The Organ of Vision and the Stomatognathic System-Review of Association Studies and Evidence-Based Discussion

Correlation between refractive error, muscle thickness, and bioelectrical activity of selected masticatory muscles

OBJECTIVE

The aim of this study was to analyze the correlation between the refractive error, muscle thickness, and the bioelectrical activity of selected masticatory and neck muscles in subjects with myopia.

METHODS

For bioelectrical activity analysis within the masticatory muscles, an 8-channel BioEMG III electromyograph was used. An M-Turbo ultrasound machine was used to analyze the masticatory and neck muscle thickness.

RESULTS

Statistical analysis showed significant positive correlations between masseter muscle thickness at rest on the right side. Statistical analysis showed negative correlations between the digastric muscle and Activity Index within masticatory muscles at rest on the left side when the eyes were closed.

CONCLUSIONS

As refractive error increases in myopic subjects, the resting tension on the temporal muscles increases, an increase in masseter muscle thickness is noted, and a decrease in bioelectrical activity on the digastric muscle at rest.

The Influence of Temporomandibular Joint Disorders and Mandibular Position on Visual Capacities: A Case-Control Study

Aims

To verify the possible association between the stomatognathic and the visual system by analyzing the effects that different mandibular postures may have on the accommodative capacity and ocular convergence and by assessing whether temporomandibular disorders (TMD) can influence visual abilities.

Materials and Methods

A case-control study was performed during a 1-year period on a sample of 100 subjects (50 cases and 50 controls). The subjects underwent a gnathological examination, and two visual tests were performed in three different jaw positions: maximum intercuspation, resting position, and open mouth. The statistical analyses were performed using the software SPSS program based on t-test to compare the different jaw positions and the odds ratio to understand the prevalence of visual defects in TMD patients.

Results

A statistically significant worsening was observed comparing the visual capacities measurements from the maximum intercuspation to the open mouth position; "case group" measurements showed a worsening trend compared to the "control group" (P value < 0.05 in all comparisons). Furthermore, the examinations showed statistically significant results with reference to the relationship between TMD and their negative influence on visual abilities (P value = 0.007 for convergence and P value = 0.012 for accommodation).

Conclusions

Based on our data, TMD individuals performed worse in vision tests compared to healthy subjects and the presence of occlusal contacts appears to improve convergence and accommodation. The reduced reproducibility and accuracy of the orthoptic tests and the small sample number were the principal limitations of our study. The future perspective could be to investigate whether the visual apparatus could benefit from the treatment of stomatognathic disorders.

Gender Difference of the Association Between Sleep Duration and Myopia Among Children and Adolescents

Purpose

With girls typically exhibiting higher rates of myopia than boys, however, the mechanisms behind this gender difference remain unclear. This study aims to investigate the gender disparities in the relationship between myopia, sleep duration, physical activity, and BMI.

Patients and Methods

A total of 3138 primary and secondary school students were included. Mplus 8.3 was used to perform the multiple mediation analysis.

Results

Sleep duration was indicated to directly affect myopia (β=0.273, 95% CI=0.184-0.356) and through physical activity, BMI, physical activity and BMI three significantly mediation pathways, respectively. In terms of gender, the mediating direct effect of sleep duration on myopia of boys was 66.96%, which is much higher than that of girls' 50.91%. And the mediating indirect effect of sleep duration on myopia through physical activity and BMI are 32.65% and 12.10% respectively among girls, both of which are significantly higher than that of boys.

Conclusion

The study found that there are significant differences in the impact of sleep duration on myopia in children and adolescents of different genders. In this regard, while paying attention to the sleep duration of children and adolescents, special attention should also be paid to the indirect impact of girls' physical activity and BMI on myopia, and targeted measures should be formulated according to children of different genders to effectively protect the eye health of children and adolescents.

