Study on The Dentinal Native Non-collagenous Protease

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The objectives of this research project were 1) to extract the non-collagenous dentin protein hydrolyzable protease from dentin, 2) to study the hydrolytic ability of the protease against the dentin proteins and proteoglycans, 3) to establish the mineralizing cell culture and 4) to investigate the influence of different dentin adhering mechanisms on shear and fatigue bond strength.The results obtained were as follows :1.Several proteases were extracted from human and bovine dentin. The approximate molecular weight of 59KDa (59K P-ase) showed the major enzymatic activity and its optimum pH was 9.59K P-ase was inhibited by EDTA and TIMP, and cleaved osteopontin. It was suggested that 59K P-ase is a phophoprotein protease and play an important role in both dentin matrix development and degradation process.2.Both the EDTA and guanidium chloride extracted dentin proteoglycans were degraded into small fragments by 59K P-ase. It was conceivable that the 59K P-ase was one of metalloproteases b … More ut not a collagenase, and play an important role in the process of mineralization and maturation of dentin.3.Several dentin proteoglycans were obtained, ther molecular weights were 150-180KD, 300KD, 130-150KD and 180-210KD on SDS/PAGE.59K P-ase degraded all of these proteoglycans. E-ext proteoglycan has several core proteins which were stained blue with Stains-all and these core proteins were also cleaved by 59K P-ase. These results demonstrate that the 59K P-ase has a stromelysin-like activities.4.Odontoblast derived from bovine incisors was cultured on a reconstituted gel of basement membrane components, produced a dentin-specific protein phosphopholyn and grew mineralized nodules. The highest concentration of the enzyme related in the matrix was observed between day 22 and day 36 coinciding with the initiation of mineralization. The described sequence of developmental expression of proteins in this mineralizing dentin cell culture is very similar to that in bone which suggests common mechanisms of matrix mineralization in bone and dentin.The shear and fatigue shear bond strength of a third generational dentin bonding agent (KB-110) was compared with a conventional one. KB-110 showed significantly higher shear and fatigue bond strength than conventional, though its fatigue strength decreased rapidly as the storage period prolonged. These results suggest that the fatigue strength reflects more accurately the retentive properties of the dentin matrix than the shear bond strength. Less