Marginal adaptation of CAD/CAM milled lithium disilicate glass ceramic crowns

Aim The purpose of this in vitro study was to evaluate the fit of abutment tooth and crown made of lithium disilicate glass -ceramic blocks for CAD/CAM processing submitted or not to glaze firing process.Materials and methods Sample crowns were fabricated using GC Initial (R) LiSi Block (GC Corp) (LS), IPS e.max CAD (Ivoclar) (EM) and Cerec TesseraTM (Dentsply Sirona) (TE) by means of a CAM software (inLab CAM SW 20.0.1) and a dental milling machine (Cerec MC XL, Dentsply Sirona) after importing the STL file of the crown. In addition, the duration of the milling process was recorded as well as the temperature at which samples reached maximum linear expansion.Results LS showed a smaller marginal gap compared to EM and TE; the marginal gap at the crown-abutment tooth interface before and after heat treatment was on average significantly smaller for LS than EM and TE. No change was observed before and after heat treatment in LS, whereas the marginal gap of EM was significantly increased by heat treatment. This may be due to the fact that the temperature was higher than that at which dynamic softening occurs.Conclusion Since LS showed, in the present study, the best marginal fit before and after heat treatment, it can be considered as a valid lithium disilicate material for clinical use in prosthetic dentistry.