Marginal and internal fit of pressed ceramic crowns made from conventional and computer-aided design and computer-aided manufacturing wax patterns: An in vitro comparison

Abstract Statement of problem To our knowledge, no studies have evaluated the influence of the wax fabrication technique on the internal adaptation and marginal accuracy of pressed ceramic single crowns. Purpose The purpose of this in vitro study was to compare the marginal and internal fit of a lithium disilicate crown fabricated either from conventional waxing or from a subtractive milled wax pattern. Material and methods Ten silicone impressions were made for a maxillary canine prepared to receive a complete crown. Two pressed lithium disilicate glass ceramic copings were made on the die poured from each impression. The first was from a conventional wax pattern and the second from milled wax blocks. The replica technique was used to measure the fit by scanning electron microscope at ×80 magnification. Collected data were analyzed with the paired Student t test for the marginal and wall fit. For the occlusal fit, the difference in scores did not follow a normal distribution, and the Wilcoxon signed ranks test was used (α=.05). Results The mean values +SD were 170.3 ±50.7 μm for the marginal fit and 130.3 ±21.6 μm for the internal fit with the conventional technique. For the computer-aided design and computer-aided manufacturing (CAD-CAM) technique, they were 105.1 ±39.6 μm and 98.1 ±26.1 μm. Statistical significance was found for the marginal and internal fit ( P P >.05). Conclusions The subtractive CAD-CAM waxing technique resulted in the improved fit of a pressed lithium disilicate crown by decreasing the marginal discrepancies and internal adaptation.