{"paper_id":"36c04274-184e-4038-a629-7ce19754e640","body_text":"Temporomandibular disorder (TMD) is currently considered a complex disorder with \nmultiple etiologies that follow the biopsychosocial model [ 1 ]. TMD is defined as \n“a group of musculoskeletal and neuromuscular conditions that involve the \ntemporomandibular joints (TMJs), the masticatory muscles, all associated \nstructures of mastication, and associated tissues” [ 2 ].\nThe Research Diagnostic Criteria for TMD (RDC/TMD) [ 3 ] was established to \novercome multiple classifications of TMD [ 4 ,  5 ] that posed a major obstacle for \nresearch by creating uniform diagnostic criteria. The RDC/TMD was accepted \nworldwide for more than 2 decades as the preferred diagnostic criteria for \nresearch purposes. The DC/TMD [ 6 ], the revised version of the RDC/TMD, which was \npublished in 2014, improved the sensitivity and specificity of diagnostic \ncriteria, in part by refining the criteria for the identification of \nmusculoskeletal pain-related disorders. In addition, diagnoses were divided into \npainful and non-painful TMD, although multiple diagnoses for the same patients \nwere still permitted [ 7 ]. Nevertheless, criticism was raised by leading \nresearchers [ 8 ,  9 ,  10 ] as to grouping pain-related diagnoses and joint-related \ndiagnoses under the umbrella term “TMD” and as to the use of the term “TMD”. \nLaskin proposed to eliminate the term “TMD” and to evaluate myogenous and \narthrogenous findings as independent musculoskeletal conditions [ 8 ]. Huff & \nBenoliel noted that the term TMD should not be viewed as an adequate diagnosis, \nbut merely as a classification and that there are over 30 diagnoses under the \nterm “TMD” [ 10 ]. This notion had been implemented in the International \nClassification of Orofacial Pain (ICOP), 1st edition [ 11 ] that stated that the \nterm TMD is maintained only to align with the DC/TMD protocol. In addition, the \nICOP adopted a clear division between muscle-related diagnoses (Myofascial \norofacial pain) and painful TMJ-related diagnoses (Temporomandibular joint (TMD) \npain), while differentiating between primary and secondary pain etiologies \nfor each diagnosis, and also addressed chronicity status for each diagnosis.\nIndeed, one of the main obstacles that restrict and hampers our understanding of \nTMD-related disorders is derived from viewing TMD as a single diagnostic entity \nand combining painful and non-painful diagnoses in the same patient. This \napproach may lead to falsely relating these diagnoses to each other as cause and \neffect, while dual diagnoses may represent comorbidity or incidental findings \nonly [ 12 ]. Another important issue that is not addressed by the DC/TMD relates to \npain mechanisms. As stated by Svensson [ 13 ]: “the specific criteria rely on \nclustering of specific symptoms and clinical signs without addressing putative \nunderlying pain mechanisms”. Svensson emphasizes a specific painful TMD \ndiagnosis may reflect a heterogenous pain mechanism which clinically may appear \nvery similar [ 13 ]. Thus, current diagnostic criteria, although improved, are \nstill lacking important information as to etiology, chronicity and underlying \npain mechanisms even when addressing specific pain diagnosis listed as painful \nTMD. Each diagnosis listed in the DC/TMD can represent a primary or secondary \ncondition, nociceptive pain or inflammatory pain. It can represent a neuropathic \npain or even a nociplastic pain condition [ 14 ]. Moreover, in a broader view, \nTMD-related conditions may coexist with other chronic pain conditions such as \nfibromyalgia, irritable bowel syndrome, myalgic encephalomyelitis/chronic fatigue \nsyndrome, vulvodynia, interstitial cystitis/painful bladder syndrome, chronic \ntension-type headache, migraine headache, endometriosis and chronic lower back \npain. Associated with these patients are elevated levels of Axis II components, \nsuch as anxiety and depression. These conditions are referred to as chronic \noverlapping pain conditions (COPCs) [ 15 ]. This important information is not \naddressed by the DC/TMD. Failure to acknowledge COPSs and address TMD only might \ncompromise treatment outcomes.