The purpose of this study is to evaluate the effect of Photobiomodulation (PBM) in postoperative pain after endodontic microsurgery (EMS) in patients from the University of Texas Health Science Center at Houston, School of Dentistry Graduate Endodontic Clinic and to assess the soft tissue healing of the vertical releasing incision (VRI) after PBM

From the University of Texas Health Science Center School of Dentistry at Houston (UTHealth), forty patients needing endodontic microsurgery (EMS) (where the tissue flap design includes vertical releasing incisions) will be recruited for this study.

Photobiomodulation (PBM) has been used for decades in medicine and dentistry showing promising results in the healing capabilities, however, an accepted protocol has still not been created for its regular use in endodontics. PBM functions on the principle of harnessing light energy to stimulate cellular activity, particularly with the mitochondria (Karu, 2008). When specific wavelengths of light, typically in the red or near-infrared spectrum, penetrate the tissue, a series of photochemical reactions occur. This light energy enhances the production of adenosine triphosphate (ATP), the primary source of cellular energy, leading to improved cellular function and metabolism. Additionally, photobiomodulation can influence various cellular processes, such as reducing oxidative stress and inflammation, ultimately promoting less postoperative pain and enhanced soft tissue healing (Sobouti et al., 2015, Fulop et al., 2010, Sanz-Moliner et al., 2013).

Findings regarding the quality of life after apical surgery suggest that patients commonly hold negative beliefs and perceive it as one of the most painful among endodontic procedures (Morse et al., 1990), when in fact, it could be less unpleasant than expected (Iqbal et al., 2007). Apical surgery has significantly evolved with the introduction of the surgical operating microscope and microsurgical instruments, transforming it into a distinct and more successful procedure. The adoption of microsurgical techniques has been associated with reduced postoperative pain (Pecora et al., 1993), likely due to minimized tissue trauma and enhanced precision facilitated by superior visualization.

Consequently, since PBM can promote pain relief, tissue repair, and regeneration, it may serve as a valuable tool for EMS, reducing postoperative pain and improving overall healing (Mizutani et al., 2016).

Forty adult patients will be invited to participate in this study. They will be divided into two groups: (A) Experimental group (n=20) where patients will receive conventional EMS and PBM treatment, and (B) Control group (n=20) where patients will receive conventional EMS and PBM sham treatment. Preoperative and postoperative pain will be assessed using a visual analog pain scale and the tissue healing will be evaluated by visual inspection and photographs.

Inclusion Criteria:

• American Society of Anesthesiologists (ASA) I or II.
• At least one tooth will receive EMS.
• Flap design that includes at least one VRI (triangular, rectangular, papilla base or submarginal rectangular).

Exclusion Criteria:

• ASA III or IV.
• Current heavy smokers (>10 cigarettes/day)
• Uncontrolled diabetes (HbA1c ≥ 7%) or other uncontrolled systemic diseases that may comprise healing, such as vitamin C deficiency, neutrophil deficiencies, immunodeficiency syndromes, or leukemia.
• Surgical access on the palatal surface.
• Acute swelling or abscess present on the day of the surgery.
• Any event or condition that would make continued participation in the study not in the best interest of the subject, as determined by the investigator.
• Pregnancy.
• Development of any medical condition that might affect the treatment and clinical outcomes, as determined by the investigator.
• Initiation of any treatment or exposure that might affect therapy's healing, as determined by the investigator.