Influences of different fiber-reinforced biobases on the fracture strength and failure mode of lithium disilicate overlay restorations (a comparative in vitro study).

Background: Ceramic restorations are commonly employed in restorative dentistry. However, their inherent brittleness poses a challenge, particularly in extensive restorations. Limited data exist regarding the fiber reinforcement's role in the efficiency of lithium disilicate overlay restorations. This research sought to evaluate the fracture strength and failure mode of lithium disilicate overlay restorations using various biobase techniques.

Material and methods: Fifty sound maxillary first premolars of equivalent dimensions received a full-bevel overlay preparation design with a 3-mm occlusal reduction. Samples were allocated randomly to five experimental groups (n = 10): Group A: (delayed dentin sealing); Group B: (immediate dentin sealing with Optibond FL); Group C: immediate dentin sealing was coated with a 1-mm flowable composite layer (Clearfil AP-X Flow); Group D: following immediate dentin sealing, a 1-mm short fiber reinforced composite layer (EverX Flow) was applied; and Group E: immediate dentin sealing followed by a 1-mm flowable composite layer reinforced with polyethylene Ribbond fibers. Following tooth preparation, digital impressions were made via a Medit i700 intraoral scanner, and overlays were digitally designed via Sirona inLab CAD software and milled via a 4-axis milling machine. The overlays were luted with a preheated composite. The fracture load was assessed (in Newtons) utilizing a universal testing unit. A one-way analysis of variance was employed to perform statistical analysis.

Results: The one-way ANOVA test indicated no significant difference between the groups (P> 0.05). Nevertheless, the fiber-reinforced biobases in Groups D and E exhibited less catastrophic failure modes than those in Groups A, B, and C.

Conclusions: All of the tested overlay restorations displayed sufficient strength to endure the normal masticatory force. The incorporation of fiber-reinforced biobases positively influenced the failure mode. Key words:Biobase, Ever X flow, Full bevel, Overlay, Ribbond fiber.