Three-Dimensional Cell Printed Lock-Key Structure for Oral Soft and Hard Tissue Regeneration

Alveolar ridge resorption after tooth extraction remains a significant clinical challenge. The loss of bone and soft tissue volume limits implant rehabilitation options. Prior research has shown that alveolar ridge preservation is critical for successful dental restoration. However, current methods lack the ability to simultaneously regenerate both soft and hard tissues. Three-dimensional (3D) cell printing has emerged as a promising technique due to its spatial control and personalization capabilities. This gap motivated researchers to explore a combined soft-hard tissue construct. No prior work had resolved the integration of both tissue types in a single construct. The need for a biocompatible and structurally stable material remains unmet. This study addresses the challenge of developing a functional construct for alveolar ridge preservation. The potential of 3D cell printing to deliver a customized solution is now being explored.

The aim of this study was to develop a 3D cell printed soft-hard construct for alveolar ridge preservation. Alveolar ridge resorption after tooth extraction limits implant options, so a solution that supports both bone and soft tissue is needed. The researchers focused on creating a lock-key structure using two different bioinks. One bioink contained gingival fibroblasts for soft tissue regeneration, while the other included mesenchymal stem cells for bone formation. The motivation was to address the lack of integrated tissue regeneration strategies. The study aimed to test the biocompatibility and structural stability of the construct. The goal was to determine whether the printed structure could support tissue healing in vivo. The researchers proposed that this approach could provide a novel solution for alveolar ridge preservation.

The study used 3D cell printing to fabricate a soft-hard construct with a lock-key design. Two bioinks were prepared: one with alginate/gelatin and gingival fibroblasts, and another with alginate/gelatin/nano-hydroxyapatite and mesenchymal stem cells. The physicochemical properties of the bioinks were analyzed using X-ray diffraction and mechanical testing. Scanning electron microscopy was used to assess cell attachment and morphology. Cell viability was measured using MTT assays at day 7 post-printing. Gene expression levels of ALP, RUNX-2, and OCN were analyzed via polymerase chain reaction. The constructs were implanted into the dorsum of nude mice for 8 weeks. Histological and structural assessments were conducted to evaluate integration and healing outcomes.

The addition of nano-hydroxyapatite to the bioink preserved its crystalline phase and increased viscosity. The compressive modulus of the AGH bioink was significantly higher than that of AG (p < 0.01). The AGH bioink also showed a slower degradation rate (p < 0.01). SEM images revealed that cells stretched and adhered well on the printed structure. At day 7, GF viability in AG was 94.80% ± 1.14%, and BMSC viability in AGH was 86.59% ± 0.75%. PCR results indicated higher expression of ALP, RUNX-2, and OCN in AGH compared to AG. After 8 weeks of implantation, the cellular construct showed better integration and healing than the acellular version. These findings suggest that the AGH bioink supports bone-related gene expression and tissue regeneration.

The 3D cell printed soft-hard construct demonstrated favorable biocompatibility and structural integration. The lock-key design allowed for the simultaneous regeneration of soft and hard tissues. The addition of nano-hydroxyapatite improved the mechanical and degradation properties of the bioink. The study found that the AGH bioink supported higher expression of bone-related genes. The printed construct showed better healing outcomes in vivo compared to the acellular version. These findings suggest that the construct has potential for alveolar ridge preservation. The authors propose that this approach could lead to customized plugs for post-extraction healing. The results indicate that 3D cell printing can deliver a functional solution for tissue regeneration.