Inclusion Criteria: Main project
* Provide signed and dated informed consent form.
* Willing to comply with all study procedures and be available for the duration of study participation.
* All participants will be females (biological sex by self-report) between ages 18 to 65 years (inclusive), as this includes the majority of the patient population at risk for chronic TMD pain.
* Cases and controls will be matched for age within ±3 years, and all participants must be able to understand commands in English to follow study procedures (e.g., during sensory testing).
Pain-free controls
* TMD-Pain screener score less than 3 out of 7 (Screener available as part of the DC/TMD)
* No previous diagnosis for the most common pain-related TMD as defined in the DC/TMD criteria (myalgia, arthralgia, headache attributed to TMD)
* No significant orofacial pain (jaw pain, TMJ pain) in past 3 months ("significant" meaning 5 or more days in any month or any pain during the past month)
* No report of significant pain in the last 3 months elsewhere in the body ("significant" meaning 5 or more days in any month or any pain during the past month), e.g., low back pain, fibromyalgia, migraine headaches
* Not meeting any of the most common pain-related TMD diagnosis as described in the DC/TMD criteria (myalgia, arthralgia, headache attributed to TMD) upon clinical examination following the DC/TMD protocol
Chronic painful TMD cases
* TMD-pain screener score equal to or greater than 3
* Primary TMD caseness criteria: myalgia (masticatory muscle pain) based on clinical exam following the DC/TMD protocol
* Concurrent arthralgia (TMJ pain) and/or headache attributed to TMD allowed
* Myofascial pain must meet the following criteria:
* Onset \>3 months, occurring \>15 days/month on average for \>3 months
* Minimum 10 jaw pain episodes since onset, each episode lasting at least 30 minutes and no less than 2 hours within the day, OR unremitting
* Low-impact TMD pain cases: Graded Chronic Pain Scale (GCPS) grade IIa or lower
* High-impact TMD pain cases: GCPS grade IIb or greater
Inclusion criteria: Patients in MRI Optimization group
* Be age 18-65 (inclusive)
* Provide a signed and dated informed consent form.
* Be willing to comply with all study procedures and be available for the duration of study participation.
* Be able to understand commands in English to follow study procedures.
Exclusion Criteria: Main project
* Traumatic facial injury or surgery on the face/jaw, arms or hands
* Presence of pain related to dental or periodontal pathology
* Currently undergoing active orthodontic treatment
* Pregnant or nursing
* Has any of the following medical conditions by self-report:
* Renal failure or dialysis
* Heart disease (examples: uncontrolled arrhythmia or hypertension, cardiomyopathy) or heart failure
* Non-allergic bronchospasm (chronic obstructive pulmonary disease and emphysema)
* Diabetes (Type I or II) that is not controlled with medication or diet
* Hyperthyroidism
* Uncontrolled seizures
* Used any injection therapy (i.e. tender or trigger point injections, steroid injections), acupuncture, biofeedback, or TENS for the management of facial pain within 2 weeks prior to the screening assessment
* If undergoing botulinum toxin injections in the head and neck areas, must be 3 months since last set of injections and refrain from this treatment until study has ended
* History of major depression or other major psychiatric disorder requiring hospitalization within the last 6 months prior to the screening assessments
* History of treatment for drug or alcohol abuse within the last 12 months
* Current pain medication use (e.g. opioids, ibuprofen, acetaminophen) that cannot be stopped \<24 hours prior to each study visit
* Other conditions/diseases associated with altered pain perception: neurological or developmental disorders (dementia, autism spectrum disorder), neoplasm, multiple sclerosis, trigeminal neuralgia
* MRA contraindications including claustrophobia
* GCPS grade assigned at Visit 1 that does not match grade from screening GCPS (low-, high-impact pain) and it is not possible to assign the potential participant to the correct final group, due to the latter having met their recruitment quota
* Strictly left-handedness by self-report
* Thermal threshold for Pain-50 (determined at Visit 1) is outside the temperature range of 40-49 degrees Celsius
* Lack of access to electronic device with internet connection during the study
* Inability or unwillingness to receive daily text messages during the study
* Inability to complete at least four daily ratings between the Informed consent, Pre- visit 1 procedures and in-person visit 1
* Anything that would place the individual at increased risk or preclude the individual's full compliance with study procedures or completion of the study.
Exclusion criteria: MRI Optimization group
Pregnant or nursing;
* MRI contraindications including claustrophobia;
* Adults lacking capacity to provide informed consent for themselves;
* Unable to understand instructions for sensory testing in English;
* Anything that would place the individual at increased risk or preclude the individual's full compliance with study procedures or completion of the study.