once developed in your mouth can not be reverted back. If you don't have any pain in the teeth having cavities and the Cavities are not that deep then get them filled with normal fillings
. Various types of tooth filling material are there. You can go for Composites, Glass Ionomer Cements (both of these are tooth coloured) and Silver colour fillings. For further prevention of caries or cavities. Rinse your mouth every time you anything. Limit the use of chocolates and sugary foods. Brush twice daily. Brushing at night time before going to bed is much more important.