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.

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.

Agreement between quantitative and qualitative sensory testing of changes in oro-facial somatosensory sensitivity.

Qualitative somatosensory testing (QualST) is a simple chairside test. It can be used to roughly assess the presence or absence of altered somatosensory function. To use QualST clinically, it is important to assess its agreement with quantitative sensory testing (QST). The aims of this study were to assess the agreement between QST and QualST when testing the modulation of facial sensitivity by capsaicin in healthy participants and to explore the agreement between QST and QualST in assessing the intraoral sensory function in clinical atypical odontalgia (AO) patients. Eighteen healthy pain-free adults and data from 27 AO patients were included in the study. Thirteen QST and three QualST parameters were evaluated at each site. Z-scores were computed for healthy participants, and Loss-Gain scores were created. The agreement observed between QST and QualST in participants with no alterations in facial sensation (placebo) was good, that is ranging from 89% to 94%. A poorer agreement was seen after capsaicin application in all test modalities with agreement ranging from 50% to 72%. The commonest misclassification observed was participants classified as normal according to QST, but hyper- or hyposensitive according to QualST after capsaicin application, especially for cold and pinprick. A similar trend was observed in AO patients where patients classified as normal using QST were misclassified as hypersensitive and in few patients as hyposensitive by QualST. In conclusion, the study showed that QualST may be used as a screening tool in the clinical setting, especially to show that subjects have normal sensory function.

[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.

Comparison of direct and indirect occlusal contact examinations with different clenching intensities.

The aims of this study were to examine the change of occlusal contact area following the increment of clenching intensity using silicone materials and electromyography (EMG) in normal subjects and to compare direct intra-oral examination with indirect examination using dental casts mounted by means of two impression methods. Participants were 7 men and 5 women with no more than one missing tooth per quadrant and no pain in the head and neck region. During the task, intercuspal position was maintained with minimal force, 20% maximum voluntary contraction (MVC) and 40% MVC using electromyography visual feedback. Three types of occlusal contact examinations were performed with the aid of blue silicone material in randomised order: (i) intra-oral direct occlusal contact examination (DE), (ii) indirect occlusal contact examination with dental casts using conventional impression method (IEC) and (iii) using occlusal impression method (IEO). Total occlusal contact area during DE and IEO significantly increased from baseline to 20% MVC and from baseline to 40% MVC, but not during IEC. Total occlusal contact area during DE in all tooth clenching conditions was significantly larger compared to IEO and IEC (P < 0·05). At 40% MVC, total occlusal contact area during IEO was significantly larger than during IEC (P < 0·05). These findings suggest that indirect occlusal contact examinations may not accurately reflect the intra-oral occlusal condition. If the intra-oral condition is reproduced using dental casts, these findings also suggest the occlusal impression method was more accurate compared to the conventional method (240 words).

Tactile sensory and pain thresholds in the face and tongue of subjects asymptomatic for oro-facial pain and headache.

The aim of this study was to examine the tactile sensory and pain thresholds in the face, tongue, hand and finger of subjects asymptomatic for pain. Sixteen healthy volunteers (eight men and eight women, mean age 35·7 years, range 27-41) participated. Using Semmes-Weinstein monofilaments, the tactile detection threshold (TDT) and the filament-prick pain detection threshold (FPT) were measured at five sites: on the cheek skin (CS), tongue tip (TT), palm side of the thenar skin (TS), dorsum of the hand (DH) and the finger tip (FT). The difference between the tactile sensory and pain threshold (FPT-TDT) was also calculated. Both for the TDT and FPT, TT and DH had the lowest and highest values, respectively. As for the FPT-TDT, there were no significant differences among the measurement sites. As the difference between FPT and TDT (FPT-TDT) is known to be an important consideration in interpreting QST (quantitative sensory testing) data and can be altered by neuropathology, taking the FPT-TDT as a new parameter in addition to the TDT and FPT separately would be useful for case-control studies on oro-facial pain patients with trigeminal neuralgia, atypical facial pain/atypical odontalgia and burning mouth syndrome/glossodynia.

Influence of different narrative instructions to record the occlusal contact with silicone registration materials.

