Thomas List

Aarhus University, Aarhus, Central Jutland, Denmark

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Publications (105)208.9 Total impact

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    ABSTRACT: Chronic oro-facial pain conditions such as persistent idiopathic facial pain (PIFP), atypical odontalgia (AO) and burning mouth syndrome (BMS), usually grouped together under the concept of idiopathic oro-facial pain, remain a diagnostic and therapeutic challenge. Lack of understanding of the underlying pathophysiological mechanisms of these pain conditions is one of the important reasons behind the problems in diagnostic and management. During the last two decades, neurophysiological, psychophysical, brain imaging and neuropathological methods have been systematically applied to study the trigeminal system in idiopathic oro-facial pain. The findings in these studies have provided evidence for neuropathic involvement in the pathophysiology of PIFP, AO and BMS. The present qualitative review is a joint effort of a group of oro-facial pain specialists and researchers to appraise the literature on idiopathic oro-facial pain with special focus on the currently available studies on their pathophysiological mechanisms. The implications of the findings of these studies for the clinical diagnosis and treatment of idiopathic oro-facial pain conditions are discussed. © 2014 John Wiley & Sons Ltd.
    Journal of Oral Rehabilitation 12/2014; · 2.34 Impact Factor
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    ABSTRACT: The reliability of comprehensive intra-oral quantitative sensory testing (QST) protocol has not been examined systematically in patients with chronic oro-facial pain. The aim of the present multicentre study was to examine test–retest and interexaminer reliability of intra-oral QST measures in terms of absolute values and z-scores as well as within-session coefficients of variation (CV) values in patients with atypical odontalgia (AO) and healthy pain-free controls. Forty-five patients with AO and 68 healthy controls were subjected to bilateral intra-oral gingival QST and unilateral extratrigeminal QST (thenar) on three occasions (twice on 1 day by two different examiners and once approximately 1 week later by one of the examiners). Intra-class correlation coefficients and kappa values for interexaminer and test–retest reliability were computed. Most of the standardised intra-oral QST measures showed fair to excellent interexaminer (9–12 of 13 measures) and test–retest (7–11 of 13 measures) reliability. Furthermore, no robust differences in reliability measures or within-session variability (CV) were detected between patients with AO and the healthy reference group. These reliability results in chronic orofacial pain patients support earlier suggestions based on data from healthy subjects that intra-oral QST is sufficiently reliable for use as a part of a comprehensive evaluation of patients with somatosensory disturbances or neuropathic pain in the trigeminal region.
    Journal of Oral Rehabilitation 10/2014; · 2.34 Impact Factor
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    ABSTRACT: AimsThe aim was to study achieved competences in temporomandibular disorders (TMD)/orofacial pain (OP) at two universities by comparing student's knowledge and understanding, satisfaction with their education and confidence in their clinical competences of TMD/OP.Methods The study was conducted in collaboration between Malmö University, Sweden—which uses problem-based learning—and the University of Naples Federico II, Italy—which uses traditional educational methods. Final-semester dental students responded to a self-report questionnaire regarding their knowledge and understanding, interpretation of cases histories, clinical experience, satisfaction and confidence in clinical examination, management and treatment evaluation.ResultsNo significant difference was found between the students regarding knowledge and understanding. Eighty-seven per cent of the Malmö students and 96% of the Naples students met the criterion on achieved competence. Malmö students had a higher per cent of correct diagnoses than Naples students in the interpretation of case histories. Overall, Malmö students reported most clinical experience and higher confidence than Naple students.Conclusions The main findings were that students from Malmö and Naples were, similar in knowledge and understanding of TMD/OP and in satisfaction with their clinical competences. However, Malmö students perceived more confidence in clinical management of patients with TMD/OP. This may reflect that, besides the theoretical part of the programme, a sufficient level of clinical exposure to patients with TMD/OP is essential to gain competences in TMD/OP.
