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

Does Tension Headache Have a Central or Peripheral Origin? Current State of Affairs

PURPOSE OF REVIEW

The aim of this narrative review is to analyze the evidence about a peripheral or central origin of a tension headache attack in order to provide a further clarification for an appropriate approach.

RECENT FINDINGS

Tension headache is a complex and multifactorial pathology, in which both peripheral and central factors could play an important role in the initiation of an attack. Although the exact origin of a tension headache attack has not been conclusively established, correlations have been identified between certain structural parameters of the craniomandibular region and craniocervical muscle activity. Future research should focus on improving our understanding of the pathology with the ultimate goal of improving diagnosis. The pathogenesis of tension-type headache involves both central and peripheral mechanisms, being the perpetuation over time of the headache attacks what would favor the evolution of an episodic tension-type headache to a chronic tension-type headache. The unresolved question is what factors would be involved in the initial activation in a tension headache attack. The evidence that favors a peripheral origin of the tension headache attacks, that is, the initial events occur outside the brain barrier, which suggests the action of vascular and musculoskeletal factors at the beginning of a tension headache attack, factors that would favor the sensitization of the peripheral nervous system as a result of sustained sensory input.

Cervical Range of Motion Analysis Performed with an Accelerometer: A Study of Intersession Reliability for Dental Practice

During the clinical examination of subjects with temporomandibular disorders (TMDs), the dentist sometimes must evaluate the cervical spine, due to the anatomical and functional connections between the cervical portion of the spine and the stomatognathic apparatus. The accelerometer is a device that evaluates the Range of Motion (ROM) of the main movements of the head on the neck. To date, only a few studies have investigated the repeatability of the use of the accelerometer in the assessment of cervical ROM. Therefore, the present longitudinal observational study analyzed the repeatability of acquired cervical movements on a sample of volunteer subjects who underwent accelerometer testing. A sample of 32 subjects was tested twice within 14 days to assess cervical ROM using a standardized protocol based on a review of existing literature. The results show that the examination is reliable for all the positions of the jaw, except for the parameters regarding the asymmetries of rotation and bending. In conclusion, the accelerometer can be considered a reliable tool for evaluating the active cervical ROM. However, further studies will be necessary to make better evaluations.

The effect of a controlled mandible position mouthguard on upper body strength and power in trained rugby athletes - A randomized within subject study

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.

Occlusal Splints and Exercise Performance: A Systematic Review of Current Evidence

The role of the dento-mandibular apparatus and, in particular, occlusion and jaw position, received increased attention during last years. In the present study, we aimed to systematically review, on the light of the new potential insights, the published literature covering the occlusal splint (OS) applications, and its impact on exercise performance. A structured search was carried out including MEDLINE^®/PubMed and Scopus databases with additional integration from external sources, between March and June 2021. To meet the inclusion criteria, studies published in the English language, involving humans in vivo, published from 2000 to 2021 and that investigated the role of occlusal splints on athletes' performance were selected. Starting from the 587 identified records, 17 items were finally included for the review. Four main aspects were considered and analyzed: (1) occlusal splint characteristics and occlusion experimental conditions, (2) jump performance, (3) maximal and explosive strength, and (4) exercise technique and biomechanics. The results of the systematic literature analysis depicted a wide heterogenicity in the experimental conditions and suggested the application of the OS as a way to improve athletes' or individuals' oral health, and as a potential tool to optimize marginal aspects of exercise performance.

Physiological Responses of a Jaw-Repositioning Custom-Made Mouthguard on Airway and Their Effects on Athletic Performance

Martins, RS, Girouard, P, Elliott, E, and Mekary, S. Physiological responses of a jaw repositioning custom-made mouthguard on airway and their effects on athletic performance. J Strength Cond Res 34(2): 422-429, 2020-Advanced dental techniques such as jaw-repositioning have shown to increase lower body muscular power such as vertical jump, but its effects on acceleration and speed have not been studied. Similarly, jaw repositioning is commonly used to increase airways volume and ventilation in a special population (i.e., obstructive sleep apnea); however, its ergogenic effects on aerobic performance have yet not been studied. The purpose of the cross-over study was to investigate the effects of a jaw-repositioning custom-made mouthguard (JCM) on volumetric changes in airway and jaw position and determine the effects this may have on aerobic and anaerobic performance. Results indicated that jaw-repositioning custom-made mouthguard may have an ergogenic effect on performance. The JCM condition showed an increase of 13% in upper airway volume (p = 0.04), 10% in upper airway width (p = 0.004), 7% in ventilation (p = 0.006), 5% in maximal aerobic power (p = 0.003), 4% in time to exhaustion (p = 0.03), 3% in vertical jump (p = 0.03), 2% in broad jump (p = 0.009), and a decrease of 4% in 20-m (p = 0.04) and 2% in 40-m (p = 0.001) sprint times. This is the first study to demonstrate a significant link between jaw repositioning, airway volumetric change, and performance enhancement in both aerobic and anaerobic performances. The results of this study may lead to a change in culture for the use of mouthguards in different sports applications, from high orofacial injury risk sports to other sports, specifically for ergogenic enhancement.

