The proposed design is a triple-blind, placebo-controlled randomized prospective phase II trial to assess the feasibility of employing the Temporo-masseteric Nerve Block (TMNB) injection to decrease jaw muscle pain, overall pain, improve mouth opening and minimize pain medication consumption. 80 participants undergoing lower third molar removal under sedation will be enrolled. Those who develop significant jaw muscle pain on the following day will be randomized to receive either the TMNB injection or a placebo. Daily ecological momentary assessments (EMAs) will be collected reflecting elements of patient experience for all participants. On Day 8, participants return for an end-of-study evaluation and return their unused pain medications. Up to 40 participants who are randomized to receive TMNB/placebo will be recruited to participate in a qualitative interview regarding their experience.

The study is designed as a parallel, blinded, randomized phase II pilot study to assess the ability of the Temporo-masseteric Nerve Block (TMNB) injection to reduce post-operative pain in patients who undergo removal of lower third molar/s under sedation. It is not known how often and in whom jaw muscle pain significantly contributes to post-operative pain, limitation in mouth opening, and function. and develop significant jaw muscle pain. Hence the study is designed to assess the development of such jaw muscle pain before testing the placebo-controlled TMNB intervention. Accordingly, 80 subjects who undergo lower third molar extractions under intravenous sedation are randomized to receive either the TMNB (standard-of-care local anesthetic, 1.8 ml 2% lidocaine with 1:100,000 epinephrine), or a placebo (TMNB injection technique, but with 1.8 ml of sterile isotonic saline instead) the day following their extraction/s should they report significant pain (≥5 on a scale of pain rating from 0 to 10) when the jaw muscles are 'palpated' or examined with firm finger pressure. The assessment will be repeated 15 minutes after the injection. On the other hand, those who report less pain (<5) to jaw muscle palpation will not receive any injection. The participant, TMNB administrator and the evaluator will be blinded from randomization assignment. All participants will fill out daily remote surveys administered through REDCap® that will assess peak NRS pain score for the previous 24 hours, limitation in mouth opening and function, oral health related quality of life, pain medication consumption, and adverse effects from pain medications. Patient responses will be collected remotely and will include patient-uploaded cropped selfies of spontaneous mouth-opening with a disposable millimeter ruler (Orastretch®) propped between the upper and lower incisors.

It is anticipated that approximately 50% of patients will develop significant jaw muscle pain following the procedure. Hence, of the 80 participants, 40 are anticipated to be eligible for randomization, with 20 participants receiving the placebo or the TMNB injection, respectively.

Participants will return for an in-person assessment on Day 8, will return unused medications and will get an opportunity to participate in a qualitative interview to interrogate their experience receiving the injection (those randomized to TMNB/placebo), and their recovery experience. The duration of participation is a week from undergoing the procedure.

Inclusion Criteria:

All patients recommended extraction/s of at least 1 lower wisdom (third) molar that is partially/fully 'impacted' under intravenous sedation, are eligible to participate in this study so long as they

• are 18 years or older,
• are healthy,
• have no cognitive/intellectual disability,
• have no past/recent pain or reduced range of motion in their jaw joint/ muscle complex, no trauma or surgery in their jaw region.
• have an electronic device such as a smart phone or a tablet/ computer with internet connection.
• are willing to participate in the study and not be excluded by the following criteria below.

Exclusion Criteria:

An individual who meets any of the following criteria will be excluded from participation in this study:

• Compromised ability to guard their self-interest, for e.g., prisoners, children, pregnant women, patients with intellectual/cognitive disability are not enrolled in the study.
• Those patients who present with infection/inflammation involving the third molars slated for extractions, on the day of their procedure, may not take part in the study.
• Those who have had opioid pain medication/s in the past 3 months to address short term or long-standing pain, or those who are on long term prescription of anti-inflammatory pain medication, are unable to participate.
• Those with long standing painful limitation of movement of the jaw joint or muscles.
• Those patients who are allergic to/unable to tolerate either the dental local anesthetic or its components, opioids, acetaminophen or ibuprofen also may not take part in the study

Final results will be posted no later than 12 months after the trial's primary completion date and will include participant flow, demographic and baseline characteristics, outcomes and statistical analyses, adverse events, the protocol, statistical analysis plan and administrative information.

The PI will share the individual non-identified subject data no later than acceptance for the publication's main findings from the final data analysis or 18 months after completion of the study, whichever is earlier. Data to be posted will include the study protocol, reference to study publication of primary outcome variable, the data set in both SAS and ASCII formats, data dictionary and study specific de-identification notes.

Deidentified data will be released within 12 months of primary completion date.

Upon written request to the PI, survey instruments or other materials developed for use during the clinical trial will be made electronically available to other researchers.

The participant and investigators will be blinded to the treatment assignment- namely, the Temporo-masseteric Nerve Block using a placebo (sterile saline) or dental local anesthetic medication