    European Journal Of Dental Education 08/2014; · 1.45 Impact Factor
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    ABSTRACT: Noxious tooth pulp stimulation elicits changes in central neurons in the trigeminal brainstem complex in animals. Also, painful electrical tooth stimulation (TS) in humans has been shown to evoke changes in gingival blood flow suggesting an axon-reflex mediated neurogenic inflammation. No human studies have so far investigated the effect of experimental tooth pain on the somatosensory sensitivity of the gingiva adjacent to the stimulated tooth. Objective: The aim of this study was to evaluate the possible effect of painful electrical tooth stimulation on gingival somatosensory sensitivity in a randomized cross-over design. Method: Thirteen healthy volunteers (6 women, 7 men; 28.4 ± 5.0 years) participated in two experimental sessions (Pain vs. Control) in randomized order. Thirteen standardized quantitative sensory testing (QST) measures were obtained on the buccal attached gingiva of an upper central incisor before, immediately after and 30 min after 3 x 2 min of moderately painful (50 on a 0-100 numerical rating scale) electrical TS (5 Hz, 10 ms pulses). TS below the individual sensory threshold served as the non-painful control. Result: Painful TS evoked significant decreases in warmth and heat pain thresholds (increased sensitivity) (P < 0.001) and increases in mechanical detection thresholds as well as pressure pain thresholds (decreased sensitivity)(P < 0.050). Similar thermal threshold changes (P < 0.019) but no changes in mechanical sensitivity (P > 0.086) were found in the control session. No significant somatosensory changes were found in either session regarding cold detection and cold pain thresholds, thermal sensory limen, mechanical pain threshold, mechanical pain sensitivity, wind-up, or vibration detection (P > 0.061). Conclusion: Subtle differential effects on in gingival thermal and mechanical somatosensory sensitivity were detected up to 30 min after short-term painful TS, indicating involvement of competing facilitatory and inhibitory mechanisms. Only effects on mechanical sensitivity were specific to painful TS.
    IADR General Session and Exhibition 2014; 06/2014
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    ABSTRACT: Objective: Results from several studies indicate that serotonin (5-HT) may have a role in the pathogenesis of chronic muscle pain. The aim of this study was to investigate if the 5-HT3 receptor antagonist granisetron reduces experimental myalgia induced by hypertonic saline. Method: Sixty healthy subjects (30 women and 30 men) participated in the study. Blood or saliva was sampled for later genetic analyses to investigate if polymorphisms of the HTR3A and HTR3B genes, coding for the 5-HT3A and 5-HT3B receptors respectively, contribute to pain perception and the efficacy of granisetron. A bilateral injection of hypertonic saline (5.5%, 0.2 mL) was administered into the masseter muscle as an internal control (injection 1). Thirty minutes later 0.5 mL granisetron (1 mg/mL) was injected into the masseter muscle on one side and 0.5 mL isotonic saline (9 mg/mL) on the contralateral side in a randomized, double-blind order. This followed by another bilateral hypertonic saline injection (injection 2) after 2 min. Pain induced by each saline injection was assessed on a visual analogue scale (VAS) immediately after the injections and then every 15 sec until pain subsided. Result: The first injection of hypertonic saline induced pain of similar intensity on both sides (median 37.9) that lasted for less than 5 min. However, the second injection of hypertonic saline induced pain of significantly less intensity (P < 0.001) and shorter duration (P < 0.05) on the side pretreated with granisetron compared with the control side. The genetic analyses are ongoing. Conclusion: This study showed that blocking of the 5-HT3 receptor with granisetron decreased experimental pain induced by intramuscular injection of hypertonic saline in healthy subjects and thus that granisetron may serve as a potential analgesic drug for myalgic conditions. Further studies are needed to explore the effect of granisetron in chronic myalgia.
