Due to the unremitting study of the dentine adhesive, the phase separation phenomenon during bonding process becomes a hot issue in recent years. It is known that Dehydration on dentin due to establishment of hydrogen bond in peptide of collagen fiber. It doesn′t benefit for the formation of hybrid layer and resin tags. On the contrary, water-rich condition in dentin may cause the phase separation between hydrophilic and hydrophobic monomers. It will reduce the bonding strength and the bonding durability between the dentin and composite resin ultimately. Thus, reducing phase separation of adhesives in the presence of water and keeping homogenous penetration of adhesives into wet demineralized dentin are very critical factors during the dentin bonding process. Therefore, the research of phase separation phenomenon in dentine adhesive will be report in this review.
