A glass composition having the general empirical formula given below, expressed in weight percent of the element: P: 16 24, F: 5 30, O: 20 40 and at least one of Na, K, Li or Al in an amount up to a total of 40 wt. % and optionally, up to 5 wt. % of boron and/or silicon. The composition may be used for the treatment and/or prevention of dental caries by providing a slow fluoride releasing device that may be attached to a tooth to release fluoride into the saliva or an individual.