My son is two weeks, his right canine grow from about 6 months later, there was a tooth on the hole in the tooth at the bottom. Now the cavities have been about a millimeter wide and a millimeter deep. I do not know should not take him to fill a tooth.
1 mm or so really is not. Is no way to complement.
If it has a tendency to expand, you can put him to the dentist, rubbed some lesions. Treatment for small cavities are first removed the lesion, and then fill 1 mm is no way to fill.