Effects of Laser Stimulation on Wound Healing of Human Palatal Tissue

Effects of Er:YAG Photobiomodulation Therapy on Wound Healing of Human Palatal Mucosa After Connective Tissue Graft Harvesting: A Pilot Study

The purpose of this study is to assess the effects of photobiomodulation (PBM) with an Er:YAG laser on the palatal donor site following subepithelial connective tissue graft (SECTG) surgery. Patient-centred outcomes and wound healing will be compared between a control group, who receives no laser treatment, and the test group receiving PBM therapy. It is hypothesized that laser stimulation will have a beneficial effect on the patient's post-operative experience as well as the healing of the tissues.

The study is a randomized clinical trial comparing palatal donor sites that receive PBM with an Er:YAG laser and palatal donor sites receiving no additional treatment, following SETG surgery. A computerized randomization program will assign patients to one of two groups. Participants will be block-randomized to ensure balance between the operators. The palate is anesthetized with 2% lidocaine (1:100000 epinephrine) by greater palatine nerve block, nasopalatine nerve block, and local infiltration. The thickness of the tissue at donor site of the palate is measured by transgingival probing ("bone sounding"). The palatal tissue is harvested from the area bordered mesially by the root of the canine and distally by the palatal root of the first molar, extending laterally to approximately 2 mm from the gingival margin and medially far enough to obtain an adequate area of tissue for the required size of the graft while ensuring not to encroach on the palatal neurovascular bundle. A horizontal incision, corresponding to the necessary length of the graft, is made at 90 degrees to the bone approximately 2 mm from the gingival margin. Within this first incision, the scalpel is angled at approximately 135 degrees and a split-thickness dissection of the palatal tissue is extended medially. As the scalpel is advanced, the angle of the blade is further flattened until it is nearly parallel to the surface of the bone. The incision is extended until the necessary dimensions of the graft tissue are reached. Incisions are then made to the bone at the mesial, distal, and medial borders of the graft. The donor tissue is detached from the bone with a periosteal elevator and placed on a saline-soaked gauze. The length, width, and thickness of the graft, the thickness of the remaining flap of palatal tissue, and the length of the palatal incision will be measured with digital calipers to the nearest 0.1 mm. The palatal incision will be closed with cyanoacrylate. Immediately following completion of the surgical procedure, Group A will receive PBM of the donor site and Group B will receive sham treatment with the laser unit turned off. The parameters used for PBM will be those shown to induce maximal proliferation of gingival fibroblasts using an Er:YAG laser: Energy [80 mJ], Duration [30 s], and Pulse Rate [25 Hz]. Post-operatively, both groups receive 2 g of Amoxicillin (or 600 mg of Clindamycin in cases of penicillin allergies) and the standard post-surgical instructions given to patients at the Graduate Periodontics clinic. Patients are then provided a Visual Analog Scale (VAS) questionnaire to rate their pain from 0-10 each night for 1 week and 30 Ibuprofen (200 mg) tablets. Patients will be followed up with at 1-week, 2-week, and 6-week post-operative appointments. Photographs will be taken at all appointments. At the first appointment, participants will return their completed VAS and any remaining Ibuprofen tablets. The donor site will be examined by a clinician who did not perform the surgery and assessed according to Fickl's Modified Early-Wound Healing Index (MEHI) and Landry's Healing Index (HI). Patients will also answer a modified Oral Impacts on Daily Performance (OIDP) questionnaire. At the 2-week appointment, the palate will again be evaluated by the same operator and assessed according to the MEHI and HI. At the 6-week appointment, the donor site will be anesthetized with local infiltration of 2% lidocaine (1:100000 epinephrine), ensuring not to inject anesthetic into the tissue overlying where the graft was harvested from. Tissue thickness at the donor site will be measured via transgingival probing, in the same method as was used pre-operatively, and a histological specimen of the tissue will be harvested and placed in 10% neutral buffered formalin. Barring any ongoing post-surgical complications at this point, the patient's participation in the study is now complete.

Immediately following completion of the surgical procedure, this group will receive photobiomodulation treatment of the palatal tissue donor site with Er:YAG laser according to the parameters recommended by experts in this field and which have shown to induce maximal proliferation of human gingival fibroblasts (Energy Setting: 80 mJ, Pulse Rate: 25 Hz, Duration: 30 s).

This group will receive sham treatment of the palatal tissue donor site. The laser unit will be turned off. The clinician will simulate usage of the Er:YAG laser in a manner that is indistinguishable to the patient from the experimental group.

At the end of their surgical appointment, patients will be given a Visual Analogue Scale (VAS) questionnaire to rate their post-operative pain by making a mark along a 10-cm line (0 = no pain, 10 = unbearable pain) for each night of the first post-operative week. At the one-week post-operative appointment, the participants will return their VAS questionnaires and their reported post-operative discomfort for each night of the initial post-operative week will be tabulated.

At the end of their surgical appointment, patients will be provided with a bag of 30 200-mg Ibuprofen tablets. At the one-week post-operative appointment, the participants will return any remaining Ibuprofen tablets and their total analgesic consumption for the initial post-operative week will be tabulated.

At the one-week post-operative appointment, patients will complete a modified Oral Impacts on Daily Performance (OIDP) questionnaire to assess the effect of the palatal wound on their oral-health related quality of life during the first post-operative week. They will rate the overall frequency of disruptions that the palatal surgical site had on eating, speaking, oral hygiene, light physical work, participation in regular outings, sleeping, relaxing, smiling and laughing, their mood, and interpersonal interactions by making a mark along a 10-cm line (0 = never, 10 = constantly) for first post-operative week. When applicable, they will also rate the overall severity of the disruptions for these same categories by making a mark along a 10-cm line (0 = barely noticeable, 10 = extremely disruptive) for first post-operative week.

At a six-week post-operative appointment, a histological specimen will be harvested with a tissue punch. Samples of laser-treated and non laser-treated palatal tissues will be histologically compared with respect to concentration of inflammatory cells, amount of Type I collagen present, and amount of Type III collagen present.

At the one-week and two-week post-operative appointments, a clinician who did not perform the surgery and is blinded to which treatment group the patient belongs will assess the donor site according to the Modified Early-Wound Healing Index (MEHI) proposed by Fickl. The clinician will evaluate the palatal tissue donor site and rate it from 1 to 5 (1 = complete flap closure without fibrin line at the palate, 5 = incomplete flap closure with >50% necrosis of the palatal flap tissue). The progression of post-operative healing at one week and two weeks will be compared between experimental and control groups.

At the one-week and two-week post-operative appointments, a clinician who did not perform the surgery and is blinded to which treatment group the patient belongs will assess the donor site according to the Healing Index (HI) proposed by Landry, Turnbull, and Howley. The clinician will evaluate the palatal tissue donor site and rate it from 1 to 5 (1 = very poor, 5 = excellent) based on the parameters of tissue colour, bleeding response to palpation, presence of granulation tissue, presence of suppuration, exposure of underlying connective tissue, and epithelialization along incision margins. The progression of post-operative healing at one week and two weeks will be compared between experimental and control groups.

At a six-week post-operative appointment, tissue thickness at the donor site will be measured in millimetres via bone sounding with a periodontal probe. This will be compared to pre-operative measurements taken at the site.

Inclusion Criteria: ASA I or II Full Mouth Plaque Score (FMPS) < 20% Full Mouth Bleeding Score (FMBS) < 20% Exclusion Criteria: Any contraindications for periodontal surgery, Anticoagulant usage Corticosteroid usage Smoking > 10 cigarettes/day.

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