\nAnother issue that supports abandoning the term TMD is the realization that many \nvariables may change the composition of TMD as a group of diagnoses: age, gender, \nclinic location (family physician  vs.  dental academic center or \nhospital-based clinic), and clinic type: primary clinic, in which most cases have \na good prognosis,  vs.  tertiary clinic, which is composed of a higher \nproportion of chronic primary pain patients [ 16 ], who may require a variety of \ntreatment strategies to address the psychosocial components associated with their \nchronic pain condition [ 17 ]. These variables may hamper our ability to compare \nbetween studies, even when unified diagnostic criteria, such as the DC/TMD is \nused.\nAdditional factors that may affect the different diagnoses profile of \nTMD-related diagnoses that haven’t been addressed so far to the best of our \nknowledge are clinic location and the referring physician profile. It is logical \nto assume that dental academic centers that rely on dentists as the major \nreferring source will show a higher percentage of mechanical TMJ findings, such \nas joint noises and limited mouth opening, while referred otalgia will be one of \nthe major etiologies of referral from otolaryngologists or family physicians once \nprimary otalgia was ruled out.\nThe purpose of this study, therefore, was to explore demographic and Axis I \ndiagnoses differences between two orofacial pain clinics, each located in a \ndifferent setting: the first, located in a dental school in which the majority of \nreferring physicians are dentists, while the second clinic is located in a \nhospital-based Orofacial pain clinic within Oral surgery department, in which the \nmajority of referring Physicians are not dentists.\n\nThis retrospective study included two Orofacial pain clinics located in two \nseparate cities: A university dental school-based Orofacial pain clinic \n(DentalOFP), and a hospital-based Orofacial pain clinic, which is a subdivision \nof an Oral surgery department (HospitalOFP). All the patients in both clinics \nwere examined by the same senior staff member (EW) who worked in both clinics and \nis certified in the DC/TMD Training and Calibration Course at the Department of \nOrofacial Pain and Jaw Function at the Faculty of Odontology at Malmö, \nSweden. Each patient who was seen in both clinics was diagnosed according to the \nHebrew version [ 18 ] of the DC/TMD [ 6 ]. Patients’ medical records were \nretrospectively analyzed and compared.\nThe nonpainful Axis I diagnoses included intra-articular disorders (IAD) (disc \ndisplacement with reduction, disc displacement with reduction with intermittent \nlocking, disc displacement without reduction with limited opening, and disc \ndisplacement without reduction without limited opening), degenerative joint \ndisease (DJD) and subluxation. Painful Axis I diagnoses included in the analysis \nincluded arthralgia, local myalgia and myofascial pain with referral.\nOverall, 164 patients were examined in the HospitalOFP clinic by EW during \n2019–2020 (pre-COVID-19 pandemic). Excluded from the study were 13 patients \nyounger than 18 years, 28 did not meet the criteria to receive an Axis I \ndiagnosis of TMD according to the DC/TMD specifications and were diagnosed as \nhaving other orofacial pain conditions. Nine patients were excluded due to \nreceiving a diagnosis of bruxism only. The data of 10 patients was missing \ninformation necessary for analysis, such as symptom duration, and therefore were \nexcluded from the study. The final study population of the HospitalOFP clinic \nincluded 104 patients (Fig.  1 ).\nFlowchart for HospitalOFP and DentalOFP clinics. DentalOFP: \nDental school orofacial pain clinic; HospitalOFP: Hospital orofacial pain clinic. \nAll 172 patients were examined by Prof. EW. *Excluded: (1) 13 patients younger \nthan 18 years. (2) 28 did not meet the criteria to receive an Axis I diagnosis of \nTMD according to the DC/TMD specifications and were diagnosed as having other \norofacial pain conditions. (3) 9 patients were excluded due to receiving a \ndiagnosis of bruxism only. (4) 10 patients—missing information necessary for \nanalysis such as symptoms duration, and therefore were excluded from the study. \n**Excluded: (1) 11 patients younger than 18 years. (2) 35 did not meet the \ncriteria to receive an Axis I diagnosis of TMD according to the DC/TMD \nspecifications and were diagnosed as having other orofacial pain conditions. (3) \n15 patients were excluded due to receiving a diagnosis of bruxism only, and one \npatient was excluded due to obstructive sleep apnea as the only diagnosis. (4) 22 \npatients—missing information necessary for analysis, such as symptom duration, \nand therefore were excluded from the study.