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.

Depressive symptoms account for differences between self-reported versus polysomnographic assessment of sleep quality in women with myofascial TMD.

Patients with temporomandibular disorder (TMD) report poor sleep quality on the Pittsburgh Sleep Quality Index (PSQI). However, polysomnographic (PSG) studies show meagre evidence of sleep disturbance on standard physiological measures. The present aim was to analyse self-reported sleep quality in TMD as a function of myofascial pain, PSG parameters and depressive symptomatology. PSQI scores from 124 women with myofascial TMD and 46 matched controls were hierarchically regressed onto TMD presence, ratings of pain intensity and pain-related disability, in-laboratory PSG variables and depressive symptoms (Symptoms Checklist-90). Relative to controls, TMD cases had higher PSQI scores, representing poorer subjective sleep and more depressive symptoms (both P < 0·001). Higher PSQI scores were strongly predicted by more depressive symptoms (P < 0·001, R2 = 26%). Of 19 PSG variables, two had modest contributions to higher PSQI scores: longer rapid eye movement latency in TMD cases (P = 0·01, R2 = 3%) and more awakenings in all participants (P = 0·03, R2 = 2%). After accounting for these factors, TMD presence and pain ratings were not significantly related to PSQI scores. These results show that reported poor sleep quality in TMD is better explained by depressive symptoms than by PSG-assessed sleep disturbances or myofascial pain. As TMD cases lacked typical PSG features of clinical depression, the results suggest a negative cognitive bias in TMD and caution against interpreting self-report sleep measures as accurate indicators of PSG sleep disturbance. Future investigations should take account of depressive symptomatology when interpreting reports of poor sleep.

Is bruxism a disorder or a behaviour? Rethinking the international consensus on defining and grading of bruxism.

Inspired by the international consensus on defining and grading of bruxism (Lobbezoo F, Ahlberg J, Glaros AG, Kato T, Koyano K, Lavigne GJ et al. J Oral Rehabil. 2013;40:2), this commentary examines its contribution and underlying assumptions for defining sleep bruxism (SB). The consensus' parsimonious redefinition of bruxism as a behaviour is an advance, but we explore an implied question: might SB be more than behaviour? Behaviours do not inherently require clinical treatment, making the consensus-proposed 'diagnostic grading system' inappropriate. However, diagnostic grading might be useful, if SB were considered a disorder. Therefore, to fully appreciate the contribution of the consensus statement, we first consider standards and evidence for determining whether SB is a disorder characterised by harmful dysfunction or a risk factor increasing probability of a disorder. Second, the strengths and weaknesses of the consensus statement's proposed 'diagnostic grading system' are examined. The strongest evidence-to-date does not support SB as disorder as implied by 'diagnosis'. Behaviour alone is not diagnosed; disorders are. Considered even as a grading system of behaviour, the proposed system is weakened by poor sensitivity of self-report for direct polysomnographic (PSG)-classified SB and poor associations between clinical judgments of SB and portable PSG; reliance on dichotomised reports; and failure to consider SB behaviour on a continuum, measurable and definable through valid behavioural observation. To date, evidence for validity of self-report or clinician report in placing SB behaviour on a continuum is lacking, raising concerns about their potential utility in any bruxism behavioural grading system, and handicapping future study of whether SB may be a useful risk factor for, or itself a disorder requiring treatment.

Perspectives on next steps in classification of oro-facial pain - part 2: role of psychosocial factors.

This study was initiated by a symposium, in which the present authors contributed, organised by the International RDC/TMD Consortium Network in March 2013. The purpose of the study was to review the status of biobehavioural research - both quantitative and qualitative - related to oro-facial pain (OFP) with respect to the aetiology, pathophysiology, diagnosis and management of OFP conditions, and how this information can optimally be used for developing a structured OFP classification system for research. In particular, we address representation of psychosocial entities in classification systems, use of qualitative research to identify and understand the full scope of psychosocial entities and their interaction, and the usage of classification system for guiding treatment. We then provide recommendations for addressing these problems, including how ontological principles can inform this process.

Perspectives on next steps in classification of oro-facial pain - part 1: role of ontology.

