Aberrant occlusal sensitivity in adults with increased somatosensory amplification: a case-control study.

OBJECTIVES: Occlusal sensitivity (OS)-the ability to detect fine objects between opposing teeth-mainly relies on the activity of mechanoreceptors located in the periodontal ligament. We tested whether somatosensory amplification (SSA)-the tendency to perceive normal somatic sensations as being intense, noxious, and disturbing, which plays a critical role in hypervigilance-affects OS. MATERIALS AND METHODS: We measured OS in 66 adults divided into three groups based on their SSA scores (LowSSA, Intermediate - IntSSA, HighSSA) by asking them to bite on aluminum foils (8 to 72 µm thick) and a sham foil, and report whether they felt each foil. We performed 20 trials for each thickness and sham condition (each participant was tested 120 times), and compared the frequency of correct answers (%correct) among groups after adjusting for participants' trait anxiety, depression, self-reported oral behaviors, and masseter cross-sectional area. RESULTS: %correct was affected by the interaction Foil Thickness-by-SSA (p = 0.007). When tested with the 8 µm foil, the HighSSA group had a lower %correct than the IntSSA (contrast estimate [95% CI]: -14.2 [-25.8 - -2.6]; p = 0.012) and the LowSSA groups (-19.1 [-31.5 - -6.6]; p = 0.001). Similarly, with the 24 µm foil, the HighSSA group had a lower %correct compared to the IntSSA (-12.4 [-24.8-0.1]; p = 0.048) and the LowSSA groups (-10.8 [-22.5-0.8]; p = 0.073). CONCLUSION: Individuals with high SSA present with an aberrant occlusal sensitivity. CLINICAL RELEVANCE: Our findings provide novel insights into the relationship between occlusal perception and psychological factors, which may influence an individual's ability to adapt to dental work.

Continuing professional development needs in pain management for Canadian health care professionals: A cross sectional survey.

Background: Continuing professional development is an important means of improving access to effective patient care. Although pain content has increased significantly in prelicensure programs, little is known about how postlicensure health professionals advance or maintain competence in pain management. Aims: The aim of this study was to investigate Canadian health professionals' continuing professional development needs, activities, and preferred modalities for pain management. Methods: This study employed a cross-sectional self-report web survey. Results: The survey response rate was 57% (230/400). Respondents were primarily nurses (48%), university educated (95%), employed in academic hospital settings (62%), and had ≥11 years postlicensure experience (70%). Most patients (>50%) cared for in an average week presented with pain. Compared to those working in nonacademic settings, clinicians in academic settings reported significantly higher acute pain assessment competence (mean 7.8/10 versus 6.9/10; P < 0.002) and greater access to pain specialist consultants (73% versus 29%; P < 0.0001). Chronic pain assessment competence was not different between groups. Top learning needs included neuropathic pain, musculoskeletal pain, and chronic pain. Recently completed and preferred learning modalities respectively were informal and work-based: reading journal articles (56%, 54%), online independent learning (44%, 53%), and attending hospital rounds (43%, 42%); 17% had not completed any pain learning activities in the past 12 months. Respondents employed in nonacademic settings and nonphysicians were more likely to use pocket cards, mobile apps, and e-mail summaries to improve pain management. Conclusions: Canadian postlicensure health professionals require greater access to and participation in interactive and multimodal methods of continuing professional development to facilitate competency in evidence-based pain management.

Contexte: Le développement professionnel continu est un moyen important d'améliorer l'accès à des soins efficaces pour les patients. Bien que le contenu lié à la douleur ait augmenté de manière significative dans les programmes préalables à l'autorisation d'exercer, on sait peu de choses sur la façon dont les professionnels de la santé après licenciés améliorent ou maintiennent leurs compétences en matière de gestion de la douleur.Objectifs: Étudier les besoins, les activités et les préférences de développement professionnel continu des cliniciens canadiens en matière de gestion de la douleur.Méthodes: Enquête Web transversale d'auto-évaluation.Résultats: Le taux de réponse au sondage était de 57 % (230/400). Les répondants étaient principalement des infirmières (48 %), des diplômés universitaires (95 %), des employés en milieu hospitalier universitaire (62 %), avec ≥11 ans d'expérience après l'obtention du permis (70 %). La plupart des patients (> 50 %) pris en charge dans une semaine moyenne présentaient des douleurs. Comparativement à ceux qui travaillent dans des milieux non universitaires, les cliniciens en milieu universitaire ont signalé une compétence d'évaluation de la douleur aiguë significativement plus élevée (moyenne de 7,8/10 contre 6,9/10; P < 0,002) et un meilleur accès aux consultants en gestion de la douleur (73 % contre 29 %; P < 0,0001). La compétence d'évaluation de la douleur chronique n'était pas différente entre les groupes. Les principaux besoins d'apprentissage comprenaient la douleur neuropathique, la douleur musculo-squelettique et la douleur chronique. Les modalités d'apprentissage récemment achevées et préférées étaient respectivement informelles et basées sur le travail: lecture d'articles de journaux (56 %, 54 %), apprentissage indépendant en ligne (44 %, 53 %) et participation à des visites à l'hôpital (43 %, 42 %); 17 % n'avaient effectué aucune activité d'apprentissage de la douleur au cours des 12 derniers mois. Les répondants hors les médecins et ceux employés dans des milieux non universitaires étaient plus susceptibles d'utiliser des cartes de poche, des applications mobiles et des résumés par e-mail pour améliorer la gestion de la douleur.Conclusions: Les professionnels de la santé canadiens après l'obtention du permis d'exercice ont besoin d'un meilleur accès et d'une plus grande participation aux méthodes interactives et multimodales de développement professionnel continu pour faciliter la compétence en gestion de la douleur fondée sur des données probantes.

