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1.  Factor Analyses of the Oral Health Impact Profile - Overview and studied population 
Purpose
A desideratum of oral health-related quality of life (OHRQoL) instruments - such as the Oral Health Impact Profile (OHIP) - is that they accurately reflect the structure of the measured construct(s). With this goal in mind, the Dimensions of Oral Health-Related Quality of Life (DOQ) Project was proposed to investigate the number and nature of OHRQoL dimensions measured by OHIP. In this report, we describe our aggregate data set for the factor analyses in the project, which consists of responses to the 49-item OHIP from general population subjects and prosthodontics patients from 6 countries, including a large age range of adult subjects and both genders.
Material and methods
The DOQ Project's aggregate data set combines data from 35 individual studies conducted in Croatia, Germany, Hungary, Japan, Slovenia, and Sweden.
Results
The combined data set includes 10,778 OHIPs from 9,348 individuals (N=6,349 general population subjects, N=2,999 prosthodontic patients). To elucidate the OHIP latent structure, the aggregated data were split into a Learning Sample (N=5,173) for exploratory analyses and a Validation Sample (N=5,022) for confirmatory analyses. Additional data (N=583) were assigned to a third data set.
Conclusion
The Dimensions of Oral Health-Related Quality of Life Project contains a large amount of international data and is representative of populations where OHIP is intended to be used. It is well-suited to assess the dimensionality of the questionnaire.
doi:10.1016/j.jpor.2013.11.002
PMCID: PMC4024446  PMID: 24440578
Oral Health Impact Profile; Factor analysis; questionnaire; general population; prosthodontic patients
2.  Exploration of dimensionality and psychometric properties of the Pittsburgh Sleep Quality Index in cases with temporomandibular disorders 
Background
This study assessed the dimensional structure of sleep quality with the Pittsburgh Sleep Quality Index (PSQI) and investigated its psychometric properties in cases with temporomandibular disorders (TMD).
Methods
A convenience sample of 609 TMD cases (age: 37.1 ± 13.1 yrs, 18–67 yrs, 85% female) of the multi-center Validation Project meeting Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) and with sufficient PSQI data were included in this study. To investigate PSQI scores’ dimensionality, exploratory factor analysis was used. Factors were identified using the Scree plot. To investigate internal consistency, Cronbach’s alpha was calculated. Analyses were separately performed for TMD cases with (N = 496) and TMD cases withouta pain-related diagnosis (N = 113).
Results
The mean PSQI score for all TMD cases was 7.1 ± 4.0 units, range: 0–19. The exploratory factor analysis identified one factor for cases with at least one pain-related TMD diagnosis as well as one factor for cases with a pain-free TMD diagnosis that explained 41% of the variance in cases with pain-related TMD and 37% in cases with pain-free TMD. Internal consistency for PSQI scores was alpha of 0.75 in cases with pain-related TMD, alpha of 0.66 in cases with pain-free TMD and alpha = 0.75 for all TMD cases.
Conclusions
Sleep quality in TMD patients is a unidimensional construct and can therefore be represented by one summary score; a finding that is in line with previous reports in TMD patients.
doi:10.1186/1477-7525-12-10
PMCID: PMC3902412  PMID: 24443942
Temporomandibular disorders; Sleep disorders; Factor analysis; Psychometrics; Reliability and validity; Orofacial pain; Chronic pain; Self-assessment; Questionnaires; Quality of life
3.  SELF-REPORTED SEVERITY OF TASTE DISTURBANCES CORRELATES WITH SEVERITY OF TMD PAIN 
Journal of oral rehabilitation  2009;36(11):792-800.
Altered central neural processing of sensory information may be associated with temporomandibular joint disorders (TMD) pain. The study objectives were to compare the prevalence of self-reported taste disturbances in TMD pain patients and in a control population, and to determine whether frequency of taste disturbances is correlated with TMD pain severity. Subjects were 2026 people within a German population sample and 301 consecutive TMD pain patients diagnosed using the Research Diagnostic Criteria. Taste disturbances were measured using two questions from the Oral Health Impact Profile. Severity of TMD pain was measured using the Graded Chronic Pain Scale. A two-sample test of proportions revealed that TMD pain patients reported a greater frequency of taste disturbances, 6%, than did the general population subjects, 2% (p<0.001). Moreover, the frequency of taste disturbances correlated with the severity of TMD pain. For each 1-unit increase in taste disturbance, the odds of observing a higher grade of TMD pain increased by 29% (95%CI: 3–63%, p=0.03). Analysis by individual taste question and adjustment for age and gender did not substantially affect the results. Self-reported frequency of taste disturbances is greater in TMD pain patients than in the general population and the frequency of taste disturbances correlates with severity of TMD pain. These findings are consistent with a central neural dysfunction in TMD pain and suggest that a common neural substrate may underlie sensory disturbances of multiple modalities in chronic pain patients. Further research regarding taste disturbances and trigeminally-mediated pains, such as in TMD, is warranted.
