Myofascial pain is one of the most prevalent conditions within temporomandibular disorders. Despite its high prevalence, health systems pay insufficient attention to it. Patients frequently receive multiple unnecessary and sometimes aggressive treatments. In this context, acupuncture has been studied as a plausible therapy for these conditions. However, researchers have encountered various methodological difficulties when demonstrating its actual effect. The main historical challenge in this area involves the difficulties inherent to using appropriate acupuncture controls such as placebos that allow for double blinding and cause minimum tactile stimulation.

In a previous study, a validated an improved novel placebo acupuncture non-penetrating device with double blinding capability was presented. This project will allow to test the performance of this new placebo acupuncture device in a clinical experimental setting. The study will try to determine the actual effectiveness of acupuncture in treating craniomandibular pain of myofascial origin. The design will be a randomized, triple blind, placebo controlled, crossover clinical trial. The protocol follows the STRICTA (Standards for Reporting Interventions in Controlled Trials of Acupuncture) recommendations, and ethical approval was obtained.

The central hypothesis is that acupuncture will be more effective than a placebo. Another hypothesis is that neither patients nor acupuncturists will be able to distinguish real acupuncture devices from placebo devices.

The study will include consecutive patients diagnosed with pain in the craniomandibular region of muscular/myofascial origin according to accepted criteria. Sample size calculations were made with the assumption of an 80% power and a statistical difference accepted at the 5% level. A total of 60 patients will be included.

Patients will be randomly divided into two groups: real acupuncture or placebo. Five sessions will be performed on each patient on a weekly basis. The total time for each intervention will be 30 minutes. A crossover design will be applied after a "washout" period of 14 days.

Outcome measures will include pain, stress levels, quality of life, and mandibular dynamics, using validated and published criteria. Baseline measurements will be taken pre-treatment and at each treatment session. Follow-up outcomes will be measured after three and six months.

A strict protocol for bias control will be followed. The triple-blind design will prevent the patient, the acupuncturist, and the person performing the statistical analysis from knowing what type of treatment each patient receives each time. Examiners will be calibrated and blinded to the treatment status.

Data will be analyzed using a generalized mixed model framework and logistic regression models. Also, Fisher's exact test will be used to analyze the devices' blinding capability.

Inclusion Criteria:

• Diagnosis of miofascial pain in the craniomandibular/temporomandibular region (DC-TMD published criteria).

Exclusion Criteria:

• Pregnant woman
• Recent history of facial trauma
• Systemic diseases that can affect the musculoskeletal system (e.g. rheumatoid arthritis, lupus, etc).

All IPD that underlie results in a publication.

Starting one month after publication and for one year.

IPD and any additional supporting information will be shared to researchers worldwide upon direct request to the Principal Investigator (Marcelo Kreiner).

The intervention is unknown to the patients, the acupuncturist and the persons who assess the outcomes. Both devices (placebo and real acupuncture) have the exactly same visual appearance. Its double blinding potential was confirmed in preliminary validation studies.