihypertensives or tranquillizers, but a significant association between falls and the use of hypnotics and antidepressants was found.
Discriminant analysis of selected medical and anthropometric variables indicated that handgrip strength in the dominant hand and reported symptoms of arthritis, giddiness and foot difficulties were most influential in predicting reports of recent falls.
The aim of this study has been to present firmer evidence that during stance functionally related postural muscles in the legs are activated according to fixed patterns. The importance of fixed patterns of activation for stabilization, balance, and movement control has received considerable theoretical and experimental attention. With regard to postural adjustment in humans, however, evidence for fixed activation patterns has been circumstantial only. Previous studies could not rule out the possibility that fixed patterns were caused by the mechanical coupling of rotatory movements among the joints of the body.
A method is described to relate jaw muscle EMG-activity to static bite forces. Bite forces are measured bilaterally in several reproducible positions on the human dentition by means of small wedge shaped transducers. Electromyographic methods are used to derive a relative measure of the activity in the opener and closer muscles. Visual feedback methods are used to obtain bite recordings at various levels of bite force and muscle activity. There is no reason to doubt the linear relationship between integrated EMG-activity and the force exerted by individual muscles in isometric conditions. The anterior and posterior parts of the temporal muscle show a different functional behaviour. The role of the opener muscles as antagonists is of such importance, that it should not be neglected in a muscle force analysis.
Doubt about the role of stretch reflexes in movement and posture control has remained in part because the questions of reflex “usefulness” and the postural “set” have not been adequately considered in the design of experimental paradigms. The intent of this study was to discover the stabilizing role of stretch reflexes acting upon the ankle musculature while human subjects performed stance tasks requiring several different postural “sets”. Task specific differences of reflex function were investigated by experiments in which the role of stretch reflexes to stabilize sway during stance could be altered to be useful, of no use, or inappropriate.
Because the system has available a number of alternate inputs to posture (e.g., vestibular and visual), stretch reflex responses were in themselves not necessary to prevent a loss of balance. Nevertheless, 5 out of 12 subjects in this study used long-latency (120 msec) stretch reflexes to help reduce postural sway. Following an unexpected change in the usefulness of stretch reflexes, the 5 subjects progressively altered reflex gain during the succeeding 3–5 trials. Adaptive changes in gain were always in the sense to reduce sway, and therefore could be attenuating or facilitating the reflex response. Comparing subjects using the reflex with those not doing so, stretch reflex control resulted in less swaying when the task conditions were unchanging. However, the 5 subjects using reflex controls oftentimes swayed more during the first 3–5 trials after a change, when inappropriate responses were elicited.
Four patients with clinically diagnosed cerebellar deficits were studied briefly. Among the stance tasks, their performance was similar to normal in some and significantly poorer in others. Their most significant deficit appeared to be the inability to adapt long-latency reflex gain following changes in the stance task.
The study concludes with a discussion of the role of stretch reflexes within a hierarchy of controls ranging from muscle stiffness up to centrally initiated responses.
The maximum bite force and position of the hyoid bone during natural and extended head posture were studied in 15 adults. All participants had normal occlusions and full dentitions. In addition, there were no signs or symptoms of craniomandibular disorders. The bite force was measured with a bite force sensor placed between the first molars. Six registrations of gradually increasing bite force up to a maximum were made with randomized natural and extended head postures. With one exception, the mean maximum bite force value was found to be higher for every subject with extended head posture compared to natural head posture. The sample mean was 271.6 Newton in natural head posture and 321.5 Newton with 20 degrees extension. With changed head posture, the cephalometric measurements pointed towards a changed position of the hyoid bone in relation to the mandible and pharyngeal airway. The cephalometric changes in the position of the hyoid bone could be due to a changed interplay between the elevator and depressor muscle groups. This was one factor which could have influenced the registered maximum bite force.
The balance in the electromyographic (EMG) activities of the left and the right masseter and the left and right anterior temporal muscles during chewing and during submaximal clenching at 10% and 50% of the maximum voluntary contraction in the inter-cuspal position was investigated in twenty healthy adults. Muscular asymmetry patterns during chewing and clenching were positively correlated for both pairs of masticatory muscles investigated at the 50% level (P less than 0.01-P less than 0.001) and for the masseter muscles, also at the 10% level (P less than 0.01). Stronger correlations in muscular asymmetry were found for the masseter muscles and at the higher submaximal clenching level. In general, the masseter muscles displayed a greater degree of asymmetric activity than the anterior temporal muscles during both chewing and clenching (0.05 less than P less than 0.1-P less than 0.025). The average EMG amplitudes of both masseter or both anterior temporal muscles within each subject showed no correlation between clenching and chewing. The correlations between muscular asymmetries observed during static (clenching) and dynamic (chewing) conditions suggest that there are common factors influencing these activities.
