Abstract Background:-Community water fluoridation is the more cost effective than other forms of fluoride treatment and it gives small amount of fluoride to children and adults over time which prevents cavities and improves oral health. According to US Department of Health And Human Services the optimum level of fluoride should be 0.7 milligrams per liter. Material and Method- Tap water from different major cities of both the countries including Canada and India has collected to estimate the fluoride content in them. Result: Tap water of different cities of India state Punjab has unsatisfactory content of fluoride. All samples of India have less than optimum level of fluoride content whereas on the other side tap water of Canada has much more fluoride content as compared to India but four cities of Ontario state of Canada named Brampton, Hamilton, Mississauga, Toronto has less fluoride content as compared to optimum content of fluoride which is 0.7 milligrams per liter. Only Water loo city of Ontario state of Canada has optimum level of fluoride which is 0.7milligram per liter. Conclusion: water fluoridation plays a very important role in the prevention of dental caries. There should be opimum of 0.7 mg per liter of water. If optimum content of fluoride less than 0.7mg then it causes dental caries.