Here is the design of a clinical trial:

Official Title: Preventing Early Childhood Caries With Silver Diamine Fluoride - a Randomised Clinical Trial

Included conditions:
- Dental Caries

Study Armgroups:
- {'label': 'silver diamine fluoride', 'type': 'EXPERIMENTAL', 'description': '38% silver diamine fluoride', 'interventionNames': ['Device: silver diamine fluoride']}
- {'label': 'sodium fluoride', 'type': 'ACTIVE_COMPARATOR', 'description': '5% sodium fluoride', 'interventionNames': ['Device: sodium fluoride']}

Interventions:
- {'type': 'DEVICE', 'name': 'silver diamine fluoride', 'description': '38% SDF on primary upper anterior teeth', 'armGroupLabels': ['silver diamine fluoride']}
- {'type': 'DEVICE', 'name': 'sodium fluoride', 'description': '5% NaF on primary upper anterior teeth', 'armGroupLabels': ['sodium fluoride']}

Primary Outcomes:
- {'measure': 'caries prevention', 'description': 'the number of sound tooth surfaces that become cavitated caries per child', 'timeFrame': 'at 30-month follow-up'}

Please estimate the sample size based on the assumption: 
Statistical power set at 0.9, type I error rate of 5% for a two-sided test, and a dropout rate of 20%.
Sample size calculation
        The mean number of cavitated teeth of a 3-year-old child was five in our previous study [16]. The mean number of new cavitated caries surfaces found in the 62 children in the SDF group was 0.47 (standard deviation (SD) 0.87), and the mean new cavitated caries surfaces in the 61 children in the NaF group was 0.70 (SD 0.84) at the 30-month review. This difference corresponded to a prevented fraction of 33% more in the SDF group when compared to the NaF group, which is considered clinically significant. With the statistical power set at 0.9 and type I error rate of 5% for a two-sided test, the required sample size would be 292 for each group. Considering a dropout rate of 20%, the total number of children to be recruited at baseline should be 365 in each group. Therefore, a total of 730 children need to be recruited at baseline examination for this trial.