Mini-review: Pathways of postural disturbances tracing to the stomatognathic system

Postural alignment is strongly shaped by inborn anatomical and nonvolitional neural factors, whereas postural stability is dynamic in nature and driven by both automatic and volitional sensorimotor processes. The sensory and motor systems responsible for these functions are tightly integrated with the central nervous system, several vital structures of which are in close proximity to the stomatognathic system. Interventions in the oral cavity have therefore been stipulated to provide sensory feedback, which may then be translated into motor function. Since the early 90 s, numerous intervention studies have provided evidence of this correlation, with traditional views advocating that causative factors are mainly indirect. Dynamic postural responses were thus predominantly considered manifestations of head displacement, with most studies identifying potential connections along active and passive muscular interactions. The consideration however, that neuromuscular adaptations of whole-body dynamics might extend beyond biomechanical responses and involve direct pathways as well, has led to a recent paradigm shift, challenging conventional perspectives. Among the suggested pathways are central projections of trigeminal afferents, providing inputs for the oculomotor system, as well as active and passive muscular interactions. Further intervention studies indicate a sensory integration of the stomatognathic system to proprioception, likely through neural networks that work in concert with visual cues and the vestibular organs. Building on this accumulating pool of evidence, a timely perspective is provided on a critical yet underexplored aspect of neurophysiology: the intricate interplay between the cranio-cervico-mandibular system and the broader framework of body posture.

Role of Sport Vision in Performance: Systematic Review

Sport Vision is a speciality of multidisciplinary interest aimed at improving the performance of the visual system to achieve benefits in practiced sports, as well as in daily life and in preventive care. The type of training practiced by the athlete, his or her physical condition, cognitive level, and level of fatigue condition affects the speed of the reaction time and, consequently, the speed of motor response. Specific orthoptic exercises, the use of technological devices, the recovery of static and dynamic postural stability by using unstable platforms and the dual-task paradigm can help to achieve the expected results. The aim of this systematic review of Sport Vision was to assess the overall existing literature on Sport Vision, paying particular attention to the effects of visual training and its application in different sports and in rehabilitation and preventive settings. We analysed published English language studies about the role of sport vision in athletic performance from 1950 to 2023. We searched through the Medline database. The PRISMA 2020 checklist was used to assess the transparency and reproducibility of this review. The enrolled papers were evaluated with the Jadad Scale, Amstar 2 Scale and Newcastle-Ottawa Scale. 25 (16 studies, 5 reviews, 2 comments, 1 editorial, 1 descriptive paper) out of 476 studies met the inclusion criteria. Due to the variability in the age of the samples, the different techniques, the treatments among the participants in the studies and the finding of non-evaluable articles, a meta-analysis was not conducted. The limitations of this review are the single database research, the studies analyzed contain a non-statistically representative sample size and the lack of a control group. There is no standardized test to measure performance. It was shown that the development of visual skills can benefit athletes in injury prevention, and can lead to improved sports performance and motor function at any age, acquiring adaptive motor behaviour even when the visual system is impaired, due to task repetition and familiarity of the gesture. We intended to identify a multidisciplinary approach and a manual treatment scheme to optimize the circuitry involved in sport vision in order to increase the results that are achieved, but further studies will be needed to this end.

Pharmacologically Induced Accommodation Palsy and the Bioelectrical Activity of the Muscular System: A Preliminary Investigation

The aim of this study was to pharmacologically induce accommodative paralysis and evaluate its effects on the bioelectrical activity of the muscular system. The study included two participant groups: those with myopia and those with normal vision (emmetropes). Electromyographic assessments were performed using the Noraxon Ultium DTS 8-K MR 3 myo Muscle Master Edition system. The muscles analyzed in this study were the temporalis, masseter, sternocleidomastoid, trapezius, abdominal muscles, biceps brachii, and the external oblique muscles of the abdomen. It is important to acknowledge that, based on the current findings, it cannot be definitively stated that the observed effects have clinical significance, and additional studies are encouraged.

Predictors of apical periodontitis in root canal treated teeth from an adult Nepalese subpopulation: a cross-sectional study

BACKGROUND

Endodontic literature search revealed that no study has been conducted to evaluate the prevalence of apical periodontitis (AP) in root canal treated teeth from an adult Nepalese population of Madhesh Province. Consequently, little is known about the extent and risk factors associated with it. This study aimed to determine AP prevalence in root canal treated teeth from an adult Nepalese subpopulation and to analyze the related risk factors including age, sex, tooth type, type of coronal restoration and quality of root canal treatment and coronal restoration as predictors of AP.

