Thirty-one (n=31) participants from the Department of Orthodontics and Pediatric Dentistry, University of Szeged will be randomly assigned using a split-mouth design, to avoid inter-individual variability between participants from confounding our results.

Patients' upper and lower dental arches will be divided into right and left halves (i.e. quadrants). In each participant, three quadrants will be used to administer the different LLLT treatment regimens, while the fourth quadrant will be designated for placebo. The random assignment of quadrants to receive LLLT or placebo will be determined using cards denoting the possible four quadrants and the four treatment variations, respectively. Participants will be asked to blindly choose from among the prepared cards to determine assignment; to ensure adherence to double-blinding, patients and the operator will be blinded to the assignment of quadrants and treatments.

In the treatment quadrants a low-level medical gallium-aluminum-arsenide (GaAlAs) diode laser device (wavelength 980 nm, power: 0.1-0.2W, producing 6-12 J energy), with either a continuous or pulsed wave mode will be used on the first permanent molars in the appropriate treatment (R1-R3) quadrants. The efficacy of the treatment will be evaluated in two energy-levels (i.e. intensity; 6 and 12 J, respectively) and regimes (continuous vs. pulsed). The assigned LLLT treatments in the appropriate three quadrants will be applied as follows: regiment 1 (R1: 6 J, continuous), regiment 2 (R2: 12 J, continuous), regiment 3 (R3: 6 J, pulsed), while placebo treatment (P) will be applied in the remaining, fourth quadrant. Using the split mouth design, patients will receive only a single dose immediately after the placement of orthodontic separators. Specified points in each quadrant will be treated from mesial, central and distal directions on the mucosa both buccally and lingually/palatinally with 10-10 sec for each, altogether for 60 sec, producing either 36 or 72 J of energy per molar. During the placebo treatment session, a similar procedure to that of the laser treatment session will be carried out, but with no laser irradiation. Therefore, to control the patient's pain-related behavior, and to maintain the blinded protocol, the handpiece will also be held on the placebo treatment side without laser irradiation following a similar application protocol.

Patients will be instructed to denote their pain sensation levels (which is expected to be the primary come measure of the study), using a self-administered, standardized questionnaire at the given appointments following the treatments: at 0 hours (i.e. within 5 minutes of placing the elastic separators), at 6 hours , at 12 hrs , at 24 hrs , at 48 hrs and at 72 hrs ,after treatment (R1-R2-R3-placebo) in resting position of the mandible (spontaneous pain) and during mastication, on a Visual Analog Scale (VAS), ranging from 0 (no pain) to 100 (severe pain).

Effective reduction of pain is crucial during a variety of dental treatments - in-cluding orthodontic therapy, especially during treatments with fixed appliances - to ensure adequate compliance of patients. Existing evidence has highlighted that over 9 out of 10 patients reported experiencing substantial pain during orthodontic treatment, with as much as 30% opting to discontinue therapy. In practice, before the initiation of effective orthodontic interventions, orthodontists place elastomeric separators (ES) to make enough room for the subsequent use of orthodontic bands. This intervention may result in a considerable pain experience for the patients. In recent years, Low Level Laser Therapy (LLLT), a non-surgical, minimally invasive method, has received substantial attention in a variety of dental domains, including tooth movement, tissue regeneration and healing, implant stability, and increasingly, as an effective analgesic treatment modality. LLLT, as defined by devices operating with an output below 0.5 W, have a low energy output to preclude an increase in temperature above normal body temperature in target tissues. If used carefully, under the supervision of an experienced operator, LLLTs has substantial advantages over conventional analgesic modalities (e.g., pharmaceuticals, such as non-steroidal anti-inflammatory drugs (NSAIDs)), as they do not present with the adverse systemic effects (e.g., altering bone resorption processes, xerostomia) associated with their use.