Identification of central amygdala and trigeminal motor nucleus connectivity in humans: An ultra-high field diffusion MRI study.

The neuroanatomical circuitry of jaw muscles has been mostly explored in non-human animals. A recent rodent study revealed a novel circuit from the central amygdala (CeA) to the trigeminal motor nucleus (5M), which controls biting attacks. This circuit has yet to be delineated in humans. Ultra-high diffusion-weighted imaging data from the Human Connectome Project (HCP) allow in vivo delineation of circuits identified in other species-for example, the CeA-5M pathway-in humans. We hypothesized that the CeA-5M circuit could be resolved in humans at both 7 and 3 T. We performed probabilistic tractography between the CeA and 5M in 30 healthy young adults from the HCP database. As a negative control, we performed tractography between the basolateral amygdala (BLAT) and 5M, as CeA is the only amygdalar nucleus with extensive projections to the brainstem. Connectivity strength was operationalized as the number of streamlines between each region of interest. Connectivity strength between CeA-5M and BLAT-5M within each hemisphere was compared, and CeA-5M circuit had significantly stronger connectivity than the BLAT-5M circuit, bilaterally at both 7 T (all p < .001) and 3 T (all p < .001). This study is the first to delineate the CeA-5M circuit in humans.

Ten-year mixed-method evaluation of prelicensure health professional student self-reported learning in an interfaculty pain curriculum.

Introduction: Student perspectives on interprofessional pain education are lacking. Objectives: The purpose of this study was to evaluate ratings of knowledge acquisition and effective presentation methods for prelicensure health professional students attending the University of Toronto Centre for the Study of Pain Interfaculty Pain Curriculum (Canada). Methods: A 10-year (2009-2019) retrospective longitudinal mixed-methods approach comprising analysis and integration of quantitative and qualitative data sets was used to evaluate 5 core University of Toronto Centre for the Study of Pain Interfaculty Pain Curriculum learning sessions. Results: A total of 10, 693 students were enrolled (2009-2019) with a mean annual attendance of 972 students (±SD:102). The mean proportion of students rating "agree/strongly agree" for knowledge acquisition and effective presentation methods across sessions was 79.3% (±SD:3.4) and 76.7% (±SD:6.0), respectively. Knowledge acquisition or presentation effectiveness scores increased, respectively, over time for 4 core sessions: online self-study pain mechanisms module (P = 0.03/P < 0.001), online self-study opioids module (P = 0.04/P = 0.019), individually selected in-person topical pain sessions (P = 0.03/P < 0.001), and in-person patient or interprofessional panel session (P = 0.03). Qualitative data corroborated rating scores and expanded insight into student expectations for knowledge acquisition to inform real-world clinical practice and interprofessional collaboration; presentation effectiveness corresponded with smaller session size, individually selected sessions, case-based scenarios, embedded knowledge appraisal, and opportunities to meaningfully interact with presenters and peers. Conclusion: This study demonstrated positive and increasing prelicensure student ratings of knowledge acquisition and effective presentation methods across multifaceted learning sessions in an interfaculty pain curriculum. This study has implications for pain curriculum design aimed at promoting students' collaborative, patient-centered working skills.See commentary: Trouvin A-P. "Ten-year mixed method evaluation of prelicensure health professional student self-reported learning in an interfaculty pain curriculum": a view on pain education. PAIN Rep 2022;7:e1031.Students attending learning sessions at the University of Toronto Interfaculty Pain Curriculum (2009-2019) in Toronto, Canada, self-report high ratings of knowledge acquisition and effective presentation methods.

