Influence of Crystallization Firing on Fit of Lithium Silicate Inlays
Objectives: The purpose of this study was to investigate the influence of the crystallization firing process on the marginal and internal fit of lithium silicate glass-ceramic inlays fabricated with computer-aided design / computer-aided manufacturing (CAD/CAM).
Methods: In this study, we prepared the Typodont (Nissin, D16-500E) mandibular left first molar for a class II mesio-occlusal inlay.
The inlay materials tested were three types of blocks: IPS e.max CAD (Ivoclar Vivadent, code: EX) and VITA SUPRINITY (VITA, code SP), both of which require crystallization firing after milling; and GC Initial LiSi Block (GC, code: LS), which is fully crystallized without additional firing.
After tooth preparation, 10 individual optical impressions were taken by the same operator using a CEREC Omnicam according to the manufacturer's instructions. The operator designed and machined the inlays in lithium silicate glass-ceramics blocks (n = 10) using the CEREC system. Marginal and internal gaps were measured using the replica technique. A stereomicroscope was used to measure the marginal gaps (occlusal edge, cervical edge) and internal gaps (pulp wall, axial wall) at 17 points per inlay. All data were statistically analyzed using one-way ANOVA and the Tukey test (a = .05).
Results: The EX and SP groups had significantly larger gaps at the occlusal and cervical edges when compared with the LS group (p < 0.01).
No statistical differences were found between the groups for internal gaps (pulp wall, axial wall).
Conclusions: For occlusal and cervical edges, the LS inlay presented a better fit than the other inlays.
These findings confirm that lithium silicate glass-ceramic blocks that do not require a crystallization firing step after milling produce a good marginal fit.