doi:10.1111/j.1365-2842.2009.01996.x
PMCID: PMC3766965  PMID: 19747196
Taste; Orofacial Pain; Temporomandibular Disorders; Inhibitory Pain Control; Pain Modulation
4.  Interpreting one oral health impact profile point 
Background
Interpretation of scores from oral health-related quality of life (OHRQoL) instruments, such as the Oral Health Impact Profile (OHIP) is challenging. It was the aim of this study to determine how many oral impacts correspond to one point of the 49-item OHIP using a new approach which translates numeric problem counts into the traditionally used ordinal OHIP response categories.
Methods
A sample of 145 consecutively recruited prosthodontic patients seeking treatment or having a routine examination completed the German version of the 49-item OHIP with the original ordinal response format as a self-administered questionnaire. In addition, the numerical frequencies of impairment during the previous month were requested in personal interviews. Based on a multilevel mixed-effects linear regression, we estimated the mean difference with 95% confidence interval (CI) in numerical frequency between two adjacent ordinal responses.
Results
A numerical frequency of 15.2 (CI: 14.8 – 15.7) impacts per month corresponded to one OHIP point. This translates to approximately one impact every other day in the past month.
Conclusions
The oral problem count per day that corresponds to one OHIP-49 point can be used to interpret this instrument’s scores in cross-sectional and longitudinal studies. This number can help to better understand OHRQoL burden for patients, clinicians, and researchers alike.
doi:10.1186/1477-7525-11-12
PMCID: PMC3598229  PMID: 23363450
OHIP; Response format; OHRQoL; Assessment
5.  Validation of the Orofacial Esthetic Scale in the general population 
Background
The Orofacial Esthetic Scale (OES) is an eight-item instrument to assess how patients perceive their dental and facial esthetics. In this cross-sectional study we investigated dimensionality, reliability, and validity of OES scores in the adult general population in Sweden.
Methods
In a random sample of the adult Swedish population (response rate: 39%, N=1159 subjects, 58% female, mean age (standard deviation): 49.2 (17.4) years), dimensionality of OES was investigated using factor analytic methods to determine how many scores are needed to characterize the construct. Reliability of scores was calculated using Cronbach’s alpha. Score validity was determined by correlating the OES summary score with a global indicator of orofacial esthetics (OE).
Results
Factor analyses provided support that a single score can sufficiently characterize OE. A Cronbach’s alpha of 0.93 indicated excellent reliability. A validity coefficient of r=0.89 (95% confidence interval: 0.87-0.90) indicated that OES summary scores correlated highly with a global OE assessment.
Conclusions
The OES is a promising instrument to measure the construct OE. Factor analyses supported that this construct can be assessed with one score, offering a feasible and acceptable standardized assessment of OE. The present study extends the OES use to the general population, an important target population for assessment of orofacial esthetics.
doi:10.1186/1477-7525-10-135
PMCID: PMC3534548  PMID: 23158767
6.  Influence of headache frequency on clinical signs and symptoms of TMD in subjects with temple headache and TMD pain 
Pain  2010;152(4):765-771.
The relationship of the frequency of temple headache to signs and symptoms of temporomandibular disorders (TMD) was investigated in a subset of a larger convenience sample of community TMD cases. The study sample included: 86 painful TMD, non-headache subjects; 309 painful TMD subjects with varied frequency of temple headaches; and 149 subjects without painful TMD or headache for descriptive comparison. Painful TMD included Research Diagnostic Criteria (RDC) diagnoses of myofascial pain, TMJ arthralgia and TMJ osteoarthritis. Mild to moderate intensity temple headaches were classified by frequency using criteria based on the ICHD-II classification of TTH. Outcomes included TMD signs and symptoms (pain duration, pain intensity, number of painful masticatory sites on palpation, mandibular range of motion), PPTs and temple headache resulting from masticatory provocation tests. Trend analyses across the painful TMD groups showed a substantial trend for aggravation of all of the TMD signs and symptoms associated with increased frequency of the temple headaches. In addition, increased headache frequency showed significant trends associated with reduced PPTs and reported temple headache with masticatory provocation tests. In conclusion, these findings suggest that these headaches may be TMD-related, as well as a possible role for peripheral and central sensitization in TMD patients.
doi:10.1016/j.pain.2010.11.007
PMCID: PMC3065515  PMID: 21196079
temporomandibular disorders; headache; signs; symptoms; myofascial pain; TMD pain
7.  Frequency of Non-Odontogenic Pain After Endodontic Therapy: A Systematic Review and Meta-Analysis 
Journal of endodontics  2010;36(9):1494-1498.
