<prompt> Recommended flouride concentration in water to prevent caries is: March 201000.5 ppm1ppm1.5 ppm  <response>: Ans. C: 1ppm Water fluoridation is the process of adding fluoride to the water supply so that the level reaches approximately 1 pa fluoride per million pas water ppm or 1 milligram fluoride per liter of water mg L; this is the optimal level for preventing tooth decay. 