Effect of digital scans on marginal and internal discrepancies of zirconia crowns

Abstract

Statement of problem: A few studies have compared the accuracy of newly introduced intraoral scanners (IOSs); however, limited evidence is available concerning which system provides the best marginal and internal adaptation of zirconia crowns.

Purpose: The purpose of this in vitro study was to compare the marginal and internal discrepancies of zirconia crowns fabricated with 4 digital scanners by a silicone replica technique.

Material and methods: A maxillary central incisor was prepared for a ceramic crown and duplicated to form 10 metal abutments. Four groups of zirconia crowns with different scanning methods were produced for each die: 1 laboratory scanner, L (Ceramill Map 400), and 3 different IOSs, CS (CS3600), TR (TRIOS3), and CE (CEREC Omnicam). The marginal and internal discrepancies were measured by a silicone replica technique under a static load of 50 N. The replica specimens were sectioned buccolingually and mesiodistally and then examined by using a stereomicroscope (JTZ-7XT) at ×200 magnification. Fifteen reference points were measured on each specimen. One-way ANOVAs with the Duncan multiple range tests were used for statistical analysis of the data (α=.05).

Results: The mean marginal discrepancies of zirconia crowns were 12.7 μm for group L, 12.6 μm for group CS, 14.8 μm for group TR, and 15.8 μm for group CE. No significant differences were found in marginal and incisal discrepancies among 4 groups. However, groups CS and L showed significantly better cervical and axial discrepancies than groups TR and CE. Group TR showed significantly better axial discrepancy than group CE.

Conclusions: Zirconia crowns made by using the CS3600 and the laboratory scanner with a conventional impression showed significantly better internal discrepancies than those made by using TRIOS3 and CEREC Omnicam.