My son (9) has had his first set of molars for barely a couple of years, and based on a "shadow" seen on the X-ray for one of these molars, the dentist recommends drilling the tooth, cleaning out the decay and filling in the cavity with a composite. Is a shadow on the X-ray conclusive evidence of tooth decay? Does this necessitate an invasive procedure for such a new tooth (he cleans regularly, and does not have high sugar foods)? Would it be advisable to apply sealant and wait and watch?