Effect of sintering on the translucency of CAD-CAM lithium disilicate restorations: a comparative in vitro study.

PURPOSE: The available independent data on the translucency of novel pre and fully sintered chair-side computer-aided design and computer-aided manufacturing (CAD-CAM) lithium disilicate are limited. This comparative in vitro study evaluated the translucency degree of pre and fully sintered chairside CAD-CAM lithium disilicate crowns after optional, required, and additional firing processes.

MATERIALS AND METHODS: One hundred and five maxillary left central incisor crowns manufactured by three different CAD-CAM lithium disilicate brands shade A1 were assigned into 7 groups as follows (n = 15): (1) n!ce Straumann without sintering; (2) n!ce Straumann with one additional sintering process; (3) n!ce Straumann with two additional sintering processes; (4) Amber Mill with one sintering process; (5) Amber Mill with two sintering processes; (6) IPS e.max CAD with one sintering process; (7) IPS e.max CAD with two sintering processes. The translucency of all crowns was evaluated with a color imaging spectrophotometer. All statistical analyses were performed using statistical software. A standard level of significance was set at α < 0.05.

RESULTS: All the milled crowns presented different degrees of translucency, and additional sintering processes altered it. IPS E.max CAD with two (4.33 ± 0.26) and one (4.01 ± 0.15) sintering processes displayed the highest translucency, whereas n!ce Straumann with no sintering process provided the lowest value (2.82 ± 0.16).

CONCLUSIONS: The translucency of chairside lithium disilicate single-unit full-coverage restorations manufactured with subtractive technology was significantly influenced by the brand and the number of sintering processes. The traditional presintered IPS e.max CAD and the fully crystallized glass-ceramic n!ce Straumann considerably increased the translucency after one additional firing process, whereas Amber Mill decreased its translucency. This article is protected by copyright. All rights reserved.