My son has a white spot on his gums. He has a cap over his baby molar. He has been to the dentist about 3 weeks ago to get some cement that was causing his gums to be swallon and red. After going to the dentist and doing that the gums have felt better and he no longer has pain. However, today I see that there is a white spot above his took with that cap. Wondering if it is a canker sore or somthing more serious.