Brought my LO when her first 2 teeth were out at 6 months. You need to start brushing as soon as even one tooth is out. Twice a day. And at night, you’re right.. you should be worried about your LO’s teeth if she drinks milk before bed. It’s a must to brush the teeth after the milk, before bed. Otherwise tooth decay will set in soon. This is especially also since your LO has started eating already. The sugars in the food will speed up bacteria growth. Get a soft and slim toothbrush, with toothpaste that has a small amount of fluoride in it. The amount put should be that of a grain of rice, since baby doesn’t know how to rinse off the toothpaste and might swallow some. When you see the dentist, the dentist will check your brushing technique and also the condition of your LO’s teeth