This prospective longitudinal observational study aims to evaluate the diagnostic performance and agreement of Smartphone photography, intraoral 3D imaging, Quantitative Light-Induced Fluorescence Digital (QLF-D), and ICDAS clinical criteria for assessing non-cavitated caries lesion activity in post-orthodontic patients under a preventive follow-up program. Thirty participants aged 11 to 46 years with active initial caries lesions will be followed for three months. Clinical examinations, QLF-D imaging, smartphone photographs, and intraoral 3D scans will be obtained at baseline and follow-up visits combined with professional prophylaxis and oral hygiene reinforcement. The study will analyze changes in lesion activity, fluorescence parameters, and surface characteristics over time, as well as the agreement and diagnostic performance among the evaluated methods.