This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
[{'content': 'Active fluoride concentration in the cavity varnish duraphat is: \nSelect and explain. \nA. 22,900 ppm, B. 7,600 ppm, C. 22,600 ppm, D. 11,600 ppm', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Duraphat, the first fluoride varnish developed in Germany.\n\tIt is a viscous yellowish material, containing 22,600 ppm fluoride as sodium fluoride in a neutral colophonium base (NaF varnish containing 2.26% fluoride in organic lacquer).\xa0\nDuraphat has shown caries reduction\xa0between 30% and 40% in the permanent dentition and in between 7% and\xa044% in the primary dentition.\n\nEssentials of preventive and community dentistry\nSoben Peter\n5th edition\npage no. 255', 'role': 'assistant'}]