Non-destructive characterization of resin-based filling materials using Electronic Speckle Pattern Interferometry

Objectives. The aim of this study was to develop a non-destructive test for characterizing the modulus of resin-based filling materials. Methods. Five different visible-light-cured composites (Filtek A110 [AO], Z100 [ZO], Filtek Z250 [ZT], F2000 [FT] and Filtek Flow [FF]; 3M-ESPE) were selected for this study. An ESPI (Electronic Speckle Pattern Interferometry) apparatus involving cantilever beam specimens (28 mm long, 8 mm wide and 2 mm thick) was developed for determining modulus. Out-of-plane displacement upon force application was measured using two focus region lengths (22 mm [EI1]; 11 mm [EI2]) and modulus (n=7) was subsequently computed based on cantilever beam equations. Data was compared to those obtained from three-point-bend flexural testing (n=7) based on ISO4049:2000 specifications [ISO]. Specimens were stored in distilled water at 37 °C for 1 week prior to evaluation for all tests. Results were analyzed using ANOVA/Scheffeʹs post-hoc tests (p<0.05) and Pearsonʹs correlation (p<0.01). Results. Modulus ranged from 5.53 to 13.99, 5.78 to 14.24 and 4.26 to 11.30 GPa for EI1, EI2 and ISO, respectively. For all three tests, the modulus of ZO and FT was significantly greater than ZT, which in turn was significantly greater than AO and FF. Correlation of EI1 and EI2 to ISO was significant, positive and very strong (r=0.94 for EI1 and EI2). Significance. ESPI may be a viable method of characterizing the modulus of resin-based filling materials. As it is a non-destructive test, time-dependent effects of composites can be determined using the same specimens leading to substantial time and material savings.