Surface electromyographic patterns of masticatory, neck, and trunk muscles in temporomandibular joint dysfunction patients undergoing anterior repositioning splint therapy

Selected muscle tone and asymmetry of the occlusal plane in case of intracapsular temporomandibular joint disorder

Objective: To discover the extent of the connection between occlusal plane asymmetry and the rest tone of the four muscle groups of the orofacial region with temporomandibular joint pathology.Methods: Eighty-seven subjects were divided into two groups. The following methods were applied: clinical examination, roentgenological examination, and electromyography. Data were evaluated and statistically analyzed.Results: The variability of occlusal plane inclination in relation to the porion plane was 0-4.6º.The tonus of masseter muscle was higher in the experimental group: 1.45 mV more than in the control group: 1.23 mV (p < 0.05).Conclusion: Asymmetry of the occlusal plane inclination was found for nearly all subjects in both groups. It can be compensated for by adaptation mechanisms and does not cause temporomandibular joint disorders. Undertaken research shows the existence of a proven correlation between TMJ disorders and the resting tonus of the masseter muscle.

Impact of clear aligner therapy on masticatory musculature and stomatognathic system: a systematic review conducted according to PRISMA guidelines and the Cochrane handbook for systematic reviews of interventions

BACKGROUND

Clear aligner therapy has gained popularity as a minimally invasive orthodontic treatment option. However, its impact on the masticatory musculature and the stomatognathic system is an area of growing interest, as it involves the adjustment of occlusion and tooth movement. This systematic review aims to comprehensively assess and synthesise existing evidence regarding the influence of clear aligner therapy on the masticatory musculature and the stomatognathic system.

METHODS

An exhaustive search was performed on electronic databases that adhered to PRISMA guidelines. Clinical studies that evaluated the impact of patients receiving aligner orthodontic treatment on the muscles of the mastication and stomatognathic systems were included. A standardised data extraction form was devised for relevant variables. Two reviewers extracted the data variables. ROB-2 was used for bias evaluation in the selected studies.

RESULTS

A total of six studies met the inclusion criteria. The wearing of clear aligners significantly impacted the muscles of mastication. Muscle activity and discomfort showed a significant alteration in the initial days of appliance placement. but this observation was temporary, with no significant changes thereafter in subsequent follow-up. Bite force reduction was also noted. All the studies evaluated showed good methodological quality.

CONCLUSION

The review found that aligned orthodontic treatment may have a variable impact on muscles of mastication, with a potential for initial exacerbation of symptoms followed by possible improvement. However, due to the limited number of studies and their heterogeneous nature, further robust research is recommended to fully understand the relationship between aligned orthodontic treatment and masticatory muscles.

Do Temporomandibular Disorder Patients with Joint Pain Exhibit Forward Head Posture? A Cephalometric Study

Purpose

To evaluate head and cervical posture in individuals with or without temporomandibular disorders (TMDs) and to assess the correlations between pain, severity of symptoms, and posture.

Methods

A total of 384 patients (129 males and 255 females) was included. The Fonseca Anamnestic Index (FAI) was used to assess the severity and prevalence of TMD and the presence of temporomandibular joint (TMJ) pain. Patients were divided into three groups: the TMD-free group, TMD without TMJ pain group, and TMD with TMJ pain group. Subsequently, the patients with TMJ pain were further divided into mild TMD and moderate/severe TMD groups. Nine parameters were traced on cephalograms to characterize the head and cervical posture.

Results

TMD patients with TMJ pain showed increased forward head posture (FHP) than patients without TMJ pain and TMD-free subjects. No significant difference was observed between the TMD patients without TMJ pain and TMD-free subjects. In the TMD patients with the TMJ pain group, the moderate/severe TMD patients demonstrated increased FHP compared to mild TMD patients. TMD patients with joint pain had greater CVT/RL (B = 3.099), OPT/RL (B = 2.117), and NSL/C2' (B = 4.646) than the patients without joint pain after adjusting for confounding variables (P < 0.05).

Conclusion

TMD patients with TMJ pain showed increased FHP compared to other groups, and FHP became more significant as TMD severity increased in male patients, indicating the FHP might play an important role in the development of TMJ pain. In the clinical assessment of TMD, the patients' abnormal head and cervical posture might be considered.

Effects of orthodontic treatment on masticatory muscles activity: a meta-analysis

Context: A comprehensive meta-analysis was carried out to investigate the impact of orthodontics on masticatory muscles.Methods: A thorough search of various databases, including CNKI, Wan Fang, VIP, CBM, MEDLINE, PubMed, Cochrane Library, EMBASE, Web of Science, and Google Scholar, was performed to identify relevant studies on patients undergoing orthodontics or functional corrections. Six case-control studies were finally included in this analysis, which specifically examined the effect of orthodontic treatment on masticatory muscle function.Results: The results revealed that the mean masticatory muscle voltage in patients treated with orthodontics was found to be higher after treatment compared to before treatment [odds ratio (OR)=1.57, 95% confidence interval (CI) (0.57, 2.57), p = 0.002], which could potentially have an impact on masticatory muscle function, particularly in individuals with Class II Division 1 malocclusion.Conclusion: These findings contribute to our understanding of the effects of orthodontic interventions on masticatory muscles, further highlighting the importance of orthodontics in optimising masticatory function.