    IADR General Session and Exhibition 2014; 06/2014
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    ABSTRACT: Objective: Dopaminergic pathways could be involved in the pathophysiology of myofascial TMD. Therefore, the aim of this study was to investigate the levels of dopamine as well a serotonin (5-HT) in plasma between patients with myofascial temporomandibular disorders (M-TMD) and healthy subjects. Method: Fifteen M-TMD patients (mean age: 31.8 ± 13.4 yrs) and 15 age and sex-matched healthy subjects (mean age: 31.6 ± 12.4 yrs) were included in this study. The Diagnosis M-TMD was established according to the research Diagnostic Criteria for TMD. A venous blood sample was collected and present pain intensity (0-10 numeric rating scale) and the pressure pain threshold (PPT, kPa) over the masseter muscles were assessed. Independent samples t-test and Pearson’s correlation test was used for statistical analyses. Result: The plasma level of dopamine differed significantly between M-TMD patients (4.98 ± 2.55 nM) and healthy controls (2.73 ± 1.24 nM; P < 0.01). A significant difference for plasma 5-HT was not observed between groups (P = 0.75). The M-TMD patients had significantly higher present pain intensity (P < 0.001), and lower PPT (P < 0.01) compared to the healthy controls. Importantly, the level of dopamine correlated significantly with pain intensity (r = 0.518, n = 28, P < 0.01), but not with PPT (r = -0.133, n = 28, P = 0.498). Conclusion: The M-TMD patients had significantly higher levels of dopamine, present pain intensity and lower PPT, but a significant difference for 5-HT was not observed. Dopamine had a significant positive correlation with pain intensity. This and previous studies suggest that dopaminergic pathways could play a role in the pathophysiology of M-TMD but more research is required.
    IADR General Session and Exhibition 2014; 06/2014
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    ABSTRACT: To examine (1) the occurrence of magnetic resonance imaging (MRI) signal changes in the painful regions of patients with atypical odontalgia (AO) and (2) the correlation of such findings to periapical bone defects detected with a comprehensive radiographic examination including cone beam computed tomography (CBCT).
    Journal of oral & facial pain and headache. 06/2014; 28(3):233-42.
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    ABSTRACT: Aims: To investigate the association between experimental tooth clenching and the release of β-endorphin in patients with myofascial temporomandibular disorders (M-TMD) and healthy subjects. Methods: Fifteen M-TMD patients and 15 healthy subjects were included and assigned an experimental tooth-clenching task. Venous blood was collected and pain intensity was noted on a visual analog scale. The masseter pressure pain threshold (PPT) was assessed 2 hours before the clenching task and immediately after. A mixed-model analysis of variance was used for statistical analyses. Results: Significant main effects for time and group were observed for pain intensity and PPT, with significantly lower mean values of pain intensity (P < .001) and PPT (P < .01) after the clenching task compared with baseline. M-TMD patients had significantly higher pain intensity (P < .001) and significantly lower PPT (P < .05) than healthy subjects. No significant time or group effects were observed for the level of β-endorphin. Neither pain intensity nor PPT correlated significantly with β-endorphin levels. Conclusion: This experimental tooth-clenching task was not associated with significant alterations in β-endorphin levels over time, but with mechanical hyperalgesia and low to moderate levels of pain in healthy subjects and M-TMD patients, respectively. More research is required to understand the role of the β-endorphinergic system in the etiology of M-TMD.
    Journal of oral & facial pain and headache. 03/2014; 28(2):159-64.
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    ABSTRACT: We reported the development and psychometric evaluation of a Swedish 14-item and a five-item short form of the Oral Health Impact Profile. The 14-item version was derived from the English-language short form developed by Slade in1997. The five-item version was derived from the German-language short form developed by John et al. in 2006. Validity, reliability and normative values for the two short form summary scores were determined in a random sample of the adult Swedish population (response rate: 46%, N = 1366 subjects). Subjects with sufficient OHRQoL information to calculate a summary score (N = 1309) were on average 50·1 ± 17·4 years old, and 54% were women. Short form summary scores correlated highly with the 49-item OHIP-S (r ≥ 0·97 for OHIP-S14, r ≥ 0·92 for OHIP-S5) and with self-report of oral health (r ≥ 0·41). Reliability, measured with Cronbach's alpha (0·91 for OHIP-S14, 0·77 for OHIP-S5), was sufficient. In the general population, 50% of the subjects had ≥2 OHIP-S14 score points and 10% had ≥11 points, respectively. Among subjects with their own teeth only and/or fixed dental prostheses and with partial removable dental prostheses, 50% of the population had ≥2 OHIP-S14 score points, and 10% had ≥11 points. For subjects with complete dentures, the corresponding figures were 3 and 24 points. OHIP-S5 medians for subjects in the three population groups were 1, 1 and 2 points. Swedish 14-item and 5-item short forms of the OHIP have sufficient psychometric properties and provide a detailed overview about impaired OHRQoL in Sweden. The norms will serve as reference values for future studies.
