Here is the design of a clinical trial:

Official Title: Effectiveness of Biannual Application of Silver Nitrate Solution Followed by Sodium Fluoride Varnish With or Without Functionalized Tricalcium Phosphate in Arresting Caries in Preschool Children

Included conditions:
- Early Childhood Caries

Study Armgroups:
- {'label': 'NaF without fTCP', 'type': 'ACTIVE_COMPARATOR', 'description': '25% AgNO3 solution followed by 5% NaF.', 'interventionNames': ['Drug: 25% AgNO3 solution followed by 5% NaF']}
- {'label': 'NaF with fTCP', 'type': 'EXPERIMENTAL', 'description': '25% AgNO3 solution followed by 5% NaF with fTCP.', 'interventionNames': ['Drug: 25% AgNO3 solution followed by 5% NaF with fTCP']}

Interventions:
- {'type': 'DRUG', 'name': '25% AgNO3 solution followed by 5% NaF', 'description': 'Dosage: 25% AgNO3 solution 7.9mg(Ag+)/0.05ml (max dose), 5% NaF: 11.6mg (F-)/0.5ml (max dose).', 'armGroupLabels': ['NaF without fTCP'], 'otherNames': ['5% NaF without fTCP']}
- {'type': 'DRUG', 'name': '25% AgNO3 solution followed by 5% NaF with fTCP', 'description': 'Dosage: 25% AgNO3 solution 7.9mg(Ag+)/0.05ml (max dose), 5% NaF with fTCP: 11.6mg (F-)/0.5ml (max dose).', 'armGroupLabels': ['NaF with fTCP'], 'otherNames': ['5% NaF with fTCP']}

Primary Outcomes:
- {'measure': 'The hardness of cavity on tooth by probing', 'description': 'The effectiveness of adjunctive application of 25% AgNO3 solution and 5% NaF varnish with or without fTCP is expected to be equivalent in arresting dentine caries of primary teeth.', 'timeFrame': 'The follow-up oral examinations will be conducted every 6 months for 30 months totally'}

Please estimate the sample size based on the assumption: 
The power of the study is set at 90% (β = 0.1) and a two-sided 95% confidence interval (α = 0.05). The anticipated dropout rate is 15%.
Sample size and power calculation
        The results of previous clinical trials showed that around 70% of the active dentine caries became arrested after 30Â months [18]. The anticipated caries-arresting rates of group B would be 80%. An absolute difference of 10% for the caries-arresting rates between treatment groups is considered to be clinically significant. The sample size calculation is based on the expected proportion of caries that become arrested, with the power of the study set at 90% (Î²â=â0.1) and a two-sided 95% confidence interval (Î±â=â0.05) as the statistical significance level by using the G*Power Version 3.1.9.2 (Franz Faul, UniversitÃ¤t Kiel, Germany). Therefore, at least 820 active carious tooth surfaces need to be included, or 410 in each study group. Based on the results of epidemiological surveys, we anticipate that the mean number of active caries tooth surfaces of 3-year-old children in Hong Kong is approximately three [25]. The intraclass correlation coefficient for dental caries data at the surface level within the individual would be approximately 0.13 [26]. Following the equation for the required sample size in a multilevel study [27], the design effect will be 1.26. Thus, the estimated sample size would be at least 346 children, or 173 per group. The anticipated dropout rate is 15% [24]; thus, 408 children (204 children in each group) will be needed at baseline.