Comparative Analysis of 24-Hour Post-Polymerisation Colour Change in Experimental Rice Husk Silica-Incorporated Flowable Composites with Different Photoinitiator Systems Across Three Colour-Assessment Devices.

BACKGROUND/OBJECTIVES: Rice husk silica (RHS) is a biosustainable filler with potential application in dental flowable composites (FCs). However, early post-polymerisation colour change in RHS-incorporated FCs may vary with material formulation, particularly resin composition and photoinitiator system, and may also be affected by the colour-assessment device used. This study compared the 24 h post-polymerisation colour change of 10 experimental RHS-incorporated FC groups formulated with five photoinitiator systems and two commercial FCs used as control, using three colour-assessment devices. METHODS: Two UDMA/TEGDMA formulations (U50 and U40), each containing 50 wt% nanohybrid RHS, were prepared with different photoinitiator systems (CQ, PPD, CQ/PPD, BAPO, or TPO). CIELAB coordinates were recorded immediately after curing and after 24 h of dry, dark storage at 37 °C using D1 (VITA Easyshade), D2 (Ds-700d Portable Spectrophotometer), and D3 (ColorMeter Pro). The same specimens were measured with all three devices, with five matched specimens from each of the 12 composite groups (N = 60). A mixed repeated-measures ANOVA was performed with device as the within-subject factor and composite as the between-subject factor; agreement was additionally assessed using Bland-Altman analysis and an absolute-agreement intraclass correlation coefficient (ICC). RESULTS: Device, composite, and the device × composite interaction were significant (all p < 0.001). Estimated mean ΔE*ab was highest for D1 (5.019), followed by D3 (2.368) and D2 (1.777), and all device pairs differed significantly after Bonferroni adjustment. Bland-Altman analysis showed systematic positive bias for D1 relative to D2 and D3. The absolute-agreement ICC was 0.130 (95% CI 0.078-0.177), indicating poor agreement. CONCLUSIONS: The magnitude of early 24 h colour change depended on both the composite material and the measurement device. The three devices should not be assumed to be directly interchangeable for ΔE*ab assessment; the same calibrated device should be used throughout a longitudinal comparison.