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.     

Psychometric evaluation of a motor control test battery of the craniofacial region

The primary objective of this study was to determine the structural and known‐group validity as well as the inter‐rater reliability of a test battery to evaluate the motor control of the craniofacial region. Seventy volunteers without TMD and 25 subjects with TMD (Axes I) per the DC/TMD were asked to execute a test battery consisting of eight tests. The tests were video‐taped in the same sequence in a standardised manner. Two experienced physical therapists participated in this study as blinded assessors. We used exploratory factor analysis to identify the underlying component structure of the eight tests. Internal consistency (Cronbach's α), inter‐rater reliability (intra‐class correlation coefficient) and construct validity (ie, hypothesis testing‐known‐group validity) (receiver operating curves) were also explored for the test battery. The structural validity showed the presence of one factor underlying the construct of the test battery. The internal consistency was excellent (0.90) as well as the inter‐rater reliability. All values of reliability were close to 0.9 or above indicating very high inter‐rater reliability. The area under the curve (AUC) was 0.93 for rater 1 and 0.94 for rater two, respectively, indicating excellent discrimination between subjects with TMD and healthy controls. The results of the present study support the psychometric properties of test battery to measure motor control of the craniofacial region when evaluated through videotaping. This test battery could be used to differentiate between healthy subjects and subjects with musculoskeletal impairments in the cervical and oro‐facial regions. In addition, this test battery could be used to assess the effectiveness of management strategies in the craniofacial region.     

Development of the Chinese version of the Oro‐facial Esthetic Scale

The aim of this study was to investigate the psychometric properties of the Oro‐facial Esthetic Scale among Chinese‐speaking patients. The original Oro‐facial Esthetic Scale was cross‐culturally adapted in accordance with the international standards to develop a Chinese version (OES‐C). Unlike the original Oro‐facial Esthetic Scale, the version employed in this study used a 5‐point Likert scale with items rated from unsatisfactory to most satisfactory. Psychometric evaluation included the reliability and validity of the OES‐C. The reliability of the OES‐C was determined through internal consistency and test–retest methods. The validity of OES‐C was analysed by content validity, discriminative validity, construct validity and convergent validity. The corrected item‐total correlation coefficients of the OES‐C ranged from 0·859 to 0·910. The inter‐item correlation coefficients between each two of the eight items of the OES‐C ranged from 0·766 to 0·922. The values of ICC ranged from 0·79 (95% CI = 0·54–0·98) to 0·93 (95% CI = 0·87–0·99), indicating an excellent agreement. Construct validity was proved by the presence of one‐factor structure that accounted for 83·507% of the variance and fitted well into the model. Convergent validity was confirmed by the association between OES‐C scores and self‐reported oral aesthetics and three questions from the Oral Health Impact Profile related to aesthetics (correlation coefficients ranged from ?0·830 to ?0·702, P < 0·001). OES‐C scores discriminated aesthetically impaired patients from healthy controls. This study provides preliminary evidence concerning the reliability and validity of the OES‐C. The results show that the OES‐C may be a useful tool for assessment of oro‐facial esthetics in China.     

Jaw sensorimotor control in healthy adults and effects of ageing

The oro‐facial sensorimotor system is a unique system significantly distinguished from the spinal sensorimotor system. The jaw muscles are involved in mastication, swallowing and articulatory speech movements and their integration with respiration. These sensorimotor functions are vital for sustaining life and necessitate complex neuromuscular processing to provide for exquisite sensorimotor control of numerous oro‐facial muscles. The function of the jaw muscles in relation to sensorimotor control of these movements may be subject to ageing‐related declines. This review will focus on peripheral, brainstem and higher brain centre mechanisms involved in reflex regulation and sensorimotor coordination and control of jaw muscles in healthy adults. It will outline the limited literature bearing on age‐related declines in jaw sensorimotor functions and control including reduced biting forces and increased risk of impaired chewing, speaking and swallowing. The mechanisms underlying these alterations include age‐related degenerative changes within the peripheral neuromuscular system and in brain regions involved in the generation and control of jaw movements. In the light of the vital role of jaw sensorimotor functions in sustaining life, normal ageing involves compensatory mechanisms that utilise the neuroplastic capacity of the brain and the recruitment of additional brain regions involved in sensorimotor performance and closely associated functions (e.g. cognition and memory). However, these regions are themselves susceptible to detrimental age‐related changes. Thus, better understanding of the peripheral and central mechanisms underlying age‐related sensorimotor impairment is crucial for developing improved treatment approaches to prevent or cure impaired jaw sensorimotor functions and to thereby improve health and quality of life.     

