summarize  this text in one paragaph :Painful temporomandibular disorder (TMD) is the most common orofacial pain condition
and the second most common musculoskeletal condition resulting in pain and disability
after chronic low back pain.1 TMD prevalence is 5% through 12% among US adults,2
annual incidence is nearly 4%,3 and annual TMD health care costs are $4 billion,2 highlighting
treatment needs.
The Orofacial Pain Prospective Evaluation and Risk Assessment (OPPERA) study was the first
large prospective study, to our knowledge, in which investigators enrolled 3,258 participants free of
TMD to identify clinical, biological, psychosocial, and health status characteristics that contribute
to the risk of developing first-onset TMD and its persistence.4 Embedded in OPPERA’s prospectivestudy enrollment phase was a case-control study of chronic TMD. By enrolling 185 participants
with examiner-verified chronic TMD and comparing them with participants free of TMD, the study
investigators identified that greater age, being female, and being white were associated with
increased odds of chronic TMD.5 Worse psychosocial status6 and heightened pain sensitivity7 also
were associated with greater odds of chronic TMD. Results from genetic analyses revealed suggestive
associations between a few genetic variants and risk of developing chronic TMD.8 Clinical characteristics
associated with increased odds of chronic TMD included greater facial pain severity and
pain-related interference, limitations in mandible function, more frequent joint noises, increased
pain with function, and enhanced palpation sensitivity, among others.9 By following participants
free of TMD, the OPPERA prospective study investigators identified that greater age, being African
American, having sleep disturbances, and smoking, as well as other aspects of general health, were
associated with higher TMD incidence.10,11 Although heightened sensitivity to experimental pain
was only a modest predictor of TMD onset,12 psychological characteristics exhibited strong effects.13
No single genetic variant was associated with TMD onset.14 Condition-specific risk incidence
factors included self-reported oral parafunctional behaviors and history of temporomandibular joint
(TMJ) mechanical problems, among others.
We measured the aforementioned risk factors either when participants already had chronic TMD
(case-control study of chronic TMD) or before they developed TMD (prospective study of first-onset
TMD). In clinical settings, clinicians generally assess patients for a condition after they develop
symptoms, when they seek evaluation and diagnosis (for example, with use of the Diagnostic Criteria
for Temporomandibular Disorders [DC-TMD]15). On the basis of available data, clinicians also
should assess patients with acute pain disorders for comorbid aspects of the pain condition and,
ideally, prognosis for whether the acute pain will become chronic to determine who should benefit
from targeted treatment approaches.16 It is plausible that characteristics within DC-TMD Axes I and
II might be useful predictors for persistence. Because one-half to two-thirds of patients with TMD are
likely to experience persistent pain when reexamined 6 months later,17,18 the initial episode is an
important opportunity for clinicians potentially to identify increased risk of developing persistence
and allow better informed decision making about which patients should receive which type of
treatment16 to avoid TMD persistence and the disorder eventually becoming chronic.
Our goals in this study were to develop a predictive model by using biopsychosocial variables that
clinicians can assess easily and that are part of a validated assessment system to identify patients with
first-onset TMD whose pain persists. We also compared our predictive model with a prognostic
approach used to define future chronic pain.19-23