The effect of aging on the fracture toughness of esthetic restorative materials

Abstract

Purpose: To compare the fracture toughness (KIc) of tooth-colored restorative materials based on a fourpoint bending; to assess the effect of distilled water and a resin surface sealant (G-Coat Plus) on the resistance of the materials to fracture. Methods: Specimens were prepared from six materials: Quix FiI; Dyract (Dentsply), Freedom (SDI), Fuji VII (GC), Fuji IX (GC); Fuji II LC (GC). Fuji II LC and Fuji IX were tested both with and without applying G-Coat Plus (GC). The specimens were divided into the three groups which were conditioned in distilled water at 37°C for 48 hours, 4 and 8 weeks. The specimens were loaded in a four-point bending test using a universal testing machine. The maximum load to specimen failure was recorded and the fracture toughness calculated. Results: There were significant differences among most of the materials (P< 0.001). Quix FiI had the highest mean KIc value and Fuji VII the lowest. Immersion in distilled water for the resin composite and polyacid-modified resin composites caused a significant decrease in KIc as the time interval increased. For glass-ionomer cements, KIc decreased significantly after 4 weeks, and after 8 weeks immersion slightly increased. G-Coat Plus affected Fuji II LC positively while it had no effect on the Fuji IX.