In our previous study, the researchers assessed the efficacy of LLLT - in the form of a 980 nm wavelength, 0.1 W energy diode laser - as a modality for pain reduction following orthodontic separation in individuals treated with fixed ortodontic appliances, within the framework of a double-blind, placebo controlled split-mouth study design. Our findings demonstrated that continuously applied LLLT with 6 J energy may have beneficial effects on orthodontic pain caused by ES, especially after 6 hrs of ES placement. However, as there is a dearth of evidence pertaining to the specifics on the most effective utilization of LLLT for or-thodontic pain reduction (e.g., energy, application mode, time), the present clinical study aims to evaluate the effect of LLLT vs. placebo, following orthodontic ES placement in patients treated with fixed orthodontic appliances, introducing variables not assessed in our earlier placebo controlled study.

Thirty-one (n=31) participants from the Department of Orthodontics and Pediatric Dentistry, University of Szeged will be randomly assigned using a split-mouth design, to avoid inter-individual variability between participants from confounding our results.

Patients' upper and lower dental arches will be divided into right and left halves (i.e. quadrants). In each participant, three quadrants will be used to administer the different LLLT treatment regimens, while the fourth quadrant will be designated for placebo. The random assignment of quadrants to receive LLLT or placebo will be determined using cards denoting the possible four quadrants and the four treatment variations, respectively. Participants will be asked to blindly choose from among the prepared cards to determine assignment; to ensure adherence to double-blinding, patients and the operator will be blinded to the assignment of quadrants and treatments.

In the treatment quadrants a low-level medical gallium-aluminum-arsenide (GaAlAs) diode laser device (wavelength 980 nm, power: 0.1-0.2W, producing 6-12 J energy), with either a continuous or pulsed wave mode will be used on the first permanent molars in the appropriate treatment (R1-R3) quadrants. The efficacy of the treatment will be evaluated in two energy-levels (i.e. intensity; 6 and 12 J, respectively) and regimes (continuous vs. pulsed). The assigned LLLT treatments in the appropriate three quadrants will be applied as follows: regiment 1 (R1: 6 J, continuous), regiment 2 (R2: 12 J, continuous), regiment 3 (R3: 6 J, pulsed), while placebo treatment (P) will be applied in the remaining, fourth quadrant. Using the split mouth design, patients will receive only a single dose immediately after the placement of orthodontic separators. Specified points in each quadrant will be treated from mesial, central and distal directions on the mucosa both buccally and lingually/palatinally with 10-10 sec for each, altogether for 60 sec, producing either 36 or 72 J of energy per molar. During the placebo treatment session, a similar procedure to that of the laser treatment session will be carried out, but with no laser irradiation. Therefore, to control the patient's pain-related behavior, and to maintain the blinded protocol, the handpiece will also be held on the placebo treatment side without laser irradiation following a similar application protocol.

Patients will be instructed to denote their pain sensation levels (which is expected to be the primary come measure of the study), using a self-administered, standardized questionnaire at the given appointments following the treatments: at 0 hours (i.e. within 5 minutes of placing the elastic separators), at 6 hours , at 12 hrs , at 24 hrs , at 48 hrs and at 72 hrs ,after treatment (R1-R2-R3-placebo) in resting position of the mandible (spontaneous pain) and during mastication, on a Visual Analog Scale (VAS), ranging from 0 (no pain) to 100 (severe pain).

Eligible participants of the study are going to be included from the pool of patients at the Department of Orthodontics and Pediatric Dentistry (Faculty of Dentistry, University of Szeged) who were recommended orthodontic treatment.

Inclusion Criteria:

• individuals aged between 18 and 50 years
• completely erupted second molars without open interproximal contacts of the first molars
• good overall health, without the existence of known systemic disorders
• being caries-free without gingivitis or any other periodontal problems
• no previous orthodontic treatment in the medical history
• willing to participate in the study

Exclusion Criteria:

• those who did not fulfill the general inclusion criteria or unwilling to take part in the study
• prior oral LLLT treatment in the medical history
• use of NSAIDs, other analgesic drugs or local anesthetics for pain management 6 weeks before the initiation of orthodontic treatment
• consumption of any type of tobacco products
• pregnant or lactating women