Introduction
Little is known about ill-defined pain that persists following endodontic procedures, including an estimate of the problem’s magnitude. We conducted a systematic review of prospective studies that reported the frequency of non-odontogenic pain in patients who had undergone endodontic procedures.
Methods
Non-odontogenic pain was defined as dentoalveolar pain present for 6 months or more after endodontic treatment without evidence of dental pathology. Endodontic procedures reviewed were non-surgical root canal treatment, retreatment, and surgical root canal treatment. Studies were searched in four databases electronically, complemented by hand searching. A summary estimate of non-odontogenic tooth pain frequency was derived using random-effects meta-analysis.
Results
Of 770 articles retrieved and reviewed, 10 met inclusion criteria and 9 had data on both odontogenic and non-odontogenic causes of pain. A total of 3,343 teeth were included; 1,125 had follow-up information regarding pain status. We identified 48 teeth with non-odontogenic pain and estimated a 3.4% (95% CI: 1.4 to 5.5%) frequency of occurrence. In 9 articles containing data regarding both odontogenic and non-odontogenic causes of tooth pain, 56% (44/78) of all cases were thought to have a non-odontogenic cause.
Conclusions
Non-odontogenic pain is not an uncommon outcome following root canal therapy and may represent half of all cases of persistent tooth pain. These findings have implications for diagnosis and treatment of painful teeth that were previously root canal treated since therapy directed at the tooth in question would not be expected to resolve non-odontogenic pain.
doi:10.1016/j.joen.2010.06.020
PMCID: PMC2941431  PMID: 20728716
Tooth; Dentoalveolar; Pain; Root canal therapy; Systematic review
8.  Assessment of the Validity of the Research Diagnostic Criteria for Temporomandibular Disorders: Overview and Methodology 
Journal of orofacial pain  2010;24(1):7-24.
AIMS
The purpose of the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) Validation Project was to assess the diagnostic validity of this examination protocol. An overview is presented, including Axis I and II methodology and descriptive statistics for the study participant sample. This paper details the development of reliable methods to establish the reference standards for assessing criterion validity of the Axis I RDC/TMD diagnoses. Validity testing for the Axis II biobehavioral instruments was based on previously validated reference standards.
METHODS
The Axis I reference standards were based on the consensus of 2 criterion examiners independently performing a comprehensive history, clinical examination, and evaluation of imaging. Intersite reliability was assessed annually for criterion examiners and radiologists. Criterion exam reliability was also assessed within study sites.
RESULTS
Study participant demographics were comparable to those of participants in previous studies using the RDC/TMD. Diagnostic agreement of the criterion examiners with each other and with the consensus-based reference standards was excellent with all kappas ≥ 0.81, except for osteoarthrosis (moderate agreement, k = 0.53). Intrasite criterion exam agreement with reference standards was excellent (k ≥ 0.95). Intersite reliability of the radiologists for detecting computed tomography-disclosed osteoarthrosis and magnetic resonance imaging-disclosed disc displacement was good to excellent (k = 0.71 and 0.84, respectively).
CONCLUSION
The Validation Project study population was appropriate for assessing the reliability and validity of the RDC/TMD Axis I and II. The reference standards used to assess the validity of Axis I TMD were based on reliable and clinically credible methods.
PMCID: PMC3157055  PMID: 20213028
reference standard; gold standard; validity; diagnostic criteria; temporomandibular disorders; temporomandibular muscle and joint disorders
9.  Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD): Development of Image Analysis Criteria and Examiner Reliability for Image Analysis 
Introduction
As a part of a multi-site RDC/TMD Validation Project, comprehensive TMJ diagnostic criteria were developed for image analysis using panoramic radiography, magnetic resonance imaging (MRI), and computed tomography (CT).
