Photobiomodulation vs. Palatal Stent for Palatal Donor Site Healing After Free Gingival Grafting

Background and Rationale Autogenous soft tissue grafting remains the gold standard in periodontal plastic surgery for augmenting keratinized tissue and modifying thin gingival phenotypes around teeth and dental implants. The palate is the primary donor site due to its anatomical availability and histological suitability. However, harvesting a free gingival graft leaves an open donor wound that heals by secondary intention, resulting in substantial morbidity including pain, localized bleeding, delayed epithelialization, and functional impairment during mastication. Photobiomodulation therapy (PBMT) utilizes low-level laser irradiation to trigger biological responses via mitochondrial chromophore activation, enhanced adenosine triphosphate (ATP) synthesis, stimulation of fibroblast and keratinocyte proliferation, angiogenesis, and inflammatory modulation. While PBMT shows potential for accelerating soft tissue repair, direct comparative evidence regarding its clinical effectiveness versus conventional mechanical protection using an acrylic palatal stent remains limited and inconsistent. This study is designed to directly evaluate the clinical effectiveness of diode laser PBMT versus conventional acrylic palatal stent protection.

Study Design and Setting This study is a single-center, parallel-group, single-blinded randomized controlled clinical trial with a 1:1 allocation ratio, conducted at Thumbay Dental Hospital, Gulf Medical University Complex in Ajman, United Arab Emirates. The study protocol will enroll 50 adult participants needing free gingival graft harvesting. Preoperative Assessment and StandardizationAll participants undergo initial periodontal therapy to achieve a Full-Mouth Plaque Score (FMPS) $\le 20\%$ and Full-Mouth Bleeding Score (FMBS) $\le 20\%$. Palatal tissue thickness is evaluated transgingivally under local anesthesia at the premolar-molar region using a No. 15 endodontic reamer with a silicone stopper and digital caliper measurements. A minimum palatal tissue thickness of 3 mm is required for inclusion to allow harvesting of a 1.5 mm graft while preserving sufficient connective tissue cover over the palatal bone.

Surgical Protocol All surgical procedures are performed by a single experienced periodontist under local anesthesia using 4% Articaine with 1:100,000 epinephrine. Recipient site preparation follows standard mucogingival surgical principles. Donor wound dimensions are standardized to approximately $10 \times 15\text{ mm}$ using a sterile aluminum foil template. A free gingival graft with a uniform thickness of 1.5-2.0 mm is harvested using a No. 15 surgical blade. Primary hemostasis is achieved by gentle manual compression with sterile wet gauze. Participants are then randomly allocated via computer-generated sequence and sequentially numbered opaque sealed envelopes to one of two treatment groups: Test Group (Photobiomodulation): Receives PBMT using a claros® pico diode laser ($808 \pm 10\text{ nm}$ wavelength, 1 W continuous wave output, $5\text{ J/cm}^2$ energy density per point, 30 seconds exposure per point). The laser application is performed in non-contact mode at approximately 1 mm distance from the wound bed across 5 standardized points (4 peripheral corners and 1 central point). Irradiation is performed immediately after surgery (Day 0) and on postoperative Days 1, 3, and 7. Control Group (Palatal Stent): Receives a customized acrylic palatal stent fabricated from preoperative impressions. The stent is fitted immediately after surgery, and participants are instructed to wear it continuously for the first 7 postoperative days, removing it only for oral hygiene routines. Postoperative ProtocolAll participants receive standardized postoperative systemic therapy consisting of Amoxicillin/clavulanic acid 1 g twice daily for 5 days (or an alternative in cases of penicillin allergy), Ibuprofen 600 mg three times daily for 3 days (or as needed for pain), and twice-daily 0.12-0.2% chlorhexidine mouth rinses for 2 weeks. Mechanical tooth brushing at the surgical sites is restricted during the early healing phase, and a soft diet is required for 1 week.

Assessment Timeline and Follow-Up Protocols

Clinical examinations, digital 3D intraoral scans (STL files), photographic documentation, and questionnaire evaluations are performed by a calibrated examiner blinded to group allocation at scheduled time points: Baseline ($T_0$): Post-harvesting digital intraoral STL scan and clinical photography to document baseline wound area. Day 3: Evaluation of early wound healing using the Palatal Mucosal Wound Healing Index (PMWHI; immediate healing parameters), VAS pain scores (0-100 mm), daily analgesic tablet count, functional morbidity VAS scores (0-10), and complication tracking. Day 7: 3D intraoral STL scan superimposition to calculate percentage wound closure; 3% hydrogen peroxide ($\text{H}_2\text{O}_2$) bubbling test for re-epithelialization; PMWHI score; tissue color match VAS score (0-10); VAS pain, functional morbidity, and analgesic consumption counts. Day 14: Delayed healing PMWHI evaluation; 3% $\text{H}_2\text{O}_2$ re-epithelialization test; 3D STL scan superimposition; tissue color match VAS score; VAS pain and morbidity scores. Day 21: PMWHI score; 3% $\text{H}_2\text{O}_2$ re-epithelialization test; 3D STL scan superimposition; tissue color match VAS score; functional morbidity tracking. Day 28: Final 3D STL scan superimposition for primary outcome (% wound closure); 3% $\text{H}_2\text{O}_2$ re-epithelialization test; PMWHI score; tissue color match assessment; overall patient satisfaction score; comprehensive adverse event and complication record. 3 Months: Extended follow-up PMWHI assessment.