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.

Sleep bruxism etiology: the evolution of a changing paradigm.

Various definitions, classifications and theories been ascribed to bruxism. Knowledge gained through expanding research initiatives have transformed some of the concepts that were once held as truths. Sleep bruxism is no longer considered a parasomnia nor is its etiology believed to be based on purely mechanical factors or psychological Issues. It is now considered to be primarily a sleep-related movement disorder with a yet to be determined multifactorial etiology involving complex multisystem physiological processes. Dental practitioners should recognize the transformation occurring in the study of sleep bruxism, understand the evolution in both definitions and classification of this phenomenon and embrace and consider new concepts related to its etiology. This paradigm shift will certainly affect the daily practice of dentistry.

Bruxism defined and graded: an international consensus.

To date, there is no consensus about the definition and diagnostic grading of bruxism. A written consensus discussion was held among an international group of bruxism experts as to formulate a definition of bruxism and to suggest a grading system for its operationalisation. The expert group defined bruxism as a repetitive jaw-muscle activity characterised by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible. Bruxism has two distinct circadian manifestations: it can occur during sleep (indicated as sleep bruxism) or during wakefulness (indicated as awake bruxism). For the operationalisation of this definition, the expert group proposes a diagnostic grading system of 'possible', 'probable' and 'definite' sleep or awake bruxism. The proposed definition and grading system are suggested for clinical and research purposes in all relevant dental and medical domains.

Somnology 101: a primer on sleep disorders, their impact on society, and a role for dentistry.

Sleep is necessary for our existence. It is one-third of a commitment to health along with nutrition and exercise. While we spend one-third of our lives asleep, studies show one-third of the U.S. population suffers with a significant sleep disorder at some point in their lifetime. This manuscript introduces sleep and sleep disorders, focuses on those sleep disorders within the domain of dentistry, and addresses contributions the dental community can make toward specific sleep problems.

Occlusion factors influencing the magnitude of sleep bruxism activity.

The biomechanical load during strong bruxism activity reportedly causes many dental/oral problems. However, it is unknown whether the magnitude of muscle activity during sleep is controllable. In this study, the relationship between the magnitude of muscle activity during sleep and types of tooth contacts was examined, including anterior and posterior guidance, in order to clarify how occlusion factors contribute to sleep bruxism (SB). An EMG-2-axis accelerometer system was used for monitoring patterns and activities of SB. Bruxchecker was used to evaluate tooth contacts during SB, and a condylograph was used to measure posterior guidance (sagittal condylar inclination). Results show that grinding rather than clenching or tapping was observed in the high SB group, and there was Incisor-Canine-Premolar-Molar (ICPM) tooth contact during SB grinding movement. The canine occlusal guidance (COG) was flatter in the low SB group than in the moderate SB group. Relative canine occlusal guidance (rCOG), which is the difference between the sagittal condylar inclination (SCI) and COG, was larger in the low SB group than that in the high SB group. These findings suggest that the grinding pattern must be controlled to prevent strong bruxism, and that the muscle activity during bruxism can be reduced by controlling the tooth contact pattern during SB grinding.

Relationship of tooth grinding pattern during sleep bruxism and temporomandibular joint status.

The purpose of this study was to investigate the relationship between tooth grinding pattern during sleep bruxism and temporomandibular joint (TMJ) status based on condylar movement. Fifty subjects (21 males and 29 females) wore a bruxism recording device, BruxChecker, to record their grinding pattern during sleep bruxism. The grinding pattern was categorized into laterotrusive grinding (LG) and mediotrusive side grinding (MG). Furthermore, LG was divided into three types; incisor-canine (IC), incisor-canine-premolar (ICP) and incisor-canine-premolar-molar (ICPM) type. Condylar movements were also recorded using computer-aided axiograph to evaluate the signs of TMJ hypermobility. The average maximum separation distance of excursion and incursion and the average maximum condylar lateral deviation during protrusion/retrusion and open/close movements in the ICPM type and the ICPM+MG type were larger than those of the IC and ICP types. While reconstructing the occlusion, it is important to take into consideration the presence of bruxing patterns of the ICPM type and mediotrusive side grinding.

