This randomized controlled clinical trial aims to evaluate the effectiveness of plaque disclosing agents used as photosensitizers in antimicrobial photodynamic therapy (aPDT) for the control of dental biofilm in children aged 3 to 7 years. Participants will be allocated into groups to receive different treatment protocols, and biofilm levels will be assessed before and after the interventions. The primary outcome is the reduction of dental biofilm, aiming to determine whether disclosing agents can be an effective alternative photosensitizer in aPDT for pediatric patients.

This randomized controlled clinical trial aims to evaluate the effectiveness of plaque disclosing agents used as photosensitizers in antimicrobial photodynamic therapy (aPDT) for the control of dental biofilm in children aged 3 to 7 years. Dental biofilm is a major etiological factor for dental caries, especially in pediatric populations, and alternative strategies for its control are relevant in minimally invasive dentistry. A total of 72 children will be randomly allocated into three parallel groups (n = 24 per group): (1) mechanical prophylaxis (control group), (2) aPDT using erythrosine as a photosensitizer, and (3) aPDT using GC TriPlaque ID Gel as a photosensitizer. In the experimental groups, the photosensitizer will be applied to the dental surface followed by blue light-emitting diode (LED) irradiation using a dental curing light. In the control group, only mechanical prophylaxis will be performed using a Robinson brush at low speed with water. Dental biofilm samples will be collected from the cervical vestibular surface of primary molars before and immediately after the intervention. Microbiological analysis will be performed to quantify colony-forming units per milliliter (CFU/mL), allowing the evaluation of antimicrobial effectiveness. Secondary outcomes include clinical feasibility, assessed by the duration of the procedure using a stopwatch, and behavioral acceptance, evaluated using the Frankl Behavior Rating Scale. The study is designed as a single-blind trial, in which the outcomes assessor is blinded to group allocation.

Inclusion Criteria:

• Children aged 3 to 7 years
• Both sexes
• Good general health status
• Classified as high caries risk according to the CAMBRA protocol (score ≥ +4 or presence of at least one disease indicator associated with two or more biological risk factors)
• Written informed consent obtained from a parent or legal guardian

Exclusion Criteria:

• Presence of systemic diseases
• Use of antibiotics within the last 30 days
• Use of antimicrobial mouthwash within 48 hours prior to sample collection
• Presence of structural dental alterations that may interfere with the standardization of the procedure
• Uncooperative behavior preventing safe clinical examination and intervention

Single-blind study in which the laboratory outcomes assessor is blinded to group allocation.