Effectiveness of the Lorodent Probiotic Lozenge in Reducing Plaque and Streptococcus mutans Levels in Orthodontic Patients: A Double-Blind Randomized Control Trial.

Orthodontic patients are at a significant risk for oral diseases due to increased plaque accumulation and oral bacterial dysbiosis. We aimed to determine the efficacy of the commercially available Lorodent Probiotic Complex at reducing plaque accumulation and Streptococcus mutans bacterial levels in adolescent orthodontic patients. Sixty adolescents undergoing fixed orthodontic treatment for a minimum of 6 months were recruited in a randomized, double-blind, parallel-group, placebo-controlled trial. They received either Lorodent probiotic lozenge (intervention, n = 30) or placebo lozenge (control, n = 30) orally every day for a 28-day administration period. Participants were assessed at four appointments (T1-T4) over a total of 56 days. Compliance and lozenge satisfaction were monitored. Saliva samples and supragingival plaques were collected for evaluation of S. mutans levels. Clinical assessment using a Plaque Index (PI) was used. Compliance with lozenge intake of all participants was over 90%. There was no significant change in the PI and composite PI scores in both placebo and probiotic groups at each time frame (all p > 0.05) or the relative S. mutans DNA levels in the saliva and plaque between the probiotic and placebo groups. The findings of high compliance and satisfaction with the probiotic lozenges combined with the study's rigorous design offer a baseline for subsequent testing of further potential probiotics (of varying formulations, concentrations), especially in adolescents.

Impact of Stress and Trait Anxiety on the Sensory and Jaw Motor Responses to a Tonic Orofacial Nociceptive Stimulus.

AIMS: To investigate how trait anxiety and stress jointly affect the sensory and jaw motor responses to a tonic orofacial nociceptive stimulus. METHODS: Orthodontic separators were placed between the first molars in 45 adults with low (n = 14), intermediate (n = 17), and high (n = 14) trait anxiety. Tooth pain, occlusal discomfort, tooth clenching (as a jaw motor behavior), and situational stress were measured three times a day for 5 days using visual analog scales. Mixed-effects regression models were used to evaluate the sensory and motor outcome measures. RESULTS: Pain, discomfort, and frequency of tooth-clenching trajectories were affected by trait anxiety (P = .007, P < .001, and P = .055, respectively) and stress (P < .001, P < .001, and P = .044, respectively). Individuals with high anxiety reported their highest pain (17.7 ± 2.9 mm) and discomfort (35.2 ± 4.1 mm) 24 hours earlier than those with low anxiety (pain: 15.9 ± 2.6 mm, discomfort: 28.8 ± 3.7 mm). Tooth clenching decreased progressively in response to the stimulus (P < .001). CONCLUSION: A tonic orofacial nociceptive stimulus triggers an avoidance jaw motor behavior. Both trait anxiety and situational stress heighten the sensory response to such a stimulus, but weakly affect the motor response to it.

Short-term Effects of a First-Line Treatment Including Counseling and Self-Management Strategies on Chronic TMD Muscle Pain and Awake Bruxism in Women.

AIMS: To evaluate the short-term effects of a standardized first-line noninvasive approach (FL-A) including counseling and self-management strategies on pain, masticatory muscle tenderness, and awake bruxism in women with chronic temporomandibular disorder myalgia (mTMD) and to test whether patients' trait anxiety predicted their response to treatment. METHODS: FL-A was administered to 14 women with chronic mTMD (mean age ± SD = 33.8 ± 11.1 years; 8 with Graded Chronic Pain Scale [GCPS] grade I and 6 with grade II). Its effects on facial pain, masticatory muscle tenderness, and spontaneous awake bruxism episodes were evaluated using questionnaires, surface electromyography, and quantitative sensory testing. General linear models were used to test FL-A efficacy after 1 (T1) and 2 (T2) months. RESULTS: FL-A reduced pain (from baseline [T0] to T2, P = .010), the frequency of awake bruxism episodes (T0 to T1, P = .024), and their intensity by about 30% (T0 to T1, P < .001). Pressure pain thresholds at the masticatory muscle locations increased significantly from T0 to T2 (P < .001). Patients' trait anxiety decreased significantly from T0 to T2 (P = .030). Trait anxiety measured at baseline was not correlated with relative changes in pain (T0 to T2, P = .248). CONCLUSION: In the short term, FL-A reduces facial pain, masticatory muscle tenderness, and awake bruxism in women with chronic mTMD with low disability. A conservative management strategy should be prioritized for the initial management of these patients.

