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Rues S, Schwindling FS et al. Eur J Oral Sci 2017;125: 310–313

How does a dentist remove a prematurity at the try-in stage of an all-ceramic crown? It has even been advocated to perform occlusal recontouring of the opposing tooth. In this in vitro study, the fracture resistance of veneered zirconia crowns following adjustment with fine-, medium-, or coarse-diamond-coated burs (grit sizes 46, 107, or 151 μm, respectively) was measured. There was increased fracturing of the ceramic with larger grit size burs; deep scores within the veneering layer may result in crack propagation. Crowns that were not adjusted 'exceeded, by far, the values measured in the present study for adjusted and polished crowns'. This revisits the the thorny question as to whether or not recontouring the opposing tooth is the preferred option. This study also examined the effect of simulated aging of crowns. Not unexpectedly aged crowns failed more readily.