Methods
Inter-examiner reliability was estimated using the kappa (k) statistic, and agreement between rater pairs was characterized by overall, positive, and negative percent agreement. CT was the reference standard for assessing validity of other imaging modalities for detecting osteoarthritis (OA).
Results
For the radiological diagnosis of OA, reliability of the three examiners was poor for panoramic radiography (k = 0.16), fair for MRI (k = 0.46), and close to the threshold for excellent for CT (k = 0.71). Using MRI, reliability was excellent for diagnosing disc displacements (DD) with reduction (k = 0.78) and for DD without reduction (k = 0.94), and was good for effusion (k = 0.64). Overall percent agreement for pair-wise ratings was ≥ 82% for all conditions. Positive percent agreement for diagnosing OA was 19% for panoramic radiography, 59% for MRI, and 84% for CT. Using MRI, positive percent agreement for diagnoses of any DD was 95% and for effusion was 81%. Negative percent agreement was ≥ 88% for all conditions. Compared to CT, panoramic radiography and MRI had poor to marginal sensitivity, respectively, but excellent specificity, in detecting OA.
Conclusion
Comprehensive image analysis criteria for RDC/TMD Validation Project were developed, which can reliably be employed for assessing OA using CT, and for disc position and effusion using MRI.
doi:10.1016/j.tripleo.2009.02.023
PMCID: PMC3139469  PMID: 19464658
RDC/TMD; osteoarthritis; temporomandibular disorders; panoramic radiography; MRI; CT; diagnostic criteria
10.  The Revised Research Diagnostic Criteria for Temporomandibular Disorders: Methods used to Establish and Validate Revised Axis I Diagnostic Algorithms 
Journal of orofacial pain  2010;24(1):63-78.
AIMS
To derive reliable and valid revised Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) Axis I diagnostic algorithms for clinical TMD diagnoses.
METHODS
The multi-site RDC/TMD Validation Project’s dataset (614 TMD community and clinic cases, and 91 controls) was used to derive revised algorithms for Axis I TMD diagnoses. Validity of diagnostic algorithms was assessed relative to reference standards, the latter based on consensus diagnoses rendered by 2 TMD experts using criterion examination data, including temporomandibular joint imaging. Cut-offs for target validity were sensitivity ≥ 0.70 and specificity ≥ 0.95. Reliability of revised algorithms was assessed in 27 study participants.
RESULTS
Revised algorithm sensitivity and specificity exceeded the target levels for myofascial pain (0.82, 0.99, respectively) and myofascial pain with limited opening (0.93, 0.97). Combining diagnoses for any myofascial pain showed sensitivity of 0.91 and specificity of 1.00. For joint pain, target sensitivity and specificity were observed (0.92, 0.96) when arthralgia and osteoarthritis were combined as “any joint pain.” Disc displacement without reduction with limited opening demonstrated target sensitivity and specificity (0.80, 0.97). For the other Group II disc displacements and Group III osteoarthritis and osteoarthrosis, sensitivity was below target (0.35 to 0.53), and specificity ranged from 0.80 to meeting target. Kappa for revised algorithm diagnostic reliability was ≥ 0.63.
CONCLUSION
Revised RDC/TMD Axis I TMD diagnostic algorithms are recommended for myofascial pain and joint pain as reliable and valid. However, revised clinical criteria alone, without recourse to imaging, are inadequate for valid diagnosis of two of the three disc displacements and osteoarthritis/osteoarthrosis.
PMCID: PMC3115779  PMID: 20213032
reference standard; validity; reliability; research diagnostic criteria; temporomandibular disorders; temporomandibular muscle; joint disorders
11.  Research Diagnostic Criteria for Temporomandibular Disorders: Reliability of Axis I Diagnoses and Selected Clinical Measures 
Journal of orofacial pain  2010;24(1):25-34.
AIM
To estimate inter-examiner reliability of the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) protocol.
METHODS
Kappa (k), computed by generalized estimate equation procedures, was selected as the primary estimate of inter-examiner reliability. Intersite reliability of six examiners from 3 study sites was assessed annually over the 5-year period of the RDC/TMD Validation Project. Intrasite reliability was monitored throughout the validation study by comparing RDC/TMD data collections performed on the same day by the test examiner and a criterion examiner.