Ten years of interfaculty pain curriculum at the University of Toronto: impact on student learning.

INTRODUCTION: Delivery of interprofessional pain education for prelicensure healthcare professionals is strongly recommended to advance a workforce ready for collaborative practice and to improve the quality and outcomes of pain care. OBJECTIVES: We report a 10-year (2009-2019) longitudinal evaluation of a 20-hour undergraduate Interfaculty Pain Curriculum (IPC) delivered to students in the Faculties of Dentistry, Nursing, Pharmacy, and Medicine (also including the Departments of Physical Therapy, Occupational Therapy and Physician Assistant) at the University of Toronto, Canada. The IPC follows a constructivist approach to facilitate interactive and multifaceted learning. METHODS: Evaluation methods based on the Kirkpatrick model were used to appraise changes in participating students' pain knowledge and beliefs and their ability to collaboratively develop an interprofessional pain management plan. RESULTS: A total of 10,693 students participated over the 10-year study period. The mean annual attendance was 972 students and participation to the program increased significantly over the years. Overall, the IPC was effective in improving students' mean pain knowledge and beliefs scores; however, the mean knowledge score gains were negatively correlated with time, likely related to increased uniprofessional pain education. Although an increasing trend in mean interprofessional pain management plan scores was observed, the scores were not significantly correlated with time. CONCLUSIONS: The interactive and multifaceted IPC is consistently effective in improving knowledge and beliefs and interprofessional pain management care plan development among participating student cohorts. Future inquiry is required to better understand the mechanisms behind student learning in interprofessional pain education to enhance pain curriculum development and delivery.

Baseline resting-state functional connectivity determines subsequent pain ratings to a tonic ecologically valid experimental model of orofacial pain.

ABSTRACT: Pain is a subjective experience with significant individual differences. Laboratory studies investigating pain thresholds and experimental acute pain have identified structural and functional neural correlates. However, these types of pain stimuli have limited ecological validity to real-life pain experiences. Here, we use an orthodontic procedure-the insertion of an elastomeric separator between teeth-which typically induces mild to moderate pain that peaks within 2 days and lasts several days. We aimed to determine whether the baseline structure and resting-state functional connectivity of key regions along the trigeminal nociceptive and pain modulatory pathways correlate with subsequent peak pain ratings. Twenty-six healthy individuals underwent structural and resting-state functional MRI scanning before the placement of a separator between the first molar and second premolar, which was kept in place for 5 days. Participants recorded pain ratings 3 times daily on a 100-mm visual analogue scale. Peak pain was not significantly correlated with diffusion metrics of the trigeminal nerve or gray matter volume of any brain region. Peak pain did, however, positively correlate with baseline resting-state functional connectivity between the thalamus contralateral to the separator and bilateral insula, and negatively correlated with connectivity between the periaqueductal gray (PAG) and core nodes of the default mode network (medial prefrontal and posterior cingulate cortices). The ascending (thalamic) nociceptive and the descending (PAG) pain modulatory pathways at baseline each explained unique variation in peak pain intensity ratings. In sum, preinterventional functional neural architecture of both systems determined the individual pain experience to a subsequent ecologically valid pain stimulus.

Sex Differences in the Temporalis Tendon-Aponeurotic Complex: An in vivo MRI Macroscopic Analysis in Children and Adolescents.

The tendon-aponeurosis complex (TAC) of the temporalis dissipates forces produced during function. Abnormally reduced temporalis TACs have been found in individuals with chronic muscular temporomandibular disorders - a painful musculoskeletal condition that is more frequent in women than men. Whether there are sex differences in the temporalis TAC in healthy individuals is currently unknown. Here, we characterized and measured the temporalis TAC in healthy male and female young individuals between 5 and 15 years old to determine whether the volume of the temporalis TAC and the TAC-to-muscle ratio are different between males and females. We collected MRI studies from 90 healthy individuals, including equal numbers (15 M and 15 F) of young children (ages 5-7), children (9-11), and adolescents (13-15) and segmented the right temporalis and its TAC using software. Using general linear models, we tested the effect of sex, age, and their interaction on the volumes of the temporalis and its TAC, and the TAC-to-muscle ratio. The volumes of the temporalis and its TAC increased with age (both p < 0.001) and were not affected by sex (p = 0.252 and p = 0.179) or by the interaction sex-by-age (p = 0.079 and p = 0.095, respectively). The TAC-to-muscle ratio did not change significantly with age (p = 0.655) and was not affected by sex (0.438) or by the interaction sex-by-age (0.524). We provide, for the first time, volumetric data of the temporalis TAC in children and adolescents. The volumes of the temporalis TAC and the TAC-to-muscle ratio are not different between male and female individuals until the age of 15.