METHODS

Digital panoramic radiographs were evaluated. Periapical status of 300 root canal-treated teeth was scored by using the periapical index. The quality of root canal treatment and coronal restorations were categorized as adequate or inadequate through radiographic and clinical evaluation. The data were analyzed using univariate and multivariate logistic regression models.

RESULTS

Prevalence of AP in the present study was 31.7%. In 45.7% of the treated teeth, quality of root canal treatment was adequate whereas 46% of the cases had adequate coronal restorations. Multivariate logistic regression analysis revealed statistically significant associations and remarkably increased risk for AP in teeth with inadequate root canal treatment (odds ratio [OR] = 7.92; 95% CI: 3.96-15.82; p < 0.001) whereas lower risk for AP was found in females (OR = 0.51; 95% CI: 0.28-0.90; p = 0.021) and in teeth restored with crown (OR = 0.22; 95% CI: 0.09-0.51; p < 0.001) and filling (OR = 0.18; 95% CI: 0.08-0.42; p < 0.001). Quality of coronal restoration, tooth type and age of the patient were not found to be the predictors of AP.

CONCLUSIONS

Within the limits of this study, a high prevalence of AP and poor overall quality of root canal treatment and coronal restoration was found in the subpopulation studied. Quality of root canal treatment, type of coronal restoration and sex of the patient are significant predictors of possible AP development in root canal treated teeth. Substantial efforts are needed to improve the endodontic treatment standards.

Myopia & painful muscle form of temporomandibular disorders: connections between vision, masticatory and cervical muscles activity and sensitivity and sleep quality

The main aim of this study is to evaluate the effects of painful muscle form of temporomandibular disorders and myopia on the connections between the visual organ, the bioelectrical activity and sensitivity of the masticatory and cervical muscles, and sleep quality. Subjects were divided into 4 groups (Myopia & TMDs, Myopia (Without TMDs), Emmetropic & TMDs and Emmetropic (Without TMDs)). The study was conducted in the following order of assessment: examination for temporomandibular disorders, assessment of the muscle activity by electromyograph, pressure pain thresholds examination, ophthalmic examination and completion of the Pittsburgh Sleep Quality Index. It was observed that the Myopia & TMDs group had higher muscle tenderness, higher resting and lower functional muscle bioelectrical activity. The visual organ is clinical related to the masticatory and cervical muscles. TMDs and myopia alter masticatory and cervical muscle activity. The thickness of the choroid in people with myopia is related to muscle tenderness. TMDs and myopia impair sleep quality. It is recommended to determine the number of people with refractive error and its magnitude in the sEMG study in order to be able to replicate the research methodology.

Study protocol: Accommodative effects on the musculoskeletal system

Accommodation is a phenomenon of the eyeball, which consists of adapting to view objects at different distances. The main aim of this study is to evaluate the effect of accommodations on the musculoskeletal system in myopic and emmetropic subjects. To date, the effect of accommodative paralysis on the musculoskeletal system has not been studied. The research hypothesis based on the current research reports is that accommodation affects the musculoskeletal system in myopic and emmetropic subjects. A smaller aim of the study is to evaluate the effect of unilateral accommodative palsy on the musculoskeletal system in myopic and emmetropic subjects. According to the authors of the previous reports, unilateral accommodative palsy will affect increased musculoskeletal asymmetry in myopic and emmetropic subjects. The surface electromyography (sEMG) of the musculoskeletal system will be performed by using the Noraxon Ultium DTS 8-K MR 3 myo Muscle Master Edition. Cycloftyal (10 mg/ml, eye drops, solution) will be used to paralyze accommodation. After the paralysis of unilateral accommodation, the test will be repeated. Both-sided accommodation will be paralyzed next, and the test will be repeated. The study may provide insight into the effects of accommodation on the musculoskeletal system, and it may also help in understanding the connections between these systems.