\nOverall, 172 patients were examined in the DentalOFP clinic by WE during \n2015–2018 (pre-COVID-19 pandemic). Excluded from the study were 11 patients \nyounger than 18 years, 35 did not meet the criteria to receive an Axis I \ndiagnosis of TMD according to the DC/TMD specifications and were diagnosed as \nhaving other orofacial pain conditions such as neuropathic pain, systemic \ndiseases such as rheumatoid arthritis, fibromyalgia, migraine, burning mouth \nsyndrome, dental diseases and others). Fifteen patients were excluded due to \nreceiving a diagnosis of bruxism only, one patient was excluded due to \nobstructive sleep apnea as the chief complaint, with no TMD signs and symptoms. \nThe data of 22 patients was missing information necessary for analysis such as \nsymptoms duration, and therefore were excluded from the study. The final study \npopulation of the DentalOFP clinic included 88 patients (Fig.  1 ).\nCategorical variables were summarized as frequency and percentage. Continuous \nvariables were evaluated for normal distribution using histogram and \nKolmogorov-Smirnov Test and reported as median and interquartile range. The \nChi-Square Test and Fisher’s Exact Test were used to compare categorical \nvariables between the two clinics and the Mann-Whitney test was used to assess \ndifferences in continuous variables. Multivariable Logistic Regression was used \nto study the association between the clinics and the diagnosis while controlling \nage, gender, symptoms duration and referring physician. IBM SPSS Statistics for \nWindows, Version 28.0. Armonk, NY, USA: IBM Corp. was used for all statistical \nanalyses. A  p -value < 0.05 was considered statistically significant.\n\nFig.  2  summarizes demographic information for both clinics: In the DentalOFP \nclinic male: female ratio was 1:4.88, mean age (of 39.25 ± 15.98), while in \nthe HospitalOFP clinic male: female ratio was 1:2.15, and the mean age (47.89 \n± 18.49). Significant differences between the two clinics were shown as to \nage, gender, symptom duration, and referring physicians; Overall, DentalOFP \npatients were significantly younger ( p  = 0.002), and 87.5% reported \nsymptom duration which was over 3 months, compared to 69.2% of HospitalOFP \npatients ( p  < 0.001). 55.7% of referring sources in the DentalOFP \nclinic were dentists, while in the HospitalOFP clinic, only 13.5% were referred \nby dentists. While 84.6% of referring physicians in the HospitalOFP clinic were \nfamily physicians/specialized physicians (such as ear, nose and throat \nspecialists (ENT) and neurologists), only 10.2% of the patients in the DentalOFP \nclinic were referred by General/Specialized physicians.\nComparison between DentalOFP and HospitalOFP clinics: gender, \nage, symptom duration, and referring physician. Gender:  p  = 0.019; Age: \n p  = 0.002; Symptom duration:  p  < 0.001; Referring physician: \n p  < 0.001. DentalOFP: Dental school orofacial pain clinic; \nHospitalOFP: Hospital orofacial pain clinic.\nAs to Axis I diagnoses, Fig.  3  presents percentages of all Axis I diagnoses. \nsignificant differences were found for all non-painful Axis I diagnoses \nindividually, including, IAD ( p  = 0.019), DJD ( p  = 0.041), and \nsubluxation ( p  = 0.015). 37.5% of the patients in DentalOFP were \ndiagnosed with IAD compared to 22.1% in HospitalOFP ( p  = 0.019), 26.9% \nof the patients from HospitalOFP received a diagnosis of DJD compared to 14.8% \nin DentalOFP ( p  = 0.041) and 13.5% of HospitalOFP’s patients were \ndiagnosed with subluxation while only 3.4% were in DentalOFP ( p  = \n0.015). However, when analyzing painful and non-painful diagnoses as two separate \ngroups: In the group of patients receiving only non-painful diagnoses (IAD, DJD, \nsubluxation), there were no significant differences ( p  = 0.058), while \nin the group of patients receiving painful diagnoses (local myalgia, myofascial \npain with referral, and arthralgia), significant differences were found \n( p  = 0.040).