Intraoral somatosensory abnormalities in patients with atypical odontalgia--a controlled multicenter quantitative sensory testing study

Beyond numbers: integrating qualitative analysis into quantitative sensory testing for neuropathic pain

This article investigates the benefits of adopting qualitative and quantitative sensory testing (QQST) in sensory assessment, with a focus on understanding neuropathic pain. The innovative QQST method combines participant qualitative experiences with quantitative psychophysical measurements, offering a more varied interpretation of sensory abnormalities and normal sensory function. This article also explores the steps for the optimization of the method by identifying qualitative signs of sensory abnormalities and standardizing data collection. By leveraging the inherent subjectivity in the test design and participant responses, the QQST method contributes to a more holistic exploration of both normal and abnormal sensory experiences. This article positions the QQST approach as a foundational element within the Sensory Evaluation Network, uniting international experts to harmonize qualitative and quantitative sensory evaluation methods.

Clinical features of chronic primary pain in individuals presenting painful temporomandibular disorder and comorbidities

BACKGROUND

The diagnosis of chronic primary pain (CPP), according to the recently released International Classification of Disease (ICD-11) criteria, refers to conditions with complex aetiologies. CPP is characterized by specific clinical features such as generalized sensory hypersensitivity and widespread pain, and is associated with functional disability and emotional distress.

OBJECTIVE

This study investigated clinical features of CPP in individuals with painful temporomandibular disorders (TMD) and comorbidities (fibromyalgia, migraine and/or tension-type headache).

METHODS

This cross-sectional study was conducted with a sample of 129 individuals. Painful TMD, fibromyalgia and primary headaches were evaluated based on well-established international criteria. Generalized sensory hypersensitivity was assessed using psychophysical tests. Symptoms of anxiety and depression were assessed by the Generalized Anxiety Disorder-7 and Patient Health Questionnaire-9. The Central Sensitization Inventory was applied to assess central sensitization-related symptoms and the Pittsburg Sleep Quality Index to evaluate the quality of sleep. The presence of widespread pain was assessed using a body map. The sample was stratified into three groups: control (n = 25), TMD-painful TMD only (n = 35) and TMD + Cm-painful TMD and comorbidities (n = 69). Statistical analysis was performed using one-way ANOVA, chi-squared test and ANCOVA, considering gender as a covariate (α = .05).

RESULTS

Compared to controls, individuals presenting painful TMD and comorbidities showed lower pressure pain thresholds in all evaluated areas (p ≤ .012) and a higher number of painful areas in the body (p = .001). They presented more symptoms of anxiety (p = .040) and depression (p = .018), and a higher score in the Central Sensitization Inventory (p ≤ .006) than the other groups.

CONCLUSION

Individuals with painful TMD and comorbidities presented more clinical features of CPP compared to those affected by TMD only.

Somatosensory and Gustatory Profiling in the Orofacial Region

Quantitative sensory testing (QST) is a standard procedure in medicine to describe sensory patterns in various pathologies. The aim of this prospective clinical study was to define reference values of the trigeminal nerve (V3), including taste qualities, to create a compatibility for sensory loss or gain in pathologies. Fifty-one patients were included, and a standardized testing battery with 11 QST parameters according to the German Research Network on Neuropathic Pain (DFNS) was applied complemented by quantitative gustatory assessments. Significant somatosensory differences were found between the test sites (MDT at the chin, WDT at the lower lip) but no effect was detected for gender, age, and between body types. Taste sensitivity was dependent on concentration, gender (females being more sensitive) and increasing age (for bitter and sour taste). We provide reference values for somatosensory and gustatory testing of the facial area. Our data facilitate the detection of neurosensory abnormalities in the orofacial region. This might also serve as a control setting for COVID-19.

Thinking Outside the Tooth: Diagnosis and Management of Patients with Neuropathic Orofacial Pain

Nonodontogenic orofacial pain exists, and diagnosis and management of those conditions can be challenging. This article highlights and discusses how to take a complete and systematic pain history and the important red flags to recognize in patients presenting with perplexing nonodontogenic orofacial pain. Cause and epidemiology, clinical presentation, clinical evaluation and diagnosis, and management options for common neuropathic pain conditions are included. Neuralgia and neuropathic pain conditions and red flags as secondary cause of orofacial pain are more common in older-aged patients.

Effect of aging and tooth loss on sensory function of alveolar mucosa

BACKGROUND

Maintain Quality of Life of elderly denture wearers is one of the most crucial tasks for dentists in the super-aged society. Although external mechanical load on removable dentures has been investigated to minimize a risk of soreness caused by dentures, sensory perception of the alveolar mucosa remains obscure.

OBJECTIVES

This study aimed to investigate effect of aging and tooth loss in sensory function on the alveolar mucosa for deep understanding of the characteristics of pain sensitivity in edentulous individuals.

METHODS

Eighteen edentulous participants(ED), as well as 18 age-matched dentate participants(EC) and 18 young dentate participants(YC), participated in this study. Tactile detection threshold(TDT) and pain threshold(PT) were measured with von Frey filaments (0.125-512 mN). Mechanical pain sensitivity(MPS) after a 2-sec application of 1 kg palpation was assessed with a 0-50-100 Numerical Rating Scale(NRS) (0: no pain, 50: slight pain, and 100: the worst pain imaginable). Furthermore, entropy scores of TDT, PT, and NRS on MPS were calculated.

RESULTS

In both maxilla and mandible, EC showed significantly higher TDT and PT, compared to YC, whereas ED showed significantly lower TDT and PT, compared to EC. NRS on MPS in ED was significantly higher than that in EC. The entropy scores of all the outcome parameters showed no significant difference between groups.

CONCLUSION

Both aging and tooth loss can alter tactile and pain perception in the oral mucosa. This suggest that it might be beneficial to assess sensory function of the alveolar mucosa in edentulous patients clinically in prior to denture fabrication.

Classification of Qualitative Fieldnotes Collected During Quantitative Sensory Testing: A Step Towards the Development of a New Mixed Methods Approach in Pain Research

PURPOSE

Quantitative sensory testing (QST) is a standardized method to assess somatosensory function. The collection of qualitative information, during the QST procedure, could be an interesting way to facilitate the characterization of altered sensory perception and the identification of different pain phenotypes. The aims of this study were 1) to classify qualitative fieldnotes of sensory abnormalities collected during an independent QST study, and 2) to generate a qualitative interview guide that could be included in the traditional QST procedure as a step towards the implementation of a mixed methods approach.

PATIENTS AND METHODS

QST data were collected from 48 chronic neuropathic pain patients treated with spinal cord stimulation (SCS). Three body areas, with or without SCS, were tested: the painful limb targeted by SCS, the contralateral area, and the ipsilateral upper limb. After each trial of each QST modality, patients were encouraged to report any sensory abnormalities they could identify with a pain quality scale or using their own words.