The Difference in Electromyographic Activity While Wearing a Medical Mask in Women with and without Temporomandibular Disorders

Wearing a medical mask influences resting activity of the temporalis anterior and masseter muscles in healthy young women. However, no studies link medical mask-wearing with masticatory muscle activity in patients with temporomandibular disorders (TMDs). Therefore, this study aims to compare electromyographic patterns while wearing a medical mask between women with and without temporomandibular disorders. Based on the Research Diagnostic Criteria for Temporomandibular Disorders, 115 adult women qualified for the study. Participants were divided into the following two groups: diagnosed TMDs (n = 55; mean age: 23.5 ± 2.3 years) and healthy women (n = 60; mean age: 23.7 ± 2.6 years). Examinations of the resting and functional electromyographic activity of the temporalis anterior (TA), superficial masseter (MM), anterior bellies of the digastric muscle (DA), and the middle part of the sternocleidomastoid muscle (SCM) were carried out using the BioEMG III™. Both groups showed statistically significant decreases in resting masticatory muscle activity during medical mask examination compared to no mask measurement. The significant differences in no mask measurement between both groups were noted regarding resting masticatory activity, clenching in the intercuspal position, and clenching on dental cotton rollers. During medical mask examination, women with TMDs showed differences in resting masticatory activity and clenching on dental cotton rollers compared to the healthy group. In all analyzed variables, both groups showed similar electromyographic patterns in the maximum mouth opening measurement during medical mask and no mask examination. A medical mask influences the resting bioelectric activity of the masticatory muscles in women with temporomandibular disorders and healthy women. We observed differences and some similarities in resting and functional electromyographic patterns within masticatory and neck muscles in both groups during medical mask and no mask examination.

Changes in Maximum Mandibular Mobility Due to Splint Therapy in Patients with Temporomandibular Disorders

Splint therapy is widely used in the treatment of myofascial pain, but valid studies on the efficacy of this therapy are rare. The purpose of the present study was to investigate which qualifiable and quantifiable effects of splint therapy are detectable. For this purpose, 29 patients (21 women, mean age 44.6 ± 16 years) diagnosed with myofascial pain (RDC/TMD) were investigated in this prospective clinical trial (10/6/14An). Patients were treated with Michigan splints applied overnight for three months. Before (T1) and after three months of treatment (T2), patients were registered with an electronic ultrasound device with qualitative and quantitative evaluation of the registrations and a qualitative assessment of pain symptoms using a verbal analog scale. Significant differences were found between maximum mouth opening (MMP) (p < 0.001) and right condylar movement (CM) at MMP (p = 0.045). Qualitative assessment revealed that 24 of 29 patients experienced an improvement in pain symptoms, 17 of whom experienced complete remission. The results of the qualitative and quantitative analysis provide indications of the effectiveness of the splint therapy. In addition to quantitative measurements, the ultrasound facebow technique was also able to provide qualitative information.

Effects of Radial Extracorporeal Shock Wave Therapy in Reducing Pain in Patients with Temporomandibular Disorders: A Pilot Randomized Controlled Trial

Temporomandibular disorders (TMD) are primarily characterized by pain as well as issues concerning the proper functioning of individual elements of the stomatognathic system. The aim of the study was to assess the safety and efficacy of physical exercise, with or without radial Extracorporeal Shock Wave Therapy (rESWT), in patients with TMD. Eligible patients were adults (≥18 years) with diagnosed myofascial pain with or without mouth opening limitation (Group Ia, Ib) based on the Diagnostic Criteria for TMD (DC/TMD). Enrolled patients (n = 15) were randomly assigned 1:1 to receive physical exercise combined with rESWT (n = 8) or sham rESWT (n = 7) for four weeks. The primary endpoint was the pain intensity measured by a visual analogue scale (VAS). The secondary endpoints were muscle activity and function assessed through the surface electromyography evaluation of the anterior temporalis and the masseter muscles. The rESWT group (mean age: 28.50 ± 8.85 years) showed a statistically significant pain reduction (VAS Right side: ΔT0-T1 MD = −3.00; p = 0.023, Left side: ΔT0-T1, MD = 3.57, p = 0.021), whereas patients in the sham WBV group (mean age: 30.71 ± 8.98 years), did not reach statistical significance (VAS: Right side: ΔT0-T1 MD = 1.00, p = 0.155; Left side: ΔT0-T1 MD = 1.25 SE = 0.25, p = 0.094). Concurrently, muscle activity and performance significantly improved in the active rESWT group, with an improvement in the percentage of the overlapping coefficient (POC) compared to the control group. No dropouts and no side effects were recorded. Taken together, the findings of this pilot RCT suggested that rESWT combined with physical therapy could be effective in relieving pain and improving function in muscle-related TMD patients.