The following study examined two aspects of balance control in the older adult: the coordination of the timing and the amplitude of muscle responses to postural perturbations, and the ability of the participant to reorganize sensory inputs and subsequently modify postural responses as a consequence of changing environmental conditions. Coordination of muscle activity in postural responses of twelve elderly (sixty-one to seventy-eight years) participants were compared to those of young (nineteen to thirty-eight years) adults using a movable platform and recording the electromyographic activity of muscles of the legs. The following changes were noted in the timing and amplitude of muscle activity within a postural response synergy: increases in the absolute latency of distal muscle responses were observed in all older adults; in five of the twelve older adults temporal reversals of proximal and distal muscle response onset were observed; and there was a breakdown in the correlation of the amplitude of responses within a synergy. The ability of the older adult to balance under conditions of reduced or conflicting sensory information was also impaired. When confronted with functionally inappropriate visual and/or somatosensory inputs, half of the older group lost balance. In most instances, however, the older participants were able to maintain stability during subsequent responses to conflicting stimuli.
A retrospective comparative chart audit was conducted to identify patient characteristics associated with falls in the acute care setting, to examine the extent to which the significant characteristics explained if falls occurred, and to test the ability of variables believed to be risk factors to predict falls. Patients aged 60 and older who fell during hospitalization (n = 331) were compared with a random sample of patients aged 60 and older who were hospitalized during the same time period but did not fall (n = 300). Two days of documentation were sampled: admission day and day preceding the fall for the fall group, and admission day and a random day of hospital stay for the no-fall group. Findings supported the idea that fall-prone patients can be identified and that significant differences between those who do and do not fall are evident at hospital admission. The findings also suggested an alteration in the constellation of characteristics nurses use to identify fall-prone patients. Of 11 variables representing standard risk factors, only 6 were significantly related to fall status; 5 entered the regression equation as significantly contributing to the 22% explained variance. When potential predictor variables were expanded to include additional patient characteristics, the explained variances for fall status were 31% from the admission day data and 34.5% from the fall/random day data.
Vestibular, visual, and proprioceptive influences on muscle activity correcting for backwards body tilt were investigated in normals and patients with bilateral peripheral vestibular deficits. Body tilt was induced by a dorsi-flexion rotation of the feet about the ankle joints while the subject stood on a force measuring platform. Ankle muscle activity and torque were monitored as upright stance was reestablished, and correlated with head angular accelerations and neck muscle activity. In normals with eyes closed, soleus stretch reflex activity at 50-80 ms was followed by two bursts of tibialis anterior (TA) EMG activity at ca 80 and 125 ms from the onset of 36 deg/s, 3 deg amplitude platform rotations. Neck muscle activity rotated the head backwards at the same time as TA activity rotated the body forwards about the ankle joints. Under the influence of vision, i.e. eyes open, slight increases in the second burst of TA activity, and ankle torque were observed. When the subjects sat, and were instructed to activate TA rapidly on onset of the platform movement, TA EMG activity increased gradually at ca. 150 ms and not as a burst. In patients with long-lasting bilateral vestibular deficits, both bursts of TA activity were significantly less than normal with eyes closed. Consequently sway correcting torques were abnormally low and all but one of the patients fell over backwards. With eyes open, TA activity was slightly less than, and ankle torques were approximately equal to normal values. In contrast to normals, TA responses obtained in standing and sitting positions were not significantly different. Neck EMG activity varied from normal, consisting of a long burst 100 ms in duration. The present data indicate that a coordinated pattern of ankle, and neck muscle activity occurs during the first 150 ms following induced backward tilt. Ankle muscle activity corrects for the body sway, and neck muscle activity attempts to stabilise the head with respect to earth fixed coordinates. It is proposed that the vestibulo-spinal reflex system predominantly underlies the genesis and coordination of this muscle activity.