RESULTS

Qualitative self-reported sensory abnormalities were dichotomized into two groups: altered sensory intensities and altered sensory perceptions. Altered sensory intensities were classified as sensory loss or sensory gain subgroups. Altered sensory perceptions were classified as paresthesia and dysesthesia subgroups Overall, 630 qualitative fieldnotes of altered sensations were collected: 385 on the painful limb, 173 at the contralateral area, and 72 at the ipsilateral upper limb. Based on these qualitative data, we propose a standardized method to collect qualitative data involving 9 open- and close-ended questions and 21 codes.

CONCLUSION

Our findings have highlighted the value of qualitative sensory evaluation during QST and constitute an important milestone in the development of a mixed methods protocol in phenotyping research.

Sensory recovery and oral health-related quality of life following tongue reconstruction using non-innervated radial forearm free flaps

OBJECTIVES

This study aimed to monitor the recovery of somatosensory function and oral health-related quality of life after tongue reconstruction using a non-innervated radial forearm free flap (RFFF).

METHODS

Twenty patients (9 men, age: 42-67 years) underwent tongue reconstruction with non-innervated RFFFs, and twenty age- and sex-matched controls were included in this study. Quantitative sensory testing (QST), including cold, warm, and mechanical detection thresholds (CDT, WDT, MDT); cold, heat, and mechanical pain thresholds (CPT, HPT, MPT); and static two-point, sharp/blunt, and direction discrimination (S2-PD, S/BD, DD) were determined 9 months and 18 months after surgery on the surgical (9 M, 18 M) and contralateral sides (9Mc, 18Mc). Oral Health Impact Profile-49 (OHIP-49) was used to determine the oral-related quality of life of participants.

RESULTS

All parameters showed significantly lower sensitivity at 9 M and 18 M (p < 0.001) compared to those for the controls and the contralateral side, except for DD (p = 0.101). In addition, the parameters showed a significant decrease in sensitivity for 9Mc and 18Mc (p ≤ 0.043) compared to those for the controls, except for MPT, HPT, S/SD, and DD (p ≥ 0.453). Findings on WDT, MPT, S2-PD, and DD (p ≤ 0.046) indicated significantly higher somatosensory function at 18 M than that at 9 M. MDT and MPT (p ≤ 0.038) showed significantly higher sensitivity at 18Mc than at 9Mc. Scores for all dimensions of OHIP-49 were significantly higher in patients (decrease in quality of life, p ≤ 0.002) than in controls, except for physical discomfort (p = 0.51). However, the scores were significantly higher at 18 M than at 9 M (p ≤ 0.011), except for handicap (p = 0.36). Postoperative chemotherapy was significantly correlated with impaired thermal sensitivity of the flaps (WDT, p = 0.049).

CONCLUSION

The present findings showed significant impairment in somatosensory function on both the surgical and contralateral sides of patients with RFFFs. However, a significant increase in somatosensory function was observed on both sides over time. Somatosensory disturbances observed after surgery were associated with poor oral health-related quality of life.

Neuropathic orofacial pain: Characterization of different patient groups using the ICOP first edition, in a tertiary level Orofacial Pain Clinic

OBJECTIVE

To characterize patients with chronic neuropathic orofacial pain in accordance with the International Classification of Orofacial Pain (ICOP first edition) criteria.

STUDY DESIGN

A retrospective chart review of 108 patients was conducted. The most common categories observed were trigeminal neuralgia (TN) (25.9%), burning mouth syndrome (BMS) (11.1%), persistent idiopathic facial pain (PIFP) (26.9%), and posttraumatic trigeminal neuropathic pain (PTTNP) (26.9%); 9.3% of patients could not be categorized.

RESULTS

TN and BMS was more prevalent in the sixth decade, and PIFP and PTTN were more prevalent in the fifth decade. All categories showed female predilection. The pain in TN was predominantly episodic, described as "sharp shooting" and like an "electric shock," unilateral and affecting the V2 division, and with trigger zones in 50% of patients. Pain in BMS was predominantly constant and described as "burning," with the tongue being the most common site. Pain in PIFP and PTTNP was as follows: varied from constant to episodic; described as "burning," "sharp shooting," "throbbing," or "dull aching"; intraoral or extraoral; and mostly involving the V2 or V3 division.

CONCLUSION

This study is the first to characterize patients with neuropathic orofacial pain using the new ICOP criteria. PIFP and PTTNP were most commonly misdiagnosed categories. Using diagnostic criteria will increase the understanding of this patient group.

Psychophysical evaluation of somatosensory function in oro-facial pain: achievements and challenges

AIM

This critical review describes key methodological aspects for a successful oro-facial psychophysical evaluation of the somatosensory system and highlights the diagnostic value of somatosensory assessment and management perspectives based on somatosensory profiling.

METHODS

This topical review was based on a non-systematic search for studies about somatosensory evaluation in oro-facial pain in PubMed and Embase.

RESULTS

The recent progress regarding the psychophysical evaluation of somatosensory function was largely possible due to the development and application of valid, reliable and standardised psychophysical methods. Qualitative sensory testing may be useful as a screening tool to rule out relevant somatosensory abnormalities. Nevertheless, the patient should preferably be referred to a more comprehensive assessment with the quantitative sensory testing battery if confirmation of somatosensory abnormalities is necessary. Moreover, the identification of relevant somatosensory alterations in chronic pain disorders that do not fulfil the current criteria to be regarded as neuropathic has also increased the usefulness of somatosensory evaluation as a feasible method to better characterise the patients and perhaps elucidate some underpinnings of the so-called 'nociplastic' pain disorders. Finally, an additional benefit of oro-facial pain treatment based on somatosensory profiling still needs to be demonstrated and convincing evidence of somatosensory findings as predictors of treatment efficacy in chronic oro-facial pain awaits further studies.

CONCLUSION

Psychophysical evaluation of somatosensory function in oro-facial pain is still in its infancy but with a clear potential to continue to improve the assessment, diagnosis and management of oro-facial pain patients.

Chronic Orofacial Pain: Models, Mechanisms, and Genetic and Related Environmental Influences

Chronic orofacial pain conditions can be particularly difficult to diagnose and treat because of their complexity and limited understanding of the mechanisms underlying their aetiology and pathogenesis. Furthermore, there is considerable variability between individuals in their susceptibility to risk factors predisposing them to the development and maintenance of chronic pain as well as in their expression of chronic pain features such as allodynia, hyperalgesia and extraterritorial sensory spread. The variability suggests that genetic as well as environmental factors may contribute to the development and maintenance of chronic orofacial pain. This article reviews these features of chronic orofacial pain, and outlines findings from studies in animal models of the behavioural characteristics and underlying mechanisms related to the development and maintenance of chronic orofacial pain and trigeminal neuropathic pain in particular. The review also considers the role of environmental and especially genetic factors in these models, focussing on findings of differences between animal strains in the features and underlying mechanisms of chronic pain. These findings are not only relevant to understanding underlying mechanisms and the variability between patients in the development, expression and maintenance of chronic orofacial pain, but also underscore the importance for considering the strain of the animal to model and explore chronic orofacial pain processes.