Jaw muscle activity patterns in women with chronic TMD myalgia during standardized clenching and chewing tasks.

Objective: To examine jaw muscle activity of women with chronic temporomandibular myalgia (mTMD). It was hypothesized that mTMD patients had a different masticatory muscle activity, increased work during isometric clenching, and a reduced chewing frequency as compared to TMD-free subjects.Methods: The electromyographic (EMG) activity of temporalis anterior (TA) and masseter (MM) of 27 women with mTMD and 18 TMD-free women was recorded during clenching tasks and while chewing. EMG indices comparing the activity of paired jaw muscles were computed.Results: Women with TMD myalgia had greater muscular work than controls (p = 0.025). The activity of TA and MM were similar between right and left sides in both groups. mTMD patients had a greater activity of MM than TA (p = 0.028). No between-groups differences were found in chewing rate.Conclusion: Women with mTMD showed an abnormal recruitment of the jaw-closing muscles during functional tasks, which may predispose to further tissue injury.

Evaluation of masticatory muscle response to clear aligner therapy using ambulatory electromyographic recording.

INTRODUCTION: Patients undergoing clear aligner therapy (CAT) report muscle tenderness and produce wear facets on their aligner trays. However, little is known about the masticatory muscle response to clear aligners. Here, we measured the activity of the masseter during CAT using ambulatory electromyography. We also explored whether psychological traits modulate the masticatory muscle response to CAT. METHODS: Using portable data loggers, we recorded the electromyographic (EMG) activity in the right masseter muscle of 17 healthy adults without temporomandibular disorder (16 females, 1 male; mean age ± standard deviation, 35.3 ± 17.6 years) commencing treatment with CAT over 4 weeks, under the following conditions: week 1 without aligners (baseline), week 2 with a passive aligner (dummy), week 3 with their first active aligner (active1), and week 4 with their second active aligner (active2). We used a mixed-effect model to test differences in EMG activity over the 4-weeks and a general linear model to test the effect of psychological traits on EMG activity. RESULTS: The EMG activity of the masseter increased significantly with aligners compared with baseline. The largest relative increase in EMG activity was seen during the dummy (152%; P <0.001) and active1 (155%; P <0.001) stages. During active2, the activity of the masseter decreased significantly toward baseline levels. Participants' trait anxiety was positively associated with increases in EMG activity (P = 0.027). CONCLUSIONS: CAT is associated with a transient increase in masticatory muscle activity, possibly because of an increase in wake-time parafunctional tooth clenching. Temporomandibular disorder-free patients adapt well to CAT as the masticatory muscle activity decreases toward baseline levels after 2 weeks.

Increased somatosensory amplification is associated with decreased pressure pain thresholds at both trigeminal and extra-trigeminal locations in healthy individuals.

BACKGROUND: The diagnosis of temporomandibular disorders (TMD) is based on patient history and physical examination, and may require medical imaging. Masticatory muscle palpation is essential to make a diagnosis of TMD. However, the response of masticatory muscles to mechanical pressure stimuli depends on many physical and psychological factors. OBJECTIVE: This study aimed at determining the impact of somatosensory amplification (SSA)-an estimate of somatic awareness and bodily hypervigilance-on pressure pain thresholds (PPTs) measured at both trigeminal and extra-trigeminal locations in healthy individuals. METHODS: PPTs were measured at the right anterior temporalis and superficial masseter, and the thenar eminence of the right hand in one hundred healhty individuals (69F, 31M), divided in three groups based on their SSA scores: low (N = 32), intermediate (N = 34) and high (N = 34). General linear models were used to test between-group differences in PPTs including sex as a covariate. The level of significance was set at P < .05. RESULTS: Individuals with high SSA had lower PPTs at the anterior temporalis than individuals with low (P = .006) and intermediate (P = .001) SSA. No significant between-group differences were found in PPTs measured at the masseter (P = .372). PPTs measured at the thenar eminence were significantly lower in the high than the low SSA group (P = .009). Females had lower PPTs at the masseter than males (P = .021) but not at other muscle locations (all P > .05). CONCLUSION: Increased somatosensory amplification is associated with decreased pressure pain thresholds at both trigeminal and extra-trigeminal locations in healthy individuals. SSA could be a potential confounder while diagnosing TMD and evaluating treatment outcomes.

The intensity of awake bruxism episodes is increased in individuals with high trait anxiety.