The purpose of this study was to review existing principles of oro-facial pain classifications and to specify design recommendations for a new system that would reflect recent insights in biomedical classification systems, terminologies and ontologies. The study was initiated by a symposium organised by the International RDC/TMD Consortium Network in March 2013, to which the present authors contributed. The following areas are addressed: problems with current classification approaches, status of the ontological basis of pain disorders, insufficient diagnostic aids and biomarkers for pain disorders, exploratory nature of current pain terminology and classification systems, and problems with prevailing classification methods from an ontological perspective. Four recommendations for addressing these problems are as follows: (i) develop a hypothesis-driven classification structure built on principles that ensure to our best understanding an accurate description of the relations among all entities involved in oro-facial pain disorders; (ii) take into account the physiology and phenomenology of oro-facial pain disorders to adequately represent both domains including psychosocial entities in a classification system; (iii) plan at the beginning for field-testing at strategic development stages; and (iv) consider how the classification system will be implemented. Implications in relation to the specific domains of psychosocial factors and biomarkers for inclusion into an oro-facial pain classification system are described in two separate papers.

Validity of self-reported sleep bruxism among myofascial temporomandibular disorder patients and controls.

Sleep bruxism (SB), primarily involving rhythmic grinding of the teeth during sleep, has been advanced as a causal or maintenance factor for a variety of oro-facial problems, including temporomandibular disorders (TMD). As laboratory polysomnographic (PSG) assessment is extremely expensive and time-consuming, most research testing this belief has relied on patient self-report of SB. The current case-control study examined the accuracy of those self-reports relative to laboratory-based PSG assessment of SB in a large sample of women suffering from chronic myofascial TMD (n = 124) and a demographically matched control group without TMD (n = 46). A clinical research coordinator administered a structured questionnaire to assess self-reported SB. Participants then spent two consecutive nights in a sleep laboratory. Audiovisual and electromyographic data from the second night were scored to assess whether participants met criteria for the presence of 2 or more (2+) rhythmic masticatory muscle activity episodes accompanied by grinding sounds, moderate SB, or severe SB, using previously validated research scoring standards. Contingency tables were constructed to assess positive and negative predictive values, sensitivity and specificity, and 95% confidence intervals surrounding the point estimates. Results showed that self-report significantly predicted 2+ grinding sounds during sleep for TMD cases. However, self-reported SB failed to significantly predict the presence or absence of either moderate or severe SB as assessed by PSG, for both cases and controls. These data show that self-report of tooth grinding awareness is highly unlikely to be a valid indicator of true SB. Studies relying on self-report to assess SB must be viewed with extreme caution.

Osteopenic consequences of botulinum toxin injections in the masticatory muscles: a pilot study.

Patients with temporomandibular muscle and joint disorder (TMJD) increasingly seek and receive treatment for their pain with botulinum toxin (BoNTA; botulinum toxin A). Used intramuscularly in therapeutic doses, it produces localised paresis. Such paresis creates risk of reduced bone mineral density, or 'disuse osteopenia'. Animal studies have frequently used BoNTA as a model of paralysis to induce bone changes within short periods. Osteopenic effects can be enduring in animals but have yet to be studied in humans. This is the first study in humans to examine bone-related consequences of BoNTA injections in the masticatory muscles, comparing oral and maxillofacial radiologists' ratings of trabecular bone patterns in the condyles of patients with TMJD exposed to multiple masticatory muscle injection sessions with BoNTA to a sample of patients with TMJD unexposed to masticatory muscle injections with BoNTA. Cone-beam computed tomography (CBCT)-derived images of bilateral condyles were evaluated in seven patients with TMJD receiving 2+ recent BoNTA treatment sessions for facial pain and nine demographically matched patients with TMJD not receiving BoNTA treatment. Two oral and maxillofacial radiologists evaluated CBCT images for evidence of trabecular changes consistent with osteopenia. Both evaluators noted decreased density in all participants exposed to BoNTA and in none of the unexposed participants (P < 0.001). No other abnormalities associated with reduced loading were detected. These findings need replication in a larger sample and over a longer time period, to ensure safety of patients with TMJD receiving multiple BoNTA injections for their pain.

