In vitro wear resistance of conventional and flowable composites containing various filler types after thermomechanical loading

OBJECTIVE

To comparatively assess the wear resistance of conventional and flowable composites containing different filler types using thermomechanical chewing simulation.

MATERIALS AND METHODS

Six different composite resin materials were used: a conventional and flowable composite from each of three manufacturers respectively classified by different filler characterizations: (1), a nanohybrid conventional (G-aenial Posterior, GC) and flowable (G-aenial Universal Injectable, GC), (2) a nanofilled conventional (Filtek One Bulk-fill Restorative, 3M) and flowable (Filtek Ultimate Flow, 3M), and submicron-filled conventional (Estelite Posterior Quick, Tokuyama) and flowable (Estelite Bulk-Fill Flow, Tokuyama). The buccal surfaces of extracted human premolars were planarly abraded and used as control (n = 12). The prepared surfaces were subjected to wear using a thermocycler chewing simulator against 6-mm diameter steatite balls for 240,000 cycles, simulating 1 year of in vivo use. Digital profiles of treated sample surfaces were scanned using a laser scanner, and the volume loss and maximum depth of loss were calculated. Two-way MANOVA was used to compare the wear volume loss and depth according viscosity (conventional/flowable) and filler type (nanohybrid, nanofilled, submicron-filled), and multiple comparisons were performed using Duncan's test.

RESULTS

Wear volume loss and loss depth were significantly lower in enamel than in all composite resin groups. The wear volume loss and loss depth of nanofilled composites were significantly higher than the other composite filler types, with no significant difference in either parameter between the nanohybrid and submicron-filled composite groups. With respect to apparent viscosity, wear volume loss and loss depth of conventional composites were significantly lower than the flowable composites.

CONCLUSIONS

The type of composite filler and its apparent viscosity significantly influence the in vitro wear resistance of the material. All composite materials tested demonstrated a susceptibility to simulated wear that was two to three times greater than that of human enamel.

CLINICAL SIGNIFICANCE

Flowable composite resins provide a level of convenience in clinical application. Despite advancements in their wear characteristics, they continue to display inferior wear resistance compared to conventional composite resins. Nevertheless, all tested composite resins exhibited a significantly higher potential for wear than human enamel.