Electromyographic evaluation of the effect of hard and soft stabilizing appliances on masseter and anterior temporalis muscles in asymptomatic individuals

Background/Aim: Stabilization appliances have traditionally been used for the treatment of temporomandibular disorders and bruxism. The aim of this study was to evaluate the effect of two appliances (hard and soft) with different thicknesses on the electromyographic (EMG) activities of masseter and anterior temporalis muscles. Material and Methods: 30 healthy subjects have been divided into two groups of 15, according to the appliance material used (soft, hard). For each subject in both groups, two appliances have been prepared with 3 mm and 6 mm thickness. EMG recordings of bilateral masseter and anterior temporalis muscles were taken for each appliance. Results: The results showed that, the decrease in average EMG values during maximum voluntary clenching with a 3-mm and 6-mm-thick hard appliance was statistically significant compared with the average EMG of maximum voluntary clenching in the intercuspal position. The increase in average EMG values during maximum voluntary clenching with a soft appliance of 3 mm and 6 mm thickness was statistically significant. Conclusions: The hard stabilization appliances decrease the activity of the masseter and temporalis muscles, while the soft appliances increase the activity of the masseter and temporalis muscles.

New Method for Analysis of the Temporomandibular Joint Using Cone Beam Computed Tomography

Modern dentistry commonly uses a variety of imaging methods to support diagnosis and treatment. Among them, cone beam computed tomography (CBCT) is particularly useful in presenting head structures, such as the temporomandibular joint (TMJ). The determination of the morphology of the joint is an important part of the diagnosis as well as the monitoring of the treatment results. It can be accomplished by measurement of the TMJ gap width at three selected places, taken at a specific cross-section. This study presents a new approach to these measurements. First, the CBCT images are denoised using curvilinear methods, and the volume of interest is determined. Then, the orientation of the vertical cross-section plane is computed based on segmented axial sections of the TMJ head. Finally, the cross-section plane is used to determine the standardized locations, at which the width of the gap between condyle and fossa is measured. The elaborated method was tested on selected TMJ CBCT scans with satisfactory results. The proposed solution lays the basis for the development of an autonomous method of TMJ index identification.

Short-Term Effect of Orthodontic Treatment with Clear Aligners on Pain and sEMG Activity of Masticatory Muscles

Background and objectives: The aim of this study is to evaluate mandibular elevator muscles activity and pain on palpation in the early stages of orthodontic treatment with clear aligners using surface electromyography (sEMG). Materials and methods: Surface electromyography (sEMG) activity and pain level on muscle palpation of masseter and anterior temporalis muscles were recorded in a sample of 16 adult subjects (aged 18–32 years; mean 22.5 +/− 3.5 SD) undergoing orthodontic treatment with clear aligners before the treatment (T0), after 1 month of treatment (two clear aligners) (T1), and after 3 months of treatment (T2) (six clear aligners). A chi-square test for nominal data, a Friedman test, and a Wilcoxon-signed rank test as post hoc analysis were applied. Results: No statistically significant differences in muscular pain were observed. At T1, the sEMG activity of masseter muscles at mandibular rest position showed a statistically significant reduction, but after 3 months (T2), the data appeared similar to T0 (p = 0.03 and p = 0.02). Conclusions: During the treatment with clear aligners, subjects could experience an initial reduction in the masseter basal activity after 1 month of treatment. This effect tends to decrease to baseline levels after 3 months of therapy.

Changes in jaw and neck muscle coactivation and coordination in patients with chronic painful TMD disk displacement with reduction during chewing

The treatment of a complex temporomandibular disorder (TMD), such as disk displacement with reduction (DDR) associated with arthralgia and myalgia, may depends on understanding the impairments in muscle function. The aim of this study was to investigate the behavior of the anterior temporalis, masseter and sternocleidomastoid muscles in the time and frequency domains during chewing in patients with chronic painful TMD-DDR using electromyographic (EMG) analysis. Thirty-three patients who met the diagnostic criteria for TMD and 32 volunteers without TMD (control group) underwent clinical examination, chewing pattern classification and EMG analysis. For the EMG analyses, the side of habitual unilateral chewing, as determined by the chewing pattern classification, was selected for recording; in cases of bilateral chewing, the recording side was randomly selected. The EMG-EMG coherence function and EMG-EMG transfer function (gain and phase) values were obtained at the first chewing frequency peak, and the working-side masseter signal was used as a reference in the analyses of the other muscles. Compared to the control group, the TMD group showed a longer chewing stroke duration (P = 0.01) as well as changes in the coactivation and coordination strategies of the jaw muscles, evidenced by greater relative energy expenditure (P< 0.01) and impaired differential recruitment (P< 0.05) and coherence (P< 0.01). Delays in peak and temporal asynchrony occurred in the jaw and neck muscles (P< 0.05). Patients with chronic painful TMD-DDR during chewing presented changes in the jaw and neck muscles, with more compromised function of the former, which are specific to chewing.

