Collagen degradation by host-derived enzymes during aging

Incompletely infiltrated collagen fibrils in acid-etched dentin are susceptible to degradation. We hypothesize that degradation can occur in the absence of bacteria. Partially demineralized collagen matrices (DCMs) prepared from human dentin were stored in artificial saliva. Control specimens were stored in artificial saliva containing proteolytic enzyme inhibitors, or pure mineral oil. We retrieved them at 24 hrs, 90 and 250 days to examine the extent of degradation of DCM. In the 24-hour experimental and 90- and 250-day control specimens, we observed 5- to 6-μm-thick layers of DCM containing banded collagen fibrils. DCMs were almost completely destroyed in the 250-day experimental specimens, but not when incubated with enzyme inhibitors or mineral oil. Functional enzyme analysis of dentin powder revealed low levels of collagenolytic activity that was inhibited by protease inhibitors or 0.2% chlorhexidine. We hypothesize that collagen degradation occurred over time, via host-derived matrix metalloproteinases that are released slowly over time.published_or_final_versio

Adhesion concepts in dentistry: tooth and material aspects

Adhesion concepts require understanding of substrate material properties, surface conditioning methods and chemical interactions, formation of interfaces/interphases between different material combinations, changes at interfaces with time, failure mechanisms and failure modes of the interfaces as a consequence of aging phenomenon. In dentistry, different methods are being used to test adhesion of resin-based materials to various biological and artificial substrates that require individual conditioning protocols. Variations among specimen configurations, material properties and chemical compositions of adhesives, test methods and test conditions all have effect on adhesion of similar or dissimilar substrates. Selection of the test, its proper execution, as well as the interpretation of the data through chemistry of the materials involved is of importance. Although adhesion to enamel is not a major concern today, effective adhesion to dentin requires several steps where failure in any of these consecutive events might result in failure of the whole system after long-term clinical use. Test methodologies used for assessment of mechanical behavior of materials in engineering may not directly apply to tooth–material combinations in dentistry. The objective of this review on adhesion in dentistry is to summarize current materials and methods used in dental materials testing and to summarize the current state-of-the-art in adhesion durability and quality with respect to the material type