Determination of Mandibular Position and Mouth Opening in Healthy Patients and Patients with Articular and/or Muscular Pathology: A Pilot Study with 3D Electromagnetic Articulography and Surface Electromyography

Temporomandibular disorders (TMDs) are a group of pathologies that affect the temporomandibular joint and its related structures, producing intracapsular and muscular pathologies. The aim of this study is to describe, by electromagnetic articulography (EMA) and simultaneous electromyography (sEMG), the mandibular postural position and mouth opening in healthy patients and with articular and/or muscular pathology.

MATERIALS AND METHODS

A pilot study was conducted with a sample of sixteen participants aged 18 years or older who attended the TMDs and Orofacial Pain Polyclinic of the University of La Frontera due to TMDs. The physiological inoculation space was evaluated from the mandibular postural position (MPP) with swallowing command and without command, in both healthy patients and patients with articular, muscular, and mixed TMDs, measured simultaneously with EMA and sEMG. An angular measurement of the oral opening was also performed with the data obtained.

RESULTS

The physiological inoculation space was obtained from the determination of the MPP through the procedures with swallowing command and without command, and different mouth opening degrees were evaluated.

CONCLUSIONS

Simultaneous position and sEMG records can be produced from EMA, and different characterization variables such as the vertical distance, Euclidean distance, and angle can be obtained.

Post-Traumatic Craniocervical Disorders From a Postural Control Perspective: A Narrative Review

Mild traumatic brain injury (mTBI) and whiplash injury (WI) may lead to long-term disabling consequences known as post-concussive syndrome (PCS) and whiplash-associated disorders (WADs). PCS and WAD patients commonly complain of conditions encompassing dizziness, vertigo, headache, neck pain, visual complaints, anxiety, and neurocognitive dysfunctions. A proper medical work-up is a priority in order to rule out any acute treatable consequences. However investigations may remain poorly conclusive. Gathered in the head and neck structures, the ocular sensorimotor, the vestibular, and the cervical proprioceptive systems, all involved in postural control, may be damaged by mTBI or WI. Their dysfunctions are associated with a wide range of functional disorders including symptoms reported by PCS and WAD patients. In addition, the stomatognathic system needs to be specifically assessed particularly when associated to WI. Evidence for considering the post-traumatic impairment of these systems in PCS and WAD-related symptoms is still lacking but seems promising. Furthermore, few studies have considered the assessment and/or treatment of these widely interconnected systems from a comprehensive perspective. We argue that further research focusing on consequences of mTBI and WI on the systems involved in the postural control are necessary in order to bring new perspective of treatment.

High Myopia and Thickness of Extraocular and Masticatory Muscles-7T MRI, Preliminary Study

(1) Background: Myopia is one of the most common refractive errors in the world. The aim of this study was to evaluate the transverse dimensions of selected masticatory muscles (temporalis muscle and masseter muscle) versus the transverse dimensions of selected extraocular muscles (superior rectus, inferior rectus, medial rectus and lateral rectus) in emmetropic and high myopic subjects. (2) Methods: Twenty-seven individuals were included in the analysis, resulting in 24 eyeballs of patients with high myopia and 30 eyeballs of emmetropic subjects. A 7 Tesla resonance was used to analyze the described muscles. (3) Results: Statistical analysis showed differences in all analyzed extraocular muscles and all analyzed masticatory muscles between emmetropic subjects and high myopic subjects. In the high myopic subject group, statistical analysis showed four correlations. The three negative correlations were between the lateral rectus muscle and an axial length eyeball, refractive error and an axial length eyeball, and the inferior rectus muscle and visual acuity. The positive correlation was between the lateral rectus muscle and the medial rectus muscle. (4) Conclusions: The high myopic subjects are characterized by a larger cross-sectional area of extraocular muscles and masticatory muscles compared to the emmetropic subjects. Correlations were observed between the thickness of the extraocular muscles and the masticatory muscles. The lateral rectus muscle was related to the length of the eyeball. The phenomenon requires further study.

