Accuracy of the marginal fit of all-ceramic crowns fabricated by direct and indirect digital scanning methods

Abstract

Marginal fit is important in treatment using fixed dental prostheses. Poor marginal adaptation can result in dental caries and a periodontal disease. The objective of this study was to analyze and to compare the marginal fit of all-ceramic crowns fabricated from impressions acquired by direct digital scans intraorally and by indirect digital scans extraorally from working models. Twenty-three posterior teeth were prepared to receive all-ceramic crowns and, then, were digitally scanned intraorally (direct). Impressions were made for working model fabrication and then digitally scanned extraorally (indirect). A total of 46 all-ceramic crowns (Feldspathic ceramic, VITA Mark II; VITA Zahnfabrik) were fabricated by using a CEREC 3D computer-aided design/computer-aided machining system (Sirona). The marginal fit was evaluated by measuring a silicone replica of the gap between the intaglio of the full-veneer crown and the margin of the prepared tooth. The 46 specimens were examined by using an MM-40 Measuring Microscope (Nikon, Japan) at a magnification of 50×. Statistical differences in the marginal fit of the all-ceramic crowns were found between crowns fabricated from direct digitally scanned (70.1 μm ± 13.3) and indirect digitally scanned (82.3 μm ± 12.2) impressions (P < 0.05). The all-ceramic crowns fabricated from the direct digitally scanned impressions were significantly more accurate than those from the indirect digitally scanned impressions.