title: Strategies to prevent hydrolytic degradation of the hybrid layer-A review.
abstract: OBJECTIVE
  Endogenous dentin collagenolytic enzymes, matrix metalloproteinases (MMPs) and cysteine cathepsins, are responsible for the time-dependent hydrolysis of collagen matrix of hybrid layers. As collagen matrix integrity is essential for the preservation of long-term dentin bond strength, inhibition of endogenous dentin proteases is necessary for durable resin-bonded restorations.
  
  
  METHODS
  Several tentative approaches to prevent enzyme function have been proposed. Some of them have already demonstrated clinical efficacy, while others need to be researched further before clinical protocols can be proposed. This review will examine both the principles and outcomes of techniques to prevent collagen hydrolysis in dentin-resin interfaces.
  
  
  RESULTS
  Chlorhexidine, a general inhibitor of MMPs and cysteine cathepsins, is the most tested method. In general, these experiments have shown that enzyme inhibition is a promising approach to improve hybrid layer preservation and bond strength durability. Other enzyme inhibitors, e.g. enzyme-inhibiting monomers, may be considered promising alternatives that would allow more simple clinical application than chlorhexidine. Cross-linking collagen and/or dentin matrix-bound enzymes could render hybrid layer organic matrices resistant to degradation. Alternatively, complete removal of water from the hybrid layer with ethanol wet bonding or biomimetic remineralization should eliminate hydrolysis of both collagen and resin components.
  
  
  CONCLUSIONS
  Understanding the function of the enzymes responsible for the hydrolysis of hybrid layer collagen has prompted several innovative approaches to retain hybrid layer integrity and strong dentin bonding. The ultimate goal, prevention of collagen matrix degradation with clinically applicable techniques and commercially available materials may be achievable in several ways.
authors: Institute of Dentistry, University of Oulu/Oulu University Hospital, Oulu, Finland; Institute of Dentistry, University of Turku, Turku, Finland; The NordicInstitute of Dental Materials (NIOM), Oslo, Norway. Electronic address: leo.tjaderhane@oulu.fi.
authors: Leo
authors: L
authors: Tjäderhane
authors: Fabio D
authors: FD
authors: Nascimento
authors: Lorenzo
authors: L
authors: Breschi
authors: Annalisa
authors: A
authors: Mazzoni
authors: Ivarne L S
authors: IL
authors: Tersariol
authors: Saulo
authors: S
authors: Geraldeli
authors: Arzu
authors: A
authors: Tezvergil-Mutluay
authors: Marcela
authors: M
authors: Carrilho
authors: Ricardo M
authors: RM
authors: Carvalho
authors: Franklin R
authors: FR
authors: Tay
authors: David H
authors: DH
authors: Pashley
mesh_terms: D002403:Cathepsins / Q000378:metabolism; D003094:Collagen / Q000378:metabolism*; D006868:Hydrolysis; D020782:Matrix Metalloproteinases / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D011480:Protease Inhibitors / Q000494:pharmacology
chemical_list: D011480:Protease Inhibitors; D003094:Collagen; D002403:Cathepsins; D020782:Matrix Metalloproteinases
keywords: Chlorhexidine; Cysteine cathepsins; Degradation; Dentin bonding; Durability; Enzyme inhibition; Enzymes; Hybrid layer; Matrix metalloproteinases; Review
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