\nAxis I diagnoses: comparison between DentalOFP clinic and \nHospitalOFP clinic. IAD: Intra-articular disorders; DJD: Degenerative joint \ndisease; HospitalOFP: Hospital orofacial pain clinic; DentalOFP: Dental school \norofacial pain clinic.\nAt this stage, a Multivariable Logistic Regression analysis was performed while \ncontrolling for gender and age. The results of the multivariable logistic \nregression are presented in  Table 1 . The odds for diagnosis of local myalgia in \nthe DentalOFP clinic were 1.47 times higher than in the HospitalOFP clinic \n( p  = 0.205). The odds for diagnosis of myofascial pain with referral at \nthe DentalOFP clinic was 1.18 times higher compared to HospitalOFP ( p  = \n0.627). As to arthralgia, the odds in the DentalOFP clinic were 2.58 times higher \nthan at the HospitalOFP clinic ( p  = 0.018). For diagnosis of DJD, the \nodds in the HospitalOFP clinic were 1.63 times higher than at the DentalOFP \nclinic ( p  = 0.215). The odds for IAD diagnosis in the DentalOFP clinic \nwere 1.48 times higher than in the HospitalOFP clinic ( p  = 0.268). \nHowever, the odds for subluxation in the HospitalOFP clinic were 5.31 times \nhigher than in the DentalOFP clinic ( p  = 0.015).\nMultivariable logistic regression while controlling for gender \nand age (HospitalOFP).\nIAD: Intra-articular disorders; DJD: Degenerative joint disease; HospitalOFP: \nHospital orofacial pain clinic; DC/TMD: Diagnostic Criteria for Temporomandibular \nDisorders; OR: Odds Ratio; CI: Confidence Interval.\nAs to Painful Axis I Diagnoses as a group (local myalgia, myofascial pain with \nreferral, and arthralgia), the odds in the DentalOFP clinic were 2.43 higher than \nin the HospitalOFP clinic ( p  = 0.046). On the other hand, the odds for \nnon-painful Axis I Diagnoses (DJD, IAD and Subluxation) in the HospitalOFP clinic \nwere 2.27 higher than in the DentalOFP clinic ( p  = 0.067).\nAt this stage, a Multivariable Logistic Regression analysis was performed while \ncontrolling for gender, age and symptom duration. Results are presented in  Table 2 .\nMultivariable logistic regression while controlling for gender, \nage and symptom duration (HospitalOFP).\nIAD: Intra-articular disorders; DJD: Degenerative joint disease; HospitalOFP: \nHospital orofacial pain clinic; DC/TMD: Diagnostic Criteria for Temporomandibular \nDisorders; OR: Odds Ratio; CI: Confidence Interval.\nThe odds for diagnosis of local myalgia in the DentalOFP clinic were 1.54 times \nhigher than in the HospitalOFP clinic ( p  = 0.180). The odds for \ndiagnosis of myofascial Pain with referral in the DentalOFP clinic was 1.10 times \nhigher than in the HospitalOFP clinic ( p  = 0.786). For arthralgia, the \nodds in the DentalOFP clinic were 2.62 times higher than in the HospitalOFP \nclinic ( p  = 0.023). For diagnosis of DJD, the odds in the HospitalOFP \nclinic were 1.74 times higher than in the DentalOFP clinic ( p  = 0.176). \nThe odds for IAD diagnosis in the DentalOFP clinic were 1.14 times higher than in \nthe HospitalOFP clinic ( p  = 0.727). However, the odds for subluxation in \nthe HospitalOFP clinic were 6.81 times higher than in the DentalOFP clinic \n( p  = 0.007).\nAs to Painful Axis I Diagnoses as a group (local myalgia, myofascial pain with \nreferral, and arthralgia), the odds in the DentalOFP clinic were 2.41 times \nhigher than in the HospitalOFP clinic ( p  = 0.061). On the other hand, \nthe odds for only non-painful Axis I Diagnoses (DJD, IAD and Subluxation) in the \nHospitalOFP clinic were 2.18 times higher than in the DentalOFP clinic \n( p  = 0.102).\nAt this stage, a Multivariable Logistic Regression analysis was performed while \ncontrolling gender, age, symptom duration and referring Physician. Results are \npresented in  Table 3 .\nMultivariable logistic regression while controlling for gender, \nage, symptom duration and referring physician (HospitalOFP).\nIAD: Intra-articular disorders; DJD: Degenerative joint disease; HospitalOFP: \nHospital orofacial pain clinic; DC/TMD: Diagnostic Criteria for Temporomandibular \nDisorders; OR: Odds Ratio; CI: Confidence Interval.