Marginal and Internal Gap of Zirconia Copings Obtained From Digital Impression

Objectives: To evaluate the marginal and internal gap of zirconia copings created with different methods of digital impressions.
Methods: A human lower first molar was mounted on a typodont with its adjacent and antagonist teeth and prepared for an all-ceramic crown. Zirconia copings were fabricated using one intraoral (3shape, Denmark) and two extraoral (D700, 3shape, Denmark) digital impression methods (n = 10). For the intraoral group, full arch scans were obtained using an intraoral digital scanner. For the extraoral groups, digital scans were obtained both from full arch polyvinylsiloxane impressions and from type IV stone dies. The marginal and internal gap was assessed by the silicone replica technique. Four sections of each replica were obtained and each section was evaluated in four points: marginal gap (P1), axial wall (P2), axio-occlusal edge (P3) and centro-occlusal wall (P4) using an image analyzing software (ImageJ). Data were submitted to two-way ANOVA and Tukey’s test (alpha = 0.05).
Results: The intraoral scanning resulted in the lowest overall gap (98.5 µm^a), whereas no statistical significant difference was found between the impression (174.1 µm^b) and die (200.5 µm^b) extraoral digital scanning groups. For P1 and P2, no statistical difference was found among the digital impression methods. However, for P3 and P4 the intraoral scanning showed the lowest gap means.
Conclusions: In conclusion, the intraoral scanning provided the lowest gap mean. For marginal gap, there was no difference among the methods. Regarding the internal gap, the intraoral scanning showed the lowest values.