Impact of printing layer thickness on the flexural strength of nanocomposite 3D printed resins: An in vitro comparative study
Mohammed M. Gad, Fatimah Abdullah Alzaki, Fatimah Ahmed Abuwarwar, Ali Alhammad, Mohammed Al Hussain, Soban Q. Khan, Essam Nassar, Neveen M. Ayad
Abstract
This study evaluated the influence of various printing layer thicknesses with silicon dioxide nanoparticles (SiO2NPs) incorporated as a reinforcement material on the flexural strength of 3D-printed denture base resins. Asiga (DentaBASE, Asiga, Erfurt, Germany) and NextDent (Denture 3D+, NextDent B.V., Soesterberg, The Netherlands) 3D-printed resins were modified with different concentrations of SiO2NPs (0.25 % and 0.5 wt%). A total of 180 specimens (bar-shaped, 64 × 10 × 3.3 mm) were fabricated (N = 90/resin). Each resin was subdivided into three groups (n = 30) according to the SiO2NP concentration (0 %, 0.25 %, and 0.5 wt%) Each concentration was divided into three groups (n = 10) according to the printing layer thickness (50 µm, 75 µm, and 100 µm). Specimens were printed according to the manufacturer’s instructions and then subjected to 10,000 thermal cycles. A three-point bending test was used to measure the flexural strength (MPa). One-way analysis of variance (ANOVA) and Tukey’s post hoc tests were used to analyze the data (α = 0.05). For both resins, printing layer thicknesses of 50 µm and 75 µm exhibited significantly higher flexural strength than 100 µm (P < 0.001). The 50 µm thickness showed the greatest flexural strength values (81.65 ± 4.77 MPa and 84.59 ± 6.21 MPa for Asiga and NextDent, respectively). The 100 µm thickness showed the lowest flexural strength values (74.35 ± 5.37 and 73.66 ± 5.55 MPa) for Asiga and NextDent, respectively. The flexural strength significantly increased with the addition of SiO2NPs with printing layer thicknesses of 50 µm and 75 µm (P < 0.001), whereas the modified and unmodified groups printed with a 100 µm layer thickness did not differ significantly. Asiga 0.25 %/50 µm and NextDent 0.5 %/50 µm showed the highest flexural strength values (97.32 ± 6.82 MPa and 97.54 ± 7.04 MPa, respectively). Scanning electron microscopy fractured surfaces analysis revealed more lamellae and irregularities with lower printing layer thicknesses and SiO2NP concentrations. The flexural strength increased with printing layer thicknesses of 50 µm or 75 µm combined with SiO2NP reinforcement.