OBJECTIVES: Trait anxiety is associated with an increased occurrence of awake bruxism episodes, a behavior characterized by clenching of the teeth contributing to temporomandibular disorders in some individuals. Here we measured the activity of the masseter and the intensity and duration of spontaneous wake-time tooth clenching episodes in healthy individuals with different levels of trait anxiety (TA). MATERIALS AND METHODS: Two hundred fifty-five individuals completed a web survey. Using their TA scores, we allocated them in low (< 20th percentile of the TA score distribution), intermediate (between 20th and 80th ), and high (> 80th) TA groups. We analyzed the electromyographic (EMG) activity of the right masseter during a 15-min silent reading task in forty-three individuals with low (n = 12), intermediate (n = 17), and high TA (n = 14). We tested between-group differences in EMG activity of the masseter, as well as postural activity-the muscular activity that maintains mandibular posture, and amplitude and duration of spontaneous tooth clenching episodes. RESULTS: The activity of the masseter (mean ± SEM %maximum voluntary contraction/MVC) was greater in the high TA (10.23 ± 0.16%MVC) than the intermediate (8.49 ± 0.16%MVC) and low (7.97 ± 0.22%MVC) TA groups (all p < 0.001). Postural activity did not differ between groups (all p > 0.05). The EMG amplitude of tooth clenching episodes was greater in the high TA (19.97 ± 0.21 %MVC) than the intermediate (16.40 ± 0.24%MVC) and low (15.48 ± 0.38 %MVC) TA groups (all p < 0.05). The cumulative duration of clenching episodes was not different between groups (p = 0.390). CONCLUSIONS: Increased TA is associated with both increased masseter muscle activity and intensity of wake-time tooth clenching episodes. CLINICAL RELEVANCE: TA may contribute significantly to masticatory muscle overload.

Impact of clear aligner therapy on tooth pain and masticatory muscle soreness.

BACKGROUND: Clinical findings suggest that orthodontic treatment with clear aligners (clear aligner therapy/CAT) may cause masticatory muscle soreness in some patients. OBJECTIVE: This multi-site prospective study investigated tooth pain and masticatory muscle soreness and tenderness in patients undergoing CAT and explored whether psychological traits affected these outcomes. METHODS: Twenty-seven adults (22F, 5M; mean age ± SD=35.3 ± 17.6 years) about to start CAT were recruited at three clinics. During CAT, they reported on 100-mm visual analogue scales their tooth pain, masticatory muscle soreness and stress three times per day over 4 weeks (week 1 = baseline; week 2 = dummy aligner; week 3 = first active aligner; week 4 = second active aligner). Pressure pain thresholds (PPTs) were measured at the masseter and temporalis at baseline and after week 4. Mixed models were used to evaluate the outcome measures over time. RESULTS: Clear aligner therapy caused mild tooth pain, which was greater with the passive than the first and second active aligners (both P < .001). Mild and clinically not relevant masticatory muscle soreness was produced by all aligners (all P < .05), with the first active aligner producing less soreness than the dummy aligner (P < .001). PPTs did not change significantly after 4 weeks. Both tooth pain and masticatory muscle soreness were affected by stress and trait anxiety, whilst muscle soreness was affected also by oral behaviours. CONCLUSIONS: In the short term, CAT produces tooth pain and masticatory muscle soreness of limited significance. Frequent oral behaviours are related to increased masticatory muscle soreness during CAT. The medium- and long-term effects of CAT should be further explored.

Music Modulates Awake Bruxism in Chronic Painful Temporomandibular Disorders.

