Effects of orthodontic aligners on 24-hour masseter muscle activity: a multiple-day electromyographic study.

OBJECTIVE: This study aimed to assess the effects of aligners on masseter muscle activity by using an electromyographic device in the home environment. METHODS: The study was performed on healthy patients who required orthodontic treatment. Three different 24 h-EMG recording sessions were performed in different conditions: without aligners, with passive aligners, and with active aligners. The non-functional MMA work index (nfMMA-WI) and the non-functional MMA time index (nfMMA-TI) for both awake and sleep hours were assessed. ANOVA test was used to compare the average activity during the three recording conditions. RESULTS: On average, a total recording time of 204.7 ± 7.9 hours were provided for each patient. For most patients, ANOVA test showed an absence of significant differences between the recording sessions. CONCLUSIONS: The impact of our results is not negligible: clinicians can find remarkable support to the hypothesis that the use of aligners affects the MMA only in a minority of subjects.

EPA Consensus Project Paper: The Relationship Between Prosthodontic Rehabilitations and Temporomandibular Disorders.

AIM: The aim of this systematic review is to evaluate the relationship between prosthodontic treatment and temporomandibular disorders (TMD). MATERIALS AND METHODS: Two clinical questions have been raised. Can prosthodontic treatment be used as a strategy to manage temporomandibular disorders? Is there any causal relationship between prosthodontic rehabilitation and the onset of TMD? A systematic search was performed in four medical databases to identify Clinical Trials (CT) and Randomized Clinical Trials (RCT) that could answer the two clinical questions. RESULTS: Any articles fulfilling the inclusion criteria were found. Therefore, the best available evidence on TMD management and aetiology is discussed in a scoping review with focus on the relationship with prosthodontic treatment. CONCLUSIONS: Based on current scientific evidence, prosthetic rehabilitation cannot be proposed as a treatment option for TMD patients, based on the effectiveness of other more conservative options as well as the absence of association between features of dental occlusion and TMD. Thanks to the high neuro plastic adaptation skills of the stomatognathic system, prosthodontic rehabilitation cannot be identified as a direct cause of TMD, but clinicians should pay caution when performing relevant occlusal modifications.

Correlation between Parental-Reported Tooth Grinding and Sleep Disorders: Investigation in a Cohort of 741 Consecutive Children.

Purpose: A possible relationship between sleep bruxism (SB) and several sleep disorders has been suggested in children, which could influence sleep quality and quality of life. This study aims to assess such correlations in a large sample of school children. Methods: Parents of 741 consecutive children aged between 8 and 12 years filled the Sleep Disturbance Scale for Children (SDSC). It evaluated 45 items grouped in 8 components: duration of night-time sleep, sleep latency, bedtime problems, sleep quality, night awakenings, nocturnal symptoms, morning symptoms, and daytime sleepiness. An item evaluating parental-reported tooth grinding was also included. Correlation analysis was performed between parental-reported tooth grinding and all the other items. Results: A significant correlation between parental-reported tooth grinding and several sleep disorders concerning bedtime problems, night awakenings, nocturnal symptoms, and morning symptoms has been found. In general, correlation strength of significant pairs was low, ranging from 0.092 (sleep apnea) to 0.234 (movement while falling asleep). Conclusions: Parental-reported tooth grinding in children is correlated, even if weakly, with some sleep disorders concerning the sphere of bedtime problems, night awakenings, nocturnal symptoms, breathing symptoms, and morning symptoms. Further studies are needed to confirm these findings, with particular regard to the consistency of correlation outcomes between the parental reports and the sleep laboratory measures.

International consensus on the assessment of bruxism: Report of a work in progress.

