3D-printed strong hybrid materials with low shrinkage for dental restoration

Flowable photocurable resins can be printed effectively by stereolithographic 3D printing for dental applications; however, the 3D-printed objects' mechanical properties cannot meet the requirements for the dental restorative materials. In this study, a strong customized crown for tooth repair was first prepared via direct ink writing 3D printing from a high-viscosity hybrid paste of acrylic monomer and multi-scale inorganic particles. The results showed that the hybrid resin-based composites (RBCs) could be printed successfully and smoothly through a metal nozzle with a gradually shrinking channel. The theoretical simulation of finite element methods was consistent with the experiment results. The printed objects were preliminarily cured incrementally and exhibited a low shrinkage ratio of only 2.58 +/- 0.11%. The printed samples with criss-crossed layers by interrupting crack propagation exhibited superior mechanical properties (a flexural strength of 120.8 +/- 4.1 MPa and a compressive strength of 323.6 +/- 5.6 MPa) than their traditional molding counterparts. Since the deposited layers exhibited improved resistance to bending forces, the flexural strength of the sample with a print orientation in adjacent layers (45-135 degrees) even reached 145.5 +/- 8.7 MPa. The RBCs were successfully used to print strong, highperformance and biocompatibility dental crowns, expected to provide a customized component for the clinical restoration of teeth.

Automated summary

In this study, a strong customized dental crown was successfully prepared using high-viscosity hybrid paste and direct ink writing 3D printing technology, demonstrating low shrinkage ratio and superior mechanical properties. The printed samples showed higher flexural strength and compressive strength compared to traditional molding counterparts.