Bioprinted enamel–dentin inlays: a future direction in regenerative dentistry

The emergence of stem-cell-derived enamel organoids and dentin-producing dental pulp stem cell constructs presents new possibilities for restoring carious lesions using autologous enamel–dentin inlays. This overview outlines the biological and technological advances supporting this approach and proposes a workflow oriented toward clinical application. The benefits of tissue-based inlays, including inherent biomechanical compatibility, aesthetic accuracy, and potential for biological integration, are contrasted with those of purely artificial materials. Significant regenerative developments include the formation of human enamel organoids and odontoblast-lineage cells in vitro, 3D bioprinting of tooth-shaped constructs with demineralised dentin matrix and poly(ε‑caprolactone) scaffolds, and fibre-guiding periodontal ligament scaffolds that restore Sharpey’s fibres in vivo. The mechanical performance of adhesive resin cements, with bond strengths of approximately 4–7 MPa to enamel and dentin, and their durability in reattaching natural tooth fragments, supports the feasibility of bonding biological inlays. Practical considerations include controlling the slow degradation and hydrophobicity of poly(ε-caprolactone) through the use of ceramic or natural polymer additives, employing multi-material 3D printing to co-print mineralized enamel and cell-laden dentin layers, and achieving the desired shade, microstructure, and mechanical properties, exemplified by a compressive strength of approximately 677 MPa for 3D-printed zirconia crowns. Despite regulatory and translational challenges, the integration of digital dentistry, bioprinting, and stem cell science points toward future “grow and glue” restorations that may replace traditional drill-and-fill methods.