Gingival enlargement (GE) is one of the most common soft tissue problems in patients undergoing orthodontic fixed treatment, particularly when spaces are rapidly closed and oral hygiene is poor. The mechanism by which GE occurs during orthodontic treatment is not fully understood. The initiation and development of periodontal disease depend on a dynamic equilibrium between the microbial challenge and the host's immune-inflammatory responses. The presence of fixed appliances influences plaque accumulation around the retentive components attached to the teeth and the colonization of important periodontopathic bacteria. Chronic inflammation of the soft tissues is caused by a significant increase in edema and inflammatory cells that can influence the sub-gingival ecosystem by creating an appropriate anaerobic environment, leading to a shift in the composition of the microflora. When gingival tissues are enlarged, varying from mild enlargement of isolated interdental papillae to segmental or uniform and marked enlargement affecting one or both jaws, the tooth surfaces become difficult to access, inhibiting good oral hygiene and resulting in more inflammation and bleeding because enlarged gingival tissues. In artificially deeper periodontal pockets, the root surfaces are contaminated with an accumulation of plaque and calculus, as well as infiltration of bacteria and bacterial endotoxins into cementum. Complete removal of these harmful substances is essential for the healing of periodontal tissue. However, nonsurgical periodontal treatment (including oral hygiene instruction, scaling, root planing, and prophylaxis) is not always effective when GE is extensive and self-care is compromised. When GE further impedes the maintenance of oral hygiene (thereby resulting in further damage to periodontal tissues), causes aesthetic and functional problems, and compromises orthodontic tooth movement, it is necessary to provide additional surgery treatment such as gingivectomy, in order to correct gingival border contours. Gingivectomy can be performed by conventional scalpels, electrosurgery, chemosurgery, and laser. Preservation of biologic width is the therapeutic endpoint of all these procedures. 3 mm of tooth structure above the osseous crest is considered safe to prevent any attachment loss. The conventional surgery performed by a small scalpel has been considered the most common method because of its ease of use, accuracy, and minimal damage to tissues. However, scalpels do not provide a good hemostasis, which is important on highly perfused tissues such as in the oral cavity. The advent of diode lasers highly absorbable by melanin and hemoglobin allows soft-tissue manipulations providing sound results in periodontal surgery, tissue alterations related to orthodontic treatment, and oral lesions. The diode laser separates and coagulates at the same time, facilitating immediate hemostasis and resulting in minimal bleeding. Healing is rapid and there is reduced potential for infection. The diode laser has an affinity for only soft tissue, thereby preventing damage to the surrounding bone and enamel. Therefore, using diode lasers might be advantageous because of better control, potentially lower pain and inflammation, and improved wound healing. In literature, no studies directly compared conventional scalpel surgery versus diode laser-assisted surgery in orthodontic patients with GE. Moreover, the majority of the studies comparing laser gingivectomy with scalpel gingivectomy show some limits: they are not randomized, they are not prospective, and they have no control group. Therefore, the aim of the present study was to compare the use of the 810nm diode laser with conventional surgery and to evaluate the effectiveness of gingivectomy as an adjunct to nonsurgical periodontal treatment in the management of GE during orthodontic treatment. The Consolidated Standards of Reporting Trials (CONSORT) checklist was used as a guideline for conducting and reporting this trial. The present Randomized Clinical Trial was designed as a prospective three-arm parallel group randomized clinical trial with 1:1:1 allocation ratio. The study was approved by the Ethics Committee at the University of Rome "Tor Vergata", (protocol number 206/17), and informed consent was obtained from the patients' parents. A total of 60 (33 Males; 27 Females) subjects, with a mean age of 14.4 ± 1.9 years (range 11.7-19.8 years), undergoing orthodontic treatment at the Department of Orthodontic of the University of Rome "Tor Vergata" were recruited for the study. Gingival overgrowth diagnosis was defined as presence of quadratic anterior teeth (crown width/length ratio ≤0.85), gingival margin located incisal to the tooth cervical convexity and presence of mean Probing Pocket Depths (PPD) ≥ 4mm coronal to the cement-enamel junction (CEJ) at three buccal points around each tooth of the anterior segment (mesial, mid-point, distal). Crown Width (CW) and Clinical Crown Length (CCL) were measured pre-operatively with a digital caliper: CCL, measured as the distance between incisal edge and gingival margin along the tooth long axis; CW measured at the point between incisal and middle third of CCL. All subjects received ongoing nonsurgical periodontal treatment and instructions on oral hygiene. After the conventional management approach for gingival enlargement, patients with persistent gingival overgrowth were enrolled in the study and blindly assigned to three groups. In the first group (TG1), all subjects underwent a conventional scalpel gingivectomy of the maxillary anterior sextant. In the second group (TG2), all subjects were treated using laser-assisted gingivectomy; while subjects assigned to the third group underwent only nonsurgical periodontal treatment and served as the control group (CG). Both TGs were consecutively treated by one clinician. The PPDs were recorded to determine the biologic width and to assess how much tissue could be contoured without involving osseous surgery, using a North Carolina periodontal probe. Remembering that there exists a 3.0 mm biologic zone, the maximum amount of tissue removal could be calculated. The periodontal probe was placed apically to the alveolar crest, and the marginal gingival level was measured. An explorer was used to mark reference spots of the biologic zone, serving as the visual finishing point. At baseline (before surgery) all patients of the three groups underwent a full periodontal screening. Their oral hygiene and gingival inflammation were assessed using CCL, PPD, Plaque Index (PI) and Gingival Index (GI) at three buccal points around each tooth of the anterior segment (mesial, mid-point, distal). All measures were repeated at 1, 3 and 6 months post-surgery or nonsurgical periodontal treatment. Overall patient data were calculated as mean value by averaging measurements in all sites of six upper anterior teeth. A sample size for this trial was calculated according to the method proposed by Whitehead et al. For a standardized effect size of 1 (a clinically relevant change of 0.75 mm with a combined SD of 0.68 mm derived from Mavroggianis et al.) for the primary outcome variable PPD at 3 months, a sample size of 17 subjects per group was required for a type I error rate of 5% and a power of 80%. To account for potential dropouts, 20 subjects per group were recruited. Allocation of patients to the three groups was determined by a computer-generated randomization list using Rv.0.1 software and by a block size of 4. Then, the allocation information (randomization results) was concealed in opaque and sealed envelopes by the statistician. The observer who performed all the measurements was blinded to the group assignment. The study was blinded in regard to the statistical analysis: blinding was obtained by eliminating from the elaboration file every reference to patient group assignment. Reliability of the periodontal assessments was conducted among 10 patients throughout the study. Exploratory statistics revealed that all periodontal variables were normally distributed (Kolmogorov-Smirnov test) with equality of variances (Levene's test). All statistical computations were performed with SPSS software (Statistical Package for the Social Sciences, SPSS, Version 12, Chicago, IL, USA).