The Effect Of Green Or～(TM) On The Crown Retention And Shear Bond Strength Using Standardized Tooth Preparations

Objective To evaluate the effect of Green OrTM on the crown retention and shear bond strength using standardized tooth preparations.Methods The first part: forty recently extracted molars were prepared by lathe, with a cervical diameter of 7mm, height of 4mm. Total oclussal convergence angle(TOC) of half of the molars were 10-degree and the others were 20-degree. The cast crowns were made and the samples within each degree were randomly divided into two groups (n=10). In the experimental group, Green OrTM was applied to the samples before the cast crown cemented with glass ionomer; in the control group, the samples were only cemented with glass ionomer. The samples were stored in 37℃artificial saliva for 24-hour before tensile testing on an Instron testing machine at a crosshead speed of 1mm/min until failure. The surface of the specimen was observed by means of an optical and a scanning electron microscope.The second part: the occlusal surfaces of twenty recently extracted molars were prepared to create to flat dentin surfaces. The IPS-Empress restorations were made and the samples were were randomly divided into two groups(n=10). In the experimental group, Green OrTM was applied to the samples before the IPS-Empress restorations were bonded with VariolinkⅡresin cement; in the control group, the samples were only bonded with VariolinkⅡresin cement. All samples were stored in 37℃artificial saliva for 24-hour before shear bond strength testing on an Instron testing machine at a crosshead speed of 0.5mm/min until failure. The surface of the specimen was observed by means of a scanning electron microscope.