RESULTS
Intersite calibrations included a total of 180 subjects. Intersite reliability of RDC/TMD diagnoses was excellent (k > 0.75) when myofascial pain diagnoses (Ia or Ib) were grouped. Good reliability was observed for discrete myofascial pain diagnoses, Ia (k = 0.62) and Ib (k = 0.58), for disc displacement with reduction (k = 0.63), disc displacement without reduction with limited opening (k = 0.62), arthralgia (k = 0.55), and when joint pain (IIIa or IIIb) was grouped (k = 0.59). Reliability of less frequently observed diagnoses such as disc displacements without reduction without limited opening, and osteoarthrosis (IIIb, IIIc), was poor to marginally fair (k = 0.31- 0.43). Intrasite monitoring results (n = 705) approximated well intersite reliability estimates. The greatest difference in paired estimates was 0.18 (IIc).
CONCLUSION
Reliability of the RDC/TMD protocol was good to excellent for myofascial pain, arthralgia, disc displacement with reduction, and disc displacement without reduction with limited opening. Reliability was poor to marginally fair for disc displacement without reduction without limited opening and osteoarthrosis.
PMCID: PMC3098131  PMID: 20213029
temporomandibular joint disorders; temporomandibular muscle and joint disorders; diagnostic criteria; reliability; temporomandibular muscle and joint disorders
12.  Oral health in the Japan self-defense forces - a representative survey 
BMC Oral Health  2011;11:14.
Background
The oral health of military populations is usually not very well characterized compared to civilian populations. The aim of this study was to investigate two physical oral health characteristics and one perceived oral health measure and their correlation in the Japan self-defense forces (JSDF).
Methods
Number of missing teeth, denture status, and OHRQoL as evaluated by the Japanese 14-item version of the Oral Health Impact Profile (OHIP-J14) as well as the correlation between these oral health measures was investigated in 911 personnel in the JSDF.
Results
Subjects did not have a substantial number of missing teeth and only 4% used removable dentures. The mean OHIP-J14 score was 4.6 ± 6.7 units. The magnitude of the correlation between the number of missing teeth with OHIP-J14 scores was small (r = 0.22, p < 0.001). Mean OHIP-J14 scores differed between subjects with and without dentures (8.6 and 4.4, p < 0.001).
Conclusions
Compared to Japanese civilian populations, personnel of the JSDF demonstrated good oral health. Two physical oral health characteristics were associated with perceived oral health.
doi:10.1186/1472-6831-11-14
PMCID: PMC3100240  PMID: 21501526
13.  Frequency of Persistent Tooth Pain Following Root Canal Therapy: A Systematic Review and Meta-Analysis 
Journal of endodontics  2010;36(2):224-230.
Introduction
Little is known about the frequency of persistent pain after endodontic procedures, even though pain is a core patient-oriented outcome. We estimated the frequency of persistent pain, regardless of etiology, following endondontic treatment.
Methods
Persistent tooth pain was defined as pain present ≥ 6 months after endodontic treatment. Endodontic procedures included in the review were pulpectomy, non-surgical root canal treatment, surgical root canal treatment, as well as retreatment. Four databases were searched electronically, complemented by hand searching. Two independent reviewers determined eligibility, abstracted data, and assessed study quality. A summary estimate of persistent all-cause tooth pain frequency was established by using a random-effects meta-analysis. Using subgroup analyses, we explored the influence of treatment approach (surgical/non-surgical), longitudinal study design (prospective/retrospective), follow-up rate, follow-up duration, initial treatment versus re-treatment, and quality of reporting (STROBE rankings) on the pain frequency estimate.
Results
Of 770 articles retrieved and reviewed, 26 met inclusion criteria. A total of 5,777 teeth were enrolled, and 2,996 had follow-up information regarding pain status. We identified 168 teeth with pain and derived a frequency of 5.3% (95%CI: 3.5–7.2%, p<0.001) for persistent all-cause tooth pain. High and statistically significant heterogeneity among studies (I2=80%) was present. In subgroup analysis, prospective studies had a higher pain frequency (7.6%) than retrospectives studies did (0.9%). Quality of study reporting was identified as the most influential reason for study heterogeneity.
Conclusions
Frequency of all-cause persistent tooth pain following endodontic procedures was estimated to be 5.3%, with higher report quality studies suggesting >7%.
doi:10.1016/j.joen.2009.11.007
PMCID: PMC2832800  PMID: 20113779
Pain; Outcome; Root canal therapy; Frequency; Systematic review; Meta-analysis
14.  Psychometric properties of the modified Symptom Severity Index (SSI) 
Journal of oral rehabilitation  2009;37(1):11-20.
