The effect of tooth age on the fracture toughness of four dental bonding systems

Objective: The purpose of this in vitro study was to evaluate the effect of dentin age on the fracture toughness (Kic) of dental bonding systems using the notchless triangular prism (NTP) specimen Kic test. Methods: 80 human molars and pre-molars, 40 of them from patients not older than 45 years ("young") and 40 from patients not younger than 65 years ("old"), were wet ground on 600-grit silicon carbide abrasive paper to obtain a 4x4x4x4mm triangular prisms with the labial surface exposed for bonding. Within each of the two groups, the specimens were randomly assigned to four subgroups (n=10) according to the bonding system to be used for composite bonding: Adper Prompt L-pop (3M ESPE), Clearfil SE (Kuraray), Prime & Bond NT (Dentsply) and Scotch Bond MP (3M ESPE). The composite, Z-100 (3M ESPE), was bonded to each of the treated surfaces as per the manufacturer's instructions to obtain a 4x4x4x8mm dentin-composite NTP specimens. The specimens were stored in water for 24h at 37°C and tested to determine Kic. The data was analyzed using Levene's test for normality, two-way univariate analysis of variance (ANOVA), and Bonferroni tests for multiple means comparisons. A significance level of 0.05 was used for all tests. Results: While Adper Prompt L-pop and Clearfil SE achieved the highest Kic values for both age groups, Prime & Bond NT showed the lowest values. SEM observations of fractured samples revealed differences in fracture path. No statistically significant differences were observed between age groups. Conclusions: The Kic values of the four dental bonding systems were not affected by age. Furthermore, statistically significant differences were observed between the Kic values of the four bonding systems, regardless of the age of the dentin.Dentistry, Faculty ofGraduat