In 2013, consensus was obtained on a definition of bruxism as repetitive masticatory muscle activity characterised by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible and specified as either sleep bruxism or awake bruxism. In addition, a grading system was proposed to determine the likelihood that a certain assessment of bruxism actually yields a valid outcome. This study discusses the need for an updated consensus and has the following aims: (i) to further clarify the 2013 definition and to develop separate definitions for sleep and awake bruxism; (ii) to determine whether bruxism is a disorder rather than a behaviour that can be a risk factor for certain clinical conditions; (iii) to re-examine the 2013 grading system; and (iv) to develop a research agenda. It was concluded that: (i) sleep and awake bruxism are masticatory muscle activities that occur during sleep (characterised as rhythmic or non-rhythmic) and wakefulness (characterised by repetitive or sustained tooth contact and/or by bracing or thrusting of the mandible), respectively; (ii) in otherwise healthy individuals, bruxism should not be considered as a disorder, but rather as a behaviour that can be a risk (and/or protective) factor for certain clinical consequences; (iii) both non-instrumental approaches (notably self-report) and instrumental approaches (notably electromyography) can be employed to assess bruxism; and (iv) standard cut-off points for establishing the presence or absence of bruxism should not be used in otherwise healthy individuals; rather, bruxism-related masticatory muscle activities should be assessed in the behaviour's continuum.

Frequency of awake bruxism behaviours in the natural environment. A 7-day, multiple-point observation of real-time report in healthy young adults.

The aim of this study was to assess awake bruxism (AB) behaviours in a sample of healthy young adults using a smartphone-based application for a real-time report (ie, ecological momentary assessment [EMA], also called experience sampling method [ESM]). Forty-six dental students used a smartphone application that sent 15 alerts at random intervals during the day for 1 week to collect AB self-reports. They had to answer on time by tapping on the display icon that refers to their current condition of jaw muscles: relaxed; teeth contact; teeth clenching; teeth grinding; jaw clenching without teeth contact (ie, bracing). The average frequency of relaxed jaw muscles, as a percentage of answers over the 7 days, was 71.7%. Teeth contact (14.5%) and jaw clenching (10.0%) were the most frequent AB behaviours. No significant gender differences were detected. Interindividual differences were quite relevant, but the overall frequency was in general only moderately variable from day-to-day. Coefficient of variation (CV) was low for the condition "relaxed jaw muscles" (0.44). At the individual level, teeth contact was the most prevalent behaviour, with a 39.1%-52.2% proportion of subjects reporting it at least once a day. During a 7-day observation period, the frequency of real-time report of AB behaviours in a sample of healthy young adults was 28.3%. The low daily variability in the average frequency value for the relaxed jaw muscles condition suggests that EMA may be a reliable strategy to get deeper into the epidemiology of oral behaviours. This investigation introduced EMA principles to the study of AB and provided data on the frequency of AB behaviours in young adults that could be compared to populations with risk/associated factors and possible clinical consequences.

Oro-facial pain and temporomandibular disorders classification systems: A critical appraisal and future directions.

It is a difficult undertaking to design a classification system for any disease entity, let alone for oro-facial pain (OFP) and more specifically for temporomandibular disorders (TMD). A further complication of this task is that both physical and psychosocial variables must be included. To augment this process, a two-step systematic review, adhering to PRISMA guidelines, of the classification systems published during the last 20 years for OFP and TMD was performed. The first search step identified 190 potential citations which ultimately resulted in only 17 articles being included for in-depth analysis and review. The second step resulted in only 5 articles being selected for inclusion in this review. Five additional articles and four classification guidelines/criteria were also included due to expansion of the search criteria. Thus, in total, 14 documents comprising articles and guidelines/criteria (8 proposals of classification systems for OFP; 6 for TMD) were selected for inclusion in the systematic review. For each, a discussion as to their advantages, strengths and limitations was provided. Suggestions regarding the future direction for improving the classification process with the use of ontological principles rather than taxonomy are discussed. Furthermore, the potential for expanding the scope of axes included in existing classification systems, to include genetic, epigenetic and neurobiological variables, is explored. It is therefore recommended that future classification system proposals be based on combined approaches aiming to provide archetypal treatment-oriented classifications.

