No Mama, its not stupid....the information is not out there like it is for medical and nutritional info. The info is here tho!! So it's not too late. In that sticky at the top, my favorite topics are "Remineralization and diet for healthy teeth" and "Caries-Causes and prevention."
I was in the same boat. My dd was (and is), such a healthy girl, I just assumed her teeth were resilient too. Little did I know. Her decay started at about 15 months. And I figured that you really start brushing when she was eating solids full on. She hadn't even had juice when her decay started! The build up was there prior to the decay.
SO, you need to be "really" brushing her teeth! Especially at the gum line. DEFINITELY do a good thorough brushing before night sleep. Studies show that breastmilk on top of food residue will contribute to decay. Also brush in the AM as well. Actually brushing/rubbing after she has eaten anything (including breastmilk) would be good but at least the two other times. Also know that it is recommended that the first dental visit be 6 months after the first tooth erupts or at 1 year old. Whichever comes first.
Also know that the bacteria that causes cavities can be passed thru sharing utensils, food bites, kisses, etc. The bacteria (smutans) is in everyone's mouth, but when it rises in numbers, that's when decay happens. So it's really important to get the buildup off her teeth to prevent the decay from happening. Cuz it happens so FAST!!!!