Evaluation of Masticatory Muscle Function Using Digital versus Traditional Techniques for Mockup Fabrication: A Controlled Prospective Study

Background: the aim of this longitudinal prospective study was to analyze the effect of digital and traditional mockup on masticatory muscle activity in patients with teeth wear, rehabilitated with an increase of occlusal vertical dimension. Subjects and Methods: a sample of 22 adult patients who were about to receive a prosthetic rehabilitation was divided into a study group (3M; 9F; mean age 42 ± 0.8 years), treated using the digital mockup; and a control group (2M; 8F; mean age 37 ± 0.5 years), treated using the conventional technique (traditional) mockup. Electromyographic activity of anterior temporalis and masseter muscles were evaluated before the beginning of the treatment (T0), at mockup insertion (T1), after treatment (T2) and each lapse of time lasted 2–5 months. Results: the comparison between the two groups at different time gaps revealed that at ∆1 (T1–T0) only the impact index (IMP) showed significant difference and no other significant variation was observed between the two groups at ∆2 (T2–T1) and ∆3 (T2–T0). It concludes that traditional and digital methods generally have nonsignificant differences. Conclusions: both methods seem to be effective in prosthetic rehabilitation and give comparable effects on masticatory muscles.

Diagnosis and management of bruxism: Evaluation of clinical practices in France

Objective: The Evaluation of Clinical Practice (ECP) conducted with a sample of French general dental practitioners aimed to measure the methods used to diagnose and manage bruxism.Methods: The ECP was performed using a declarative online questionnaire-based anonymous survey (SurveyMonkey) of 1388 practitioners. Twenty-two questions were grouped in 5 categories: (1) Sociodemographic characteristics (Q1-6); (2) Knowledge of the prevalence and definition of bruxism (Q7-9); (3) Diagnostic approach (Q10-11) and management (Q12-Q13); (4) The use of occlusal splints (Q14-21); (5) Oral rehabilitation (Q22).Results: The answers obtained (233; 16.8%) revealed a wide disparity and insufficient diagnosis (e.g. only 41% looked for sleep disorders, 22.3% for consumption of stimulants, 3% for upper airway obstruction) and management of bruxism (e.g. only 21.9% of participants proposed cognitive-behavioral therapy).Discussion: The discrepancies detected, such as the use of inappropriate splints (30 to 70%), emphasize the need for more prompt research-to-practice transfer of new knowledge.

Orofacial muscles activity in children with swallowing dysfunction and removable functional appliances

Swallowing dysfunction is a frequent disorder among children and refers to an altered tongue posture and abnormal tongue movement during swallowing. Removable functional appliance is one of the treatments applied by dentistry to correct this disorder. The aim of this study was to evaluate any differences on orofacial muscles activity in children with swallowing dysfunction with and without removable functional appliances. 68 children were eligible for the study and divided into the orthodontic group (OG) and the no-orthodontic group (NO-OG). Both groups performed a dental occlusion-class evaluation, a swallowing function test and a myoscan analysis in order to measure perioral forces (i.e. tongue extension force, lip pressure, masseter contraction force). Our results showed a significant difference (P=0.02) between OG and NO-OG for the tongue extension force, whereas no significant differences (P>0.05) were found for the other parameters. Our findings suggest that children with swallowing dysfunction and removable functional appliance show orofacial muscles activity within the range of reference values (except for the lip pressure). However, we hypothesize that orthodontic treatment can achieve more effective results with integration of myofunctional therapy.

Wind Instrumentalists and Temporomandibular Disorder: From Diagnosis to Treatment

INTRODUCTION

Temporomandibular disorders (TMD) involve the presence of pain or dysfunction on certain areas of the Cranio-Cervico-Mandibular Complex (CCMC), such as the masticatory muscles, the temporomandibular joint (TMJ) and associated structures like the postural muscles of the cervical region, can be considered as a sub-group of musculoskeletal disorders. Wind instrument players, as a consequence of their musical performance and its relation with the CCMC, can develop a TMD associated to muscle hyperactivity of certain elevator muscles, or even an increase of the intra-articular pressure in the functioning of the TMJ throughout musical activity.

AIM

The objective of this paper is to describe the necessary and elementary steps in the diagnoses and treatment of a wind instrumentalist with a temporomandibular disorder, with the introduction of infrared thermography during this procedure. This case study also has the purpose of presenting the usefulness of piezoresistive sensors in the analysis of the clarinettists' embouchure.

METHODOLOGY

A Caucasian, 30-year-old female clarinettist was assessed through a clinical examination following the Diagnostic Criteria for TMD (RDC/TMD), as a complementary tool of diagnosis, a thermal imaging infrared camera, Flir E60 (Wilsonville, OR, USA), was used in order to analyse the above referred articular and muscular regions. The complementary examination protocol implemented with this clarinet player also involved the analyses of the embouchure with the support of piezoresistive sensors.

RESULTS

The clinical outcomes resulting from this work were based on the RDC/TMD diagnoses indicated that the clarinet player had an internal derangement on both TMJ, with an osteoarthritis on the left TMJ and an anterior disc displacement with reduction on the right TMJ. The infrared thermograms that were analysed, verified the existence of a temperature differential of the anterior temporal muscle (0.1 °C), the TMJ (0.1 °C) and the masseter muscle (0.7 °C), and after the occlusal splint therapy the asymmetry related to the master muscle reduced to 0.3 °C. The high pitches can reach values of 379 g of force induced to the tooth 21 comparing to the 88 g of force applied on tooth 11. The embouchure force measurements consistently presented greater forces during the higher notes, followed by the medium notes and finally the low notes and this happened with higher pressures being transmitted always to tooth 21.