    Journal of Oral Rehabilitation 01/2014; · 2.34 Impact Factor
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    ABSTRACT: In electromyographic (EMG) and functional magnetic resonance imaging (fMRI) studies, muscle and brain activity was compared during low levels of tooth clenching using a novel biting device to control bite force. A total of 21 healthy subjects performed motor tasks, comprising tooth clenching at 5, 10 and 20 N. During all measurements, subjects kept the novel bite device between the anterior teeth during tooth clenching. The EMG study (n = 15) characterised jaw muscle activity for the three motor tasks and demonstrated significant differences in root mean square (RMS) EMG amplitude between 5-, 10- and 20-N tooth clenching (F = 46·21, P < 0·001). There were no differences in variability of muscle activity between the three tooth-clenching levels. In an fMRI pilot study (n = 6), statistical comparisons were used to identify brain regions with significant activation in the subtraction of baseline from 5- or 20-N tooth-clenching activity. 5- and 20-N tooth clenching significantly and bilaterally activated the sensorimotor cortex, supplementary motor area, cerebellum and basal ganglia (P < 0·05, corrected for multiple comparisons). However, activation of each brain region did not differ significantly between two tooth-clenching tasks. Based on these preliminary findings, we propose that the novel biting device may be useful in further fMRI studies on controlled jaw muscle activation patterns in different craniofacial pain conditions. In addition, our fMRI result suggests that there are no significant differences in brain activity within low levels of tooth clenching with controlled force.
    Journal of Oral Rehabilitation 01/2014; · 2.34 Impact Factor
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    ABSTRACT: There is a need to expand the current temporomandibular disorders' (TMDs) classification to include less common but clinically important disorders. The immediate aim was to develop a consensus-based classification system and associated diagnostic criteria that have clinical and research utility for less common TMDs. The long-term aim was to establish a foundation, vis-à-vis this classification system, that will stimulate data collection, validity testing and further criteria refinement. A working group [members of the International RDC/TMD Consortium Network of the International Association for Dental Research (IADR), members of the Orofacial Pain Special Interest Group (SIG) of the International Association for the Study of Pain (IASP), and members from other professional societies] reviewed disorders for inclusion based on clinical significance, the availability of plausible diagnostic criteria and the ability to operationalise and study the criteria. The disorders were derived from the literature when possible and based on expert opinion as necessary. The expanded TMDs taxonomy was presented for feedback at international meetings. Of 56 disorders considered, 37 were included in the expanded taxonomy and were placed into the following four categories: temporomandibular joint disorders, masticatory muscle disorders, headache disorders and disorders affecting associated structures. Those excluded were extremely uncommon, lacking operationalised diagnostic criteria, not clearly related to TMDs, or not sufficiently distinct from disorders already included within the taxonomy. The expanded TMDs taxonomy offers an integrated approach to clinical diagnosis and provides a framework for further research to operationalise and test the proposed taxonomy and diagnostic criteria.
