The nanofill (Supreme) and minifill (Esthet-X) composites presented a surface roughness comparable to a microfill (Durafill), independent of the polishing system used, and a gloss comparable to a microfill, when polished with a one-step system (Pogo). As compared with the multiple-step systems, the smoothest surfaces and the highest gloss values were achieved using the one-step system (Pogo) for all the evaluated composites.

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Overall, the L*, a*, and b* values of the enamel composite shades were significantly different from the corresponding VST. Only a few layered composites matched the L*, a*, and b* of the keyed VST. Out of the 72 combinations, 20 (28%) resulted in DeltaE*(ab) below the 3.3 clinically perceptible limit. CLINICAL SIGNIFICANCE Composite shades do not match well to the Vita shade guide tabs, even when the layering technique is used. As demonstrated in this study, only a few composites matched the corresponding Vita shade guide tabs. (J Esthet Restor Dent 22:114-126, 2010).

The article is associated with the American College of Prosthodontists' journal-based continuing education program. It is accompanied by an online continuing education activity worth 1 credit. Please visit www.wileyhealthlearning.com/jopr to complete the activity and earn credit. KeywordsCeramic; fit; restoration. Correspondence AbstractPurpose: To evaluate the marginal gaps of CAD/CAM (CEREC 3) produced crowns made from leucite-reinforced glass-ceramic (IPS Empress CAD) blocks (LG), and lithium-disilicate (IPS e.max CAD) blocks before (LD-B), and after (LD-A) crystallization firing. Materials and Methods: A human molar tooth (#19) was mounted with adjacent teeth on a typodont and prepared for a full-coverage ceramic crown. The typodont was assembled in the mannequin head to simulate clinical conditions. After tooth preparation 15 individual optical impressions were taken by the same operator using titanium dioxide powder and a CEREC 3 camera per manufacturer's instructions. One operator designed and machined the crowns in leucite-reinforced glass-ceramic blocks (n = 5) and lithium-disilicate blocks (n = 10) using the CEREC 3 system. The crowns were rigidly seated on the prepared tooth, and marginal gaps (μm) were measured with an optical microscope (500×) at 12 points, 3 on each of the M, B, D, and L surfaces of the leucite-reinforced glass-ceramic crowns and the lithium-disilicate crowns before and after crystallization firing. Results were analyzed by two-way ANOVA followed by a Tukey's post hoc multiple comparison test (α = 0.05). Results:The overall mean marginal gaps (μm) for the crowns evaluated were: LG = 49.2 ± 5.5, LD-B = 42.9 ± 12.2, and LD-A = 57.2 ± 16.0. The marginal gaps for LG and LD-B were not significantly different, but both were significantly less than for LD-A. Conclusions: The type of ceramic material did not affect the marginal gap of CAD/CAM crowns. The crystallization firing process required for lithium-disilicate crowns resulted in a significant increase in marginal gap size, likely due to shrinkage of the ceramic during the crystallization process. Clinical Relevance: The marginal gap of CAD/CAM-fabricated lithium disilicate crowns increases following crystallization firing. The marginal gap still remains within clinically acceptable parameters.Interest in and use of chairside computer-assisted design/ computer-assisted manufacturing (CAD/CAM) systems for the fabrication of indirect dental restorations have dramatically increased over the last decade. Marginal gaps of CAD/CAM fabricated all-ceramic restorations have improved, and with current technology, crowns can consistently be fabricated with marginal gaps in the clinically acceptable range. For example, Nakamura et al reported a marginal gap of 53 to 67 μm for CEREC 3 generated crowns.1 Anadioti et al found a 2D mean marginal gap of 74 ± 26 μm for IPS e.max CAD restorations fabricated from digital impressions.2 Ng et al measured CAD/CAM-fabricated lithium disilicate crown marginal gaps at 48 ± 25 μm.3 Keshvad et al investigated t...

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