This study examined the influence of narrative instructions on the occlusal contact area, occlusal contact point and masticatory muscle activities in normal subjects. Twelve healthy men and 12 healthy women with no more than one missing tooth per quadrant participated. Surface EMG was recorded from the masseter and temporal muscle. As a control measurement, intercuspal position was maintained to produce a habitual clenching record (NCR) while the occlusal contact area and occlusal contact point was recorded by means of silicone material. Subsequently, the occlusal contact area was recorded with the narrative instruction for minimum clenching record (MCR), light clenching record (LCR) and strong clenching record (HCR). While the EMG activity (%MVC) increased modestly from MCR to LCR (from 9·3 ± 2·0% to 11·5 ± 1·5%), the occlusal contact area increased rapidly (from 17·2 ± 11·3 mm(2) to 26·8 ± 15·6 mm(2) ) (P < 0·05). Both EMG activity and occlusal contact area increased gradually from LCR to NCR (to 17·7 ± 2·0% and to 31·4 ± 14·2 mm(2) , respectively). Finally, EMG activity still increased from NCR to HCR (to 44·5 ± 3·7%) (P < 0·05), but the occlusal contact area remained stable (to 36·8 ± 16·6 mm(2) ). Occlusal contact points at left posterior, right posterior, anterior and total area were not significantly different between each task. This study showed that narrative instructions while recording the bite can result in largely stable occlusal contact area. An adequate narrative instruction may therefore contribute to taking a stable occlusal recording in natural dentition.

Systematic review and recommendations for nonodontogenic toothache.

Nonodontogenic toothache is a painful condition that occurs in the absence of a clinically evident cause in the teeth or periodontal tissues. The purpose of this review is to improve the accuracy of diagnosis and the quality of dental treatment regarding nonodontogenic toothache. Electronic databases were searched to gather scientific evidence regarding related primary disorders and the management of nonodontogenic toothache. We evaluated the level of available evidence in scientific literature. There are a number of possible causes of nonodontogenic toothache and they should be treated. Nonodontogenic toothache can be categorised into eight groups according to primary disorders as follows: 1) myofascial pain referred to tooth/teeth, 2) neuropathic toothache, 3) idiopathic toothache, 4) neurovascular toothache, 5) sinus pain referred to tooth/teeth, 6) cardiac pain referred to tooth/teeth, 7) psychogenic toothache or toothache of psychosocial origin and 8) toothache caused by various other disorders. We concluded that unnecessary dental treatment should be avoided.

Influence of the thickness of silicone registration material as a means for occlusal contact examination--an explorative study with different tooth clenching intensities.

This study explored the influence of the thickness of silicone registration material on evaluation of the occlusal contact area and number of occlusal contact points, during increasing tooth clenching conditions in normal subjects. Twenty-four subjects with no more than one missing tooth per quadrant participated. Surface electro-myography was recorded from the masseter muscle. As a baseline measurement, intercuspal position was maintained with minimal force, and occlusal contact was recorded using blue silicone material. Occlusal contact was also recorded at 20% maximum voluntary contraction (MVC) and 40% MVC using visual feedback. The occlusal contact area and number of occlusal contact points were analysed using five levels of thickness of silicone registration material: Level 1 (0-149 µm); Level 2 (0-89 µm); Level 3 (0-49 µm); Level 4 (0-29 µm); and Level 5 (0-4 µm). The anterior part and the left and right posterior regions of the dental arch were analysed separately. At all detection levels, the occlusal contact area significantly increased from baseline to 20% MVC and to 40% MVC in the molar area (P < 0·05). In the anterior part, the occlusal contact area significantly increased from baseline to 20% MVC and to 40% MVC only when using Level 5. The number of occlusal contact points significantly increased from baseline to 20% MVC and to 40% MVC only when using Level 5 in the molar area (P < 0·05). It suggested that occlusal contacts may be different at low tooth clenching intensity with potential effects on the teeth or periodontal tissues.

Classifying orofacial pains: a new proposal of taxonomy based on ontology.

We propose a new taxonomy model based on ontological principles for disorders that manifest themselves through the symptom of persistent orofacial pain and are commonly seen in clinical practice and difficult to manage. Consensus meeting of eight experts from various geographic areas representing different perspectives (orofacial pain, headache, oral medicine and ontology) as an initial step towards improving the taxonomy. Ontological principles were introduced, reviewed and applied during the consensus building process. Diagnostic criteria for persistent dento-alveolar pain disorder (PDAP) were formulated as an example to be used to model the taxonomical structure of all orofacial pain conditions. These criteria have the advantage of being (i) anatomically defined, (ii) in accordance with other classification systems for the provision of clinical care, (iii) descriptive and succinct, (iv) easy to adapt for applications in varying settings, (v) scalable and (vi) transferable for the description of pain disorders in other orofacial regions of interest. Limitations are that the criteria introduce new terminology, do not have widespread acceptance and have yet to be tested. These results were presented to the greater conference membership and were unanimously accepted. Consensus for the diagnostic criteria of PDAP was established within this working group. This is an initial first step towards developing a coherent taxonomy for orofacial pain disorders, which is needed to improve clinical research and care.

