My sister is 1 years old and she have only 4 teeth is it natural or we must give her calciums?

May be normal: It's nice that you care about your sister and her teeth. Normally a 1 year old has more teeth showing, but it doesn't necessarily mean that anything is wrong. Some kids get teeth earlier and some later than others. There is no way to speed up the natural process when teeth erupt. Have mom or dad take her to a dentist who specializes in kid's teeth (pedodontist) for a check-up and answers.

No: Some babies have teeth erupt at birth and some don't have any until >15mo. It has nothing to do with their calcium level or diet.It is part of normal variation.They essentially have all their baby teeth by age 3 or so.