Applied kinesiology and dentistry - A narrative review

OBJECTIVE

To investigate the use of applied kinesiology in the field of dentistry.

METHODS

A review of the literature was carried out looking for all articles written on the topic. PubMed, Ovid Medline, and The Cochrane Central Register of Controlled Trials (CENTRAL) databases were searched.

RESULTS

Only one study was retrieved on the use of applied kinesiology in temporomandibular disorder patients, and only one study was published on dental material testing. A change in muscle strength associated with changes in dental occlusion has been observed in many of the articles selected.

DISCUSSION

The use of applied kinesiology for the diagnosis and treatment of pathologies in the field of dentistry is not supported by scientific evidence. However, a relationship between dental occlusion or maxillo-mandibular relationship and isometric muscle strength has been noted.

Effects of occlusal splints on shoulder strength and activation

Introduction: The use of oral appliances to enhance sports performance has been advocated by some authors, however, studies addressing the effectiveness of these strategies are inconclusive. Methods: Here we investigate the effects of dental occlusions on shoulder strength. Fourteen healthy male subjects (age = 21.67 ± 0.86 years) without temporomandibular joint (TMJ) disorder participated in this study. Isokinetic strength was evaluated in shoulder abduction/adduction and arm external/internal rotation tests. Three randomised conditions were assessed: (1) occlusal splint (OS), which repositioned the TMJ in centric relation; (2) placebo splint (PS); and (3) no-splint (N). The strength tests were performed at a speed of 60°/sec in concentric mode. Muscle activity was measured by surface electromyography (EMG) in the main muscles engaged in the movements. Results: Significant differences in peak torque between OS and both of the other experimental conditions were found in some of the analyzed variables. Moreover, there was significantly higher muscular EMG activation in the OS condition when compared to the other conditions for some of the tested muscles. These data suggest that splints may have a positive ergogenic effect on shoulder muscular strength in healthy male subjects. Conclusion: OS may provide an advantage for healthy subjects engaged in sports whereby shoulder and arm strength are important for performance. Key messages Occlusal splints in centric relation position have an ergogenic effect, by increasing strength and muscle activation on shoulder in healthy subjects. These results could have implications for sports or other physical activities were arm and shoulder strength are important.

Effects of Dental Occlusion on Body Sway, Upper Body Muscle Activity and Shooting Performance in Pistol Shooters

Occlusal splints, to some extent, have been related to reduced body sway in a static position and increased muscle activity in the upper limbs. However, how dental occlusion status affects sports performance remains unclear. Here, we investigated whether occlusal splints that reposition the temporomandibular joint (TMJ) influenced body posture, muscle activity, and performance in 10-meter pistol shooters. Thirteen national-level male shooters (age = 38.8 ± 10.9 yrs) were recruited for this study, and cleared of any cervical pathology. An occlusal splint (OS) and a placebo splint (PS) were fabricated for each of the subjects, with the mandibular and maxillary position verified by an expert dentist, with the aid of an adjustable articulator. Surface electromyography (EMG) was assessed in the upper limb that holds the pistol while the subjects were standing on a force platform. Subjects performed two series of 10 shots for each of the three experimental conditions (OS, PS, N (no splint)) in randomized order, with the mandible in a rest position. Results revealed similar centre of pressure (COP) parameters in all conditions, despite a reduction in the average oscillation area caused by the OS. There were also no significant differences in EMG activity between conditions in the five upper limb muscles monitored. Consistent with this, shooting performance was similar in all conditions, despite a reduction in shot dispersion in subjects using OS. Thus, changes in dental occlusion status induced by OS do not affect body posture, upper limb EMG muscle activity, or shot performance in healthy male pistol shooters.

Effects of Two Different Self-Adapted Occlusal Splints on Electromyographic and Force Parameters During Elbow Flexors Isometric Contraction

