Experimental fluoride-releasable polyurethane elastomers were prepared and evaluated for their selected properties as a tooth separation device for orthodontic treatment. Two different polyurethane elastomers (E 580 and E 880) which have higher mechanical strengths were selected as the base composition. Inorganic fluoride compounds (NaF: 1.25 wt% and SnF2: 1.25-5.0 wt%) as the fluride release sources were dispersed into these base elastomers. The results were as follows: