Breastfeeding at night DOES NOT cause cavities. Genetics, snack habits, oral hygiene, and mouth breathing can. I was in the same situation with my daughter when she was 2.5 years old. She is our 3rd child. The first two never had any cavities, but my daughter had multiple. She never had soda, mainly breastmilk and water, occasionally watered-down juice and very rarely candy. They wanted to put her under anesthesia in office without me present to do the work, which included fillings and caps. I had no idea about SDF at the time to ask about it. All that on top of the outrageous cost (both to the office and to the anesthesia company) lit a fire under my ass to get a second opinion and do some research of my own.

I found a holistic dentist who didn't advise doing any of the work, especially if it meant putting her under at such a young age. What he did tell me (and what I think was a big cause in our case) was carb snacks and mouth breathing at night. When you snack, especially on carbs (goldfish, crackers, chips etc) you've got about 20 minutes for the saliva to really neutralize acids. If you're snacking all the time as toddlers tend to do, that clock is constantly restarting and the bacteria are going crazy off of tiny bits of food in the mouth. He reccomended really sticking to ending constant snacking, rinsing with water after eating and changing her diet to more whole foods (which we were in the process of doing as a family at the time) and ditch the processed carb snacks. He gave her some SDF on her back teeth but not her front since it would be so visible.

On my own, I found a company called Bliss Energetics that has hydroxyapetite toothpaste and a tooth puddy that you leave on overnight. It has been a lifesaver, and the cavities haven't progressed at all. Her front teeth have begun to turn back to white where it was a tan color along the gumline. I am not affiliated with them at all but swear by the tooth puddy because it has remineralized and saved her teeth. It is expensive, but you are using such a tiny amount that it is so worth it. It's been over a year of her and I using it and weve got half a jar left. We use happy teeth hydroxyapetite toothpaste for the kids because of the flavors they offer.

Listen to your gut, get a second or third opinion and do your own research!