\nThe odds for diagnosis of local myalgia in DentalOFP clinic were 3.52 times \nhigher than in the HospitalOFP clinic ( p  = 0.014). The odds for \ndiagnosis of myofascial pain with referral in the HospitalOFP clinic was 1.34 \ntimes higher than in the DentalOFP clinic ( p  = 0.567). For diagnosis of \narthralgia, the odds in DentalOFP clinic were 3.45 times higher than in the \nHospitalOFP clinic ( p  = 0.042). For diagnosis of DJD, the odds in the \nHospitalOFP clinic were 2.33 times higher than in the DentalOFP clinic \n( p  = 0.137). For IAD, the odds were approximately equal in DentalOFP \n(Odds Ratio (OR) = 0.995) and in HospitalOFP (OR = 1.004,  p  = 0.995) \nHowever, the odds for diagnosis of subluxation in HospitalOFP clinic were 9.15 \ntimes higher than in the DentalOFP clinic ( p  = 0.036).\nAs to Painful Axis I Diagnoses as a group (local myalgia, myofascial pain with \nreferral, and arthralgia), the odds in the DentalOFP clinic were 5.59 times \nhigher than in the HospitalOFP clinic ( p  = 0.012). The odds for \nnon-painful Axis I Diagnoses (DJD, IAD and Subluxation) in the HospitalOFP clinic \nwere 5.41 times higher than in the DentalOFP clinic ( p  = 0.015).\n\nIn the current study two orofacial pain clinics, each from a different setting, \nwere compared. Patients in both clinics were examined by the same physician and \nreceived diagnoses of Axis I according to the DC/TMD. Results showed that both \nclinics were significantly different from each other by many parameters, \nincluding average age, female: male ratio, symptom duration, referring \nphysicians, and all non-painful diagnoses; As to gender, gender plays an \nimportant role in TMD [ 19 ]. Studies have repeatedly shown that females have a \nhigher risk for TMDs in general than males [ 20 ]. The age and gender profile of \nthe DentalOFP group was more typical to what is known so far [ 19 ]. On the other \nhand, it is noteworthy that most studies on TMD patients using the RDC/TMD or the \nDC/TMD were conducted in academic centers and not in hospital-based orofacial \npain clinics [ 21 ]. The profile of Axis I diagnoses in the DentalOFP clinic shown \nin the current study was similar to these studies, as opposed to the profile of \nthe HospitalOFP clinic. As was shown, the proportion of women increases from \ncommunity-based study to primary and tertiary clinical settings, with women \ncomprising approximately 80% or more of patient populations in tertiary academic \nclinics [ 22 ]. Considering this with longer pain duration in the DentalOFP clinic, \nmay point to the characteristics profile of tertiary clinic in the DentalOFP \nclinic compared to the HospitalOFP clinic [ 23 ]. The average younger age compared \nto the HospitalOFP clinic could explain the higher prevalence of IAD diagnoses \nfound in the DentalOFP clinic since the average age tends to be younger when it \ncomes to IAD [ 24 ], while the higher average age in the HospitalOFP clinic could \nexplain the higher prevalence of DJD since DJD are more prevalent in \nadults/elderly [ 25 ]. Indeed, after controlling for age and gender, these \nsignificant differences between IAD and DJD were eliminated. As to diagnosis of \nsubluxation, one might argue that the higher prevalence of diagnoses of \nsubluxation in the HospitalOFP clinic may reflect referral of cases such as \nrecurrent dislocation of the TMJ who did not respond to conservative treatment in \nprimary/secondary clinics and therefore were referred to the HospitalOFP clinic \nwhich is a subdivision of oral surgery department for considering surgery. The \nsignificantly higher odds of subluxation in the HospitalOFP which remained after \ncontrolling for age, gender, symptom duration and referring physicians, may \nsupport this theory. However, the finding of subluxation could also be an \nincidental finding unrelated to the patient’s chief complaint, or it might \nrepresent a functional/nociplastic disorder. Therefore, it should be noted that \nwhile the DC/TMD enables diagnosis of non-painful findings, such as IAD, DJD and \nsubluxation, it cannot differentiate between merely incidental physical findings \nor findings that may be the etiologic source for secondary painful joint pain. In \nthat respect assessing primary  vs.  secondary pain is essential for \ntailoring treatment. This aspect has been addressed by the ICOP [ 11 ], as \nmentioned in the introduction section. Thus, according to the DC/TMD, the finding \nof subluxation is recorded and considered a non-painful diagnosis, while \naccording to the ICOP, subluxation could be grouped under the category of \nsecondary TMJ pain: “Temporomandibular joint pain attributed to subluxation”. \nAs to other etiologies for non-painful diagnoses according to the DC/TMD, there \nis still missing diagnostic criteria to address these and to differentiate \nbetween primary and secondary etiologies. For example, generalized hypermobility \nin a patient can explain a finding of subluxation, while another etiology for \nsubluxation could be facial trauma.