Pediatric cavities

My son just turned 6 years old.  By the time he was 5, he had 9 cavities, all of which we had filled because they were between the molars.  He had another cavity on the front tooth but we didn't have it filled because he soon after lost it.  I am baffled because we take very good care of my son's teeth.  We brush every day and he doesn't drink an excessive amount of juice or eat alot of junk food.  He does drink about 2 juices a day and the rest of the day drinks milk and water.  He eats junk food several times a week but not every day.  Most of his snacks are fresh fruit or crackers.  I have always brushed my son's teeth and have continued to do so after he had so many cavities because I think his teeth need extra care that I don't think he would be able to give them at this age.  We did start flossing after the cavities were found.  Why does he have so many cavities when we take care of his teeth???  Is there anything else we can do to prevent them or is he just prone to this?  

[mammo]

I would address your concern with his dentist.  He may be lacking in vitamin D or calcium.

[turkee23]

i would suggest getting some milk of magnesium (spelling? sorry) have your son use it as a rinse, swish it around and spit it out..they have it in flavors so it will be easier to get him to do it...a few times a week, it almost acts like a coating over his teeth and will help keep the decay away.... my friend has been using it on her son for a few weeks now and she already sees a difference