What is hair rebonding and is it harmful?

hair rebonding is a process which related to sulphur bond in our hair. our hair is become curly is because there are a lot of sulphur bonding so hair rebonding is a process to breakdown the sulphur bond by uisng heat and so on. it can be harmful if the technique and the use of chemical when undergoes the rebonding process.... all of this data might be incorrect so refer to the expert one is more advisable... :)