The psychometric properties of the modified Symptom Severity Index were investigated to assess the relationships among dimensions of pain in temporomandibular disorders. The 15-item instrument is composed of ordinal scales assessing five pain dimensions (intensity, frequency, duration, unpleasantness, and difficulty to endure) as experienced in three locations (temple, temporomandibular joint, masseter). In 108 closed-lock subjects, Cronbach’s alpha was used to measure internal consistency resulting in 31 of the 105 pair-wise comparisons ≥0.71. Multilevel exploratory factor analysis was used to assess dimensionality between items. Two factors emerged, termed temple pain and jaw pain. The jaw pain factor comprised the temporomandibular joint and masseter locations, indicating that subjects did not differentiate between these two locations. With further analysis, the jaw pain factor could be separated into temporal aspects of pain (frequency, duration) and affective dimensions (intensity, unpleasantness, endurability). Temple pain could not be further reduced; this may have been influenced by concurrent orofacial pains such as headache. Internal consistency was high, with alphas ≥0.92 for scales associated with all factors. Excellent test-retest reliability was found for repeat testing at 2–48 hours in 55 subjects (ICC=0.97, 95%CI 0.96–0.99). In conclusion, the modified Symptom Severity Index has excellent psychometric properties for use as an instrument to measure pain in subjects with temporomandibular disorders. The most important characteristic of this pain is location, while the temporal dimensions are important for jaw pain. Further research is needed to confirm these findings and assess relationships between dimensions of pain as experienced in other chronic pain disorders.
doi:10.1111/j.1365-2842.2009.02017.x
PMCID: PMC2858780  PMID: 19889036
Pain dimensions; pain assessment; reliability; factor analysis; temporomandibular disorders (TMD); orofacial pain
15.  Evaluation of a magnetic resonance-compatible dentoalveolar tactile stimulus device 
BMC Neuroscience  2010;11:142.
Abstract
Background
Few methods exist to study central nervous system processes following dentoalveolar tactile stimulation using functional magnetic resonance imaging (fMRI), likely due to inherent technical difficulties. Our primary goal was to develop and perform feasibility testing of a novel device capable of delivering valid and reliable dentoalveolar stimuli at dental chair-side and during MRI. Details of a device designed to deliver dentoalveolar dynamic pressure stimuli are described. Device testing took place in three settings: a) laboratory testing to assess range of stimulus force intensities, b) dental chair-side to assess reliability, validity and discriminant ability in force-pain relationship; and c) MRI to evaluate magnetic compatibility and ability to evoke brain activation in painfree subjects similar to those described in the literature.
Results
A novel device capable of delivering valid and reliable dentoalveolar somatosensory stimulation was developed (ICC = 0.89, 0.78-1 [95% CI]). Psychophysical data analysis showed high discriminant ability in differentiating painfree controls from cases with chronic dentoalveolar pain related to deafferenting dental procedures (sensitivity = 100%, specificity = 86.7%, area under ROC curve = 0.99). FMRI results of dentoalveolar dynamic pressure pain in painfree subjects revealed activation of brain areas typically associated with acute pain processing including thalamus, primary/secondary somatosensory, insular and prefrontal cortex.
Conclusions
A novel psychophysical method to deliver dynamic dentoalveolar pressure stimulation was developed and validated, allowing non-invasive MRI-based exploration of central nervous system function in response to intraoral somatosensation.
Background
The organization of the trigeminal system is unique as it provides somatosensory innervation to the face, masticatory and oral structures, the majority of the intracranial contents [1] and to specialized structures (tongue, nasal mucosa, auricle, tympanic membrane, cornea and part of the conjunctiva) [2]. Somatic sensory information transmitted by the trigeminal nerve is crucial for normal orofacial function; however, the mechanisms of many chronic pain conditions affecting areas innervated by this sensory system are not well understood [3-5]. The clinical presentation of chronic intraoral pain in the area of a tooth or in a site formally occupied by a tooth with no clinical or radiological signs of pathology, referred to as atypical odontalgia (AO) [6,7], is one such chronic pain condition of particular interest to dentists that is difficult to diagnose and manage. Recent research suggests both peripheral and central nervous system mechanisms being involved in AO pathophysiology [8-10], but the majority of mechanism-based research of patients with AO has focused on the "peripheral aspect" [7].
