With increasing reaction time, the cross linking reaction proceeded from the surface to core gradually to give a gelatin material with cross-linking degree gradient across the section.

Reasonable type of road cross section could ensure the smooth vehicle flow, at the same time, it could reduce the pollution of traffic to environment through reasonable greening arrangement.

Objective:To investigate the appearance of enamel on the cross section of tooth after etched with 37% phosphoric acid for different etching time .