    Journal of Oral Rehabilitation 01/2014; 41(1):2-23. · 2.34 Impact Factor
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    ABSTRACT: The purpose of this systematic review was to describe the prevalence of whiplash trauma in patients with temporomandibular disorders (TMDs) and to describe clinical signs and symptoms in comorbid TMD/whiplash compared with TMD localised to the facial region. A systematic literature search of the PubMed, Cochrane Library and Bandolier databases was carried out for articles published from 1 January 1966 to 31 December 2012. The systematic search identified 129 articles. After the initial screening of abstracts, 32 articles were reviewed in full text applying inclusion and exclusion criteria. Six studies on the prevalence of neck trauma in patients with TMD met the inclusion criteria and were included in the review. Two of the authors evaluated the methodological quality of the included studies. The reported prevalence of whiplash trauma ranged from 8·4% to 70% (median 35%) in TMD populations, compared with 1·7-13% in the non-TMD control groups. Compared with patients with TMD localised to the facial region, TMD patients with a history of whiplash trauma reported more TMD symptoms, such as limited jaw opening and more TMD pain, and also more headaches and stress symptoms. In conclusion, the prevalence of whiplash trauma is higher in patients with TMD compared with non-TMD controls. Furthermore, patients with comorbid TMD/whiplash present with more jaw pain and more severe jaw dysfunction compared with TMD patients without a history of head-neck trauma. These results suggest that whiplash trauma might be an initiating and/or aggravating factor as well as a comorbid condition for TMD.
    Journal of Oral Rehabilitation 01/2014; 41(1):59-68. · 2.34 Impact Factor
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    ABSTRACT: Aims: The original Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) Axis I diagnostic algorithms have been demonstrated to be reliable. However, the Validation Project determined that the RDC/TMD Axis I validity was below the target sensitivity of ≥ 0.70 and specificity of ≥ 0.95. Consequently, these empirical results supported the development of revised RDC/TMD Axis I diagnostic algorithms that were subsequently demonstrated to be valid for the most common pain-related TMD and for one temporomandibular joint (TMJ) intra-articular disorder. The original RDC/TMD Axis II instruments were shown to be both reliable and valid. Working from these findings and revisions, two international consensus workshops were convened, from which recommendations were obtained for the finalization of new Axis I diagnostic algorithms and new Axis II instruments. Methods: Through a series of workshops and symposia, a panel of clinical and basic science pain experts modified the revised RDC/TMD Axis I algorithms by using comprehensive searches of published TMD diagnostic literature followed by review and consensus via a formal structured process. The panel's recommendations for further revision of the Axis I diagnostic algorithms were assessed for validity by using the Validation Project's data set, and for reliability by using newly collected data from the ongoing TMJ Impact Project-the follow-up study to the Validation Project. New Axis II instruments were identified through a comprehensive search of the literature providing valid instruments that, relative to the RDC/TMD, are shorter in length, are available in the public domain, and currently are being used in medical settings. Results: The newly recommended Diagnostic Criteria for TMD (DC/TMD) Axis I protocol includes both a valid screener for detecting any pain-related TMD as well as valid diagnostic criteria for differentiating the most common pain-related TMD (sensitivity ≥ 0.86, specificity ≥ 0.98) and for one intra-articular disorder (sensitivity of 0.80 and specificity of 0.97). Diagnostic criteria for other common intra-articular disorders lack adequate validity for clinical diagnoses but can be used for screening purposes. Inter-examiner reliability for the clinical assessment associated with the validated DC/TMD criteria for pain-related TMD is excellent (kappa ≥ 0.85). Finally, a comprehensive classification system that includes both the common and less common TMD is also presented. The Axis II protocol retains selected original RDC/TMD screening instruments augmented with new instruments to assess jaw function as well as behavioral and additional psychosocial factors. The Axis II protocol is divided into screening and comprehensive selfreport instrument sets. The screening instruments' 41 questions assess pain intensity, pain-related disability, psychological distress, jaw functional limitations, and parafunctional behaviors, and a pain drawing is used to assess locations of pain. The comprehensive instruments, composed of 81 questions, assess in further detail jaw functional limitations and psychological distress as well as additional constructs of anxiety and presence of comorbid pain conditions. Conclusion: The recommended evidence-based new DC/TMD protocol is appropriate for use in both clinical and research settings. More comprehensive instruments augment short and simple screening instruments for Axis I and Axis II. These validated instruments allow for identification of patients with a range of simple to complex TMD presentations.
    Journal of oral & facial pain and headache. 01/2014; 28(1):6-27.
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    ABSTRACT: 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.
