We as parents or other family members/ caregivers first pass our bacteria to our children. As babies, this can be through kissing, fingers in the mouth, sharing utensils, etc. If we have had a past history of cavities or we have been lacking in our own dental care, then this is passed over to our kids. Then that bacteria is dependent on certain factors: 1) diet- fermentable carbohydrates, sugars, beverages 2) amount of plaque and oral hygiene care (brushing and flossing) 3) the pH and flow of the saliva (different per individual, affected by medications) 4) strength and development of the enamel