Aah anak kita memang ada personality sendiri kan, especially kalau dah terbiasa BF! Honestly, at 2 tahun 3 bulan, kalau dia dah mau susu formula coklat tu dah lumayan bagus, lepas tu boleh slowly reduce BF sessions, biasanya anak naturally wean off when the formula becomes more exciting haha. A few of my mum friends yang ada situation similar, mereka just stick dengan one formula yang anak accept, then worry less about forcing different types, sebab tu buat anak lagi resistant. About the teeth worry, try la yang plain formula (bukan coklat) if you manage to introduce it gradually, atau kalau dia prefer coklat tu, just make sure brush gigi after, sama macam kalau minum susu coklat plain. The key is patience, jangan pressure too much, sebab the more you push the bottle, the more anak akan lawan!