Masticatory muscle sleep background electromyographic activity is elevated in myofascial temporomandibular disorder patients.

Despite theoretical speculation and strong clinical belief, recent research using laboratory polysomnographic (PSG) recording has provided new evidence that frequency of sleep bruxism (SB) masseter muscle events, including grinding or clenching of the teeth during sleep, is not increased for women with chronic myofascial temporomandibular disorder (TMD). The current case-control study compares a large sample of women suffering from chronic myofascial TMD (n = 124) with a demographically matched control group without TMD (n = 46) on sleep background electromyography (EMG) during a laboratory PSG study. Background EMG activity was measured as EMG root mean square (RMS) from the right masseter muscle after lights out. Sleep background EMG activity was defined as EMG RMS remaining after activity attributable to SB, other orofacial activity, other oromotor activity and movement artefacts were removed. Results indicated that median background EMG during these non-SB event periods was significantly higher (P < 0·01) for women with myofascial TMD (median = 3·31 µV and mean = 4·98 µV) than for control women (median = 2·83 µV and mean = 3·88 µV) with median activity in 72% of cases exceeding control activity. Moreover, for TMD cases, background EMG was positively associated and SB event-related EMG was negatively associated with pain intensity ratings (0-10 numerical scale) on post-sleep waking. These data provide the foundation for a new focus on small, but persistent, elevations in sleep EMG activity over the course of the night as a mechanism of pain induction or maintenance.

Prevalence of myofascial temporomandibular disorder in US community women.

This study estimates the prevalence of the myofascial subtype of temporomandibular disorders (M-TMD) defined by Research Diagnostic Criteria (RDC), and relates that prevalence to the surveyed report of facial pain. From among 20 000 women selected at random in the NY metropolitan area who completed a telephone survey of facial pain, 2000 were invited for an RDC/TMD examination; 782 examinations were completed. Prevalence was estimated in analyses that were weighted to correct sampling biases. Differences among demographic strata were evaluated with logistic regression. The prevalence of M-TMD was estimated to be 10.5% (95% CL = 8.5-13.0%). Prevalence was significantly higher among younger women, among women of lower socio-economic status, among Black women, and among non-Hispanic women. The report of facial pain in the telephone survey (10.1%) had high specificity for M-TMD diagnosis (94.7%), but low sensitivity (42.7%). M-TMD is a fairly common disorder among American women. Among those reporting facial pain during the last month, half met RDC palpation criteria for M-TMD; thus, a formal physical examination is imperative to establish this diagnosis. Prevalence varies with age, socio-economic status, race and Hispanic ethnicity. A substantial number of RDC-diagnosed cases of M-TMD did not report facial pain in the survey; the reason for this requires further study.

Reliability of clinician judgements of bruxism.

Bruxism is considered to be a parafunctional disorder requiring treatment and is viewed as a risk factor for the development of temporomandibular disorders (TMDs). The purpose of this investigation is to examine the reliability of clinician judgements of bruxism severity. Twenty dentists who are faculty members in a dental school examined 29 stone casts and gold-plated models of individual teeth for evidence of bruxism. Ordinal ratings of bruxism severity for the 29 augmented models were made on two occasions, approximately 3 months apart. Inter-rater reliability among all clinicians, evaluated using intraclass correlation coefficients (ICCs), was poor at both time one and time two (i.e. ICC = 0.33 and 0.32, respectively), with somewhat better reliability found among those clinicians with above-average time elapsed since completion of dental training (i.e. ICC = 0.48 and 0.50 for time 1 and time 2, respectively). Three-month test-retest reliabilities were fair (ICC = 0.46) for the full group of raters and were unrelated to clinicians' degree of confidence in their ratings. These results indicate a need to standardize methods for clinical assessment of bruxism. Additionally, they have implications for studies using clinical assessments of bruxism to test the association between bruxism and other conditions such as TMDs.

Is bruxism severity a predictor of oral splint efficacy in patients with myofascial face pain?