Displacements of the center of foot pressure, the hip and the head were recorded in six subjects standing on a platform, sinusoidally tilting in pitch (anterior-posterior). Stimulus frequencies ranged between 0.01 and 1 Hz. Stimulus amplitudes were 2, 4 and 6 degrees. With eyes open the displacements were minimal at 0.3 Hz. With eyes closed, however, induced sway was maximal at this frequency. The apparent lack of visual stabilization at the lowest frequency (0.01 Hz) might be attributed to a subthreshold velocity of the retinal image motion induced by the swaying body. A similar absence of visual stabilization of 1 Hz is assumed to indicate the limit of the working range of visual stabilization of posture. Independent of stimulus amplitude a phase lead of about 90 degrees was found at 0.01 Hz. This decreased with increasing frequency up to a phase lag of 100 degrees at the highest frequency (1 Hz). Head stabilization was generally more effective than hip stabilization. EMG recordings from the leg muscles suggest that with eyes closed the center of force is mainly stabilized by leg muscle activity, while with eyes open this stabilization is best, when vision allows for stabilization of body posture by intersegmental movements between head, trunk and legs.
1. To determine the effects of motor activity in the jaw on more general motor behavior, we examined the modulation of the soleus H reflex in association with voluntary clenching of the teeth in healthy adult volunteers. 2. The amplitude of the H reflex increased remarkably during teeth clenching. The increase during maximal teeth clenching was greater than that induced either by maximal voluntary isometric contraction of the wrist extensors or by maximal voluntary clenching of the fists. 3. The increase in amplitude of the soleus H reflex showed a positive correlation with the strength of teeth clenching, as monitored by recording electromyographic (EMG) activity from the masseter muscle. 4. The increase in amplitude of the H reflex associated with teeth clenching started before the onset of the EMG activity of the masseter muscle, reached a peak shortly after the onset, and then declined to a plateau that continued in parallel with the masseter EMG until the end of teeth clenching. 5. The increase in amplitude of the H reflex in association with teeth clenching was partially decreased during the inhibitory masseteric reflex evoked by innocuous electrical stimulation of the lip. 6. It is concluded that the soleus H reflex is facilitated in association with voluntary teeth clenching, and that descending influences from the cerebral cortex, as well as peripheral afferent impulses from the oral-facial region, are involved in this facilitation. It is proposed that oral motor activity can exert strong influences on the motor activity of the other parts of the body.
This study was conducted to elucidate the relationship between the presence of occlusal support in edentulous subjects and their ability for physical exercise. Ten complete denture wearers were selected and instructed to jump vertically while standing on a force plate with and without occlusal support (i.e. dentures). On the curve recorded by the force plate (1) reaction time (latency) (2) jump elevation time and (3) maximum kicking force were analysed. The reaction time, which is an index of physical quickness, was significantly prolonged when the subjects lost their occlusal support. This result suggests that reconstruction of occlusal support at a desirable mandibular position has significance not only for the restoration of masticatory function but also for the maintenance of physical exercise.
Patients with removable partial dentures or complete dentures do not demonstrate masticatory function to the same level as patients with a full set of natural teeth. The purpose of this study was to characterize the relationship between reduction of masticatory function, in terms of masticatory performance and bite force, and the existence of remaining natural occlusal supports as assessed by the Eichner index. One hundred and eighteen removable partial denture and complete denture wearers were selected for analyses. These subjects were divided into four groups depending upon the number of occlusal supports. Seventy dentate subjects with full occlusal support were designated as a comparison group. Bilateral bite force was measured at the first molar region in all subjects. Masticatory performance was assessed using the modified Masticatory Performance Index. Peanuts were used as the test food. Both bite force and masticatory performance were significantly associated with group classification. Moreover, both bite force and masticatory performance of the four denture groups were significantly reduced compared to the comparison group and this tendency was remarkable for the denture groups without occlusal support. These results suggest that the existence of functional tooth units may be a key factor in preservation of masticatory function.
Masticatory performance results from a complex interplay of direct and indirect effects, yet most studies employ univariate models. This study tested a multivariate model of masticatory performance for dentate subjects. Explanatory variables included number of functional tooth units, bite force, sex, age, masseter cross-sectional area, presence of temporomandibular disorders, and presence of diabetes mellitus. The population-based sample consisted of 631 dentate subjects aged 37-80 years. Covariance structure analysis showed that 68% of the variability in masticatory performance could be explained by the combined effects of the explanatory variables. Age and sex did not show a strong effect on masticatory performance, either directly or indirectly through masseter cross-sectional area, temporomandibular disorders, and bite force. Number of functional tooth units and bite force were confirmed as the key determinants of masticatory performance, which suggests that their maintenance may be of major importance for promoting healthful functional status.
