Soft Teeth is a myth. It’s the enamel that is soft. Not receiving adequate amounts of fluoride may be the cause of this. There are several contributing factors to soft enamel on teeth, including insufficient calcium in the diet and physical trauma to the mouth and jaw region. Soft enamel on teeth may also be due to a type of hereditary disease as well. Diet also plays a role in this. Toothbrush with stiff bristles and improper brushing techniques may also lead to soft enamel issues.
Apart from these, people who have been taking certain medications over an extended period of time may be prone to tooth enamel issues, and should consult with a dentist for ways to avoid this.