Both the efficacy and mechanism of any effect of oral splint therapy for patients with temporomandibular disorders (TMDs) are a matter of controversy. To address these issues, this study tested the hypothesis that oral splints produce the most marked pain relief for those TMD patients with myofascial face pain (MFP) who also brux (i.e. grind or clench) more than other MFP patients. In a 6-week randomized controlled clinical trial, 52 women with MFP were randomly assigned to receive either a full-coverage hard acrylic splint or a palatal-only splint. Bruxism was assessed both by self-report and by an objective assessment of molar microwear changes over a 2-week period prior to the start of the trial. Tested across multiple outcome measures, results indicated that those receiving the full-coverage splint had marginally better improvement on some pain-related measures than those receiving the palatal splint, but severity of bruxism did not moderate the therapeutic effect of the full-coverage splint. These findings strongly argue against the belief that oral splints reduce MFP by reducing bruxism and raise questions about the importance of bruxism in the maintenance of MFP.

Childhood victimization and pain in adulthood: a prospective investigation.

Evidence of the relationship between childhood abuse and pain problems in adulthood has been based on cross-sectional studies using retrospective self-reports of childhood victimization. The objective of the current study was to determine whether childhood victimization increases risk for adult pain complaints, using prospective information from documented cases of child abuse and neglect. Using a prospective cohort design, cases of early childhood abuse or neglect documented between 1967 and 1971 (n = 676) and demographically matched controls (n = 520) were followed into young adulthood. The number of medically explained and unexplained pain complaints reported at follow-up (1989-1995) was examined. Assessed prospectively, physically and sexually abused and neglected individuals were not at risk for increased pain symptoms. The odds of reporting one or more unexplained pain symptoms was not associated with any childhood victimization or specific types (i.e. sexual abuse, physical abuse, or neglect). In contrast, the odds of one or more unexplained pain symptoms was significantly associated with retrospective self-reports of all specific types of childhood victimization. These findings indicate that the relationship between childhood victimization and pain symptoms in adulthood is more complex than previously thought. The common assumption that medically unexplained pain is of psychological origin should be questioned. Additional research conducting comprehensive physical examinations with victims of childhood abuse and neglect is recommended.

Widespread pain and the effectiveness of oral splints in myofascial face pain.

BACKGROUND: The research literature reaches inconsistent conclusions about the efficacy of oral splints for treating myofascial face pain. This investigation hypothesizes that their effectiveness varies as a function of the presence or absence of widespread pain. METHODS: In a randomized, controlled clinical trial, 63 women with myofascial face pain were assigned to use of either an active, maxillary, flat-plane, hard acrylic splint or a palatal splint that did not interfere with occlusion. Participants also were classified according to the presence or absence of widespread pain throughout the body. After six weeks, groups were compared regarding pain on palpation, self-reported pain and functional outcome. RESULTS: Overall, the findings showed a modest tendency for subjects receiving the active vs. the palatal splint to exhibit improvement on self-reported pain and functional outcome. On further division of the sample into subjects with local vs. widespread pain, the general pattern showed that patients with widespread pain who received an active splint did not experience improvement, while patients with local pain who received the active splint did. CONCLUSIONS: The presence or absence of widespread pain may help to define the specific circumstances under which oral splints should be prescribed for patients with myofascial face pain. CLINICAL IMPLICATIONS: Clinicians should screen patients with myofascial face pain for the presence of widespread pain, since this comorbid symptom pattern may be a contraindication for the use of oral splints.

Comorbid fibromyalgia accounts for reduced fecundity in women with myofascial face pain.

OBJECTIVE: This study examined factors related to reduced fecundity among women with myofascial face pain (MFP) arising from hypotheses concerning the role of neurohormonal factors in MFP and associated conditions. DESIGN: Fecundity rates among 162 MFP cases and 173 demographically equivalent acquaintance female controls were compared. OUTCOME MEASURES: Fecundity indicators and factors underlying differential fecundity rates were investigated. RESULTS: It was determined that female cases with MFP had significantly fewer children and were more likely to have never been pregnant. Although women with MFP were more likely than controls to indicate that volitional factors related to their health discouraged them from any or additional pregnancies, these factors did not account for lower rates of fecundity. MFP cases also did not differ from controls on self-reported indicators of infertility. Moreover, we show that reduced fecundity was restricted to the subgroup of MFP cases who reported a history of fibromyalgia. CONCLUSIONS: Reduced fecundity in women with MFP is restricted to those who self-report a history of fibromyalgia. Possible mechanisms for reduced fecundity in fibromyalgia are discussed. These findings highlight the need to screen for widespread pain among women with regional myofascial pain syndromes.