CONCLUSION

Performing arts medicine should understand the major importance of the dentistry field in the daily life of a professional musician, and the significance of implementing routine screening procedures of dental examinations, with infrared thermograms examination of distinct areas of the CCMC, as well as the use of sensors on the analyses of an eventual asymmetrical embouchure. Employing these techniques in dentistry will create the chance of preventing the overuse of some anatomical structures, with an early diagnosis and the correct monitoring of these areas.

Postural stability in subjects with temporomandibular disorders and healthy controls: A comparative assessment

PURPOSE OF THE STUDY

The influence of the stomatognathic apparatus on body posture is a continuously discussed topic with contrasting results. The aim of this study is to analyze differences in postural stability between subjects with and without myogenous TMD.

METHODS

25 subjects affected by myogenous TMD according with DC/TMD (6 males, 19 females; mean age 31.75±6.68years) and a healthy control group of 19 subjects (4 Males, 15 Females; mean age 27.26±3.85years) were enrolled in the study. Both groups underwent a posturo-stabilometric force platform exam under different mandibular and visual conditions. Sway area and sway velocity of the COP (Center Of foot Pressure) posturo-stabilometric parameters were evaluated and compared applying Mann-U-Whitney statistical test.

RESULTS

The sway area and sway velocity parameters resulted statistically significantly higher in the TMD group (sway area p<0.01; sway velocity p<0.05) in mandibular maximum intercuspation and rest positions with eyes open.

CONCLUSIONS

This study demonstrates a significant difference in body postural stability between subjects with myogenous TMD and healthy controls. In particular, sway area and sway velocity postural parameters are increased in these subjects.

Investigating activity of masticatory muscles in patients with hypermobile temporomandibular joints by using EMG

Background

Temporomandibular joint hypermobility (TMJH) can manifest higher range of motions in mandible. The aim of this study was to investigate and compare the activity of masticatory muscle of TMJs in healthy individuals and patients with mild, moderate and severe TMJH.

Material and Methods

In this clinical study, 69 patients (between the ages of 22 to 42) with manifestation of TMJH were included. The patients were divided into three groups based on their maximum mouth opening (MMO): (light) with MMO of 50-55 mm; (moderate) with MMO between 55 to 65 mm; and (severe) with MMO >65 mm. Also, 20 healthy people with profiled tomography in the last 6 months were invited as control group (healthy) with normal MMO (<50 mm). All the groups subjected to electromyogram (EMG) in 2 steps: maximal voluntary clenching (MVC) of the jaws; and during chewing of bread by using one side of the jaws voluntary. The collected data were analyzed by Student T-test and Chi-Square tests using SPSS software version 15 at significant level of 0.05.

Results

Both TMJs of light, moderate and severe groups showed significant differences in frequency, time of activity and rest in comparison with healthy group during chewing and MVC (all p values < 0.01).

Conclusions

Masticatory muscles activity reduced in relation with the severity of TMJH and higher excessive mouth opening.

Key words:Electromyography, joint hypermobility, mouth opening, tempormandibular joint.

An assessment of the usefulness of Kinesiograph as an aid in the diagnosis of TMD: a review of Manfredini et al.'s studies

AIM

Performing a literature review of publications by Dr. Manfredini et al. related to their temporomandibular joint (TMJ) injection therapy outcome with conclusions on the clinical utility of computerized measurement devices used in the management of temporomandibular disorders (TMDs). In addition, reviewing their published opinion on an occlusion: TMD versus a biopsychosocial paradigm for TMD. Manfredini et al. authored an article published in the Journal of the American Dental Association (JADA) 2013, "An Assessment of the usefulness of jaw kinesiography in monitoring temporomandibular disorders," the most recent of 12 articles. In all studies, subjects received TMJ injections with an objective measurement outcome criterion; increased maximum mouth opening (MMO) and subjective symptom improvement of pain and chewing function. In the 2013 JADA article, the Mandibular Kinesiograph, referred to as KG, measured MMO before and after therapy. In 11 prior articles, all subject groups with limited mouth opening exhibited very significant increased MMO post-treatment, documenting treatment success using the same 2013 protocol. The 2013 study showed a 1·1 mm improved MMO, described as insignificant. The authors did not critique or explain the aberrant, skewed 2013 outcome data contrasted with their prior studies, which showed overwhelmingly significant increased MMO. Instead, they concluded that the MMO recording device was clinically useless. This motivated a literature review of the authors' TMD publications.

CONCLUSION

The publications by Manfredini et al. recognized proponents of the psychosocial model of TMD, including the 2013 article, appear to be part of a campaign denying an occlusion: TMD relationship and disparaging the specific computerized measurement devices and the dentists using them in the management of their TMD patients using neuromuscular occlusion dental treatment.

Possible causal relationships between competitive swimming in growing age and three-dimensional dentoalveolar development

Background

The aim of this study was to investigate possible links between competitive swimming during the growth phase and the development of the dentoalveolar arches.