Functional magnetic resonance imaging (fMRI) is an established research technique to study the central aspects of pain [11]. Of existing neuroimaging techniques, fMRI provides good spatial resolution of cortical and subcortical structures critical in the processing of nociception, acceptable temporal resolution, does not involve ionizing radiation, and can be performed using most MRI systems that already exist in research centers and the community. For these reasons, we sought to develop a protocol that allows us to use this tool to investigate the central mechanisms involved in the processes of intraoral pain arising from the dentoalveolar region. Using this device, our long-term objective is to improve our understanding of the underlying mechanisms of persistent dentoalveolar pain.
In the past few years several studies used fMRI to investigate the human trigeminal system [12,13], with a limited subset focusing on intraoral stimulation - specifically on the dentoalveolar processes, such as lip, tongue and teeth stimulation [14] or only teeth [15-17]. Some reasons for scarce literature on this topic may be the technical challenges involved in delivering facial/intraoral stimulation inside a MR scanner [17,18]: possibility of magnetic interference, detriment of image quality, subject discomfort and reduced working space between the subject's head and the radiofrequency coil. As a consequence a MR-compatible device would need to not only overcome these challenges but also be capable of delivering a controlled and reproducible stimuli [19], as reliability/reproducibility is a necessary feature of sensory testing [20].
Existing MR-compatible methods of dentoalveolar stimulation are limited and do not adequately deliver stimuli across a range of non-painful to painful intensities and/or cannot be adjusted to reach posterior aspects of the dentoalveolar region. Therefore our goal was to develop and test the feasibility of a device able to: 1) provide reliable and valid dentoalveolar stimuli, 2) deliver such stimulation within the restricted space of an MR head coil, 3) be compatible for use within an MR environment, and 4) produce brain activation in painfree controls consistent to those observed by others using fMRI.
doi:10.1186/1471-2202-11-142
PMCID: PMC2988799  PMID: 21029454
16.  Association between perceived chewing ability and oral health-related quality of life in partially dentate patients 
Background
One of the most immediate and important functional consequences of many oral disorders is a reduction in chewing ability. The ability to chew is not only an important dimension of oral health, but is increasingly recognized as being associated with general health status. Whether perceived chewing ability and oral health-related quality of life (OHRQoL) are correlated to a similar degree in patient populations has been less investigated. The aim of this study was to examine whether perceived chewing ability was related to OHRQoL in partially dentate patients.
Methods
Consecutive partially dentate patients (N = 489) without signs or symptoms of acute oral disease at Tokyo Medical and Dental University's Prosthodontic Clinic participated in the study (mean age 63.0 ± 11.5, 71.2% female). A 20-item chewing function questionnaire (score range 0 to 20) was used to assess perceived chewing ability, with higher scores indicating better chewing ability. The 14-item Oral Health Impact Profile-Japanese version (OHIP-J14, score range 0 to 56) was used to measure OHRQoL, with higher scores indicating poorer OHRQoL. A Pearson correlation coefficient was calculated to assess the correlation between the two questionnaire summary scores. A linear regression analysis was used to describe how perceived chewing ability scores were related to OHRQoL scores.
Results
The mean chewing function score was 12.1 ± 4.8 units. The mean OHIP-J14 summary score was 13.0 ± 9.1 units. Perceived chewing ability and OHRQoL were significantly correlated (Pearson correlation coefficient: -0.46, 95% confidence interval [CI]: -0.52 to -0.38), indicating that higher chewing ability was correlated with lower OHIP-J14 summary scores (p < 0.001), which indicate better OHRQoL. A 1.0-unit increase in chewing function scores was related to a decrease of 0.87 OHIP-J14 units (95% CI: -1.0 to -0.72, p < 0.001). The correlation between perceived chewing ability and OHRQoL was not substantially influenced by age and number of teeth, but by gender, years of schooling, treatment demand and denture status.
Conclusion
Patients' perception of their chewing ability was substantially related to their OHRQoL.
doi:10.1186/1477-7525-8-118
PMCID: PMC2974665  PMID: 20955614
17.  Electric toothbrush application is a reliable and valid test for differentiating temporomandibular disorders pain patients from controls 
Background
Current methods for identifying patients with pain hypersensitivity are sufficiently complex to limit their widespread application in clinical settings. We assessed the reliability and validity of a simple multi-modal vibrotactile stimulus, applied using an electric toothbrush, to evaluate its potential as a screening tool for central sensitization.