Acute and Chronic Pain from Facial Skin and Oral Mucosa: Unique Neurobiology and Challenging Treatment

The oral cavity is a portal into the digestive system, which exhibits unique sensory properties. Like facial skin, the oral mucosa needs to be exquisitely sensitive and selective, in order to detect harmful toxins versus edible food. Chemosensation and somatosensation by multiple receptors, including transient receptor potential channels, are well-developed to meet these needs. In contrast to facial skin, however, the oral mucosa rarely exhibits itch responses. Like the gut, the oral cavity performs mechanical and chemical digestion. Therefore, the oral mucosa needs to be insensitive, to some degree, in order to endure noxious irritation. Persistent pain from the oral mucosa is often due to ulcers, involving both tissue injury and infection. Trigeminal nerve injury and trigeminal neuralgia produce intractable pain in the orofacial skin and the oral mucosa, through mechanisms distinct from those seen in the spinal area, which is particularly difficult to predict or treat. The diagnosis and treatment of idiopathic chronic pain, such as atypical odontalgia (idiopathic painful trigeminal neuropathy or post-traumatic trigeminal neuropathy) and burning mouth syndrome, remain especially challenging. The central integration of gustatory inputs might modulate chronic oral and facial pain. A lack of pain in chronic inflammation inside the oral cavity, such as chronic periodontitis, involves the specialized functioning of oral bacteria. A more detailed understanding of the unique neurobiology of pain from the orofacial skin and the oral mucosa should help us develop novel methods for better treating persistent orofacial pain.

Drop homotopic effects of masseter-muscle pain on somatosensory sensitivity in healthy participants

Current pain classifications use 1.0-kg palpation of the masseter muscle to distinguish between “pain patients” and “healthy controls” but a thorough understanding of the normal physiological responses to various somatosensory stimuli is lacking. The aim of this study was to investigate somatosensory function of the skin over the masseter muscle in healthy participants that were divided into a masseter pain prone group (MPP) (n = 22) and non-MPP group (n = 22), according to the response to a 1.0-kg palpation. Quantitative sensory testing (QST) was performed at the skin above the right masseter muscle (homotopic). In an additional experiment, 13 individuals each from MPP and non-MPP received application of 60% topical lidocaine tape to the skin over the masseter muscle for 30 min. Immediately after, mechanical pain sensitivity (MPS), dynamic mechanical allodynia, and pressure pain threshold were tested. Homotopic MPS was significantly higher and PPTs significantly lower in MPP than in N-MPP (P < 0.05). Strikingly, no other differences in QST outcomes were observed between the groups (P > 0.05). After lidocaine application, no significant differences in homotopic MPS were observed between groups. The presence or absence of acute provoked pain in masseter muscle is exclusively associated with differences in homotopic MPS which is decreased following topical anesthesia.

Assessment of Pain Modulatory and Somatosensory Profiles in Chronic Tension-Type Headache Patients

Objective

The aim of this study was to thoroughly phenotype a group of chronic tension-type headache (CTTH) patients.

Methods

Fifteen CTTH patients diagnosed according to the International Classification of Headache Disorders–3 and 15 healthy controls were included in this study. Furthermore, 70 healthy controls were included to establish normative values. Quantitative sensory testing (QST), including temporal summation of pain (TSP), conditioned pain modulation (CPM), and psychological and sleep variables, was assessed in a single session. TSP and CPM were then combined to build pain modulation profiles (PMP) for each individual.

Results

No difference was found between groups for PMP, TSP, and CPM. However, 10 CTTH patients showed a pronociceptive PMP, with 8 related to a deficient CPM and 2 to both a deficient CPM and increased TSP. Increased cold detection thresholds were the most common sensory disturbance found in CTTH patients. Significant differences were seen between groups for pain catastrophizing, depression, and sleep quality although not all patient’s scores were above the clinically meaningful cutoffs.

Conclusions

In summary, CTTH patients presented with different PMP. These PMP may be related to increased TSP, deficient CPM, alterations in thermal detection that may be related to autonomic dysregulation, or a combination of all three. Overall, this suggests that due to their heterogeneous pathophysiology, CTTH patients should be managed according to their underlying pathophysiology and not with a one-size-fits-all approach.

Lack of correlation between central sensitization inventory and psychophysical measures of central sensitization in individuals with painful temporomandibular disorder

OBJECTIVE

To assess the correlation between the Central Sensitization Inventory (CSI) scores and the results of psychophysical tests and psychosocial questionnaires according to the presence of painful temporomandibular disorder (TMD).

DESIGN

It was a cross-sectional study involving 146 participants, aged 20-65 years. Painful TMD was classified using the Research Diagnostic Criteria for Temporomandibular Disorders. CSI was applied to assess "central sensitization-related symptoms", as has been suggested. Wind-up ratio, pressure pain threshold and conditioned pain modulation were used as psychophysical tests to evaluate signs and symptoms of central sensitization. Psychosocial factors were assessed by the presence of non-specific physical symptoms, depressive and anxiety symptoms. The sample was divided into two groups: Control (n = 31); Painful TMD (n = 115). Descriptive statistics characterized the sample. Correlation analysis were performed using Pearson's and Spearman's correlation coefficients (α = 5%).

RESULTS

Of the total sample, 78.8 % presented painful TMD, and the mean (standard deviation) age was 37.4 (±11.5) years. Anxiety symptoms (p = 0.028) and non-specific physical symptoms (p < 0.001) were more frequent in the painful TMD group than in controls. Painful TMD patients presented higher scores of the CSI (p < 0.001) and lower pressure pain thresholds (p ≤ 0.020) compared to controls. CSI scores were significantly correlated with psychosocial measures (p < 0.001) but not with psychophysical tests (p ≥ 0.089).

CONCLUSION

The CSI scores did not correlate with psychophysical measures of central sensitization but were positively correlated with the results of psychosocial questionnaires.

Orofacial quantitative sensory testing: Current evidence and future perspectives

BACKGROUND AND OBJECTIVE

Orofacial quantitative sensory testing (QST) is an increasingly valuable psychophysical tool for evaluating neurosensory disorders of the orofacial region. Here, we aimed to evaluate the current evidence regarding this testing method and to discuss its future clinical potential.

DATA TREATMENT

We conducted a literature search in Medline, Embase and Scopus for English-language articles published between 1990 and 2019. The utilized search terms included QST, quantitative, sensory testing and neurosensory, which were combined using the AND operator with the terms facial, orofacial, trigeminal, intraoral and oral.

RESULTS

Our findings highlighted many methods for conducting QST-including method of levels, method of limits and mapping. Potential stimuli also vary, and can include mechanical or thermal stimulation, vibration or pinprick stimuli. Orofacial QST may be helpful in revealing disease pathways and can be used for patient stratification to validate the use of neurosensory profile-specific treatment options. QST is reportedly reliable in longitudinal studies and is thus a candidate for measuring changes over time. One disadvantage of QST is the substantial time required; however, further methodological refinements and the combination of partial aspects of the full QST battery with other tests and imaging methods should result in improvement.

