More than half of children between the ages of four and 18 are suffering some degree of tooth erosion, according to the British Dental Association. And fruit juices - particularly orange juice, with its high sugar and acid content - could be a major culprit.But orange juice is still one of the best sources of vitamin C, for both children and adults alike. So what should we do?Nutritionist Sarah Schenker, from the British Nutrition Foundation, says: 'Children are drinking less milk than they used to, and more soft drinks. Although orange juice has a role in a healthy balanced diet, its sugar and acid content lowers the pH of the mouth and makes the teeth more vulnerable to dental plaque.'If you are worried about the effect on teeth, dilute it with water or drink it with food and avoid between meals.' As a guide, there are three types of sugar to look out for in orange juice products.Although all are potentially harmful to the teeth, dentists suggest the safest are the sugars naturally present in the fruit, while juices boosted with artificial sweeteners and added sugars are not as healthy.
Hope it helps but you are not 99 years old

To not give an entire explanation of what befalls kids, in short orange juice has citric acid contained in it which is what gives it its acidic qualities