Myofascial face pain. Clinical characteristics of those with regional vs. widespread pain.

BACKGROUND: The authors conducted a study to determine whether there are differences in salient clinical characteristics between patients who have both myofascial face pain, or MFP, and comorbid fibromyalgia, or FM, and patients who have MFP but not FM. METHODS: The authors enrolled in the study 162 female subjects who had histories of MFP. In physical examinations at the time of initial consultation, they recorded facial pain signs and symptoms. At the research interview follow-up (seven years post-consultation), participants were screened for a lifetime history of FM and other health problems. In addition, psychiatric interviewers conducted the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, Third Edition-Revised, to assess each patient's history of depression and other psychiatric disorders. RESULTS: Of the 162 participants, 38 (23.5 percent) reported a history of FM. At the time of treatment for MFP, both the FM and non-FM groups had similar signs and symptoms of MFP. At the time of the research interview follow-up, participants with FM histories were significantly less likely than those without FM histories to report that they were free of MFP. On recall, those with FM histories reported experiencing more symptoms of MFP. Those with FM histories also were more likely to have had major depression and to report somatization symptoms. Finally, those who had FM more commonly had a history of facial pain's interference with social and occupational functioning and had more severe pain than did those without FM. CONCLUSIONS: Patients who have MFP and a history of widespread pain suggestive of FM are likely to have more persistent and debilitating MFP and to have higher rates of depression and somatization symptoms than those who have no history of widespread pain.

Somatosensory amplification and affective inhibition are elevated in myofascial face pain.

OBJECTIVE: This study was designed to determine whether affective inhibition and somatosensory amplification are elevated in patients with a history of myofascial face pain (MFP). These processes may underlie a tendency to express distress in somatic rather than affective terms, leading to somatized or masked depression. DESIGN: Women (n = 162) with a history of MFP were compared with demographically equivalent women (n = 173) without MFP histories on self-report scales of affective inhibition and somatosensory amplification. Structured psychiatric interviews and health histories were conducted. In addition, a first-degree relative of 106 myofascial face pain subjects and 118 control subjects completed these same self-report scales. RESULTS: MFP cases and controls differed significantly on measures of affective inhibition and somatosensory amplification. History of depression or current psychological distress did not account for group differences. Elevated levels of somatosensory amplification were confined to MFP women with active symptoms. Finally, although both somatosensory amplification and affective inhibition showed a tendency to run in families, familial transmission did not account for case/control differences. CONCLUSIONS: Affective inhibition and somatosensory amplification are likely to be elevated in patients with MFP. Although not accounted for by psychiatric symptomatology, the possibility that these response styles are reactive to coping with chronic face pain cannot be ruled out.

Phantom tooth pain: a new look at an old dilemma.

UNLABELLED: The aim of this paper is to review the current knowledge of phantom tooth pain, a neuropathic facial pain disorder, thought to result from peripheral nerve injury. Phantom tooth pain is a deafferentation pain disorder of persistent toothache in teeth that have been denervated (usually by root canal treatment) or pain in the area formerly occupied by teeth prior to their extraction. The pain usually extends to the facial structures adjacent to tissues that have undergone deafferentation. The clinical characteristics, differential diagnosis, epidemiology, and treatment of phantom tooth pain are reviewed. Suggestions for further research include the need for controlled treatment trials and modification of current criteria. CONCLUSIONS: Phantom tooth pain has much in common with other phantom pain disorders. In the absence of controlled clinical trials specifically directed to phantom tooth pain, treatment should be guided by standards used for other neuropathic pain disorders. Revised diagnostic criteria for phantom tooth pain are proposed.