CONCLUSIONS

Overall, orofacial QST is a reliable testing method for diagnosing pathological neurosensory conditions and assessing normal neurosensory function. Despite the remaining challenges that hinder the use of QST for everyday clinical decisions and clinical trials, we expect that future improvements will allow its implementation in routine practice.

Assessment of somatosensory changes in Chinese temporomandibular disorders arthralgia patients by quantitative sensory testing

BACKGROUND

Somatosensory changes in Chinese temporomandibular disorders (TMD) arthralgia patients have not been fully studied by the latest technologies.

OBJECTIVE

This study aims at assessing somatosensory changes in Chinese TMD arthralgia patients quantitatively.

METHODS

Standardised quantitative sensory testing (QST) was performed on the pain sites and contralateral sites of 40 patients diagnosed with TMD arthralgia according to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) before and after medication; similar measures were taken in 40 age- and gender-matched healthy controls. Differences within and between groups were assessed through Z-scores, two-way ANOVA and loss/gain coding system.

RESULTS

The pain sites of patients presented increased sensitivity to thermal stimuli and mechanical pain stimuli together with decreased sensitivity to mechanical tactile stimuli before medication (P < .001). Before treatment, 100% of patients had somatosensory abnormalities at the pain sites; the most frequent abnormalities were somatosensory gain to cold nociceptive, pinprick and pressure stimuli, and the most frequent loss/gain score was L0G3 (no somatosensory loss with a gain of thermal and mechanical somatosensory function; 70.0%). After treatment, although the clinical symptoms and signs of 40 patients disappeared, 80.0% of the patients' pain sites still showed multiple phenotype abnormalities. The most frequent loss/gain score was L0G2 (no somatosensory loss with a gain of mechanical somatosensory function; 35.0%).

CONCLUSIONS

Multiple phenotypes of facial somatosensory abnormalities were detected in Chinese TMD arthralgia patients before and after treatment, despite the disappearance of clinical signs and symptoms. Individual variations indicate a possible need for subgroup classification, individualised management and mechanism-based treatment.

Molecular mechanisms of painful traumatic trigeminal neuropathy-Evidence from animal research and clinical correlates

Painful traumatic trigeminal neuropathy (PTTN) may occur following major craniofacial or oral trauma, or may be subsequent to relatively minor dental interventions. Following injury, pain may originate from a peripheral nerve, a ganglion, or from the central nervous system. In this review, we focus on molecular mechanisms of pain resulting from injury to the peripheral branch of the trigeminal nerve. This syndrome has been termed painful traumatic trigeminal neuropathy (PTTN) by the International Headache Society and replaces previous terms including atypical odontalgia, deafferentation pain, traumatic neuropathy and phantom toothache. We emphasize the scientific evidence supporting the events purported to lead to PTTN by reviewing the pathophysiology of PTTN based on relevant animal models. Additionally, we briefly overview clinical correlates and pathophysiological manifestations of PTTN.

Reliability of orofacial quantitative sensory testing for pleasantness and unpleasantness

BACKGROUND

Quantitative sensory testing protocols for perceptions of pleasantness and unpleasantness based on the German Research Network on Neuropathic Pain protocol were recently introduced. However, there are no reliability studies yet published.

AIM

To evaluate the intra-examiner (test-retest) and inter-examiner reliability for orofacial pleasantness and unpleasantness quantitative sensory testing protocols.

METHODS

Sixteen healthy participants from Aarhus University (11 women and five men, mean age 24, range 21-26 years) contributed. Two examiners were trained in performing the entire quantitative sensory testing protocols for pleasantness and unpleasantness, which included the additional dynamic tactile stimulation test using a goat-hair brush. Each participant underwent examination of both protocols by each examiner (inter-examiner reliability) on day 1. They returned at least 8 days following the testing to be re-examined by one examiner (intra-examiner reliability). All testing was performed on the skin of the right mandibular mental region. The intraclass correlation (ICC) was used to determine reliability.

RESULTS

For the protocol investigating pleasantness, the majority of parameters had good to excellent intra-examiner (11/14: Intraclass correlation 0.67-0.87) and inter-examiner (13/14: Intraclass correlation 0.62-0.96) reliabilities. Similarly, the protocol investigating unpleasantness had good to excellent intra-examiner (intraclass correlation 0.63-0.99) and inter-examiner (intraclass correlation 0.65-0.98) reliabilities for most (13/15) of the parameters.

CONCLUSION

Intra and inter-examiner reliabilities in the majority of quantitative sensory testing parameters (apart from the summation ratio) investigating pleasantness and unpleasantness are acceptable when assessing somatosensory function of the orofacial region.Trial registration: NA.

Modulation of experimental facial pain via somatosensory stimuli targeting sensations of different valence

BACKGROUND

Knowledge of pain modulation from oro-facial somatosensory stimuli with different valence (pleasant-unpleasant) is limited.

OBJECTIVES

To investigate (a) the modulatory effects of painful, pleasant and unpleasant somatosensory stimuli on two models of experimental facial pain, (b) whether modulation could be changed by blocking peripheral nerves via application of a local anaesthetic, EMLA, or blocking endogenous opioid receptors via naltrexone and (c) whether pain ratings were significantly correlated with participant psychological profiles.

METHODS

Thirty-eight healthy women received experimental facial skin burning pain or jaw myalgia for four randomised sessions on different days. The painful region was stimulated with mechanical or thermal painful, pleasant, unpleasant and control stimuli, with ratings recorded before and during stimulation. Sessions differed in pre-treatment: EMLA/naltrexone/placebo tablet/cream.

RESULTS

Significant effects of thermal or mechanical stimuli (P < .017), but not session (P > .102), were found on pain ratings for both models. In myalgia, painful cold resulted in a greater reduction in pain ratings than unpleasant cold, pleasant cold, control and pleasant warmth (P < .004). Decreases in pain ratings from painful, unpleasant and pleasant mechanical stimuli were greater than control (P < .002). In burning pain, painful cold resulted in a greater reduction in pain ratings than all but one of the other thermal stimuli (P < .033). The pleasant mechanical stimulus reduced pain ratings more than all other mechanical stimuli (P ≤ .003). There were no significant correlations between pain and psychometrics.

CONCLUSION

Valence-targeted thermal and mechanical stimuli modulated experimental myalgia and skin burning pain (P < .017). Partially blocking peripheral afferents or opioid receptors did not affect modulation.

