Your teeth also impact your overall health. Teeth should not be sensitive or ache. Painful teeth may prevent you from eating healthy foods and can be a sign of a serious infection. Tooth decay, or cavities, are contagious, so it is important to have a health mouth if you have children, are pregnant, or are considering becoming pregnant. If you mouth is dry, you are more likely to have cavities. Health teeth do not hurt, do not have sharp edges or holes, and their shape prevents food from packing in between the teeth.