The effect of different scanning techniques on the retention of monolithic zirconia crowns constructed with two convergence angles

Abstract

This study aims to evaluate the effect of different scanning technologies and scanning techniques on the retention and internal fit of all ceramic crowns constructed with different convergence angles. Two stainless steel dies were machined to the dimensions of prepared upper first premolar to receive all ceramic crown with two different convergence angles 12ﹾ and 20ﹾ degrees. The dies were duplicated into 42 epoxy resin dies, 21 dies with 12 degrees convergence and the other 21 with 20 degrees convergence. Each 21 dies were divided into three groups seven dies each. First group was scanned using Omnicam intraoral scanner. Then polyether impressions were taken for the other groups. Second group impressions were scanned using Identica blue hybrid extraoral scanner. Third group impressions were poured into gypsum models and the models were scanned using the same extraoral scanner. All the scanned data were exported in STL file formats to the design software.Crowns were designed using Exocad 2016 software with fixed parameters for all the groups. Wings were added on the proximal surfaces of the crowns for holding the loops to measure retention. The designed crowns were milled in ultra-translucent zirconia Anterior Bruxzir using Vhf S1 5-axis milling machine then dried and