Falls, syncope, and the associated complications are among the most serious problems that face the elderly population. The most common underlying causes and risk factors for falls include muscle weakness, gait and balance problems, visual impairment, cognitive impairment, depression, functional decline, and particular medications (especially in the presence of environmental hazards). Studies have identified the relative risks for these factors that enable a fairly accurate prediction of who is at high risk for falls and what areas to target for falls-prevention activity. Causes and risk factors for syncope have not been studied as well in the older population. The most serious types of syncope have underlying cardiac etiologies but they cause less than 25% of the reported cases. The largest category of syncope (approximately 40%) is syncope of unknown etiology, which defies careful diagnostic evaluation but seems to be fairly benign. The epidemiology of these syndromes can provide extremely helpful insights for developing falls-prevention strategies.
Clinicians have sought ways to increase trunk sway so that it is easily observed and a balance deficit more easily identified. One technique often used for this purpose is to reduce the efficacy of ankle proprioceptive inputs on sway. To achieve this reduction either a foam mat is used as an unstable support surface or the subject stands on a surface made unstable with servo-driven ankle-sway-referencing. The purpose of the current study was to investigate differences in trunk pitch and roll sway characteristics using these techniques. Trunk sway while standing quietly on two legs was measured in 25 normal subjects in the age range 20-35 years for three support-surface conditions. Each condition was tested twice for 20 s, once with eyes open and once with eyes closed. The three conditions were standing on a foam support surface, standing on a support surface with pitch (fore-aft) ankle-sway-referencing as used for the standard Sensory Organization Test (SOT) of the Neurocom Equitest System (SOT 4 and 5), and standing with roll (lateral) ankle-sway-referencing. The latter was achieved by having the subjects stand turned 90 degrees to the standard SOT position. Two angular velocity sensors mounted on a belt measured trunk sway in the pitch and roll directions. Trunk roll angle and angular velocity amplitudes for pitch sway-referencing were reduced compared to either the foam or roll sway-referencing conditions, but trunk pitch angle and angular velocities amplitudes were greater. For roll sway-referencing, the trunk roll angle was greater than for the other stimulus conditions. Analyses of the trunk sway velocity in the frequency domain indicated that ankle-sway-referencing in the pitch direction increased trunk pitch sway at 1 Hz and decreased trunk roll sway between 2 and 5 Hz compared to foam support frequency spectra. Roll ankle-sway-referencing decreased trunk roll between 2 and 4 Hz only. These results indicate that using a foam support surface provides multidirectional trunk sway with velocity content across all frequencies in the range 0.8-5.2 Hz. Roll ankle-sway-referencing, but not pitch ankle-sway-referencing, yields trunk sway with similar characteristics to those with foam. Pitch ankle-sway-referencing forces pitch trunk resonance to be around 1 Hz and yields very different trunk sway from that obtained with a foam support surface. Roll sway-referencing is an alternative means to test multidirectional control of sway. Clinically though, foam is simpler to use and provides a more difficult balance task for the patient.
Falls are a significant problem for older adults. Individuals who have sustained a fall come to the attention of health care providers and are at risk of further falls. To promote the highest quality of care and reduce variation in care, a practice guideline is needed. Summarization of evidence regarding falls may be useful to researchers in this field.
To provide evidence-based guidelines of assessment and treatment to prevent falls in older adults and to provide researchers with tables of risk factor studies and randomized controlled trials of falls prevention.
A template for the development of practice guidelines from the Agency for Health Care Policy and Research was used. Evidence for risk factors was accepted from prospective studies with more than 80% follow-up. Potentially modifiable risk factors were selected and a schema for evaluating the importance of each risk factor was used. Evidence for interventions was examined from randomized controlled trials and strength of the evidence was graded. Recommendations for aspects of care where judgment was required were made by panel consensus.
Information was drawn from 46 risk factor studies and 37 randomized controlled trials to develop a practice guideline consisting of assessment items and recommended interventions for community-dwelling and institution-dwelling older adults separately. For clinicians, a check list is provided. Summary tables of the results of studies are given to substantiate the recommendations.
For community-dwelling older adults, there is strong evidence for multi-factorial specific risk assessment and targeted treatment. Balance exercises are recommended for all individuals who have had a fall and there is evidence for a program of home physiotherapy for women over 80 years of age regardless of risk factor status. For institutional settings, the establishment of a falls program for safety checks, ongoing staff education and monitoring is substantiated by research. Residents who have fallen need to be assessed for specific risk factors and clinical indicators to determine relevant management options.
The Handbook of Balance Function Testing. Part IV. Posturographic Testing. Mosby Year Book
- L M Nashner
Nashner, L.M., 2003. The Handbook of Balance Function Testing. Part IV. Posturographic Testing. Mosby Year Book, St. Louis, pp. 259– 334.
Patient falls in the acute care setting: identifying risk factors
- Janken