Abstract: Objective：To study the difference of cement residual and adhesion in the conventional coating method and extra-oral cementation method for single zirconia crown supported by dental implants with different thickness of cement. Methods: The Ankylos standard type B 6mm implant abutment analog was scanned by the Sinora CEREC system and the 3D digital model of zirconia single crown with the thickness of 50m, 80m and 110m of the cement layer and 1mm of the thickness was designed. The zirconia single crown was cut and sintered by CAD/CAM of Sinora CEREC system. The zirconia crowns with the different thickness of cement layer was cemented on the Ankylos standard type B 6mm implant abutment analogs by traditional coating method and extra-oral cementation method with the resin reinforced glass ionic cement. The residual of cement in the artificial gingiva was observed in each group, and the adhesion of two methods in each group was detected respectively. Results: There was significant difference in the adhesion between the group with the cement layer thickness of 50 m and the other groups. However, there was no significant difference in the adhesion between the group with the cement layer thickness of 80 m and 110 m. The adhesion of the cement layer thickness of 110 m group of adhesion is significantly less than the other groups by the conventional coating method. There is no significant difference in adhesion between the cement layer thickness of 80 m and 50 m groups. The residual cement around the implant and in the artificial gingiva of the three kinds of zirconia single crowns with three different cement thickness layers cemented by conventional coating method were more than that by the extra-oral cementation method. Conclusion: The zirconia single crown was cemented by extra-oral method with the resin reinforced glass ionic cement was better to be with 50~80 m cement thickness, while by conventional coating method was better to be with 80~110 m cement thickness .