3D-Printed Strong Dental Crown with Multi-Scale Ordered Architecture, High-Precision, and Bioactivity

Natural tooth enamel features a multi-scale ordered structure of hydroxyapatite (HAp) nanocrystals, which contributes to its mechanical strength and bioactivity. Replicating this complex architecture in dental prosthetics remains a significant challenge. Traditional dental crown fabrication methods often lack the precision and structural fidelity needed to match natural enamel properties. While 3D printing has advanced dental manufacturing, achieving high-precision, multi-scale ordering of HAp remains limited. Prior research has demonstrated the potential of 3D printing for dental applications, but gaps remain in controlling nanoscale orientation and mechanical performance. This study addresses the need for a fabrication method that can produce dental crowns with both high mechanical strength and bioactive properties. The ability to mimic natural enamel could improve the longevity and integration of dental restorations. However, no prior work had resolved how to achieve such multi-scale ordering through extrusion-based printing. This gap motivated the development of a new 3D printing strategy to fabricate dental crowns with enhanced structural and functional properties.

The aim of this study is to develop a 3D printing method that can produce dental crowns with a multi-scale ordered hydroxyapatite (HAp) structure, mimicking the natural enamel of teeth. The researchers sought to overcome limitations in traditional dental crown fabrication by using extrusion-based 3D printing to achieve high precision and structural control. A specific problem addressed is the lack of methods to align HAp nanorods at multiple scales within a printed structure. This work builds on prior knowledge of HAp’s role in dental bioactivity and mechanical strength. The motivation stems from the need for dental prosthetics that offer both durability and biocompatibility. The study also aims to validate the mechanical performance of the printed crowns through experimental and simulation methods. The goal is to demonstrate that this new approach can produce crowns with superior mechanical properties compared to traditional methods. This work may help advance the clinical application of 3D-printed dental restorations.

The researchers employed extrusion-based 3D printing, specifically direct ink writing (DIW), to fabricate dental crowns with a multi-scale ordered hydroxyapatite (HAp) structure. They used hybrid resin-based composites (RBCs) containing HAp nanorods and a custom-built nozzle with a gradually shrinking channel to control the printing process. The printing path was programmed to align HAp nanorods in a specific direction within each fiber and across layers. Theoretical simulations using finite element methods were conducted to predict the mechanical behavior of the printed structures. Experimental validation was performed to confirm the alignment and mechanical performance of the printed samples. The printed crowns were tested for flexural and compressive strength using standard mechanical testing methods. The study also assessed printing accuracy by comparing the printed structure to the intended design. The alignment and distribution of HAp nanorods were analyzed using imaging techniques to confirm the multi-scale ordering.

The printed dental crowns exhibited a flexural strength of 134.1 ± 3.9 MPa and a compressive strength of 361.6 ± 8.9 MPa, which are higher than those of traditional molding methods. The HAp nanorods were successfully oriented along the printing direction within each fiber and arranged in layers according to the programmed path. The multi-scale ordering of HAp was confirmed through imaging and mechanical testing. The printed samples demonstrated a criss-crossed layer structure that interrupted crack propagation, enhancing mechanical performance. The printing accuracy reached 95%, indicating a high level of precision in fabricating the crown structure. The hybrid resin-based composites (RBCs) with HAp nanorods were successfully used to produce bioactive and strong dental crowns. The finite element simulations aligned well with the experimental results, validating the design approach. These findings suggest that the developed 3D printing method can produce dental crowns with structural and mechanical properties comparable to or exceeding those of conventional methods.

The study demonstrates that extrusion-based 3D printing can produce dental crowns with a multi-scale ordered hydroxyapatite (HAp) structure, achieving high mechanical strength and bioactivity. The alignment of HAp nanorods at multiple scales was successfully achieved through a custom nozzle and programmed printing path. The printed crowns showed superior flexural and compressive strength compared to traditional molding methods. The high printing accuracy of 95% indicates the feasibility of using this method for clinical dental restoration. The criss-crossed layer structure effectively interrupted crack propagation, contributing to the mechanical performance of the printed crowns. The hybrid resin-based composites (RBCs) with HAp nanorods proved suitable for producing bioactive dental prosthetics. The finite element simulations supported the experimental results, confirming the validity of the design approach. These findings suggest that the developed method can help provide customized dental restorations with improved structural and functional properties.