DEEP Study: does EQ‐5D‐5L measure the impacts of persistent oro‐facial pain?

The EQ‐5D‐5L is a generic quality of life (QOL) measure widely used throughout the world, which has the advantage that it allows health‐state preferences to be elicited. The aim of this study was to examine whether: a) variation in the standardised reference period for EQ‐5D‐5L from ‘today’ to ‘the last month’ had a minimal clinically meaningful difference; (b) EQ‐5D‐5L had convergent validity with a multidimensional pain measure in quantifying the impacts of pain. As part of a larger study into the effectiveness and efficiency of care pathways for persistent orofacial pain (POFP) ( http://research.ncl.ac.uk/deepstudy ), participants with POFP (n = 100) completed two versions of the EQ‐5D‐5L at the same time with different reference periods (‘today’ vs. ‘last month’). Participants also completed the first section of the West Haven–Yale Multidimensional Pain Inventory (v3) to assess convergent validity. Two‐tailed nonparametric inferential statistics, intra‐class correlation coefficients (ICC), and within‐subject change scores were used to compare the two EQ‐5D‐5L versions. Convergent validity was assessed using Spearman's rho correlation coefficients. Health‐state valuations were significantly different (P < 0·01), and there was good similarity between the two versions' ICC 0·86 (95% CI 0·79–0·91). The within‐subject mean change was 0·03 (95% CI 0·01–0·06). For convergent validity, all relationships were significant (P < 0·05) and in the expected directions. EQ‐5D‐5L demonstrates sufficient convergent validity to be used with POFP, and a change in the standard reference period may be unnecessary if a multidimensional pain measure is also used.     

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.     

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.     

Transcranial direct current stimulation and exercises for treatment of chronic temporomandibular disorders: a blind randomised‐controlled trial

To evaluate the effect of adding transcranial direct current stimulation (tDCS) to exercises for chronic pain, dysfunction and quality of life in subjects with temporomandibular disorders (TMD). Participants were selected based on the RDC/TMD criteria and assessed for pain intensity, pressure pain threshold over temporomandibular joint and cervical muscles and quality of life. After initial assessment, all individuals underwent a 4‐week protocol of exercises and manual therapy, together with active or sham primary motor cortex tDCS. Stimulation was delivered through sponge electrodes, with 2 mA amplitude, for 20 min daily, over the first 5 days of the trial. A total of 32 subjects (mean age 24·7 ± 6·8 years) participated in the evaluations and treatment protocol. Mean pain intensity pre‐treatment was 5·5 ± 1·4 for active tDCS group, and 6·3 ± 1·2 for sham tDCS. Both groups showed a decrease in pain intensity scores during the trial period (time factor – F_4·5,137·5 = 28·7, P < 0·001; group factor – F_1·0,30·0 = 7·7, P < 0·05). However, there were no differences between the groups regarding change in pain intensity (time*group interaction – F_4·5,137·5 = 1·5, P = 0·137). This result remained the same after 5 months (t‐test t = 0·29, P > 0·05). Pressure pain thresholds decrease and improvement in quality of life were also noticeable in both groups, but again without significant differences between them. Absolute benefit increase was 37·5% (CI 95%: ?15·9% to 90·9%), and number needed to treat was 2·66. This study suggests that there is no additional benefit in adding tDCS to exercises for the treatment of chronic TMD in young adults.     