Differential Diagnosis of Chronic Neuropathic Orofacial Pain: Role of Clinical Neurophysiology

Orofacial pain syndromes encompass several clinically defined and classified entities. The focus here is on the role of clinical neurophysiologic and psychophysical tests in the diagnosis, differential diagnosis, and pathophysiological mechanisms of definite trigeminal neuropathic pain and other chronic orofacial pain conditions (excluding headache and temporomandibular disorders). The International Classification of Headache Disorders 2018 classifies these facial pain disorders under the heading Painful cranial neuropathies and other facial pains. In addition to unambiguous painful posttraumatic or postherpetic trigeminal neuropathies, burning mouth syndrome, persistent idiopathic facial and dental pain, and trigeminal neuralgia have also been identified with neurophysiologic and quantitative sensory testing to involve the nervous system. Despite normal clinical examination, these all include clusters of patients with evidence for either peripheral or central nervous system pathology compatible with the subclinical end of a continuum of trigeminal neuropathic pain conditions. Useful tests in the diagnostic process include electroneuromyography with specific needle, neurography techniques for the inferior alveolar and infraorbital nerves, brain stem reflex recordings (blink reflex with stimulation of the supraorbital, infraorbital, mental, and lingual nerves; jaw jerk; masseter silent period), evoked potential recordings, and quantitative sensory testing. Habituation of the blink reflex and evoked potential responses to repeated stimuli evaluate top-down inhibition, and navigated transcranial magnetic stimulation allows the mapping of reorganization within the motor cortex in chronic neuropathic pain. With systematic use of neurophysiologic and quantitative sensory testing, many of the current ambiguities in the diagnosis, classification, and understanding of chronic orofacial syndromes can be clarified for clinical practice and future research.

Somatosensory changes in Chinese patients after coronectomy vs. total extraction of mandibular third molar: a prospective study

Objectives

This study aimed to quantitatively compare the somatosensory function changes of inferior alveolar nerve (IAN) after mandibular third molar extraction with a surgery protocol of coronectomy, as opposed to the conventional method.

Materials and methods

Patients with a lower third molar directly contacting IAN were recruited and assigned either to a test group (coronectomy group) or a control group (conventional extraction). A standardized quantitative sensory testing (QST) battery was performed for four times: one week before surgery and the second, seventh, and 28th days after surgery. Z-scores and the loss/gain coding system were applied for each participant.

Results

A total of 140 molars (test group: n = 91, control group: n = 49) were enrolled. The sensitivity of the mechanical detection threshold (MDT) and pressure pain threshold (PPT) significantly increased after surgery more than before surgery in both groups (P ≤ 0.001). After the surgery, the sensitivities of the cold detection threshold (CDT), cold pain threshold (CPT), and heat pain threshold (HPT) were significantly higher in the test group than in the control group (P ≤ 0.027). The risk of IANI was significantly larger (P = 0.041) in the test group than in the control group.

Conclusions

QST was a sensitive way to detect somatosensory abnormalities even with no subjective complaint caused by surgery. Coronectomy had less influence on IAN function than conventional total extraction.

Clinical relevance

The somatosensory function changes after mandibular third molar extraction were quantitatively studied, and coronectomy was proved a reliable alternation to reduce IAN injury rate.

Persistent dentoalveolar pain disorder: A putative intraoral chronic overlapping pain condition

Chronic overlapping pain conditions (COPCs) are conditions that share several clinical characteristics and symptomatology, are usually considered idiopathic in nature, and are frequently comorbid. Currently, there are no established inclusion criteria to determine which conditions should be included under this umbrella term despite different systems proposed. Persistent dentoalveolar pain disorder (PDAP), also referred to as atypical odontalgia and thought to be a component of persistent idiopathic facial pain, is a chronic pain condition that manifests as a persistent tooth pain or pain over a dentoalveolar site formerly occupied by a tooth in the absence of detectable pathology during clinical or radiological examination. PDAP is considered idiopathic in nature, and its pathophysiological mechanisms are not fully understood. Our objective was to investigate whether PDAP fits the conceptual paradigm of COPC given its characteristics and commonalities with other COPC, based on published literature identified through a scoping review. We found that PDAP fits 16 out of 18 common characteristics among COPCs, and based on this finding, we discuss the implications of PDAP being considered a COPC.

Acute and chronic pain in orofacial trauma patients

Trauma or injury to the dentition and supporting tissues is associated with pain and discomfort, as expected, that may present immediately, shortly afterwards, or within a few days. Pain is an essential response to injury because it allows the organism to develop avoidance behavior to potential threats and helps the organism to avoid usage of the injured organ during the healing process. Not only does external trauma induce pain, but also essential invasive dental procedures such as extractions, dental implant insertions, root canal treatments, and oral surgeries are accompanied by similar post-surgical (post-traumatic) pain. The pain intensity after trauma varies and does not always correlate with the extent of injury. Trauma to the orofacial region or the teeth may also indirectly affect and induce pain in other orofacial structures such as the masticatory muscles, the temporomandibular joint, and even the cervical spine. In most cases, the pain will resolve as soon as healing of the affected tissue occurs or after dental and routine palliative treatment. In a limited number of cases, the pain persists beyond healing and evolves into a chronic pain state. Chronic pain in the orofacial region presents diagnostic and management challenges. Misdiagnosis or delayed diagnosis of the oral chronic pain condition may lead to unnecessary dental treatment. This article will discuss diagnosis and treatment for acute and chronic pain as well as potential mechanisms involved in the undesirable transition from acute to chronic pain.

How May Placebo Mechanisms Influence Orofacial Neuropathic Pain?

The conceptualization of placebo has changed from inactive pills to a detailed understanding of how patients' perception of receiving a treatment influences pain processing and overall treatment outcome. Large placebo effects were recently demonstrated in chronic neuropathic pain, thereby opening the question of whether placebo effects also apply to orofacial neuropathic pain. In this article, we review the new definitions, magnitude, and social, psychological, neurobiologic, and genetic mechanisms of placebo effects in pain, especially neuropathic pain, to illustrate that placebo effects are not simply response bias but psychoneurobiological phenomena that can be measured at many levels of the neuroaxis. We use this knowledge to carefully illustrate how patients' perceptions of the treatment, the relationship with the health care provider, and the expectations and emotions toward a treatment can influence test and treatment outcome and potentially skew the results if they are not taken into consideration. Orofacial neuropathic pain is a new research area, and we review the status on definition, diagnosis, mechanisms, and pharmacologic treatment of neuropathic pain after trigeminal nerve injury, as this condition may be especially influenced by placebo factors. Finally, we have a detailed discussion of how knowledge of placebo mechanisms may help improve the understanding, diagnosis, and treatment of orofacial neuropathic pain, and we illustrate pitfalls and opportunities of applying this knowledge to the test of dental treatments.

Assessment of experimental orofacial pain, pleasantness and unpleasantness via standardized psychophysical testing

BACKGROUND

Somatosensory assessment within the orofacial region may be performed using highly standardized quantitative sensory testing (QST). However, the function of the C-tactile (CT) afferent, a nerve fibre linked to the perception of pleasant touch, is usually not evaluated. Furthermore, the perception of unpleasantness is also rarely assessed, a dimension not only limited to a painful experience. Therefore, the primary aim was to apply standardized QST stimuli as well as standardized pleasant stimuli and evaluate their potential capacity for evocation of perceived pain, pleasant and unpleasant sensations in the facial region.