Limonta, E, Arienti, C, Rampichini, S, Venturelli, M, Cè, E, Veicsteinas, A, and Esposito, F. Effects of two different self-adapted occlusal splints on electromyographic and force parameters during elbow flexors isometric contraction. J Strength Cond Res 32(1): 230-236, 2018-The study was aimed at determining the acute effects of 2 types of occlusal splints on maximum isometric strength and fatigue of the elbow flexors muscles. The hypothesis was that splint-induced masticatory muscle repositioning might improve primary muscles recruitment by stretching masticatory muscles especially with the thicker splint. On 9 physically active volunteers with no temporomandibular joint and masticatory muscles disorders, we assessed maximum voluntary contraction (MVC) of the elbow flexors with diurnal (OSD, 1-mm thick) and sport (OSSP, 3-mm thick) splints, and without splint (control, Ctrl). On different days, participants performed 60 seconds of isometric contraction at 100% MVC (100%60s) and 80% MVC contraction until exhaustion (80%exh) under OSD, OSSP, and Ctrl in random order. Time of force output within target (t-target), force distance from target (ΔF), and force coefficient of variation were calculated. Percentage of force decay (ΔFi-Fe) was determined during 100%60s. From the electromyographic (EMG) signal, root mean square (EMG RMS) and mean frequency (EMG MF) were determined. Neuromuscular efficiency (NE) was calculated as the ratio between force and EMG RMS. MVC contraction and NE were significantly higher in OSSP and OSD than in Ctrl. During MVC, EMG MF was significantly lower in both splint conditions, and EMG RMS showed a nonstatistical tendency to lower values under both splint conditions. During 80%exh, t-target was longer in OSD and OSSP (+7.8% and +5.2%, respectively) than in Ctrl. ΔFi-Fe was lower in OSSP than in Ctrl and OSD. These results support the hypothesis of a NE improvement of the elbow flexors possibly induced by acute, splint-induced masticatory muscles repositioning.

Effects of Jaw Clenching While Wearing a Customized Bite-Aligning Mouthpiece on Strength in Healthy Young Men

Recent studies have investigated the ergogenic effects of different types of mouthguards. There is evidence of the benefits of clenching customized mouthpieces on force and power development. The phenomenon called concurrent activation potentiation (CAP) promoted in jaw clenching seems to enhance the muscular strength and power in maximal isometric contractions and powerful actions in sport. Moreover, a bite-aligning mouthpiece may promote a more aligned and powerful clench. The objective of the present study was to investigate the effects of jaw clenching while wearing a customized bite-aligning mouthpiece (MP) on jump ability and isometric maximal strength tests in contrast to 2 other conditions: nonjaw clenching (NON-JAW) and jaw clenching without the mouthpiece (JAW). A within-subjects design was used to assess the jump performance and the maximal isometric force in 28 physically active male subjects. Statistical analyses revealed significantly higher performance in JAW and NON-JAW conditions for handgrip force (HG-peakforce) and all variables of the back-row exercise (BRW) and countermovement vertical jump (CMVJ) (p ≤ 0.05). Significant differences between NON-JAW and JAW were found for HG-peakforce (p ≤ 0.05). These findings suggest that it is advisable to use a customized bite-aligning mouthpiece to improve strength and power performance.

The effect of intrapartum dental support use among nulliparous during the second stage of labor - a randomized controlled study

OBJECTIVE

We aimed to determine the effect of a dental support device (DSD) use on the course of labor and delivery in nulliparous women.

METHODS

A randomized, controlled, open-label study of nulliparous (at 37 + 0/7 and 41 + 3/7 weeks of gestation) in a single tertiary university-affiliated medical center. Exclusion criteria included maternal chronic diseases, multi-fetal gestation and fetal chromosomal or structural anomalies. Outcomes were analyzed according to the actual use of the DSD, and satisfaction questionnaires following delivery.

RESULTS

Overall, 191 women were randomized (93in the study group and 98 in the control group). The median duration of the second stage was similar between the groups (100.0 ± 91.0 versus 98.0 ± 128.8 min, p = 0.97) and the maximal VAS score was significantly higher in the DSD group (4.0 ± 8.5 versus 3.0 ± 6.8, p = 0.04). The rate of obstetrical interventions such as operative vaginal delivery or cesarean section during the second stage was significantly higher in the control group than in the study group (28.2% versus 12.3% and 6.4% versus 1.2%, respectively, p = 0.004), mainly due to prolonged second stage of labor (24.5% versus 8.6%, p = 0.005). Of the DSD group, 50.6% rated the use of the DSD as comfortable, 32.2% rated its effect on pain relief as high, 55.6% would recommend its use to their peers and 51.9% would like to use it in their consecutive delivery.

CONCLUSION

The use of a DSD among nulliparous women appears to decrease the need for obstetrical intervention due to prolonged second stage of labor, with fair satisfaction of patients.

Analysis of the characteristics of mouthguards that affect isokinetic muscular ability and anaerobic power

PURPOSE

The purpose of this study was to estimate the effects of occlusal stability to identify action mechanisms of mouthguards, known to have a modulatory effect on limb muscle function.

MATERIALS AND METHODS

This study included 20 male subjects to perform the isokinetic muscle tests and the Wingate anaerobic power test on both knee joints under five closed-mouth conditions: without or with 4 types of mouthguards with thickness of 2 mm based on premolar area: (1) full-coverage, (2) anterior partial-coverage, (3) right posterior partial-coverage, and (4) left posterior partial-coverage. The obtained results were subjected to One-way ANOVA with repeated measures, followed by post hoc test of the contrast method (α=.05).