Unexpected self-lofting and dynamical confinement of volcanic plumes: the Raikoke 2019 case.

Recent research has provided evidence of the self-lofting capacity of smoke aerosols in the stratosphere and their self-confinement by persistent anticyclones, which prolongs their atmospheric residence time and radiative effects. By contrast, the volcanic aerosols-composed mostly of non-absorptive sulphuric acid droplets-were never reported to be subject of dynamical confinement. Here we use high-resolution satellite observations to show that the eruption of Raikoke volcano in June 2019 produced a long-lived stratospheric anticyclone containing 24% of the total erupted mass of sulphur dioxide. The anticyclone persisted for more than 3 months, circumnavigated the globe three times, and ascended diabatically to 27 km altitude through radiative heating of volcanic ash contained by the plume. The mechanism of dynamical confinement has important implications for the planetary-scale transport of volcanic emissions, their stratospheric residence time, and atmospheric radiation balance. It also provides a challenge or "out of sample test" for weather and climate models that should be capable of reproducing similar structures.

The agreement between magnetic resonance imaging and arthroscopic findings in temporomandibular joint disorders.

The aim of this retrospective observational study was to assess the potential agreement between independent magnetic resonance imaging (MRI) and arthroscopic findings and their respective contributions to a final diagnosis in patients with refractory temporomandibular joint disorders. Two dentomaxillofacial radiologists and two oral and maxillofacial surgeons scored 50 joints. All observers, who were blinded to additional clinical information, used a specific scoring form and selected one or more diagnostic labels. Agreement between MRI and arthroscopy and their contributions to the final diagnosis were assessed as primary outcomes using Fleiss' kappa. Intra-modality agreement and the correlation between signal intensity ratio (SIR) measurements on MRI and synovitis grading on arthroscopy were assessed as secondary outcomes. Agreement between MRI and arthroscopy was poor. A fair level of agreement was only reached for reduction capacity of the disc and disc perforation. Arthroscopic diagnostic labels matched better with the final diagnosis, suggesting a bigger contribution to that diagnosis. Higher SIR measurements correlated with higher synovitis grading scores for the retrodiscal tissue and the posterior band of the disc. Intra-modality agreement was better in arthroscopy. When blinded to clinical information, arthroscopy and MRI observations can lead to different conclusions. The diagnostic outcomes of both examinations should be considered and integrated into a final diagnosis.

The Indian Ocean experiment: widespread air pollution from South and Southeast Asia.

The Indian Ocean Experiment (INDOEX) was an international, multiplatform field campaign to measure long-range transport of air pollution from South and Southeast Asia toward the Indian Ocean during the dry monsoon season in January to March 1999. Surprisingly high pollution levels were observed over the entire northern Indian Ocean toward the Intertropical Convergence Zone at about 6 degrees S. We show that agricultural burning and especially biofuel use enhance carbon monoxide concentrations. Fossil fuel combustion and biomass burning cause a high aerosol loading. The growing pollution in this region gives rise to extensive air quality degradation with local, regional, and global implications, including a reduction of the oxidizing power of the atmosphere.

The effect of tooth clenching on the sensory and pain perception in the oro-facial region of symptom-free men and women.

The aim of this study was (i) to examine the effect of light tooth contact as in diurnal tooth clenching on the tactile detection threshold (TDT), the filament-prick pain detection threshold (FPT) and the pressure pain threshold (PPT) in the oro-facial region and (ii) to examine the possible gender difference in this effect on the tactile and pain perception. Twenty healthy volunteers participated. The TDT and the FPT were measured by means of Semmes-Weinstein monofilaments, on the cheek skin (CS) overlying the masseter muscles (MM) and on the skin overlying the palm side of the thenar skin (TS). The PPT was measured at the central part of the MM using a pressure algometer. Each parameter was measured before and after keeping light tooth contact for 5 min (session 1) and after keeping the jaw relaxed for 5 min (session 2) as a control. Although there were no significant session effects on any of the parameters, there were significant effects of experimental condition on the TDT in both men and women (P < 0.001). Men had a significant higher FPT of the left CS (P < 0.05) and TS (P < 0.01) and a significant higher PPT of the MM than women (P < 0.001). These results illustrate that sensitivity to pain (FPT, PPT) was higher in women than in men. Although there were no significant gender differences in habituation of sensory perception, the increase of TDT after clenching/no clenching was larger in women, which warrants further study.

