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Influence of 3D-printed, milled and pressed lithium disilicate on the bond strength to two resin cements: an in vitro
Alexey Unkovskiy1, Almira Ada Diken Türksayar2, Florian Beuer3
1Research associate, Department of Prosthodontics, Geriatric Dentistry and Craniomandibular Disorders, Charité - Universitätsmedizin Berlin, Berlin, Germany; Department of Dental Surgery, Sechenov First Moscow State Medical University, Moscow, Russia.
Objectives:
To investigate the influence of manufacturing method on the bond strength between heat-pressed, milled, and 3D-printed lithium disilicate using both conventional multi-step dual-cure resin composite and self-adhesive resin cements (SARC).
Methods:
A total of 120 ceramic specimens (n = 40/group; 15 × 9 × 2 mm size) were fabricated by 3 different methods: pressing (IPS Emax Press), milling (IPS Emax CAD), and 3D printing (LCM-printed IPS Emax with no pigments, A1, A2 and B1 pigments). The specimens were randomly divided in each material group into four subgroups according to the resin cement to be utilized for cementation (multi-step dual-cure resin composite (Variolink DC) and SARC (Relyx Unicem) and aging condition (nonaging and thermal aging) (n = 10). The specimens were tested for shear bond strength (SBS) and roughness (Ra) and statistically analyzed with 1-way ANOVA (Ra), 3-way ANOVA (SBS) and Tukey's significant honest difference tests with α=0.05.
Results:
While aging had no significant effect (p = 0.099), there was a significant effect of cement (p = 0.003), material (p < 0.001). In the case of SARC (RelyX) the milled group demonstrated significantly higher bond strength compared to 3D-printed A1-A2-B1 groups, but not to 3D-printed no-pigment group, both before and after artificial aging. In the case of the conventional dual-cure luting composite (Variolink DC) no significant difference was observed between the groups tested.
Conclusions:
In the case of SARC (RelyX) the 3D-printed lithium disilicate demonstrated comparable SBS values to the pressed group but lower than in the milled group. In the case of the conventional dual-cure luting composite (Variolink DC) no difference in SBS was observed.
Clinical Significance:
The manufacturing method of lithium disilicate may be clinically relevant when using SARC. For this reason, it may be recommended to use a conventional dual-cure luting composite for 3D-printed lithium disilicate.
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