Methods

The study sample included 100 swimmers and a control group of 100 age-matched non-swimmers who had never practised swimming or related sports. Subjects who had had previous orthodontic treatment were excluded. Overjet, overbite, sagittal and transverse parameters, arch dimension, crowding and oral habits were recorded.

Results

In the swimmers, there was a significantly higher frequency of molar symmetry (P = 0.04), together with a greater number of Class I subjects. The overjet in the swimmers was mainly normal, but the arch dimensions were significantly wider (+10% in the upper arch; P < 0.001). Similarly, the swimmers showed significantly less severe crowding (P < 0.001) and significantly reduced oral habits (P < 0.001).

Conclusions

Our data and analysis demonstrate that competitive swimming during the growth phase has a favourable effect on dental arch development in the sagittal, vertical and transverse planes.

Orthodontic-surgical treatment: neuromuscular evaluation in open and deep skeletal bite patients

BACKGROUND

The aim of this study was to compare electromyographic data of two groups of patients (open and deep skeletal bite) before and after surgical orthodontic treatment.

METHODS

All patients who underwent orthognathic surgery at the Department of Orthodontics (University of Milan) were subjected to periodic electromyographic evaluation of the masticatory muscles (masseter and anterior temporal muscles) and to electrokinesiographic evaluation of mandibular movements. The sample comprised 72 patients (35 open skeletal bite patients and 37 deep skeletal bite patients) at the end of craniofacial growth. The electromyographic instruments used in the study included a Freely and a K6-I electromyograph. Statistical evaluation was carried out with Student's t tests for independent samples.

RESULTS

Lots of differences between open and deep skeletal bite patients have been underlined by the analysis of the electromyographic data obtained. These results have been obtained with both electromyographic systems. Muscular activity in microvolts is higher in deep skeletal bite patients at the beginning of the treatment than in open bite ones, but during the following phases of the treatment, the two values became similar.

CONCLUSIONS

Morphologic differences between open and deep bite patients can also be demonstrated by instrumental examinations, and their correction after surgical treatment is observable on electromyographic and electrognatographic exams.

Effects of viewing affective pictures on sEMG activity of masticatory and postural muscles

Recently there has been an upsurge of interest in the question to what extent the human motor control system is influenced by the emotional state of the actor. The aim of this study was to evaluate whether emotional inputs modify the activity of masticatory and postural muscles. Twenty healthy young adults viewed affective pictures, while surface electromyography (sEMG) of masticatory and postural muscles was recorded to investigate the coupling between emotional reactions and body muscular activity. One hundred and twenty pictures, chosen from the International Affective Picture System (IAPS), divided in two blocks of six sets, were presented to the subjects. sEMG data were statistically analyzed (RM ANOVA on Ranks). Root Mean Square (RMS) amplitudes, comparing the subsequent sets (Neutral, Unpleasant, Neutral, Pleasant) with the first and the last Baseline set, changed significantly only randomly. The results show that emotional inputs seems not influence the activity of masticatory and postural muscles, recorded by sEMG.

Assessment of thickness and function of masticatory and cervical muscles in adults with and without temporomandibular disorders

OBJECTIVE

The aim of this study was to evaluate the maximal bite force (MBF), electromyographic (EMG) activity and thickness of the masseter, anterior part of the temporalis and sternocleidomastoid (SCM) muscles in a group of young adults with and without temporomandibular disorders (TMDs).

DESIGN

Nineteen individuals comprised the TMD group (6 males/13 females, aged 25.4±3.8 years), classified based on the Research Diagnostic Criteria for TMD (RDC/TMD), and 19 comprised the control group (6 males/13 females, aged 24.1±3.6 years). The MBF was determined with a transducer placed between the dental arches at the first molars level (N). The muscles were evaluated bilaterally at rest and during maximal voluntary clenching (MVC) by assessing EMG activity and performing ultrasonography (USG). The mean values of these measures for both sides of the mouth were used. The normality of the distributions was assessed by the Shapiro-Wilks test. Variables between groups and genders were compared using two-way factorial ANOVA test and correlated using the Spearman coefficient (α=0.05). Unpaired t test was used to compare variables between TMD subgroups. Logistic regression analysis was used to identify the variables associated with the presence of TMD.

RESULTS

MBF, EMG and USG data were similar among clinical groups and among TMD subgroups. The thickness of masseter and SCM muscles in the relaxed and clenching states were significantly higher in males than females. On the other hand, the EMG of the temporalis muscle in the rest state was significantly higher in females than males. Additionally, the MBF was positively correlated with the USG characteristics of masseter and SCM muscles, as well as with the EMG activity of masseter and temporalis muscles in the TMD group. In this group, there was also a positive correlation between the thickness of the masseter muscle and its activity. On the other hand, the thickness of the SCM muscle was negatively correlated with its activity. A lower MBF was independently associated with the presence of TMD.

CONCLUSIONS

Subjects with TMD exhibited similar values of MBF, thickness and electrical activity of masticatory and cervical muscles when compared with controls; positive correlations observed between these variables may suggest a muscular alteration in TMD patients and a co-activation of masticatory and cervical muscles during mandibular movement. This fact may also be confirmed by the negative association between bite forces and presence of TMD.

