Effect of sintering on the translucency of CAD–CAM lithium disilicate restorations: A comparative in vitro study

Abstract

AbstractPurposeThe available independent data on the translucency of novel pre and fully sintered chairside 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 methodsOne hundred and five maxillary left central incisor crowns manufactured by three different CAD–CAM lithium disilicate brands shade A1 were assigned into seven groups as follows (n = 15): (1) Straumann n!ce without sintering; (2) Straumann n!ce with one additional sintering process; (3) Straumann n!ce 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; and (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.ResultsAll 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 Straumann n!ce with no sintering process provided the lowest value (2.82 ± 0.16).ConclusionsThe 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 Straumann n!ce considerably increased the translucency after one additional firing process, whereas Amber Mill decreased its translucency.