The town of Sharon has reduced the level of fluoride in its public water in response to a change last spring to federal guidelines. The US Department of Health and Human Services issued a recommendation in April, cutting the optimal amount to prevent tooth decay to 0.7 milligrams per liter. The Sharon Board of Health voted Sept. 9 to use 0.7 parts per million, an essentially equivalent measurement. Sharon previously used 1 part per million; the longstanding federal recommendation, around since 1962, was for a range of 0.7 to 1.2 milligrams. Board of Health vice chairman Jay Schwab, a retired pediatric dentist, said it makes sense to lower the level to the minimum effective dose, particularly in an affluent community like Sharon, where children receive good dental care and, in many cases, have fluoride treatments at their dentist’s office. The board sent a survey to local dentists, dental hygienists, and technicians, and the majority favored the change, he said.