Multidirectional lip‐closing force in adults with mandibular deviation

The purpose of this study was to investigate the relationship between multidi‐rectional lip‐closing force and facial soft tissue morphology in adults with mandibular deviation. Fifteen Japanese adults with mandibular deviation participated in this study. The deviation value was defined as the horizontal distance between soft tissue menton and the facial midline. The side of the soft tissue menton relative to the facial midline was defined as the deviated side and the opposite side as the non‐deviated side. The signals of directional lip‐closing force (DLCF) were investigated in 8 directions. Total lip‐closing force (TLCF) was calculated by adding DLCFs in 8 directions. Correlations and differences between the variables were analysed statistically. Significant positive correlations between TLCF and DLCFs were determined in six directions with the exception of the horizontal direction. Significant positive correlations for seven pairs of opposing DLCFs were found. The lower non‐deviated DLCF was smaller than the three pairs of opposing lip‐closing forces. Negative significant correlation was found between the deviation value and the upper deviated DLCF (P < 0·05). In individuals with mandibular deviation, lip‐closing force in the lower non‐deviated direction was found to be smaller than the opposing lip‐closing forces. When mandibular deviation was greater, the upper deviated lip‐closing force was smaller.     

Perspectives on next steps in classification of oro‐facial pain – Part 3: biomarkers of chronic oro‐facial pain – from research to clinic

The purpose of this study was to review the current status of biomarkers used in oro‐facial pain conditions. Specifically, we critically appraise their relative strengths and weaknesses for assessing mechanisms associated with the oro‐facial pain conditions and interpret that information in the light of their current value for use in diagnosis. In the third section, we explore biomarkers through the perspective of ontological realism. We discuss ontological problems of biomarkers as currently widely conceptualised and implemented. This leads to recommendations for research practice aimed to a better understanding of the potential contribution that biomarkers might make to oro‐facial pain diagnosis and thereby fulfil our goal for an expanded multidimensional framework for oro‐facial pain conditions that would include a third axis.     

Assessment of risk factors for oro‐facial pain and recent developments in classification: implications for management

Oro‐facial pain research has during the last decades provided important novel insights into the basic underlying mechanisms, the need for standardised diagnostic procedures and classification systems, and multiple treatment options for successful rehabilitation of the patient in pain. Notwithstanding the significant progress in our knowledge spanning from molecules to chair, there may also be limitations in our ability to integrate and interpret the tremendous amount of new data and information, in particular in terms of the clinical implications and overriding conceptual models for oro‐facial pain. The aim of the present narrative review is to briefly summarise some of the current thoughts on oro‐facial pain mechanisms and recent attempts to identify biomarkers and risk factors leading to the proposal of a new risk assessment diagram for oro‐facial pain (RADOP) and a provocative new concept based on stochastic variation between multiple risk factors. Finally, the implications for novel management strategies will briefly be discussed.     

Normative values for the oro‐facial Esthetic Scale in Sweden

This study reports the findings and challenges of the assessment of oro‐facial aesthetics in the Swedish general population and the development of normative values for the self‐reporting Orofacial Esthetic Scale (OES). In a Swedish national sample of 1406 adult subjects (response rate: 47%), OES decile norms were established. The influence of sociodemographics (gender, age, and education), oral health status and general health status on OES scores was analysed. Mean ± standard deviation of OES scores was 50·3 ± 15·6 units (0, worst score; 70, best score); <1% of the subjects had the minimum score of 0, and 11% had the maximum score of 70 OES units. Orofacial Esthetic Scale score differences were (i) substantial (>5 OES units) for subjects with excellent/very good versus good to poor oral or general health status; ii) small (2 units), but statistically significant for gender (P = 0·01) and two age groups (P = 0·02), and (iii) absent for subjects with college versus no college education (P = 0·31) or with and without dentures (P = 0·90). To estimate normative values for a self‐reporting health status, instrument is considered an important step in standardisation, and the developed norms provide a frame of reference in the general population to interpret the Orofacial Esthetic Scale scores.