Low incidence of p53 mutations in UVA (365-nm)-induced skin tumors in hairless mice.

Mutations with clear "UVB fingerprints" have been observed in the p53 gene of human nonmelanoma skin tumors and of experimentally UVB-induced murine skin tumors. Although UVA (315-400 nm) radiation is also a complete carcinogen, its contribution to sunlight-induced mutagenesis remains poorly characterized. There is experimental evidence that the production of reactive oxygen species plays a more dominant role with long-wave UVA than with UVB radiation. We have induced skin tumors (n = 42) in hairless SKH:HR1 mice (n = 14) by daily exposure to long-wave UVA (365-nm) radiation. The incidence of p53 alterations in these tumors is low compared to UVB-induced tumors; positive staining for the p53 protein was observed in only 50% of the tumors, and less than 15% of the tumors showed a mutation in one of the exons 5, 7, or 8 of the p53 gene. The pattern of p53 staining was more irregular and less dense compared to UVB, and the mutations (all C-->T) were mainly (six of seven) located at codon 267. Besides a general p53 hotspot, this codon is also the main hotspot for UVB-induced skin tumors in these mice. No mutations specific for UVA, ie., mutations specific for reactive oxygen species, could be detected.

Oral pressure receptors mediate a series of inhibitory and excitatory periods in the masseteric poststimulus EMG complex following tapping of a tooth in man.

Poststimulus EMG complexes (PSECs), consisting of a series of inhibitory and excitatory waves in full-wave rectified and averaged electromyogram (EMG), were elicited in the masseter muscles of 7 subjects following controlled tapping of a tooth, at a controlled clenching level. Applying local anaesthesia to this tooth decreased the total surface of the waves, on average by 89%. The excitatory and the inhibitory waves were similarly affected, indicating that mainly pressure receptors in the periodontium mediate the entire PSEC. In 4 subjects, who were exposed to acoustic noise to exclude a contribution of acoustic receptors, the recovery of the PSEC waves from local anaesthesia was tracked. In 3 subjects, one wave (the first inhibitory or the first excitatory one, respectively) recovered differently from the other waves, indicating that they are not necessarily mediated by one type of afferent axons. The evidence, nevertheless, suggests that the different PSEC waves in man reflect the projection of the periodontal afferents upon several brain structures, involved in the control of the activity of the masseteric motorneurones, as: inhibitory and excitatory control requires different groups of interneurones; and a mediation of the first inhibitory wave by slower conducting axons than the second inhibitory wave, or a mediation of both waves by axons of similar type, is not compatible with common interneurones.

Interactive periodontal and acoustic influences on the masseteric post-stimulus electromyographic complex in man.

Post-stimulus electromyogram (EMG) complexes (PSECs) were studied in the full-wave rectified and averaged EMGs of the masseter muscles in 15 subjects, who clenched at a controlled level. The PSECs, a series of downward- and upward-going waves reflecting inhibitory and excitatory influences upon the masseteric motoneurones, were elicited by mechanical stimulation of a tooth. The stimuli selectively activated mechanoreceptors in the periodontium and, by bone-conduction, acoustic receptors. Application of acoustic masking during the periods of stimulation revealed a series of inhibitory and excitatory acoustic influences in the PSEC, which were absent after local electrical stimulation of receptors in the periodontium or their afferents. By applying local anaesthesia to the periodontium of a mechanically stimulated tooth, the durations of the acoustic influences were on the average reduced by 76%. In subjects whose PSECs consistently included a second inhibitory period, the duration of the acoustic influences with respect to that of the PSEC (30%) was larger than otherwise (13%), suggesting a central gating of periodontal pathways which can block both periodontal and acoustic influences. The acoustic influences, of which the appearance in the PSEC largely depends upon activated periodontal pathways, represent a new finding of audio-motor reflexes.