METHODS

Twenty-one female participants underwent QST as per the protocol derived from the German Research Network on Neuropathic Pain. For the first time, two modified protocols were used to investigate stimuli for perceived pleasantness and unpleasantness.

RESULTS

Thermal stimuli provided separate thresholds for each sensation. From certain mechanical stimuli (e.g., vibration), overlap between the perceived sensations of pleasantness and unpleasantness was identified. It was not possible to evoke only an unpleasant sensation without a painful contribution, and both these sensations increased significantly when utilizing an increasing pinprick force (p < 0.011). Between dynamic stimuli, the brush was rated as significantly more pleasant than the cotton wool tip (p = 0.015). A quadratic model provided the best fit for velocity against mean pleasantness ratings (R²  = 0.62 ± 0.08), supporting previous CT afferent literature to some extent.

CONCLUSION

Stimuli were generally not isolated to one sensation, highlighting the multidimensional construct of stimulus perception and the need for scales to capture this.

SIGNIFICANCE

The battery of QST tests from the DFNS protocol has been modified to investigate pleasant and unpleasant sensations. This allows the evaluation of psychophysical properties across standardized dimensions to provide a thorough view of somatosensory function and to better understand the affective spectrum of somatosensory function.

Trigeminal nociceptive function and oral somatosensory functional and structural assessment in patients with diabetic peripheral neuropathy

This case-control study primarily compared the trigeminal nociceptive function, the intraoral somatosensory profile and possible structural nerve changes between diabetic peripheral neuropathy (DPN, n = 12) patients and healthy participants (n = 12). The nociceptive blink reflex (nBR) was recorded applying an electrical stimulation over the entry zone of the right supraorbital (V1R), infraorbital (V2R) and mental (V3R) and left infraorbital (V2L) nerves. The outcomes were: individual electrical sensory (I₀) and pain thresholds (I_P); root mean square (RMS), area-under-the-curve (AUC) and onset latencies of R2 component of the nBR. Furthermore, a standardized full battery of quantitative sensory testing (QST) and intraepidermal nerve fibre density (IENFD) or  nerve fibre length density (NFLD) assessment were performed, respectively, on the distal leg and oral mucosa. As expected, all patients had altered somatosensory sensitivity and lower IENFD in the lower limb. DPN patients presented higher I₀, I_P, RMS and AUC values (p < 0.050), lower warm detection thresholds (WDT) (p = 0.004), higher occurrence of paradoxical heat sensation (PHS) (p = 0.040), and a lower intraoral NFLD (p = 0.048) than the healthy participants. In addition, the presence of any abnormal intraoral somatosensory finding was more frequent in the DPN patients when compared to the reference group (p = 0.013). Early signs of trigeminal nociceptive facilitation, intraoral somatosensory abnormalities and loss of intraoral neuronal tissue can be detected in DPN patients.

The effect of orthodontic separator and short-term fixed orthodontic appliance on inflammatory mediators and somatosensory function

BACKGROUND

Although inflammation can alter cytokines release and nerve function, it is not yet fully established if orthodontic-induced inflammation can cause significant extraoral trigeminal somatosensory alterations and release of inflammatory chemical mediators.

OBJECTIVE

The primary aim of this study was to investigate the impact of orthodontic separator and short-term fixed orthodontic appliance on the extraoral trigeminal somatosensory function and concentrations of cytokines in the gingival crevicular fluid (GCF).

METHODS

Twenty-two female patients were evaluated as follow: baseline, 24 hour-after elastomeric separator (-aES), 24 hour- and 1 month-after bonding brackets (-aBB) at both arches. The outcome variables were as follows: self-reported pain (Visual Analog Scale), QSTs (current perception threshold-CPT, cold detection threshold-CDT, warm detection threshold-WDT, mechanical detection threshold-MDT, mechanical suprathreshold-MST and wind-up ratio-WUR. All QSTs were performed at infra-orbital and mental nerve entry zone at patient`s dominant side. In addition, GCF samples in order to assess cytokines profile (IL-1β,IL-8,IL-6 and TNF-α) were collected. ANOVA and Tukey's post hoc analyses were performed (a = 5%).

RESULTS

Patients reported higher pain intensity 24 hour-aBB compared to baseline and 24 hour-aES (P < 0.050). Patients were less sensitive to pin-prick pain (MST) at 24 hour-aBB and 1 month-aBB compared to baseline (P < 0.006). Significant increases in IL-6 levels were observed 24 hour-aBB (P < 0.001). Multiple comparison analysis showed significant increase in IL-1β levels (P < 0.001) and TNF-α (P < 0.001) 1 month-aBB compared to baseline.

CONCLUSION

Elastomeric separators only induced mild pain and were not able to significantly increase proinflammatory cytokines level in the GCF. In addition, orthodontic fixed appliance may induce only minor somatosensory changes at extraoral trigeminal locations.

Jaw Exercise Therapy and Psychoeducation to Reduce Oral Parafunctional Activities for the Management of Persistent Dentoalveolar Pain

Objective

To retrospectively analyze the effects of our original combination therapy treatment on patients with nonodontogenic persistent dentoalveolar pain.

Methods

Twenty-one patients suffering from persistent dentoalveolar pain (nineteen females and two males; mean age ± standard deviation: 55.7 ± 19.6 years) participated in this study. They were treated with a therapy combination of jaw exercise and psychoeducation to reduce oral parafunctional activities every month. The intensity of pain in these subjects was evaluated using a numerical rating scale (NRS) before and after treatment.

Results

The NRSs at the baseline ranged from 5 to 10 (median, 8), from 0 to 10 (median, 2) at one month after treatment, from 0 to 10 (median, 1) at three months after treatment, and from 0 to 10 (median, 0) at the end of treatment. Pain intensity after treatment improved significantly.

Conclusion

There was a significant reduction in pain after our combination of therapies as nonpharmacological treatments, and therefore this treatment could be useful in the management of NPDP patients.

Development and preliminary evaluation of a new screening instrument for atypical odontalgia and persistent dentoalveolar pain disorder

AIM

To develop and preliminarily evaluate a new screening instrument for atypical odontalgia (AO) or persistent dentoalveolar pain disorder (PDAP). To evaluate the instrument's performance in detecting AO/PDAP amongst a heterogeneous group of orofacial pain conditions and pain-free controls and empirically compare its performance with an established neuropathic screening instrument (S-LANSS), which is the best available standard.

METHODS

The study design was cross-sectional; subjects recruited included a convenience sample of pain-free controls (n = 21) and four groups of orofacial pain conditions: AO/PDAP (n = 22); trigeminal neuralgia (n = 21); temporomandibular disorder (n = 41); and acute dental pain (n = 41). The instrument's internal reliability and factor structure were examined alongside its sensitivity and specificity and ROC-determined threshold score.