    Journal of Oral Rehabilitation 12/2013; · 2.34 Impact Factor
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    ABSTRACT: This case-control study evaluated the association of headache and other co-morbid pain with temporomandibular disorder (TMD) pain in adolescents and explored the temporal co-variance of headache and TMD pain. In a population-based sample of 12- to 19-year-olds, 350 patients with self-reported TMD pain and 350 healthy age- and sex-matched individuals were mailed questionnaires. Descriptive statistics, 95% CI, and OR analyses-logistic regression models with TMD pain as the outcome variable and adjusted for age and gender-were used for the analysis of individuals' responses. Headache, whether defined as once a week or more (OR = 6.6) or as moderate or severe (categorical), was significantly related to TMD pain. Severe headache (vs. mild) showed stronger associations with TMD (OR = 10.1) than between moderate and mild headache (OR = 5.5). Neck (OR = 4.0) and back (OR = 2.6) pain was also significantly related to TMD pain. When participants were grouped according to headache onset and TMD pain, the highest association between headache and TMD pain was found in the subgroup "Headache onset before TMD pain" (OR 9.4). In conclusion, headache appears to be independently and highly associated with TMD pain in adolescents. Neck pain and somatic complaints were also significantly associated with TMD pain. Headache seems to precede TMD pain in many adolescents with pain.
    Journal of dental research 06/2013; · 3.46 Impact Factor
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    ABSTRACT: BACKGROUND: Repeated injection of acidic saline into skeletal muscles of the leg in rodents induces a prolonged bilateral mechanical hyperalgesia that persists for up to 30 days and may be useful to model widespread muscle pain conditions. In this study, repeated injection of acidic (pH 3.3) saline solution into the masseter muscle of healthy human subjects was undertaken to determine if these injections are painful and whether they would induce a prolonged period of muscle sensitization to artificial and/or natural mechanical stimulation of the masseter and temporalis muscles. METHODS: Eighteen subjects (10 male, 8 female) participated in the study. Subjects received two injections of 0.5 mL acidic or regular isotonic saline 2 days apart, in a randomized, double blind, crossover design. RESULTS: There was no significant difference in pain intensity ratings when acidic saline injections were compared with regular saline injections. Pain area drawings were, however, significantly larger in response to the first injection of acidic saline than to the second injection of acidic saline or to either the first or second injection of regular saline. Repeated injection of acidic saline did not significantly alter pressure pain thresholds from the masseter or temporalis muscles on either the injected side or the opposite side over the 10-day post injection monitoring period. There was also no effect of injections on chewing. CONCLUSION: These findings indicate that, unlike in some rodent models, repeated injection of low pH solutions into jaw muscles of humans fails to induce a period of prolonged muscle hyperalgesia.
    European journal of pain (London, England) 05/2013; · 3.37 Impact Factor
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    ABSTRACT: Intraoral somatosensory sensitivity in patients with atypical odontalgia (AO) has not been investigated systematically according to the most recent guidelines. The aims of this study were to examine intraoral somatosensory disturbances in AO patients using healthy subjects as reference, and to evaluate the percent agreement between intraoral quantitative sensory testing (QST) and qualitative sensory testing (QualST). Forty-seven AO patients and 69 healthy control subjects were included at Universities of Washington, Malmö, and Aarhus. In AO patients, intraoral somatosensory testing was performed on the painful site, the corresponding contralateral site, and at thenar. In healthy subjects, intraoral somatosensory testing was performed bilaterally on the upper premolar gingiva and at thenar. Thirteen QST and 3 QualST parameters were evaluated at each site, z-scores were computed for AO patients based on the healthy reference material, and LossGain scores were created. Compared with control subjects, 87.3% of AO patients had QST abnormalities. The most frequent somatosensory abnormalities in AO patients were somatosensory gain with regard to painful mechanical and cold stimuli and somatosensory loss with regard to cold detection and mechanical detection. The most frequent LossGain code was L0G2 (no somatosensory loss with gain of mechanical somatosensory function) (31.9% of AO patients). Percent agreement between corresponding QST and QualST measures of thermal and mechanical sensitivity ranged between 55.6% and 70.4% in AO patients and between 71.1% and 92.1% in control subjects. In conclusion, intraoral somatosensory abnormalities were commonly detected in AO patients, and agreement between quantitative and qualitative sensory testing was good to excellent.
    Pain 04/2013; · 5.64 Impact Factor
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    ABSTRACT: Objective: To compare muscle activity and cerebral activity during low-level tooth-clenching with controlled force using electromyography (EMG) and functional magnetic resonance imaging (fMRI). Method: Twenty one subjects (20-56 years) with no pain and normal jaw function participated. The study involved three motor tasks: 5-N tooth-clenching; 10-N tooth-clenching; and 20-N tooth-clenching. During all measurements, subjects kept a custom-made biting device between the anterior teeth. This biting device was calibrated to require either 5-, 10-, or 20-N force to keep the two parts in contact, thereby providing the subject with a simple feedback about the targeted bite force level. In a series of EMG measurements, fifteen participants alternated between a 30-s rest block and a 30-s task block for 300 s. In each task block, participants alternated between a 5-s rest block and a 5-s static tooth-clenching task at a pre-defined contraction level (5-, 10-, or 20-N tooth-clenching). In a fMRI experiment, six participants alternated between a 30-s rest block and a 30-s task block for 300 s. In the task block, participants alternated between a 5-s rest block and a 5-s static tooth-clenching task at a pre-defined contraction level (5- or 20-N tooth-clenching). A single scan consisted of 1 rest block and 1 task block in all measurements. Result: The EMG study demonstrated significant differences in root mean square EMG amplitude between 5-, 10-, and 20-N tooth-clenching (F = 46.21, P < 0.001). In the fMRI study, both levels of tooth-clenching significantly and bilaterally activated the sensorimotor cortex, supplementary motor area, cerebellum, and basal ganglia (P < 0.01). However, activation of the cerebral regions did not differ significantly between tasks. Conclusion: We suggest that although there were significant differences in EMG activity between 5- and 20-N, no differences in cerebral activity exist within low-level tooth-clenching with controlled force.
    IADR/AADR/CADR General Session and Exhibition 2013; 03/2013
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    ABSTRACT: Objective: Quantitative Sensory Testing (QST) is a neurosensory testing method that delivers precise,standardized stimuli to body surfaces and obtains quantifiable responses from the test subject. Recent trigeminal QST studies have demonstrated that most intraoral QST parameters are sufficiently reliable. This ongoing pilot study aimed to compare the reliability of multi-divisional trigeminal extraoral and intraoral QST. Method: The modified German QST protocol of 13 tests (Pigg et al. PAIN, 2010) was used to measure all three divisions of the trigeminal nerve bilaterally in patients with Atypical Odontalgia (AO), a chronic pain condition, in cases and age- and sex-matched controls. QST employed controlled thermal, tactile and painful stimuli applied to the gingiva (intraoral), face (extraoral) and hand (control site). Since all QST parameters in the protocol are the average of 3 to 5 individual tests (e.g. cold detection threshold value is the average of three successive trials), the Coefficient of variation (CV) could be calculated for each parameter to evaluate test-retest reliability, and be used to potentially compare between protocols, cases, controls and anatomic sites. All CV values were multiplied by 100. Result: QST was conducted on the hand, 6 extraoral and 4 intraoral sites in all three trigeminal divisions in the first 11 controls (6 Female, aged 42-62), (5 Male, aged 21-73) and first 4 AO cases (1 Male aged 73, 3 Females, aged 39 - 59). Lower values of CV denoted higher reliability. Control values for 5 of 13 QST parameters are listed in the table; case reliability will be reported when enrollment is over 10 subjects. Table of Controls Coefficient of Variation of each QST parameter comparing Extraoral vs. Intraoral Site V2 V2 V3 V3 ALL ALL Parameter Hand Extraoral Intraoral Extraoral Intraoral Extraoral Intraoral Pressure Pain Threshold (PPT) 19 11 27 14 22 12 24 Vibration Detection Threshold (VDT) 7 10 4 7 3 8 3 Cold Detection Threshold (CDT) 19 26 22 28 24 28 23 Warm Detection Threshold (WDT) 18 15 17 20 18 17 17 Mechanical Detection Threshold (MDT) 49 76 44 50 57 63 51 Conclusion: Reliability as measured by CV differed between QST techniques, QST parameters and by anatomic site. Intraoral sites showed higher reliability for VDT, while extraoral was better for PPT, and both approaches similar for CDT, WDT and MDT.