Comparison of the outcomes of dynamic/static tests and palpation tests in TMD-pain patients.

In addition to palpation tests, dynamic/static tests have been proposed to complement temporomandibular disorders (TMD) patients' evaluation in the clinical setting. The aim of this study was to assess the intra- and inter-observer reliability of the palpation tests and of the dynamic/static tests, and to determine whether those tests would yield comparable outcomes in terms of pain diagnoses. Ninety-eight (N = 98) consecutive adult patients were examined during 2 clinical sessions by 2 independent examiners, based on muscle and joint palpation techniques described in the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). They also underwent dynamic/static tests. The intra-observer reliability of palpation tests was generally poor, with fair-to-good to excellent ICC values only for the superior masseter and intra-oral sites. The inter-observer reliability of palpation was fair-to-good for muscles, but it was poor for the TMJ lateral pole. Both intra- and inter-observer reliability for the dynamic/static tests varied from fair-to-good to excellent. The intra-observer reliability for muscle pain diagnoses based on palpation tests was between poor and fair-to-good, whereas the inter-observer reliability was excellent. The intra-observer reliability for pain diagnoses based on dynamic/static tests was fair-to-good, and the inter-observer reliability varied from fair-to-good to excellent. CONCLUSIONS: Some features of the dynamic/static tests make them potentially more useful than palpation tests for selected clinical purposes, such as discriminating between joint and muscle pain as well as monitoring symptoms course. Thus, findings from this investigation suggest that both tests should be included in the TMD diagnostic algorithms.

[Chewing on bruxism: associations, consequences and management]. / Kauwen op bruxisme. Associaties, gevolgen en behandeling.

In this second part of a diptych on bruxism, the focus is on the associations of this masticatory muscle activity with other sleep-related conditions. Its association with the obstructive sleep apnoea syndrome (OSAS) has been a particular object of study. Bruxism seems to play a protective role in OSAS, although the evidence for this is not yet conclusive. Apart from this possible positive consequence, bruxism also has several negative consequences, for which evidence is available to a greater or lesser extent. For example, bruxism has been associated with temporomandibular pain and dysfunction, periodontal and endodontic problems, failures of restorations and implants, and tooth wear. In some cases, these consequences are severe enough to justify treatment of bruxism. In all other cases, there is no indication for diagnostics and treatment, given the possible positive consequences. If treatment is indicated, modalities should be conservative, like stabilisation appliances, counselling, medication, psychology, and physiotherapy.

[Chewing on bruxism. Diagnosis, imaging, epidemiology and aetiology]. / Kauwen op bruxisme. Diagnostiek, beeldvorming, epidemiologie en oorzaken.

Since the publication of a special issue on bruxism of the NTvT in July 2000, consensus has been reached on bruxism's definition as a repetitive masticatory muscle activity that is characterised by clenching and/or grinding while awake (awake bruxism) or during sleep (sleep bruxism). As yet, however, no consensus exists about the diagnosis of bruxism: sufficient evidence to establish the reliability and validity of the commonly used techniques (self-report, clinical examination, imaging, electromyography, polysomnography) has not yet been produced. Morphological factors are no longer considered important aetiological factors, while increasing evidence suggests aetiological roles for psychosocial, physiological, biological, and exogenous factors. This review paper is the first part of a diptych and is concerned with the definition, diagnostics, epidemiology and possible causes of this disorder. In the second part, that will be published in the next issue, associations of bruxism with other conditions will be discussed, along with its (purported) consequences and its management.

Temporomandibular disorders and dental occlusion. A systematic review of association studies: end of an era?

