Influence of silica nanoparticle sedimentation on the mechanical, surface properties and trueness of DLP-printed dental resin

Abstract

Objectives This study investigated the gravitational sedimentation of silica nanoparticles in DLP-printed dental resins and assessed its impact on filler distribution, DC, mechanical and surface properties and printing trueness. Materials and methods Dental resin containing 1 wt% SiNPs was printed via DLP printing into 1 mm-thick disks at build heights ranging from 1 to 15 mm above the platform. SiNP distribution was analyzed by SEM-EDS. DC, Vickers hardness, contact angle, surface roughness (Ra), and Delta E were measured and correlated with local Si concentrations (n = 5). The printed specimens from each build height were randomly assigned to different tests. Printing trueness (n = 15) was measured using digital superimposition analysis of dental crowns by RMS values. Dental resin without SiNPs served as controls. One-way ANOVA with Tukey&apos;s post-hoc test, linear regression and t-test were used for statistical analysis. Results SEM-EDS confirmed a linear increase in Si concentration with build height in the 1 wt% group (R-2 = 0.8654). In the SiNP group, DC and hardness increased significantly with build height (R-2 = 0.3680, R-2 = 0.7964), while water contact angle and surface roughness decreased (R-2 = 0.8432, R-2 = 0.1505). Trueness decreased at higher build heights in the 1 wt% group (p < 0.05). The control group showed no such build height-dependent trends. Conclusions Sedimentation during DLP induces predictable vertical nanoparticle gradients, which in turn systematically influence DC, mechanical strength, hydrophilicity, surface smoothness, and printing trueness. Clinical relevance Nanoparticle sedimentation creates vertical property gradients within DLP-printed restorations. This causes heterogeneous mechanical and surface performance, potentially leading to localized weakness or marginal discrepancies. Clinicians should optimize print orientation to position functionally critical surfaces at appropriate build heights and implement mid-print homogenization to minimize sedimentation effects.