Methods
Fourteen female temporomandibular disorders (TMD) subjects with myofascial pain (RDC/TMD Ia or Ib) and arthralgia (RDC/TMD IIIa) were compared to 13 pain-free controls of matched age and gender. Vibrotactile stimulus was performed with an electric toothbrush, applied with 1 pound pressure for 30 seconds in four locations: over the lateral pole of the temporomandibular joint, masseter, temporalis, and mid-ventral surface of forearm. Pain intensity (0–10) was recorded following the stimulus at 0, 15, 30, and 60 seconds. Test-retest reliability was assessed with measurements from 8 participants, taken 2–12 hours apart. Case versus control differentiation involved comparison of area under the curve (AUC). A receiver operating characteristic (ROC) curve was used to determine cutoff AUC scores for maximum sensitivity and specificity for this multi-modal vibrotactile stimulus.
Results
Test-retest reliability resulted in an ICC of 0.87 for all 4 pooled sites. ROC-determined AUC cutoff scores resulted in a sensitivity of 57% and specificity of 92% for all 4 pooled sites.
Conclusion
The electric toothbrush stimulus had excellent test-retest reliability. Validity of the scores was demonstrated with modest sensitivity and good specificity for differentiating TMD pain patients from controls, which are acceptable properties for a screening test.
doi:10.1186/1471-2474-10-94
PMCID: PMC2728093  PMID: 19643013
18.  Validating an alternate version of the chewing function questionnaire in partially dentate patients 
BMC Oral Health  2009;9:9.
Background
The aim of this study was to investigate the dimensionality, reliability, and validity of an alternate version of the chewing function questionnaire in partially dentate patients in Japan.
Methods
Subjects were partially dentate patients who attended the prosthodontic clinic at Tokyo Medical and Dental University (N = 491, 71% women, mean age (± SD): 63.0 ± 11.5 years). The questionnaire asked each subject to rate his or her ability to chew 20 common Japanese foods. For each individual, responses were combined to yield a chewing function summary score, with higher scores indicating better self-reported chewing ability. We used exploratory factor analysis to investigate the scores' dimensionality. For validity assessment, we computed the correlations between the chewing function score and oral health-related quality of life (OHRQoL, as measured by the Japanese 14-item Oral Health Impact Profile (OHIP-14)) Internal consistency of scores and test-retest reliability were investigated by asking a subset of subjects (N = 62) to complete the questionnaire twice, 2 weeks apart.
Results
Exploratory factor analysis provided some evidence that self-reported chewing ability can be characterized by a summary score as the original authors suggest. Support for the validity of chewing function scores using the alternate version of the questionnaire was derived from correlations with OHIP-14 scores (r = -0.46, 95% confidence interval (CI): -0.53 to -0.39); thus, better chewing ability was associated with less impaired OHRQoL. Internal consistency was 'satisfactory,' with a Cronbach's alpha of 0.90 (lower limit of 95% CI: 0.89). The test-retest reliability was 'good,' with an intraclass correlation coefficient of 0.69 (95% CI: 0.56 to 0.82).
Conclusion
The alternate version of the chewing function questionnaire can be used as a stand-alone instrument because of the demonstrated reliability and validity of scores obtained using the questionnaire in partially dentate patients.
doi:10.1186/1472-6831-9-9
PMCID: PMC2667387  PMID: 19291293
19.  The Dutch version of the Oral Health Impact Profile (OHIP-NL): Translation, reliability and construct validity 
BMC Oral Health  2008;8:11.
Background
The purpose of this study was to make a cross-culturally adapted, Dutch version of the Oral Health Impact Profile (OHIP), a 49-item questionnaire measuring oral health-related quality of life, and to examine its psychometric properties.
Methods
The original English version of the OHIP was translated into the Dutch language, following the guidelines for cross-cultural adaptation of health-related quality of life measures. The resulting OHIP-NL's psychometric properties were examined in a sample of 119 patients (68.9 % women; mean age = 57.1 ± 12.2 yrs). They were referred to the clinic of Prosthodontics and Implantology with complaints concerning their partial or full dentures or other problems with missing teeth. To establish the reliability of the OHIP-NL, internal consistency and test-retest reliability (N = 41; 1 – 2 weeks interval) were examined, using Cronbach's alpha and intraclass correlation coefficients (ICC), respectively. Further, construct validity was established by calculating ANOVA.
Results
Internal consistency and test-retest reliability were excellent (Cronbach's alpha = 0.82 – 0.97; ICC = 0.78 – 0.90). In addition, all associations were significant and in the expected direction.
Conclusion
In conclusion: the OHIP-NL can be considered a reliable and valid instrument to measure oral health-related quality of life.
doi:10.1186/1472-6831-8-11
PMCID: PMC2329613  PMID: 18405359

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