RESULTS

The 9 AO/PDAP-specific items were found to moderately correlate with the S-LANSS (r = 0.58; P < 0.01). The 14-items of the full instrument were examined using exploratory factor analysis and reduced to ten items in a two-factor structure that explained 96% of the variance. This 10-item final instrument had a ROC area of 0.77 (95% CI: 0.67; 0.88), sensitivity of 77% (95% CI: 55; 92%), and specificity of 69% (95% CI: 60; 77%) with an intentionally higher false-positive rate than false-negative rate. In contrast, the S-LANSS exhibited sensitivity of 32% (95% CI: 14;55%) and specificity of 78% (95% CI: 70;85%) with less optimal false-positive versus false-negative rates.

CONCLUSION

This preliminary study confirms the new screening instrument for AO/PDAP merits progression to field testing.

OnabotulinumtoxinA injections for atypical odontalgia: an open-label study on nine patients

Background

Atypical odontalgia (AO) manifests as continuous pain in the region of one or several teeth, in the absence of signs of dental pathology. Currently, there is insufficient evidence to establish treatment guidelines for AO. The aim of this study was to describe the effectiveness and safety of treatment with OnabotulinumtoxinA (OnabotA) on a series of patients with AO.

Methods

Nine patients with AO (four males and five females, aged between 31 and 77 years) received injections of OnabotA in the region of pain. The dosage used in each procedure ranged between 10 and 30 U, spread between 4 and 12 injection sites along the gums (n=9), the lips (n=3), and the hard palate (n=1). The median follow-up time was 27 months (interquartile range, IQR 20–40) and the median number of injection sessions per patient was seven (IQR 4.5–9). The assessment variables included the change in the maximal intensity of pain on a 0–10 numerical rating scale (NRS), the response latency, and the duration of the effect.

Results

All patients experienced a significant improvement, with ≥50% of reduction in the intensity of the maximal pain. The median of reduction of maximal pain after treatment was six points on the NRS (IQR 5–8.5). The response latency was 2–15 days and the duration of the effect was 2–6 months. No significant adverse reactions were registered.

Conclusion

OnabotA may be a safe and effective option for the treatment of AO.

Comparison of orofacial thermal sensitivity assessed with simple devices and sophisticated equipment

BACKGROUND

Simple thermal devices providing reliable data are needed to detect somatosensory disturbances in non-specialized clinical settings. Currently, evidence is lacking about their use. Therefore, the aim was to compare the assessment of perceived thermal sensitivity/pain in healthy humans with a state-of-the-art thermotester and with simple inexpensive customized thermal aluminium devices.

METHODS

Twenty healthy volunteers participated in the study. The infraorbital region and the tip of the tongue were tested with the Medoc Pathway thermotester and simple aluminium thermal devices, with temperatures varying between 5-50°C. A numerical rating scale (NRS) from 0-50-100 was used for rating the perceived thermal sensitivity/painfulness. A control experiment was performed with 10 of the participants to test the potential impact of temporal summation of thermal stimuli with the use of temperature ramps (Medoc) compared with static temperature (simple devices).

RESULTS

In the original experiment, the scores from the thermotester stimulation were higher than the scores for stimulation with the simple thermal devices with mean NRS differences between devices of 7.2 and 10.2 for the two tested regions. In the control experiment, the mean NRS differences decreased to -0.3 and 2.2, respectively.

CONCLUSIONS

Provided that temporal summation of the thermal stimuli was avoided, there were only minor differences in perceived thermal sensitivity/painfulness between the two different assessment methods at both test sites. Therefore, the simple thermal devices can be useful for assessment of thermal sensitivity in clinical settings without access to expensive sophisticated equipment. However, more sophisticated equipment is needed for threshold measurements.

SIGNIFICANCE

This study indicates that simple thermal devices to some extent can be used in a comparable way with sophisticated thermal stimulators. Therefore, they can be useful in clinical practice, where access to further equipment is lacking.

Oral surgery II: Part 5. Chronic orofacial pain

Chronic orofacial pain syndromes represent a diagnostic challenge for any practitioner. Patients are frequently misdiagnosed or attribute their pain to a prior event such as a dental procedure, ENT problem or facial trauma. Psychiatric symptoms of depression and anxiety are prevalent in this population and compound the diagnostic conundrum. Treatment is less effective than in other pain syndromes and thus often requires a multidisciplinary approach to address the many facets of these conditions.

Mechanical sensitivity and psychological factors in patients with burning mouth syndrome

OBJECTIVES

The aim of this study was to compare mechanical sensitivity on the tongue using quantitative sensory testing (QST) and psychological factors using the General Health Questionnaire (GHQ) between burning mouth syndrome (BMS) patients and healthy participants.

MATERIALS AND METHODS

Participants comprised 20 female BMS patients (68.1 ± 7.4 years) and 20 healthy females (65.4 ± 4.6 years). Psychological factors were evaluated with GHQ. Tactile detection thresholds (TDT) and filament-prick pain detection thresholds (FPT) were used to evaluate mechanical sensitivity on the tongue in all participants. TDT and FPT were measured on the tongue within both the painful area and the non-painful area in BMS patients, and on the tongue on both sides in healthy participants. As controls, TDT and FPT were measured with Semmes-Weinstein monofilaments on the skin of the mentum and palm in all participants.

RESULTS

GHQ scores were significantly higher in BMS patients than in healthy participants (P = 0.024). No significant differences in TDT or FPT on the tongue, mentum, or palm were seen between BMS patients and healthy participants (P > 0.05). BMS patients showed no significant differences in TDT or FPT between the painful and non-painful areas on the tongue (P > 0.05). There were no significant correlations among TDT/FPT and GHQ score in BMS patients (P > 0.05).

CONCLUSIONS

These findings could indicate a more important role for psychological factors than mechanical sensitivity in BMS pathophysiology.

CLINICAL RELEVANCE

Pain on the tongue in elderly female patients with BMS may be more related to psychological factors.

Quantitative sensory testing for assessment of somatosensory function in human oral mucosa: a review

OBJECTIVE

This narrative review provides an overview of the quantitative sensory testing (QST) to assess somatosensory function in human oral mucosa.

MATERIAL AND METHODS

A literature search was conducted in the PubMed database to identify studies in vivo on human oral mucosa using QST methods. A list of 149 articles was obtained and screened. A total of 36 relevant articles remained and were read in full text. Manual search of the reference lists identified eight additional relevant studies. A total of 44 articles were included for final assessment.

RESULTS

The included studies were divided into six categories according to the study content and objective. In each category, there was a great variety of aims, methods, participants and outcome measures. The application of QST has nevertheless helped to monitor somatosensory function in experimental models of intraoral pain, effects of local anesthesia, after oral and maxillofacial surgery and after prosthodontic and orthodontic treatment.