To answer a clinical research question: 'is there any association between features of dental occlusion and temporomandibular disorders (TMD)?' A systematic literature review was performed. Inclusion was based on: (i) the type of study, viz., clinical studies on adults assessing the association between TMD (e.g., signs, symptoms, specific diagnoses) and features of dental occlusion by means of single or multiple variable analysis, and (ii) their internal validity, viz., use of clinical assessment approaches to TMD diagnosis. The search accounted for 25 papers included in the review, 10 of which with multiple variable analysis. Quality assessment showed some possible shortcomings, mainly related with the unspecified representativeness of study populations. Seventeen (N = 17) articles compared TMD patients with non-TMD individuals, whilst eight papers compared the features of dental occlusion in individuals with TMD signs/symptoms and healthy subjects in non-patient populations. Findings are quite consistent towards a lack of clinically relevant association between TMD and dental occlusion. Only two (i.e., centric relation [CR]-maximum intercuspation [MI] slide and mediotrusive interferences) of the almost forty occlusion features evaluated in the various studies were associated with TMD in the majority (e.g., at least 50%) of single variable analyses in patient populations. Only mediotrusive interferences are associated with TMD in the majority of multiple variable analyses. Such association does not imply a causal relationship and may even have opposite implications than commonly believed (i.e., interferences being the result, and not the cause, of TMD). Findings support the absence of a disease-specific association. Based on that, there seems to lack ground to further hypothesise a role for dental occlusion in the pathophysiology of TMD. Clinicians are encouraged to abandon the old gnathological paradigm in TMD practice.

Validity of different tools to assess sleep bruxism: a meta-analysis.

This systematic review and meta-analysis (MA) aimed to evaluate the diagnostic validity of questionnaires, clinical assessment and portable diagnostic devices compared to the reference standard method polysomnography (PSG) in assessing sleep bruxism (SB). Two reviewers searched electronic databases for diagnostic test accuracy studies that compared questionnaires, clinical assessment or portable diagnostic devices for SB, with the reference standard method PSG, comprising previous studies from all languages and with no restrictions regarding age, gender or time of publication. Of the 351 articles, eight met the inclusion criteria for qualitative, and seven for quantitative analysis. The methodology of selected studies was evaluated using the Quality Assessment Tool for Diagnostic Accuracy Studies (QUADAS-2). The studies were divided and analysed over three groups: three studies evaluating questionnaires, two regarding the clinical assessment of tooth wear and three covering portable diagnostic devices. The MA indicated that portable diagnostic devices showed the best validity of all evaluated methods, especially as far as a four-channel EMG/ECG recording is concerned. Questionnaires and the clinical assessment can be used as screening methods to identify non-SB individuals, although it is not that good in identifying subjects with SB. The quality of evidence identified through GRADEpro, was from very low-to-moderate, due to statistical heterogeneity between studies.

Prevalence of sleep bruxism and awake bruxism in different chronotype profiles: Hypothesis of an association.

Sleep (SB) and awake bruxism (AB) recognize a multifactorial etiology and have a relationship with several psychological factors. Psychological disorders have recently been associated also with the chronotype, which is the propensity for an individual to be especially active at a particular time during a 24-h period. Based on the chronotype, the two extreme profiles are morningness and eveningness individuals. Due to the relationship that both the chronotype and bruxism have with psychological factors and the fact that performing tasks not compatible with chronotype can trigger stress, this review presents the hypothesis that the prevalence of SB and AB can differ with the various chronotype profiles. New perspectives for the study of bruxism etiology may emerge from investigations on the topic.

Is there an association between verbal school bullying and possible sleep bruxism in adolescents?

