Smear Layer has been a focus of speculation and debate ever since it was first reported.A lot many researchers have advocated its removal but few who support its retention advocate its modification to a structure that is more stable and resistant to microleakage.This book reviews the various agents which can chemically react with the smear layer to alter its structure.This hybridized smear layer is a sterile,inert, non-toxic chemically and mechanically interlocked smear layer.Modified smear layer can prove advantageous in preventing further infection of the root canal dentin by sealing off the dentinal tubules permanently and also reduce microleakage since it is stable enough so as not to disintegrate.This review should be useful for encouraging further research in modifying the smear layer which would in turn prove to be beneficial for the long term success of endodontic therapy and certain restorative procedures.