Reactivation of inactivated endogenous proteolytic activities in phosphoric acid-etched dentine by etch-and-rinse adhesives

Annalisa Mazzoni, David H. Pashley, Yoshihiro Nishitani, Lorenzo Breschi, Ferdinando Mannello, Leo Tjäderhane, Manuel Toledano, Edna L. Pashley, Franklin R. Tay

Research output: Contribution to journalArticlepeer-review

324 Scopus citations


Auto-degradation of collagen matrices occurs in resin-infiltrated dentine by the slow action of host-derived matrix metalloproteinases. As phosphoric acid-etching inactivates these endogenous enzymes, it is puzzling how hybrid layers created by simplified etch-and-rinse adhesives can degrade in vivo. This study tested the null hypothesis that there are no differences in the relative proteolytic activities of mineralised dentine, acid-etched dentine, and etch-and-rinse adhesivetreated acid-etched dentine. Powdered dentine prepared from extracted human teeth was treated with 17% EDTA, 10% phosphoric acid, or with five simplified etch-and-rinse adhesives that were applied to 10% phosphoric acid-etched dentine. The gelatinolytic activity of the dentine powder was assayed using fluorescein-labelled gelatine. TEM examination of the air-dried, treated dentine powder was performed to confirm the presence of remnant mineralised dentine after acid-etching. 17% EDTA significantly reduced the relative proteolytic activity (73.2%) of the untreated mineralised dentine powder (control), while 10% phosphoric acid-etched dentine exhibited the highest reduction (98.1%). Treating the acid-etched dentine powder with any of the five simplified etch-and-rinse adhesives resulted in the reactivation of the proteolytic activity, with a significant negative linear correlation ( P < 0.05) between the increases in fluorescence and the corresponding pH values of the adhesives. It is concluded that simplified etch-and-rinse adhesives can reactivate endogenous enzymatic activities in dentine that are previously inactivated by phosphoric acid-etching. The amount of enzyme reactivated may even exceed the original quantity present in untreated mineralised dentine. This provides an explanation for the degradation of hybrid layers after acid-etched dentine matrices are infiltrated with these adhesives.

Original languageEnglish (US)
Pages (from-to)4470-4476
Number of pages7
Issue number25
StatePublished - Sep 2006


  • Acid-etched dentine
  • Collagen degradation
  • Etch-and-rinse adhesives
  • Fluorescence
  • Fluorometric enzymatic assay
  • Proteolytic activity

ASJC Scopus subject areas

  • Biophysics
  • Bioengineering
  • Ceramics and Composites
  • Biomaterials
  • Mechanics of Materials


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