0.05).But the amount of adhered bacteria of surface-polished with titanium alloy is greater than that of surface-polished with zirconia ceramics(P

Well designed and fabricated custom tray is the precondition to acquire qualified edentulous impression and key to successful complete denture.It has shown that primary impression without custom trays is hard to meet clinical requirements for successful restoration of complete denture.According to the fabrication techniques,edentulous custom tray can be classified into several types such as:compound trimming technique,handcrafted technique with polymerizing acrylic resin based on the study cast,and computer aided design and three dimensional printing(CAD & 3DP) technique based on the primary impression or study cast,etc.With regard to some special edentulous jaws,the custom tray and impression techniques such as open-window,frame cut,closed-mouth custom trays,and so on can be applied to acquire accurate impressions.All above technologies have their own characteristics and emphases.In clinic,appropriate custom trays should be selected according to residual ridge condition,oral status,and other clinical requirements of each edentulous patient.