The Challenges and Therapeutic Prospects in Eye Disease

A number of key insights into eye disease have been revealed in the past decade, which has resulted in the development of novel, effective, targeted therapies such as teprotumumab for the treatment of thyroid eye disease (also known as Graves' orbitopathy) [...].

It Is Time for a Multidisciplinary Rehabilitation Approach: A Scoping Review on Stomatognathic Diseases in Neurological Disorders

Patients affected by neurological disorders can develop stomatognathic diseases (SD) related to decreased bite force and quality of mastication, bruxism, severe clicking and other temporomandibular disorders (TMD), which deeply affect patients' swallowing, masticatory and phonation functions and, therefore, their quality of life. The diagnosis is commonly based on medical history and physical examination, paying attention to the temporomandibular joint (TMJ) range of movements, jaw sounds and mandibular lateral deviation. Diagnostic tools such as computed tomography and magnetic resonance imaging are used instead in case of equivocal findings in the anamnesis and physical evaluation. However, stomatognathic and temporomandibular functional training has not been commonly adopted in hospital settings as part of formal neurorehabilitation. This review is aimed at describing the most frequent pathophysiological patterns of SD and TMD in patients affected by neurological disorders and their rehabilitative approach, giving some clinical suggestions about their conservative treatment. We have searched and reviewed evidence published in PubMed, Google Scholar, Scopus and Cochrane Library between 2010 and 2023. After a thorough screening, we have selected ten studies referring to pathophysiological patterns of SD/TMD and the conservative rehabilitative approach in neurological disorders. Given this, the current literature is still poor and unclear about the administration of these kinds of complementary and rehabilitative approaches in neurological patients suffering from SD and/or TMD.

Exploratory Study on Central Sensitization and Bioelectrical Activity of the Selected Masticatory Muscles in Subjects with Myopia

BACKGROUND

Myopia is one of the most common eye disorders involving abnormal focusing of light rays. The studies recognize the association between the stomatognathic and visual systems. This compound may have a neurological basis associated with disorders such as central sensitization. The main aim of this study was to evaluate the influence of central sensitization on the bioelectrical activity of selected muscles of the masticatory organ in subjects with myopia.

METHODS

Selected masticatory and cervical spine muscles were analyzed using an eight-channel BioEMG III electromyograph. Central sensitization was analyzed using the central sensitization inventory.

RESULTS

Statistical analysis revealed significantly higher scores on the central sensitization inventory in subjects with axial myopia compared to subjects without refractive error. Repeated positive correlations were observed in the sternocleidomastoid muscle activity and negative correlations in the digastric muscle activity during open and closed eyes in myopic subjects.

CONCLUSIONS

Subjects with myopia have an increased score in the central sensitization inventory. The increase in the central sensitization inventory score is connected with the changes within the electromyographic activity of the masticatory and neck muscles. The effect of central sensitization on masticatory muscle activity in myopic subjects requires further study.

The Influence of Visual Input on Electromyographic Activity and Patterns of Masticatory and Cervical Spine Muscles in Emmetropic Caucasian Subjects by Gender

(1) Background: The objective of the research was to analyze the change of visual input on electromyographic activity and patterns of masticatory and cervical spine muscles in emmetropic Caucasian subjects by gender. Supposedly, visual input should not influence activity and electromyographic patterns of masticatory and cervical spine muscles in emmetropic Caucasian subjects by gender. (2) Methods: After applying the inclusion criteria, 50 emmetropic Caucasian subjects were included in the study. Four muscle pairs were analyzed: the temporalis muscle (TA), the masseter muscle (MM), the digastric muscle (DA), and the sternocleidomastoid muscle (SCM), during resting and functional activity. (3) Results: It was observed that there were no significant statistical differences in activity and bioelectrical patterns between open and closed eyes in women and men, with the exception of clenching on dental cotton rollers in DA-left and DA mean between tests in women. The observed statistical results had a small effect size, successively equal to 0.32 and 0.29. (4) Conclusions: Changes in the influence of visual input do not affect electromyographic activity and patterns of masticatory and cervical spine muscles in emmetropic Caucasian women and men.