\nCompared to non-painful diagnoses, there were no significant differences as to \nall painful diagnoses, including local myalgia, myofascial pain with referral, \nand arthralgia. After controlling for age and gender, the odds for diagnosis of \narthralgia were significantly higher in the DentalOFP clinic. Further controlling \nfor referring physician resulted in higher odds of a diagnosis of local myalgia. \nThese findings do not support our hypothesis of a higher prevalence of arthralgia \nin clinics where the majority of referring physicians are not dentists \n( i.e. , HospitalOFP). Again, once understanding that diagnoses \ncategorized under the umbrella of painful TMD according to the DC/TMD cannot \ndifferentiate between different etiologies of painful diagnoses such as \narthralgia of the TMJ and myofascial pain with referral, as listed in the ICOP \nand different pain mechanisms, it is problematic to extract any conclusion using \nthe DC/TMD when an attempt to compare between these two clinics is made, as was \ndone in the current study, even though the same clinician examined all the \npatients, and used a unified diagnostic criteria (DC/TMD).\nIt is interesting to note, that controlling for age, gender, symptoms duration, \nand referring physicians did not affect the diagnosis of myofascial pain with \nreferral which was the only diagnosis that remained nonsignificant when comparing \nbetween the two groups even after controlling for the above parameters. However, \nwhile using the DC/TMD information is lacking for each diagnosis regarding the \ndefinition of pain as acute  vs.  chronic primary or secondary, which is \ncrucial information that may determine the treatment approach [ 26 ]. This \nimportant information for each diagnosis is lacking in the DC/TMD, while \naddressed by the ICOP which differentiates between acute and chronic myofascial \norofacial pain conditions and further subdividing diagnosis according to \nchronicity and etiology into primary  vs.  secondary, and according to \nchronicity into acute  vs.  chronic (frequent/infrequent/highly frequent, \nand chronic persistent). Likewise, recognizing the type of pain, as suggested by \nWoolf  et al . [ 27 ] as nociceptive pain, inflammatory pain, \nneuropathic pain or functional pain/nociplastic pain [ 28 ], while improved \ncompared to the RDC/TMD, is still limited using the DC/TMD.\nAnother major contributor to differences between the two groups that was \nexplored in the current study was the profile of referring physicians. It would \nbe logical to assume that dentists will be more prone to refer patients with \nmechanical joint complaints, such as clicking and crepitation, while general \nphysicians/ear nose, and throat specialists would tend to refer patients with \nreferred otalgia complaints, once primary otalgia was ruled out. Therefore, the \nyounger age profile of the DentalOFP patients could be the result of referral of \npatients with IAD by dentists, and not the cause. In the current study, however, \ncontrolling for referring physicians, had a significant effect on local myalgia \nonly. Overall, non-painful diagnoses were more sensitive to age, and gender \ncompared to painful diagnoses. These findings highlight the heterogenicity of \nnon-painful TMJ-related diagnoses. Indeed, in a systematic review [ 5 ] that \nexamined the prevalence of intra-articular related diagnoses (arthralgia, IAD, \nDJD and subluxation) among the general population, by analyzing and comparing \nstudies that used the RDC/TMD to studies that used the DC/TMD, showed great \nvariability in prevalence of intra-articular related diagnoses in both RDC/TMD \nand DC/TMD studies: In RDC/TMD studies the prevalence of Arthralgia diagnosis \nranged between 5.7–17%, the prevalence of disc displacement with reduction \nranged between 2.1–33%, and prevalence of