Fracture Resistance of Teeth Restored With Direct Occlusal Veneers

Objectives: To evaluate the fracture resistance of occlusal veneers fabricated either from short-fiber reinforced composite (SFRC) or particulate-filled composite (PFC).
Methods: Thirty (30) extracted human molars were prepared with flat occlusal surface with preserved enamel margins simulating a worn tooth. Prior preparation, a transparent (Exaclear, GC) and conventional (Coeltene) silicone molds were obtained for each tooth for restoring the teeth and control the preparation depth, respectively. Teeth were randomly allocated to three groups (n=10) and treated following a same bonding protocol before the restorative procedure. Selective enamel etching with 36% phosphoric acid for 15s was applied prior to bonding with 2-bottle universal bonding agent (G2 Bond, GC). The teeth in groups 1 and 2 were restored with flowable SFRC (EverX Flow, dentin shade, GC) or flowable PFC (Gaenial Universal Injectable, GC) respectively. Flowable material was injected and polymerized through the transparent silicone mold. The teeth in group 3 were restored with packable PFC (Essentia Universal, GC), which was pressed with the transparent silicone mold on the tooth surface and polymerized through it. All restorations were polymerized for 20s through the transparent mold and 40s from the distance on 1mm without the mold, and stored at room temperature for 24h before testing. All restorations were then statically loaded until fracture with a 5.5mm diameter steel ball. Fracture mode and force-displacement curves analyses were additionally conducted.
Results: SFRC occlusal veneers showed higher fracture load values compared with both PFC occlusal veneer materials (p<0.0001). According to force-displacement curves, the SFRC restorations cracked gradually, whereas all PFC restorations cracked instantaneously. Fracture type analysis showed more irregular fracture sites in SFRC restorations compared with PFC veneers.
Conclusions: Within the limitations of this study, it can be concluded that SFRC occlusal veneers provided significantly higher fracture resistance compared with flowable and packable PFC occlusal veneers.