The aim of this study was to determine the association between verbal school bullying and possible sleep bruxism (SB) in adolescents. A case-control study was carried out at the population level by recruiting 13- to 15-year-old participants among the attendants of schools of Itabira, Brazil. The case group was composed of 103 adolescents with possible SB (i.e. self- or parental-reported), while the control group included 206 adolescents without possible SB. All participants answered a questionnaire on the occurrence of their involvement in verbal school bullying episodes, based on the National School of Health Research (PeNSE) as well as an evaluation of their economic class according to the criteria of the Brazilian Association of Research Companies. Pearson's chi-square, McNemar test and conditional logistic regression were performed to assess the association between possible SB, verbal school bullying and economic class. There were 134 (43·3%) participants who reported involvement in verbal school bullying episodes as a victim, bully or both. The majority of them were males (90·3%). Adolescents with possible SB were more likely to have been involved in episodes of verbal school bullying (OR: 6·20; 95% CI: 3·67-10·48). Based on these findings, it can be suggested that possible SB in young teenagers is associated with a history of episodes of verbal school bullying.

Subjects with temporomandibular joint disc displacement do not feature any peculiar changes in body posture.

The presence of body posture changes among patients with temporomandibular disorders (TMD) has been a controversial topic in dentistry. Based on that, the aim of this study was to assess postural features of pain-free subjects with internal derangement of the temporomandibular joint (TMJ), viz. disc displacement, when compared to subjects with normal disc position. A total of 21 subjects with unilateral, pain-free TMJ disc displacement (DD) and 21 subjects without any TMD signs of symptoms were assessed for body posture changes by means of posturographic evaluation of several body segments and postural balance reactions through the centre of mass during jaw movements using a balance platform. Posturographic measurements showed the absence of any significant differences between the two groups in any of the outcome parameters. Similarly, all balance platform responses to mandibular movements were not different between groups. There are no significant differences in body posture between subjects with and without unilateral disc displacement in the temporomandibular joint. Such observations, indicating a well-preserved postural balance in the presence of TMJ internal derangement, put into serious question the potential influence of TMJ disorders on whole body posture and viceversa.

Agreement between clinical and portable EMG/ECG diagnosis of sleep bruxism.

The aim of this study was to compare clinical sleep bruxism (SB) diagnosis with an instrumental diagnosis obtained with a device providing electromyography/electrocardiography (EMG/ECG) recordings. Forty-five (N = 45) subjects (19 males and 26 females, mean age 28 ± 11 years) were selected among patients referring to the Gnathology Unit of the Dental School of the University of Torino. An expert clinician assessed the presence of SB based on the presence of one or more signs/symptoms (i.e., transient jaw muscle pain in the morning, muscle fatigue at awakening, presence of tooth wear, masseter hypertrophy). Furthermore, all participants underwent an instrumental recording at home with a portable device (Bruxoff; OT Bioelettronica, Torino, Italy) allowing a simultaneous recording of EMG signals from both the masseter muscles as well as heart frequency. Statistical procedures were performed with the software Statistical Package for the Social Science v. 20.0 (SPSS 20.0; IBM, Milan, Italy). Based on the EMG/ECG analysis, 26 subjects (11 males, 15 females, mean age 28 ± 10 years) were diagnosed as sleep bruxers, whilst 19 subjects (7 males, 12 females, mean age 30 ± 10 years) were diagnosed as non-bruxers. The correlation between the clinical and EMG/ECG SB diagnoses was low (ϕ value = 0.250), with a 62.2% agreement (28/45 subjects) between the two approaches (kappa = 0.248). Assuming instrumental EMG/ECG diagnosis as the standard of reference for definite SB diagnosis in this investigation, the false-positive and false-negative rates were unacceptable for all clinical signs/symptoms. In conclusion, findings from clinical assessment are not related with SB diagnosis performed with a portable EMG/ECG recorder.

Single- or multiple-session viscosupplementation protocols for temporomandibular joint degenerative disorders: a randomized clinical trial.