RESULTS

There was no significant difference between the closed position with and without a full-coverage mouthguard in all variables. However, significant differences were observed between with and without a partial-coverage mouthguard in muscular endurance during extension of the left knee, muscular power and endurance during flexion of the right knee. Additionally, significant differences were found between occlusal states with full- and partial-coverage mouthguards in muscular power and endurance during extension of the left knee.

CONCLUSION

These findings indicate the elevation of vertical dimension by 2 mm or the inducement of occlusal stability had little effect on isokinetic muscle strength and anaerobic performance, while uneven distribution of occlusal force might have some positive effects.

Analyzing surface EMG signals to determine relationship between jaw imbalance and arm strength loss

Background

This study investigated the relationship between dental occlusion and arm strength; in particular, the imbalance in the jaw can cause loss in arm strength phenomenon. One of the goals of this study was to record the maximum forces that the subjects can resist against the pull-down force on their hands while biting a spacer of adjustable height on the right or left side of the jaw. Then EMG measurement was used to determine the EMG-Force relationship of the jaw, neck and arms muscles. This gave us useful insights on the arms strength loss due to the biomechanical effects of the imbalance in the jaw mechanism.

Methods

In this study to determine the effects of the imbalance in the jaw to the strength of the arms, we conducted experiments with a pool of 20 healthy subjects of both genders. The subjects were asked to resist a pull down force applied on the contralateral arm while biting on a firm spacer using one side of the jaw. Four different muscles – masseter muscles, deltoid muscles, bicep muscles and trapezoid muscles – were involved. Integrated EMG (iEMG) and Higuchi fractal dimension (HFD) were used to analyze the EMG signals.

Results

The results showed that (1) Imbalance in the jaw causes loss of arm strength contra-laterally; (2) The loss is approximately a linear function of the height of the spacers. Moreover, the iEMG showed the intensity of muscle activities decreased when the degrees of jaw imbalance increased (spacer thickness increased). In addition, the tendency of Higuchi fractal dimension decreased for all muscles.

Conclusions

This finding indicates that muscle fatigue and the decrease in muscle contraction level leads to the loss of arm strength.

Duration of the second stage of labor while wearing a dental support device: a pilot study

AIM

Developing a method of maximizing maternal expulsive effort should be of great value in reducing the number of cesarean sections or instrumental deliveries. Various investigations have shown that use of a dental support device (DSD) increases the isometric strength of different muscle groups. The aim of our study was to investigate the role of a DSD in second stage of pushing.

METHODS

Nulliparous women with an uncomplicated singleton pregnancy course were randomly assigned either to a DSD group or to a non-device group. Duration of the second stage of labor was evaluated. Rates of cesarean section or instrumental delivery indicated for failure to descend in the second stage of labor were also evaluated. Satisfaction scores for the DSD group were evaluated (range 1-5).

RESULTS

Sixty-four subjects were enrolled in the study. Cesarean section and instrumental delivery were performed for 12 (18.8%) and 5 (7.8%) patients, respectively. There was no difference in obstetrical and neonatal demographics between the two groups. Among 64 enrolled patients, 38 (59.3%) were evaluated for the second stage of labor (n = 19 for each group). Duration of the second stage of labor in the DSD group was significantly shorter than in the non-device group: (median 19 min (interquartile interval, IQI, 9) vs 31 min (IQI, 23)), P < 0.001. One patient in the non-device group required a vacuum extraction for failure to descend. The mode of satisfaction score for the DSD group was 5 (59.3%).

CONCLUSION

Wearing a dental support device may shorten the second stage of labor, and may decrease the number of failures to descend requiring operative intervention.

CLINICAL TRIAL REGISTRATION

NCT00629369.

The relationship between the stomatognathic system and body posture

In recent years, many researchers have investigated the various factors that can influence body posture: mood states, anxiety, head and neck positions, oral functions (respiration, swallowing), oculomotor and visual systems, and the inner ear. Recent studies indicate a role for trigeminal afferents on body posture, but this has not yet been demonstrated conclusively. The present study aims to review the papers that have shown a relationship between the stomatognathic system and body posture. These studies suggest that tension in the stomatognathic system can contribute to impaired neural control of posture. Numerous anatomical connections between the stomatognathic system's proprioceptive inputs and nervous structures are implicated in posture (cerebellum, vestibular and oculomotor nuclei, superior colliculus). If the proprioceptive information of the stomatognathic system is inaccurate, then head control and body position may be affected. In addition, the present review discusses the role the myofascial system plays in posture. If confirmed by further research, these considerations can improve our understanding and treatment of muscular-skeletal disorders that are associated with temporomandibular joint disorders, occlusal changes, and tooth loss.