Clinical Characteristics and Rehabilitation Strategies for the Stomatognathic System Disturbances in Patients with Stroke: A Systematic Review

Background: Understanding the stomatognathic system disturbances is key to diagnosing them early and implementing rehabilitation approaches to promote functional recovery. The objective of this study was to systematically review all published data that examined the assessment and rehabilitation strategies for the stomatognathic system disturbances in patients with stroke. Methods: Five databases (i.e., PubMed/MEDLINE, Scopus, Science Direct, Web of Science, and PEDro), were screened for manuscripts that included the assessment and rehabilitation strategies for stomatognathic system disturbances. The methodological quality was evaluated using the Mixed Methods Appraisal Tool. Results: Sixteen articles were included in this systematic review. The most frequently reported symptoms in patients with stroke included stiffness and thickness of the masseter muscle on the affected side and suprahyoid muscles; facial muscles' asymmetry and weakness; temporomandibular disorders; and a reduced maximum lip force, tongue pressure, and saliva flow rate. The rehabilitation strategies more frequently reported included exercises directed to the jaw, temporomandibular joint, tongue, and neck. The mean score for methodological quality was 85%. Conclusion: The stomatognathic system disturbances are frequently reported among patients with stroke, leading to dysfunction in masticatory performance or swallowing. More studies on interventions for stomatognathic system disturbances are required before conclusions may be drawn. Key Practitioner Message: This systematic review has clinical implications for rehabilitation practices, given that the results may help to develop early assessment and rehabilitation strategies for stomatognathic disturbances in patients with stroke.

The Axial Length of the Eyeball and Bioelectrical Activity of Masticatory and Neck Muscles: A Preliminary Report

Objective

The present study aimed to evaluate the correlation of eye length and bioelectric activity of temporalis, masseter, digastric, and sternocleidomastoid muscles in women with myopia compared to healthy women.

Methods

Based on the exclusion and inclusion criteria, 42 women aged 24 years (±2 years) were eligible for the study. Two equally sized groups with myopic (n = 21) and emmetropic healthy subjects (n = 21) were formed. An electromyographic study of the examined muscles was performed in four conditions: at rest, during maximal voluntary clenching in the intercuspal position, during maximal voluntary clenching on dental cotton rollers, and during maximal mouth opening using BioEMG III (BioResearch Associates, Inc. Milwaukee, WI, USA). The IOL Master 500 (Carl Zeiss Meditec, Jena, Germany) was used to examine the eyeball length. Statistical analysis showed significant positive correlations during mouth opening in both groups with open and closed eyes.

Results

A greater number of correlations between the analyzed variables was observed in emmetropic women. In almost all cases, the longer axial eye length was associated with an increase in the bioelectrical activity of the analyzed muscles. Significant correlations were most often observed within the masseter and digastric muscles during the maximum mouth opening and at rest.

Conclusion

There is a relationship between the bioelectrical activity of the masticatory muscles and the axial length of the eyeball on the same side.

Masticatory Muscle Thickness and Activity Correlates to Eyeball Length, Intraocular Pressure, Retinal and Choroidal Thickness in Healthy Women versus Women with Myopia

This study aims to examine the correlations between masticatory and neck muscle thickness and activity versus eyeball length, retinal thickness, choroidal thickness, and intraocular pressure in healthy women versus women with myopia. The study group consisted of 21 women aged 24 years and a control group of 19 women (mean age 23 years). For bioelectrical activity analysis within the temporalis anterior, the superficial part of the masseter muscle, the middle part of the sternocleidomastoid muscle, and the anterior belly of the digastric muscle, an eight-channel BioEMG III electromyograph were used. An M-Turbo ultrasound machine was used to analyze masticatory and neck muscle thickness. The eyeball length was examined by IOL Master 500; choroidal and retinal thickness by Optovue Angiovue; and intraocular pressure by Tono-Pen XL. Refractive errors are related to differences in muscle thickness and electromyographic activity. Bioelectrical activity within the temporalis anterior seems to be associated with ocular length, retinal thickness, and choroidal thickness in women with myopia.