Objective To evaluate the clinical effect of three kinds of porcelain veneer in tooth preparation.Methods 57 outpatients(399 teeth) who required laminate veneer restoration between Jan 2011 and Jan 2013 were selected as the research objects and randomly and evenly divided into experimental group 1,experimental group 2,experimental group 3.There were no significant statistical differences(P>0.05) between the general data of the three groups.Experimental group 1 patients chose the I type tooth preparation typ...