The aim of the present work is to study the effect of the application of Silver diamine fluoride (SDF) and a novel green synthesized Nano-silver fluoride (NSF) on early enamel lesions in primary teeth. Proving their positive effect would be the basis for the development of innovative dental materials and hygienic agents to combat the carious process, which is a critical prerequisite for improving the quality of dental services and reducing dental anxiety and fear.

Dental caries is a major public health concern, especially in very young children. Early detection of the disease enhances and simplifies treatment effectiveness. Non-operative treatments are particularly advantageous as they are minimally invasive, reduce future operative treatment needs and are more comfortable, thereby improving overall compliance and dental experience.

The aim of the study is to compare the clinical efficacy of Silver diamine fluoride (SDF) and laboratory prepared green synthesized Nano-silver fluoride on early enamel lesions in primary teeth.

The proposed study is a randomized controlled clinical trial. Included patients are healthy positive children aged from 3 to 8 years, requiring non-operative treatment of incipient caries lesions on smooth surfaces of primary teeth. Lesions will be assessed visually using ICDAS II, Nyvad criteria and laser fluorescence (LF pen).

Patients are randomly assigned to one of three study groups:

Group N: Green synthesized Nano silver fluoride (prepared in laboratory) Group S: SDF + KI (38% Riva Star, SDI) Group C: Control group

Prior to treatment parents are informed about the nature of the study and sign an informed consent. Children are introduced to the method of conducting treatment in a style appropriate for the child's age. Lesions are assesed using the ICDAS II system, Nyvad criteria and laser fluorescence. All patients receive professional oral hygiene with a fluoride-free brush and polishing paste. Treatment of each patient's respective teeth is performed following the treatment protocol of the respective agents. Follow-ups are performed at 1st, 3rd, 6th and 12th month.

Inclusion Criteria:

• Age: 3 - 8 years
• Signed informed consent from parents to participate in the study. Verbal consent from the child for the upcoming manipulations.
• Enrolled patients do not have any common diseases or conditions associated with decreased salivation and are not taking medications that suppress salivary flow. Study participants have no cognitive or behavioral impairment. The absence of disease will be confirmed by a history-taking interview with the parent.
• Presence of incipient carious lesions (white spots) reaching the enamel interior, assessed with ICDAS system values 01 (first visible enamel change) and 02 (localized visible enamel change) and laser fluorescence values up to 20. The diagnostic threshold of the included lesions is defined as D1 A (active enamel lesion visible after drying) or D2 A (active enamel lesion visible without drying). Criteria for active lesions: under plaque, loss of gloss, loss of smoothness, diffuse borders of the lesion, opaque appearance, white colour, at pre-selection sites (in the cervical third of the enamel). The lesions are located on tooth surfaces with no preceding obturations.
• Study participants had not performed remineralization or topical fluoride therapy on the included lesions within six months prior to study inclusion.
• Children with no history of allergy to the medications administered.

Exclusion Criteria:

• Children who are considered medically compromised or medically complex patients. The presence of a medical condition is confirmed by a history interview with the child's parent or guardian and involves common diseases or conditions associated with decreased salivation and intake of medications that suppress salivary flow, cognitive and behavioral disorders.
• Patients who underwent remineralizing or topical fluoride therapy to the included lesions in the last six months prior to study inclusion.
• Patients with a history of allergy to the administered medication.