OBJECTIVE: In this experimental study, we aimed to determine whether guided music listening (GML) - a music intervention based on models of mood mediation and attention modulation - modulates masticatory muscle activity and awake bruxism in subjects with chronic painful muscular temporomandibular disorders (TMD myalgia, mTMD), a condition causing a significant burden to patients, their families, and healthcare systems. BACKGROUND: Awake bruxism - a stress behavior characterized by clenching of the teeth - is a strong contributor to chronic mTMD. GML modulates psychological stress and motor responses and could thus reduce muscle activity in chronic musculoskeletal conditions, including mTMD. METHODS: We recorded the electromyographic (EMG) activity in the right masseter of 14 women with chronic (>6 months) mTMD (median [IQR] = 39.5.3 [24.3] years) and 15 pain-free women (median [IQR] = 30.0 [3.5] years) during a GML session, including 3 music (stressful, relaxing, and participants' favorite music) and a no-music (pink noise) control blocks, each lasting 15 minutes. We measured the motor effort of the right masseter relative to the participants' maximum voluntary contraction (MVC), the muscular effort to maintain mandibular posture (EMGposture ), and to produce spontaneous awake bruxism episodes (EMGbruxism ), and the duration and frequency of spontaneous awake bruxism episodes. We tested between-group and within-group (between blocks) differences, as well as the effect of the interaction group by experimental block on these outcome measures. RESULTS: In both groups, EMGposture was significantly affected by the interaction group by experimental block (P < .001). Compared to pink noise [mean (95% CI); mTMD: 2.2 (1.6-2.8) %MVC; Controls: 1.1 (0.5-1.7) %MVC], EMGposture increased during the stressful music block [contrast estimate (95% CI); mTMD: +0.8 (0.7-0.8) %MVC; Controls: +0.3 (0.3-0.4) %MVC; both P < .001], and decreased during the relaxing [mTMD: -0.4 (-0.5 to -0.4) %MVC; Controls: -0.3 (-0.4 to -0.3) %MVC; both P < .001] and favorite [mTMD: -0.5 (-0.6 to -0.5) %MVC; Controls: -0.5 (-0.5 to -0.4) %MVC; both P < .001] music blocks. EMGposture was greater in mTMD individuals than controls during the favorite music [contrast estimate (95% CI): +1.1 (0.2-1.9) %MVC; P = .019] and the pink noise [+1.1 (0.2-2.0) %MVC; P = .014] blocks. EMGbruxism was significantly affected by the interaction group by experimental block (P < .001). In mTMD participants, compared to the pink noise block [mean (95% CI); 23.8 (16.0-31.6) %MVC], EMGbruxism increased during the stressful music block [contrast estimate (95% CI); +10.2 (8.6-11.8) %MVC], and decreased during the relaxing [-6.2 (-8.1 to -4.3) %MVC; P < .001] and favorite [-10.2 (-12.2 to -9.1) %MVC; P < .001] music blocks. These effects were not observed in the control group [mean (95% CI); pink noise: 19.3 (10.9-27.6); stressful: 21.2 (12.9-29.4) %MVC; relaxing: 21.6 (13.3-29.9) %MVC; favorite: 24.2 (15.8-32.7) %MVC; all P > .05]. EMGbruxism was significantly greater in mTMD participants than controls during the stressful music block [contrast estimate (95% CI): +12.9 (1.6-24.2) %MVC; P = .026). GML did not affect the duration or the frequency of awake bruxism in either group (median [IQR], mTMD: 23.5 [96.7] s, range 1-1300 seconds; Controls: 5.5 [22.5], range 0-246 seconds; P = .108). The frequency of awake bruxism episodes was greater in the mTMD group compared to controls only during the pink noise block (median [IQR], mTMD: 5 [15.3] episodes, range 0-62 episodes; Controls: 1 [3] episode, range 0-27 episodes; P = .046). No significant between-group differences were found in either the overall time spent engaging in awake bruxism (median [IQR], mTMD: 23.5 [96.7] s, range 1-1300 seconds; Controls: 5.5 [22.5], range 0-246 seconds; P = .108), or during each block (all P > .05). CONCLUSIONS: In subjects with chronic mTMD, relaxing music and the individual's favorite music decreased the muscular effort during spontaneous awake bruxism episodes by 26% and 44% (relative changes), respectively. In contrast, stressful music increases it by about 43%. Because of its positive effects on awake bruxism, GML with selected music could be a promising and non-invasive component of a multimodal approach for the management of chronic mTMD.

Structural abnormalities in the temporalis musculo-aponeurotic complex in chronic muscular temporomandibular disorders.

Some forms of chronic pain are thought to be driven and maintained by nociceptive input, which can drive plasticity within nociceptive pathways. We have previously identified abnormalities along the entire nociceptive pathway in chronic myalgic temporomandibular disorders (mTMD), including the trigeminal nerves, brainstem pathways, and in the thalamus and somatosensory cortex. These data suggest that there is a peripheral nociceptive drive in mTMD, but the source of this nociceptive activity remains unknown. Here, our aim was to determine whether structural abnormalities exist in the muscles of mastication of patients with chronic mTMD. Specifically, we tested whether the volume of the temporalis muscle and its tendon-aponeurosis complex (TAC, a structure that dissipates forces in a muscle) in mTMD patients differ compared to age- and sex-matched controls. To do so, we segmented these structures on T1-weighted structural magnetic resonance images. We found that muscle volumes in mTMD were not different to controls. However, the mTMD group had significantly smaller volumes of the bilateral temporalis TAC, and thus a smaller TAC-to-muscle volume ratio. These findings were consistent across 2 independent cohorts of 17 mTMD patients, compared to 17 age- and sex-matched controls. We propose a model where reduced TAC-to-muscle ratio could result in a predisposition to muscle tissue injury. In sum, abnormalities of the temporalis muscles in mTMD supports our hypothesis that chronic mTMD pathophysiology may be related to peripheral nociceptive barrage originating from the muscles of mastication.