osteoarthrosis ranged between \n4.8–70%. This is compared to DC/TMD studies: arthralgia, 1.2–21.1%, disc \ndisplacement with reduction, 20.8–47.9%, DJD, 1.3–34.9%. Data in this \nmeta-analysis was not available as to muscle-related disorders, unfortunately. It \nseems, that as to non-painful Axis I diagnoses, a great heterogeneity exists, \neven when using standardized diagnostic criteria. In the current study, these \ndifferences were shown even though the same certified dentist examined the \npatients in both clinics while using the same diagnostic criteria. This \nhighlights the importance of parameters such as age, gender, clinic type and \nreferring physicians in determining non-painful diagnosis profiles. This also \nhighlights the need for establishing specific primary and secondary diagnostic \ncriteria for different etiologies for non-painful TMJ findings in addition to \nwhat was offered for painful diagnoses by the ICOP.\nIn that sense, the current study supports abandoning the term TMD altogether by \nhighlighting the problematic issues that may arise by using the DC/TMD as is, \nincluding assigning multiple diagnoses to the same patient without addressing \netiology, chronicity and pain mechanisms.\nAs with any study, the current study has strengths and limitations: The current \nstudy aimed for a high standardization by using DC/TMD protocol and collecting \ndata of patients who were examined by the same physician. This undoubtedly \nincreased the reliability of the study as to diagnoses in both clinics. However, \nunfortunately, the data for Axis II parameters, including levels of depression, \nanxiety, nonspecific physical symptoms, pain levels, and disability, in the \nHospitalOFP clinic were not available due to hospital clinic limitations. \nCurrently, TMD-related diagnoses are assessed according to the biopsychosocial \nmodel [ 29 ]. This is a major limitation of this study since Axis II parameters and \npain intensity contribute to disability and chronicity and may explain in part \nsymptom duration differences that were found between the two groups and the \nprevalence of painful diagnoses [ 30 ]. There is an intimate association between \nAxis II profile and painful diagnoses that was not analyzed in the current study. \nFuture studies should strive to include Axis II findings in the analysis.\n\nMultiple parameters affect the profile of an orofacial pain clinic, such as \nclinic type (primary  vs.  tertiary), clinic location, age, gender, \nsymptom duration and referring physician’s profile. Orofacial pain clinicians in \ndental academic centers should be aware of skewed diagnoses of the Axis \nI profile due to these parameters. This study supports abandoning the term TMD, \nas pointed out by several researchers. It is suggested to assess each diagnosis \naccording to the DC/TMD separately while avoiding division into painful and \nnon-painful diagnoses. While allowing multiple diagnoses in the same patient, it \nis suggested to analyze each diagnosis separately, as suggested by the ICOP, \nincluding specific information as to primary or secondary etiologies, chronicity \nand pain mechanisms involved. It should be remembered that the same diagnosis \naccording to the DC/TMD can have different etiologies, all presenting similar \nclinically. Future information as to pain mechanisms, chronicity status, Axis II \nprofile, and the existence of other chronic overlapping pain conditions can \nfurther assist in tailoring the appropriate treatment.\n\n• Multiple parameters, such as age, gender, symptom duration, Clinic \ntype (primary  vs.  tertiary), clinic location (hospital  vs.  \nacademic center), and referring physicians’ profile may affect the overall Axis I \ndiagnostic profile of TMD patients within the clinic.\n• Orofacial pain clinicians in dental academic centers should be \naware of skewed diagnoses of the Axis I profile due to these parameters.\n• This study supports abandoning the term TMD. It is suggested to \nassess each diagnosis according to the DC/TMD separately while avoiding division \ninto painful and non-painful diagnoses.\n• For each DC/TMD Axis I diagnosis, it is suggested to follow the \nICOP diagnostic criteria, as to primary and secondary etiologies, and acute \n vs.  chronic conditions.","source_license":"CC-BY-4.0","license_restricted":false}