The aim of the study was to compare the effectiveness of two single-session protocols, either adopting high- (protocol A) or medium-molecular weight hyaluronic acid (protocol B), with the reference five-session protocol of temporomandibular joint (TMJ) lavage plus viscosupplementation (protocol C) in the management of chronic TMJ degenerative disorders. A randomized clinical trial (RCT) with ten participants per treatment group was designed, with multiple observation points, ending at 6 months after treatment. Pain levels on a 10-point VAS scale were selected as the primary outcome variable to rate treatment effectiveness, along with a number of secondary outcome parameters. Findings showed that Group C patients had the highest decrease in pain levels. Nonparametric permutation analyses revealed that the global effect of treatment was significantly different between the three protocols (P = 0·024). Pairwise comparisons showed that the differences of treatment effect between the two single-session interventions were negligible (global P-value = 0·93). On the contrary, the five-session protocol was significantly superior to both single-session protocols (global P-values ranging from 0·003 to 0·012). In conclusion, in a population of age-, sex-, and psychosocial aspects-matched study groups, the standard of reference five-session protocol proved to be superior at 6 months as far as the decrease in pain levels was concerned, whilst there were no differences between the two single-session interventions. The absence of differences in treatment effect as for some other secondary clinical outcome variables may suggest that there is further space for future investigations attempting to reduce the number of multiple interventions for TMJ viscosupplementation.

Diagnostic accuracy of portable instrumental devices to measure sleep bruxism: a systematic literature review of polysomnographic studies.

This study systematically reviews the sleep bruxism (SB) literature published in the MEDLINE and Scopus databases to answer the following question: What is the validity of the different portable instrumental devices that have been proposed to measure SB if compared with polysomnographic (PSG) recordings assumed as the gold standard? Four clinical studies on humans, assessing the diagnostic accuracy of portable instrumental approaches (i.e. Bitestrip, electromyography (EMG)-telemetry recordings and Bruxoff) with respect to PSG, were included in the review. Methodological shortcomings were identified by QUADAS-2 quality assessment. Findings showed contrasting results and supported only in part the validity of the described diagnostic devices with respect to PSG. The positive predictive value (PPV) of the Bitestrip device was 59-100%, with a sensitivity of 71-84·2%, whilst EMG-telemetry recordings had an unacceptable rate of false-positive findings (76·9%), counterbalanced by an almost perfect sensitivity (98·8%). The Bruxoff device had the highest accuracy values, showing an excellent agreement with PSG for both manual (area under ROC = 0·98) and automatic scoring (0·96) options as well as for the simultaneous recording of events with respect to PSG (0·89-0·91). It can be concluded that the available information on the validity of portable instrumental diagnostic approaches with respect to PSG recordings is still scarce and not solid enough to support any non-PSG technique's employ as a stand-alone diagnostic method in the research setting, with the possible exception of the Bruxoff device that needs to be further confirmed with future investigations.

Effectiveness of treatment with viscosupplementation in temporomandibular joints with or without effusion.

The objective of this study was to determine whether the effectiveness of viscosupplementation with hyaluronic acid (HA) in patients with temporomandibular joint (TMJ) degenerative disorders depends on the presence of intra-articular effusion. In this study of case-control design, two groups of 25 patients were recruited: patients with a clinical diagnosis of painful chronic TMJ osteoarthritis and magnetic resonance imaging (MRI) signs of TMJ degeneration, with (effusion group) or without (no effusion group) MRI evidence of TMJ effusion. All patients underwent five weekly single-needle arthrocenteses plus medium molecular weight HA and 6 months of follow-up. Several clinical outcome parameters were assessed. For all variables, analysis of variance (ANOVA) for repeated measures was performed to assess the existence of significant within-group and between-group treatment effects. Over time, both groups showed significant improvements in all outcome parameters, which were maintained at the 6-month follow-up (P<0.05). Between-group comparisons showed that the treatment effects did not differ significantly for either the primary outcome variable (pain levels: F=0.849, P=0.548) or secondary outcome variables (chewing efficiency: F=0.854, P=0.544; functional limitation: F=1.35, P=0.226; mouth opening: F=0.658, P=0.707). The null hypothesis that there are no differences in treatment effectiveness between patients with and without effusion could not be rejected.