Effects Of Type Ⅰ Collagen Degradation On The Durability Of Dentin Bonding

At present, although the immediate bonding efficacy of dentin has achieved a satisfactory clinical effect, the bonding interface is remained to be very weak area. The marginal leakage and secondary caries are the most common reasons that leads to failure of adhesive restoration. Hybrid layer is the major source of dentin bonding strength. The degradation of type I collagen at the bottom of the hybrid layer is considered to play a vital role in dentin bonding durability. Present researches indicate that endogenous proteolytic enzymes which are combined with the organic matrix of dentin could degrade the exposed type I collagen in the hybrid layer. Matrix metalloproteinases, including cysteine cathepsins which are lately confirmed to present in both sound and carious dentin, play a key part in the degradation of hybrid layer into which resin penetrates incompletely.Cross-linked carboxyterminal telopeptide of type I collagen is a specific product of the process of the degradation of the mature type I collagen mediated by the MMPs. As MMPs are effecting, a small section of type I collagen protein carboxyl-terminal peptide is cut out and then ICTP is produced. Of the all known hard tissue absorption-ralated proteolytic enzymes, MMPs are the only kind of enzymes can produce ICTP.The purpose of this study is to evaluate the effects of type I collagen degradation on the durability of dentin bonding by detecting microtensile bond strength and the released quantity of ICTP and MMP-2,9.1. Methods3groups of dentin specimens respectively dealt with3different types of adhesive systems were immersed into deionized water or artificial saliva solution for24h,1m,4m. In order to determine the degradation of type I collagen, Cross-linked carboxyterminal telopeptide of type I collagen (ICTP) concentrations were then calculated by enzyme linked immunosorbent assay, and then MMP-2,9concentrations were calculated by gelatin zymography. Micro-tensile bond strength were tested before, and after1month or4months of aging in artificial saliva solution. The relationship between micro-tensile bond strength and collagen degradation was analyzed by conducting their Pearson’s correlation coefficient.2. Results1) Prolonged artificial saliva solution immersion time led to decreasing of the bond strength.2) Prolonged artificial saliva solution immersion time led to decreasing of the bond strength as well as increasing of the quantity of ICTP of all3groups adhesive systems.3) Prolonged artificial saliva solution immersion time led to decreasing of the bond strength as well as decreasing of the quantity of MMP-2and increasing of the quantity of MMP-9of all3groups adhesive systems.