Spasmodic torticollis: the dental connection

Spasmodic torticollis or cervical dystonia (CD) is the most common form of focal dystonia and is characterized by sustained abnormal muscle contractions in the head and neck area resulting in abnormal positioning or posturing of the head. The dystonic muscle spasms associated with spasmodic torticollis may affect any combination of neck muscles. Three cases are reported of spasmodic torticollis that were treated by a dental appliance with individual varying occlusal heights to open the maxillomandibular vertical dimension. Upon increasing the vertical dimension of occlusion, there was a slowing and/or discontinuance of the symptoms of cervical dystonia. The proposed hypothesis for this reversal is that there may be neuritis of the auriculotemporal branch of the trigeminal nerve, which has direct input into the reticular formation (RF), and it may activate the cells of the pontine region of the RF known for the control and deviation of head posture. There is growing clinical evidence that temporomandibular joint (TMJ) dysfunction may be a factor in this neurological and painful disorder when it coexists.

Temporomandibular disorders: A position paper of the International College of Cranio-Mandibular Orthopedics (ICCMO)

PURPOSE

Two principal schools of thought regarding the etiology and optimal treatment of temporomandibular disorders exist; one physical/functional, the other biopsychosocial. This position paper establishes the scientific basis for the physical/functional. THE ICCMO POSITION: Temporomandibular disorders (TMD) comprise a group of musculoskeletal disorders, affecting alterations in the structure and/or function of the temporomandibular joints (TMJ), masticatory muscles, dentition and supporting structures. The initial TMD diagnosis is based on history, clinical examination and imaging, if indicated. Diagnosis is greatly enhanced with physiologic measurement devices, providing objective measurements of the functional status of the masticatory system: TMJs, muscles and dental occlusion. The American Alliance of TMD organizations represent thousands of clinicians involved in the treatment of TMD. The ten basic principles of the Alliance include the following statement: Dental occlusion may have a significant role in TMD; as a cause, precipitant and/or perpetuating factor. Therefore, it can be stated that the overwhelming majority of dentists treating TMD believe dental occlusion plays a major role in predisposition, precipitation and perpetuation. While our membership believes that occlusal treatments most frequently resolve TMD, it is recognized that TMD can be multi faceted and may exist with co-morbid physical or emotional factors that may require therapy by appropriate providers. The International College of Cranio-Mandibular Orthopedics (ICCMO), composed of academic and clinical dentists, believes that TMD has a primary physical/functional basis. Initial conservative and reversible TMD treatment employing a therapeutic neuromuscular orthosis that incorporates relaxed, healthy masticatory muscle function and a stable occlusion is most often successful. This is accomplished using objective measurement technologies and ultra low frequency transcutaneous electrical neural stimulation (TENS).

CONCLUSION

Extensive literature substantiates the scientific validity of the physical/functional basis of TMD, efficacy of measurement devices and TENS and their use as aids in diagnosis and in establishing a therapeutic neuromuscular dental occlusion.

CLINICAL IMPLICATIONS

A scientifically valid basis for TMD diagnosis and treatment is presented aiding in therapy.

The Stomatognathic System's Role in the Postural Stabilization in Subjects Suffering from Whiplash Injury Part 1: Patients with Physiological Occlusion

Aim of this study is analyze the effects of dental occlusion on postural stability in patients with previous whiplash and normal occlusion. Materials and methods: 36 adult patients with previous whiplash and normal occlusion (good alignment, 1st class or mild 2nd class deep bite for mandibular retrusion) were selected. The patients were suffering from masticatory muscles pain caused by clenching during sleep. Exclusion criteria: use of psych drugs. To simulate the conditions of sleep (with a reduction of proprio-and esteroceptive inputs for postural management performed by CNS), we used postural Romberg analysis (feet together, closed eyes)on stabilometric platform changing occlusal parameters only, under the following conditions: 1) in occlusal rest position, 2) in centric occlusion, 3) in clenching, 4) with occlusal disengage with cotton rolls and 5) in clenching on cotton rolls. Time of each test: 15 seconds. It was performed a statistical analysis with T-test comparing between them the mean of all tests. Results: stabilometry data (postural ball and ellipse) show better postural performances in centric occlusion and clenching in centric occlusion, and a worsening in all tests with occlusal disengage (with statistically significant difference - p<0.05). Conclusions: postural instability caused by whiplash increases muscles tone and dental clenching as compensatory effects, with onset of facial pain. An occlusal disengage (like an occlusal splint to reduce clenching)induces a postural worsening in patients with normal occlusion, while centricocclusion increases the stability. These results suggest that stomatognathic organ has a new physiological function: the posture stabilization.

