Pacifier problems

So i have a question? I have a 5 year old that is really having a hard time letting go of a pacifier, I have two other kids one is 18 years old that I breastfed for a year and a half when he was little and at 6 months old he got rid of it, I also have a 5 month old and I am currently breast feeding him. but I only breast fed my 5 year old for 2 months I figure because he was breast fed less that is why he has that oral sensation, how do I help him over come this thing ? please no criticism just advise .