Relationship of tooth grinding pattern during sleep bruxism and dental status.

Tooth grinding during sleep is thought to be one of the important factors causing oral diseases. However, no evidence is available regarding the relationship between the dental status and tooth contact during sleep bruxism. The purpose of this clinical study was to investigate the relationship between oral diseases and tooth grinding patterns during sleep bruxism. Fifty subjects (21 men and 29 women) were selected. The clinical attachment level, tooth mobility, noncarious cervical lesion (NCL) and hypersensitivity were examined in each tooth. Subjects wore a bruxism-recording device to visualize the grinding pattern during sleep bruxism. The grinding pattern was categorized into laterotrusive grinding (LG) and mediotrusive side grinding (MG). Furthermore, LG was divided into three types: incisor-canine (IC), incisor-canine-premolar (ICP), and incisor-canine-premolar-molar (ICPM) types. The average attachment level and tooth mobility of the ICPM and ICPM+MG types were much more aggravating than those of the IC or ICP types. The NCL encountered in the ICPM type was more aggravating than the other types. The average NCL of the ICPM type was significantly larger than that of the IC (p = 0.01), the ICP (p = 0.05), the ICP+MG (p = 0.05) and the ICPM+MG (p = 0.05) types and MG (p = 0.01). The average hypersensitivity of the ICP type was significantly greater than that of the IC type (p = 0.05). There was a moderate correlation between the attachment level and mobility. It was concluded that grinding patterns during sleep bruxism should be considered as a probable causative factor in the development of dental problems related to clinical attachment level, tooth mobility, NCL, and hypersensitivity, especially the ICPM type and mediotrusive grinding that seems to be the pattern that could more easily deteriorate the dental condition.

Identification of a sleep bruxism subgroup with a higher risk of pain.

Sleep bruxism research diagnostic criteria (SB-RDC) have been applied since 1996. This study was performed to validate these criteria and to challenge the hypothesis that pain is associated with lower frequencies of orofacial activities. Polygraphic recordings were made of 100 individuals presenting with a clinical diagnosis of sleep bruxism and 43 control individuals. TwoStep Cluster analyses (SPSS) were performed with sleep bruxism variables to reveal groupings among sleep bruxers and control individuals. Participants completed questionnaires during screening, diagnosis, and recording sessions. Cluster analysis identified three subgroups of sleep bruxers. Interestingly, 45 of the 46 sleep bruxers with values below SB-RDC were classified in the low-frequency cluster. These individuals were more likely to complain of pain and fatigue of masticatory muscles than were the higher-frequency sleep bruxers (odds ratios > 3.9, p < 0.01). Sleep bruxers were distributed among three heterogeneous groups. Sleep bruxers with low frequencies of orofacial activities were more at risk of reporting pain.

Bruxism and orofacial movements during sleep.

Several issues remain to be clarified in the future research and management of SB. It is important to differentiate SB from other normal sleep orofacial activities and concomitant sleep disorders. Other orofacial activities may obscure the diagnosis of SB and may give an ambiguous clinical picture when evaluating treatment efficacy. Laboratory recordings provide a more specific diagnosis. Most of the clinical signs (e.g., tooth wear, masseter hypertrophy) are not exclusive to SB but could be concomitant with other habits or activities during wakefulness. No pathologic features in the central nervous system, such as a dysfunction of the dopaminergic system, have been observed in SB patients. Recent neurophysiologic studies have suggested that SB is a powerful microarousal event associated with central and autonomic nervous system activity during sleep. The additive contribution of psychosocial stress cannot be overlooked. There have been no recent major breakthroughs in SB management. Cognitive and behavioral managements, which include stress management, lifestyle changes, or improved coping mechanisms, may be beneficial. Oral splint appliances are useful to protect teeth from damage. A few medications (e.g., benzodiazepines, muscle relaxants) may be helpful for a short-term period, particularly when there is secondary pain, but controlled studies are needed to assess their efficacy, safety, and patient acceptance and tolerance.

