This article proposes the synthesis and characterization of (triethylene glycol dimethacrylate–N,N-dihydroxyethyl-p-toluidine) TEGDMA-DHEPT self-healing microcapsules for their inclusion in dental composite formulations. The obtaining method is the in situ emulsion polymerization of the (poly urea-formaldehyde) (PUF) coatings. The microcapsules were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), high-performance liquid chromatography (HPLC), and low-field nuclear magnetic resonance (NMR) techniques. The optimal formation of uniform microcapsules is achieved at a stirring speed of 800 rpm and centrifugation is no longer necessary. HPLC demonstrates that the microcapsules formed at 800 rpm show a better control of liquid release than the heterogeneous ones obtained at a lower stirring speed. The centrifuged samples have rounded shapes, with dimensions between 80 and 800 nm, while the non-centrifuged samples are more uniform, with a spherical shape and dimensions of approximately 800 nm.

The development of microcapsules for the controlled release of active substances offers an innovative strategy in restorative dentistry, expanding the possibilities beyond traditional methods. In this study, microcapsules loaded with triethylene glycol dimethacrylate (TEGDMA) and different concentrations of hydroxyapatite (HAP)—0%, 5%, 10%, 15%, and 20%, referred to as M0, M5, M10, M15, and M20—were synthesized through in situ polymerization within an oil-in-water emulsion. Their morphology, size, and nanostructure were examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of characteristic chemical bonds, whereas high-performance liquid chromatography (HPLC) quantified residual TEGDMA monomer. Low-field nuclear magnetic resonance (NMR) further confirmed the presence and the distribution of the liquid healing agent inside the microcapsules. The analyses indicated that microcapsules incorporating 20% hydroxyapatite exhibited superior structural organization and improved shell integrity, highlighting their potential in the remineralization processes. Overall, these results support the potential of HAP–TEGDMA microcapsules for incorporation into dental composites to facilitate microcrack repair and promote dental tissue regeneration.