    IADR/AADR/CADR General Session and Exhibition 2013; 03/2013
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    ABSTRACT: Objective: Self-reported tooth clenching is a frequently reported risk factor for myofascial temporomandibular disorders (M-TMD). Studies have shown that M-TMD patients have higher levels of 5-HT, and glutamate in the masseter muscles compared to healthy subjects. Aim: To investigate the effects of experimental tooth clenching on the release of algesic substances in the masseter muscles in M-TMD patients and healthy subjects (CON). Method: 15 patients and 15 healthy subjects participated. Intramuscular microdialysis was performed to collect masseter muscle 5-HT, and glutamate. Two hours after the start of microdialysis the participants performed a 20-min tooth clenching task (50% of maximal voluntary contraction). Pain, fatigue, and pressure pain threshold (PPT) were measured throughout the experiment. Result: The M-TMD patients had significantly higher levels of muscle 5-HT at all time-points compared to CON (P’s < .01). No significant alterations over time was observed for the M-TMD patients or CON for 5-HT (P’s > .05). No differences between groups, or alterations over time were observed for glutamate (P’s > .05). M-TMD patients had significantly lower PPTs than healthy subjects at baseline and after recovery (P’s < .05). PPT decreased significantly over time for M-TMD patients (P’s < .05), but not for CON. Pain intensity was significantly higher for M-TMD patients than CON at baseline, and after the clenching task (P’s < .05), but not after recovery. Fatigue was significantly higher at baseline and after recovery for M-TMD patients compared to CON (P’s < .05). The pain intensity and fatigue increased significantly over time for both groups (P’s < .01). Conclusion: This experimental tooth clenching model evoked moderate levels of pain and fatigue in both groups, and a mechanical hyperalgesia in the M-TMD patients. 5-HT and glutamate were not increased after experimental tooth clenching, but the level of 5-HT was significantly higher in M-TMD patients.
    IADR/AADR/CADR General Session and Exhibition 2013; 03/2013

Publication Stats

1k Citations
208.90 Total Impact Points


  • 2005–2014
    • Aarhus University
      • • Department of Dentistry
      • • Department of Clinical Oral Physiology
      Aarhus, Central Jutland, Denmark
  • 2003–2014
    • Malmö University
      • • Department of Endodontics
      • • Faculty of Odontology (OD)
      Malmö, Skåne, Sweden
  • 2013
    • University of Minnesota Duluth
      Duluth, Minnesota, United States
    • Norrköping Vatten
      Norrköping, Östergötland, Sweden
  • 2012
    • Akademiska Sjukhuset
      Uppsala, Uppsala, Sweden
  • 1998–2012
    • Karolinska Institutet
      • Institutionen för odontologi
      Solna, Stockholm, Sweden
  • 2010
    • University of British Columbia - Vancouver
      • Faculty of Pharmaceutical Sciences
      Vancouver, British Columbia, Canada
    • University of Illinois at Chicago
      Chicago, Illinois, United States
    • University at Buffalo, The State University of New York
      Buffalo, New York, United States
  • 1999–2010
    • University Hospital Linköping
      Linköping, Östergötland, Sweden
  • 2008
    • University of Copenhagen
      • School of Dentistry
      Copenhagen, Capital Region, Denmark
  • 2007
    • Uppsala University Hospital
      Uppsala, Uppsala, Sweden
  • 2006
    • Martin Luther University of Halle-Wittenberg
      Halle-on-the-Saale, Saxony-Anhalt, Germany