CONCLUSIONS

QST has been proved to be sufficiently stable and reliable, and valuable information has been obtained regarding somatosensory function in healthy volunteers, special populations and orofacial pain patients. However, as most of the studies were highly heterogeneous, the results are difficult to compare quantitatively. A standardized intraoral QST protocol is recommended and expected to help advance a mechanism-based assessment of neuropathies and other intraoral pain conditions.

Psychiatric comorbidities in patients with Atypical Odontalgia

OBJECTIVE

Atypical Odontalgia (AO) is a condition characterized by tooth pain with no apparent cause. Although psychiatric comorbidity seems to be very common, it has rarely been studied. To clarify the influence of psychiatric comorbidity on the clinical features in patients with AO, we retrospectively evaluated their examination records.

METHODS

Clinical features and psychiatric diagnoses of 383 patients with AO were investigated by reviewing patients' medical records and referral letters. Psychiatric diagnoses were categorized according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). We also analyzed visual analogue scale (VAS), self-rating depression scale (SDS), and the short-form McGill pain questionnaire (SF-MPQ) scores.

RESULTS

Of the 383 patients with AO, 177 (46.2%) had comorbid psychiatric disorders. The most common were depressive disorders (15.4%) and anxiety disorders (10.1%). Serious psychotic disorders such as bipolar disorder (3.0%) and schizophrenia (1.8%) were rare. Dental trigger of AO was reported in 217 (56.7%) patients. There were no significant correlations between psychiatric comorbidities and most of the demographic features. Higher VAS and SDS scores, higher frequency of sleep disturbance, and higher ratings of "Fearful" and "Punishing-cruel" descriptors of the SF-MPQ were found in patients with psychiatric comorbidity.

CONCLUSIONS

About half of AO patients had comorbid psychiatric disorders. Dental procedures are not necessarily causative factors of AO. In AO patients with comorbid psychiatric disorders, pain might have a larger emotional component than a sensory one. VAS, SDS, and SF-MPQ scores might aid in the noticing of underlying comorbid psychiatric disorders in AO patients.

Multifactorial assessment of measurement errors affecting intraoral quantitative sensory testing reliability

BACKGROUND AND PURPOSE (AIMS)

Measurement error of intraoral quantitative sensory testing (QST) has been assessed using traditional methods for reliability, such as intraclass correlation coefficients (ICCs). Most studies reporting QST reliability focused on assessing one source of measurement error at a time, e.g., inter- or intra-examiner (test-retest) reliabilities and employed two examiners to test inter-examiner reliability. The present study used a complex design with multiple examiners with the aim of assessing the reliability of intraoral QST taking account of multiple sources of error simultaneously.

METHODS

Four examiners of varied experience assessed 12 healthy participants in two visits separated by 48h. Seven QST procedures to determine sensory thresholds were used: cold detection (CDT), warmth detection (WDT), cold pain (CPT), heat pain (HPT), mechanical detection (MDT), mechanical pain (MPT) and pressure pain (PPT). Mixed linear models were used to estimate variance components for reliability assessment; dependability coefficients were used to simulate alternative test scenarios.

RESULTS

Most intraoral QST variability arose from differences between participants (8.8-30.5%), differences between visits within participant (4.6-52.8%), and error (13.3-28.3%). For QST procedures other than CDT and MDT, increasing the number of visits with a single examiner performing the procedures would lead to improved dependability (dependability coefficient ranges: single visit, four examiners=0.12-0.54; four visits, single examiner=0.27-0.68). A wide range of reliabilities for QST procedures, as measured by ICCs, was noted for inter- (0.39-0.80) and intra-examiner (0.10-0.62) variation.

CONCLUSION

Reliability of sensory testing can be better assessed by measuring multiple sources of error simultaneously instead of focusing on one source at a time. In experimental settings, large numbers of participants are needed to obtain accurate estimates of treatment effects based on QST measurements. This is different from clinical use, where variation between persons (the person main effect) is not a concern because clinical measurements are done on a single person.

IMPLICATIONS

Future studies assessing sensory testing reliability in both clinical and experimental settings would benefit from routinely measuring multiple sources of error. The methods and results of this study can be used by clinical researchers to improve assessment of measurement error related to intraoral sensory testing. This should lead to improved resource allocation when designing studies that use intraoral quantitative sensory testing in clinical and experimental settings.

Persistent idiopathic facial pain

Background

Persistent idiopathic facial pain (PIFP) is a chronic disorder recurring daily for more than two hours per day over more than three months, in the absence of clinical neurological deficit. PIFP is the current terminology for Atypical Facial Pain and is characterized by daily or near daily pain that is initially confined but may subsequently spread. Pain cannot be attributed to any pathological process, although traumatic neuropathic mechanisms are suspected. When present intraorally, PIFP has been termed ‘Atypical Odontalgia’, and this entity is discussed in a separate article in this special issue. PIFP is often a difficult but important differential diagnosis among chronic facial pain syndromes.

Aim

To summarize current knowledge on diagnostic criteria, differential diagnosis, pathophysiology and management of PIFP.

Methods

We present a narrative review reporting current literature and personal experience. Additionally, we discuss and differentiate the common differential diagnoses associated with PIFP including traumatic trigeminal neuropathies, regional myofascial pain, atypical neurovascular pains and atypical trigeminal neuropathic pains.

Results and conclusion

The underlying pathophysiology in PIFP is still enigmatic, however neuropathic mechanisms may be relevant. PIFP needs interdisciplinary collaboration to rule out and manage secondary causes, psychiatric comorbidities and other facial pain syndromes, particularly trigeminal neuralgia. Burden of disease and psychiatric comorbidity screening is recommended at an early stage of disease, and should be addressed in the management plan. Future research is needed to establish clear diagnostic criteria and treatment strategies based on clinical findings and individual pathophysiology.

Neuropathic orofacial pain: Facts and fiction

Definition and taxonomy This review deals with neuropathic pain of traumatic origin affecting the trigeminal nerve, i.e. painful post-traumatic trigeminal neuropathy (PTTN). Symptomatology The clinical characteristics of PTTN vary considerably, partly due to the type and extent of injury. Symptoms involve combinations of spontaneous and evoked pain and of positive and negative somatosensory signs. These patients are at risk of going through unnecessary dental/surgical procedures in the attempt to eradicate the cause of the pain, due to the fact that most dentists only rarely encounter PTTN. Epidemiology Overall, approximately 3% of patients with trigeminal nerve injuries develop PTTN. Patients are most often female above the age of 45 years, and both physical and psychological comorbidities are common. Pathophysiology PTTN shares many pathophysiological mechanisms with other peripheral neuropathic pain conditions. Diagnostic considerations PTTN may be confused with one of the regional neuralgias or other orofacial pain conditions. For intraoral PTTN, early stages are often misdiagnosed as odontogenic pain. Pain management Management of PTTN generally follows recommendations for peripheral neuropathic pain. Expert opinion International consensus on classification and taxonomy is urgently needed in order to advance the field related to this condition.