Marginal and internal fit of pressed lithium disilicate inlays fabricated with milling, 3D printing, and conventional technologies

Publication date: Available online 29 September 2017
Source:The Journal of Prosthetic Dentistry
Author(s): Foudda R. Homsy, Mutlu Özcan, Marwan Khoury, Zeina A.K. Majzoub
Statement of problemThe subtractive and additive computer-aided design and computer-aided manufacturing (CAD-CAM) of lithium disilicate partial coverage restorations is poorly documented.PurposeThe purpose of this in vitro study was to compare the marginal and internal fit accuracy of lithium disilicate glass-ceramic inlays fabricated with conventional, milled, and 3-dimensional (3D) printed wax patterns.Material and methodsA dentoform mandibular first molar was prepared for a mesio-occlusal ceramic inlay. Five groups of 15 inlays were obtained through conventional impression and manual wax pattern (group CICW); conventional impression, laboratory scanning of the stone die, CAD-CAM milled wax blanks (group CIDW) or 3D printed wax patterns (group CI3DW); and scanning of the master preparation with intraoral scanner and CAD-CAM milled (group DIDW) or 3D printed wax patterns (group DI3DW). The same design was used to produce the wax patterns in the last 4 groups. The replica technique was used to measure marginal and internal adaptation by using stereomicroscopy. Mixed-model ANOVA was used to assess differences according to the groups and discrepancy location (α=.05).ResultsGroup DIDW showed the smallest marginal discrepancy (24.3 μm) compared with those of groups CICW (45.1 μm), CIDW (33.7 μm), CI3DW (39.8 μm), and DI3DW (39.7 μm) (P<.001). No statistically significant differences were detected among groups CICW, CIDW, CI3DW, and DI3DW relative to the marginal discrepancy. The internal discrepancy was significantly larger than the marginal discrepancy within all groups (P<.001).ConclusionsLithium disilicate glass-ceramic inlays produced from digital impressions and subtractive milling of wax patterns resulted in better marginal and internal fit accuracy than either conventional impression/fabrication or additive 3D manufacturing. Three-dimensional printed wax patterns yielded fit values similar to those of the conventionally waxed inlays.



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