Different effects of nocturnal parafunction on the masticatory system: the Weak Link Theory.

It is proposed that damage to the masticatory system from intense parafunction can be assessed more accurately by the Weak Link Theory. The theory predicts that the more intense and the more prolonged the forces, the more the tendency of damage to either. 1. the periodontal tissue; 2. the teeth; or 3. the orofacial structures. To test the theory, 22 subjects were selected based on reports of nocturnal bruxism. Each was assessed for masticatory system breakdown on the Russell Periodontal Index, the Helkimo Dysfunction Index, and a Tooth Wear Index. A Bruxcore (Forgione, A. 1974 J Dent Res 53:127) was used to obtain an objective score of bruxism. Five of eleven subjects with mild bruxism scored high on only one index. Significantly more subjects (ten of eleven) with moderate to severe bruxism scored high on one index only.

Treatments for hypersensitive noncarious cervical lesions: a Practitioners Engaged in Applied Research and Learning (PEARL) Network randomized clinical effectiveness study.

BACKGROUND: The Practitioners Engaged in Applied Research and Learning (PEARL) Network conducted a three-armed randomized clinical study to determine the comparative effectiveness of three treatments for hypersensitive noncarious cervical lesions (NCCLs): use of a potassium nitrate dentifrice for treatment of hypersensitivity, placement of a resin-based composite restoration and placement of a sealant. METHODS: Seventeen trained practitioner-investigators (P-Is) in the PEARL Network enrolled participants (N = 304) with hypersensitive posterior NCCLs who met enrollment criteria. Participants were assigned to treatments randomly. Evaluations were conducted at baseline and at one, three and six months thereafter. Primary outcomes were the reduction or elimination of hypersensitivity as measured clinically and by means of patient-reported outcomes. RESULTS: Lesion depth and pretreatment sensitivity (mean, 5.3 on a 0- to 10-point scale) were balanced across treatments, as was sleep bruxism (present in 42.2 percent of participants). The six-month participant recall rate was 99 percent. Treatments significantly reduced mean sensitivity (P < .01), with the sealant and restoration groups displaying a significantly higher reduction (P < .01) than did the dentifrice group. The dentifrice group's mean (standard deviation) sensitivity at six months was 2.1 (2.1); those of the sealant and restoration groups were 1.0 (1.6) and 0.8 (1.4), respectively. Patient-reported sensitivity (to cold being most pronounced) paralleled clinical measurements at each evaluation. CONCLUSIONS: Sealing and restoration treatments were effective overall in reducing NCCL hypersensitivity. The potassium nitrate dentifrice reduced sensitivity with increasing effectiveness through six months but not to the degree offered by the other treatments. Practical Implications. Sealant or restoration placement is an effective method of immediately reducing NCCL sensitivity. Although a potassium nitrate dentifrice did reduce sensitivity slowly across six months, at no time was the reduction commensurate with that of sealants or restorations.

Does tooth wear status predict ongoing sleep bruxism in 30-year-old Japanese subjects?

PURPOSE: This study investigated whether tooth wear status can predict bruxism level. MATERIALS AND METHODS: Sixteen Japanese subjects (eight bruxers and eight age- and gender-matched controls; mean age 30 years) participated in this study. From dental casts of these subjects, the tooth wear was scored by Murphy's method. Bruxism level in these subjects was also recorded for 5 consecutive nights in the subject's home environment using a force-based bruxism detecting system. The relationship between the tooth wear score and bruxism data was evaluated statistically. RESULTS: Correlation analysis between the Murphy's scores of maxillary and mandibular dental arch and bruxism event duration score revealed no significant relationship between tooth wear and current bruxism. CONCLUSION: Tooth wear status is not predictive of ongoing bruxism level as measured by the force-based bruxism detection system in 30-year-old Japanese subjects.