Thumb sucking

Hi mummies, could you share some tips on helping my son to stop thumb-sucking? I read online that they'll slowly stop at 1 but he's 18m and still not showing signs of stopping T_T we've tried the bitter water from shopee but no difference in taste at all. My worry about this is his teeth is growing and I do not want it to affect the growth of his teeth. Would love to listen to some of your ideas. Thanks!