The muscle engram: the reflex that limits conventional occlusal treatment

The engram (the masticatory "muscle memory") is shown to be a conditionable reflex whose muscle conditioning lasts less than two minutes, far shorter than previously thought. This reflex, reinforced and stored in the masticatory muscles at every swallow, adjusts masticatory muscle activity to guide the lower arch unerringly into its ICP. These muscle adjustments compensate for the continually changing intemal and external factors that affect the mandible's entry into the ICP. A simple quick experiment described in this article isolates the engram, enabling the reader to see its action clearly for the first time. It is urged that every reader perform this experiment. This experiment shows how the engram, by hiding the masticatory muscles' reaction (the hit-and-slide), limits the success of the therapist in achieving occlusion-muscle compatibility. This finding has major clinical implications. It means that, as regards the muscle aspect of treating occlusion, the dentist treating occlusion conventionally is working blind, a situation the neuromuscular school of occlusal thought seeks to correct. The controversy over occlusion continues.

The cerebral representation of temporomandibular joint occlusion and its alternation by occlusal splints

Occlusal splints are a common and effective therapy for temporomandibular joint disorder. Latest hypotheses on the impact of occlusal splints suggest an altered cerebral control on the occlusion movements after using a splint. However, the impact of using a splint during chewing on its cerebral representation is quite unknown. We used functional magnetic resonance imaging (fMRI) to investigate brain activities during occlusal function in centric occlusion on natural teeth or on occlusal splints in fifteen healthy subjects. Comparisons between conditions revealed an increased activation for the bilateral occlusion without a splint in bilateral primary and secondary sensorimotor areas, the putamen, inferior parietal and prefrontal cortex (left dorsal and bilateral orbital) and anterior insular. In contrast, using a splint increased activation in the bilateral prefrontal lobe (bilateral BA 10), bilateral temporo-parietal (BA 39), occipital and cerebellar hemispheres. An additionally applied individually based evaluation of representation sites in regions of interest demonstrated that the somatotopic representation for both conditions in the pre- and postcentral gyri did not significantly differ. Furthermore, this analysis confirmed the decreasing effect of the splint on bilateral primary and secondary motor and somatosensory cortical activation. In contrast to the decreasing effect on sensorimotor areas, an increased level of activity in the fronto-parieto-occipital and cerebellar network might be associated with the therapeutic effect of occlusal splints.

EMG spectral characteristics of masticatory muscles and upper trapezius during maximum voluntary teeth clenching

To assess the surface electromyographic spectral characteristics of masticatory and neck muscles during the performance of maximum voluntary clench (MVC) tasks, 29 healthy young adults (15 men, 14 women, mean age 22years) were examined. Electromyography of masseter, temporalis and upper trapezius muscles was performed during 5-s MVCs either on cotton rolls or in intercuspal position. Using a fast Fourier transform, the median power frequency (MPF) was obtained for the first and last seconds of clench, and compared between sexes, muscles, sides, tests and time intervals using ANOVAs. On average, the MPFs did not differ between sexes or sides (p>0.05), but significant effects of muscle (MPF temporalis larger than masseter, larger than trapezius muscles), test (larger MPFs when clenching in intercuspal position than when clenching on cotton rolls) and time (larger MPFs in the first than in the fifth second of clench) were found. In conclusion, a set of data to characterize the sEMG spectral characteristics of jaw and neck muscles in young adult subjects performing MVC tasks currently in use within the dental field was obtained. Reference values may assist in the assessment of patients with alterations in the cranio-cervical-mandibular system.

Signs and symptoms of temporomandibular joint disorders related to the degree of mouth opening and hearing loss

Background

The temporomandibular joint is a unique bi-condylar joint involved in mastication and speech. Temporomandibular joint disorders (TMD) have a range of symptoms, including aural symptoms, and are present in approximately 75% of normal populations. The present study examined the relationship between signs and symptoms of TMD and mouth opening, gender, joint and aural symptoms, and hearing loss.

Methods

The study involved 464 healthy Greek university students (156 men and 308 women) with a mean age of 19.6 years. Age, gender and maximum mouth opening was recorded. Mouth opening was measured using Vernier calipers. An anamnestic questionnaire was used to stratify the subjects into four groups based on TMD severity. Aural symptoms and an audiogram were recorded for each subject too. Data were analyzed using multifactor ANOVA, chi-square, t-test, Mann-Whitney and Kruskal-Wallis tests.

Results

The overall incidence of TMD signs and symptoms was 73.3%. The incidence and severity was greater in females than males (p-value 0.0001 < 0.05). The number of aural symptoms was associated to the TMD severity (p-value 0.0001 < 0.05) as well as maximum mouth opening (p-value 0.004 < 0.05). Audiometry showed that moderate and severe TMD was associated with hearing loss of median and low tones respectively (p-value 0.0001 < 0.05). TMJ pain (p-value 0.0001 < 0.05), TMJ ankylosis (p-value 0.0001 < 0.05), bruxism (p-value 0.0001 < 0.05) and ear itching (p-value 0.0001 < 0.05) were also found to be statistically different between TMD and non-TMD subjects.

Conclusions

TMD signs and symptoms were more common and severe in females than males. TMD severity is correlated with the degree of mouth opening and the number of aural symptoms. The absence or presence of mild TMD are associated with normal audiograms while moderate and severe TMD are related to hearing loss in median and low tones respectively. Bruxism, joint ankylosis, joint pain and ear itching were more common in TMD than non-TMD patients.