A. De Laat

Correlation between cervical spine and temporomandibular disorders.

Abstract Neuroanatomical interconnections and neurophysiological relationships between the orofacial area and the cervical spine have been documented earlier. The present single-blind study was aimed at screening possible correlations between clinical signs of temporomandibular disorders (TMD) and cervical spine disorders. Thirty-one consecutive patients with symptoms of TMD and 30 controls underwent a standardised clinical examination of the masticatory system, evaluating range of motion of the mandible, temporomandibular joint (TMJ) function and pain of the TMJ and masticatory muscles. Afterwards subjects were referred for clinical examination of the cervical spine, evaluating segmental limitations, tender points upon palpation of the muscles, hyperalgesia and hypermobility. The results indicated that segmental limitations (especially at the C0–C3 levels) and tender points (especially in the m. sternocleidomastoideus and m. trapezius) are significantly more present in patients than in controls. Hyperalgesia was present only in the patient group (12–16%).

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.

The masseteric post-stimulus electromyographic-complex in people with dysfunction of the mandibular joint

In mandibular joint-symptom-free subjects, post-stimulus EMG complexes (PSEC) were derived by standardized mechanical stimulation of an upper central incisor during clenching at a constant level of 5 per cent of maximal masseteric EMG activity. Seventy-two sweeps per subject were processed by means of a computer program, and different morphologies of the PSEC were seen. There appears to be no correlation with the Helkimo-index as a whole or its specific components. There is a strong correlation between tooth-grinding habits and the occurrence of a single inhibitory period. Patients with myofascial pain dysfunction consistently had a single inhibitory wave. When there was one affected side, the end latency of the second inhibitory wave was significantly shorter.

The influence of clenching level on the post-stimulus EMG complex, including silent periods, of the masseter muscles in man

Standardized mechanical taps were delivered on an upper central incisor, while the nine subjects investigated maintained constant clenching levels of 5, 10, 20, 40 and 60 per cent of their maximal EMG outputs. Using statistical criteria, a computer program enabled an objective determination of the interaction between the clenching level and the sequence of upward and downward going waves following the stimulus in full-wave rectified and superimposed EMG, called a post-stimulus EMG complex (PSEC). The morphology of the PSEC, including one or two silent periods, was subject-specific and reproducible over one year. The surfaces of the waves were greatly influenced by the clenching level. In general, their total surface decreased as a function of the clenching level. However, the individual waves decreased selectively. The results suggest that the sequence of waves results from overlapping of inhibitory and excitatory inputs. The inhibitory waves, constituting the silent periods, are largely cancelled by the excitatory reflexes of the PSEC.

One-year evaluation of the effect of physical therapy for masticatory muscle pain: A randomized controlled trial

Physical therapy is widely used to decrease pain and restore function in patients suffering from masticatory muscle pain. Controlled studies on its efficacy are scarce. This study evaluated the 1‐year effect of a 6‐week physical therapy programme in a single blind, randomized, controlled trial. Fifty‐three subjects were randomly assigned to either a physical therapy group [n = 26; 19 women, mean age (SD) 36.6 years (15.5 years)] or a control group [n = 27; 20 women, mean age (SD) 42.9 years (15.1 years)]. In the physical therapy group, the patients received education, muscle stretching, exercises and homework for nine treatments in 6 weeks. In the control group, the patients received education on the evaluation days only. At baseline and after 3, 6, 12, 26 and 52 weeks, pain and masticatory function were evaluated using visual analogue scales, the McGill Pain Questionnaire, pressure pain thresholds of the masseter and temporalis muscles, the mandibular function impairment questionnaire, and active and passive maximal mouth opening. All pain rating variables decreased and all function variables increased significantly over time in both groups. No significant differences in improvement between the groups (time–treatment interaction) were found. These data suggest that the long‐term decrease in pain and the improvement of function are not related to active physical therapy.

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.

Heteronymous H-reflex in Temporal Muscle Motor Units

An electric stimulation of the masseteric nerve elicits a heteronymous H-reflex in the temporal muscle. The characteristics of this reflex response were investigated by analysis of the firing probability changes of single motor units. Eleven healthy subjects participated in the experiments. The heteronymous H-reflex of the temporal muscle was electrically elicited by stimulation of the masseteric nerve at 120% of the intensity needed for the maximal masseteric M-wave. From 8 to 24 motor units were sampled from the temporal muscle of each subject. Peri-stimulus time histograms of motor unit recordings were built with a 0.5-ms bin width. The mean firing probability was calculated for the 20 ms preceding the stimulus. The firing probability was considered increased when it exceeded the mean by 3 standard deviations. Of 104 sampled motor units, 40 motor units showed a significant increase of the firing probability, which lasted 1 ms or less in 29 of them. In 12 out of 16 motor units, a significant increase of firing probability also persisted at a lower stimulation intensity (120% of the threshold needed to elicit a masseteric M wave). These data indicate that: (1) some temporal muscle motor units are modulated by afferents from the masseter muscle, (2) the heteronymous H-reflex has a monosynaptic component, and (3) there might be a more complex than just monosynaptic organization serving the heteronymous temporal H-reflex. For the latter conclusion regarding synaptic wiring, however, PSTH studies like the present one can offer only indirect evidence, and this question could be better studied in animals.

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.

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

Summary 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, bruxismrelated masticatory muscle activities should be assessed in the behaviour’s continuum.

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.