The aim of this controlled clinical study was to evaluate the Nd:YAG laser, with or without fluoride, in prevention of occlusal caries in the primary dentition.

The aim of this controlled clinical study was to evaluate the Neodymiun:yttrium aluminum garnet laser, with or without fluoride, in prevention of occlusal caries in the primary dentition. High caries risk children (7.6±1.4 years) were selected for this study and received the following treatments: G1-1st molar was negative control, and the 2nd molar received a resin sealant; G2-1st molar was negative control, and the 2nd molar received laser irradiation (100 milliJoule, 5 Hertz - 0.5 Watts); G3-1st molar received only fluoride gel and the 2nd molar received fluoride gel + laser irradiation; G4-1st molar received only fluoride varnish and the 2nd molar received fluoride varnish + laser irradiation. Patients were followed up to 12 months to evaluate the formation of white-spot lesions and/or caries cavities by three calibrated observers.

Inclusion Criteria:

• subject age of 7 to 8 years, high caries risk (evaluated by oral hygiene, dietary habits and fluoride exposure, according to Kidd 2011), with the first permanent molars without caries cavities, restorations, enamel defects, morphological anomalies and/or signals of fluorosis. Subjects had to be willing to comply with all study procedures and protocols. They had to be residents of Ribeirão Preto or other nearby local communities with the same water fluoridation pattern (to eliminate water fluoridation as a potential con- founding variable). Subjects had to be healthy and the parents or the child legal guardian need to be willing to sign the "Authorization and informed consent for research" form. There were no gender restrictions.

Exclusion Criteria:

• suffering from systemic diseases, had a significant past or medical history with conditions that may affect oral health (i.e., diabetes, HIV, heart conditions that require antibiotic prophylaxis), were taking medications that may affect the oral flora or salivary flow (e.g., antibiotic use in the past three months, drugs associated with dry mouth / xerostomia), had in-office fluoride treatment within the last three months prior to being enrolled in the study, or were not willing to stop the use of any mouth rinse during the duration of the study.