Short-term effects of fixed orthodontic appliance on concentrations of mutans streptococci and persister cells in adolescents.

INTRODUCTION: Orthodontic patients are at an increased risk for developing caries. Dental caries is a biofilm-mediated disease, with mutans streptococci (MS) as the primary etiologic bacterial group. It has been suggested that persister cells (PCs), a subset of cells within the biofilm, contribute to the chronic infectious nature of dental caries. PC formation can be induced by environmental stressors such as orthodontic treatment. The aim of this study was to quantify MS, aerobic and facultative anaerobe bacterial PC proportions from plaque samples during the initial stage of orthodontic treatment. This study is the first to analyze the role of PCs in a population of patients highly susceptible to caries, that is, patients undergoing orthodontic treatment. METHODS: Plaque samples were collected from 17 participants (11 males and 6 females; age range: 11-18 years) before and 1 month after insertion of fixed orthodontic appliances. Percentages of MS and PCs were determined with selective media and a classical persister microbial assay, respectively. RESULTS: There was a statistically significant decrease in %MS (P = 0.039) but no statistically significant difference in %PCs (P = 0.939) after 1 month of orthodontic appliance placement. CONCLUSION: Our study illustrated the technical feasibility of analysis of PCs in plaque samples of patients during orthodontic treatment and revealed that PC formation during orthodontic treatment is highly variable across individuals.

Association of Streptococcus mutans collagen binding genes with severe childhood caries.

OBJECTIVE: An important factor in the assessment of caries risk is the presence of specific oral microflora, especially Streptococcus mutans. Some S. mutans strains possess proteins capable of binding collagen, such as the Cnm and Cbm proteins. The aim is to determine the presence of S. mutans strains carrying collagen binding proteins in a group of subjects with severe early childhood caries (S-ECC). MATERIALS AND METHODS: S. mutans strains isolated from 15 S-ECC children were analyzed for collagen binding domains (cbd) of the cnm (cbd/cnm) and cbm (cbd/cbm) genes and their ability to bind to collagen. RESULTS: S. mutans strains positive for cbd/cnm or cbd/cbm were only found in 3 subjects with the most severe caries profile, with one subject having both cbd/cnm and cbd/cbm, and the other two with one of each. cnm/cbm-positive S. mutans strains bound to collagen substrate more avidly compared with negative S. mutans strains from each of the three groups. CONCLUSIONS: Our findings of an association between the presence of the collagen binding domains of the cnm/cbm genes in plaque S. mutans and the most aggressive form of caries profile in children offer a potential strategy to identify an individual's risk for caries progression. Our study should be replicated in other settings and communities in longitudinal and longer-term studies. CLINICAL RELEVANCE: Our data offer a potential tool in the caries risk management and assessment in children.

Impact of post-orthodontic dental occlusion on masticatory performance and chewing efficiency.

BACKGROUND: Whether precise orthodontic detailing of occlusion impacts masticatory function is unknown. In this study, we aimed to assess the impact of post-orthodontic dental occlusion on masticatory performance and chewing efficiency. MATERIALS AND METHODS: Fifty-four adults who completed orthodontic treatment were categorized into two groups using the American Board of Orthodontics (ABO) model grading system: one meeting ABO standards (ABO, N = 29), the other failing to meet them (non-ABO, N = 25). The electromyographic (EMG) signals of the anterior temporalis (AT) and superficial masseter muscles were recorded bilaterally during static (clenching) and dynamic (gum chewing) tests. Chewing efficiency was measured by calculating the median particle size (MPS) and broadness of particle distribution (BPD) after five chewing trials of experimental silicone food at a standardized chewing rate. RESULTS: Participants of the ABO group had a slightly more symmetric activation of the AT muscles during clenching (P = 0.016) and chewed a gum at a slower rate (P = 0.030). During the standardized chewing test with silicone food, ABO subjects had slightly greater EMG potentials at all muscle locations than non-ABO individuals (all P < 0.05). MPS and BDP did not differ significantly between groups (all P > 0.05). LIMITATIONS: The severity of the initial malocclusion of the study participants was not in the statistical model as a potential confounder on the outcome measures. CONCLUSIONS: Meeting ABO standards contributes to a slightly more balanced activation of the temporalis muscles during clenching and more efficient muscle recruitment during chewing but does not improve chewing efficiency.