Alexis Bernardo Sabido-Barahona

Early childhood caries frequently affects maxillary anterior primary teeth, and their rehabilitation remains a clinical challenge due to the lack of suitable resorbable intracanal posts. This study aimed to develop and characterize a biodegradable polymer-ceramic biomaterial for potential application in primary tooth rehabilitation. Polycaprolactone (PCL) and polylactic acid (PLA) composite filaments (50:50), reinforced with 20 wt.% α-tricalcium phosphate and 5 wt.% zirconia, were produced using two different processing routes involving a Noztek Touch and a Brabender Plasti-Corder extruder. The developed biocomposites obtained by single extrusion with a Brabender Plasti-Corder exhibited good ceramic distribution in the polymeric matrix but exhibited lower mean compressive modulus values (155.98 MPa vs. 258.44 MPa), which were not statistically significant. The composite biomaterial showed degradation under alkaline conditions, whereas only limited mass loss was observed under acidic conditions and in hydrogen peroxide, with minimal mass loss in distilled water. These composites showed favorable biocompatibility with dental pulp stem cells, although no antimicrobial activity was observed. Furthermore, the incorporation of zirconia may contribute to radiopacity for radiographic monitoring. These findings support the potential of the developed composite biomaterial as a candidate biodegradable intracanal post for pediatric restorative dentistry applications.

Fused deposition modeling (FDM) is an emerging trend for producing nerve guidance conduits (NGCs). This technique allows distinct designs and dimensions to mimic peripheral nerve architecture and promote nerve regeneration. In this study, commercially available TPU 90A and 95A filaments were used for the fabrication of hollow simple wall (non-porous), grooved and gyroid multichannel conduits. The segmented polyurethanes were identified as PBA-MDI-BO-based polyurethanes by ¹H NMR, FTIR and Raman spectroscopy. Thermal analyses, such as DSC and TGA, demonstrated that both TPUs possess sufficient thermal stability to be processed safely under the printing conditions employed. Tensile mechanical tests accounted for their differences in hard segment content in agreement with the Shore A hardness. The measured elastic modulus, in particular, was within a range that may be advantageous for peripheral nerve repair. The gyroid multichannel design showed enhanced resistance to radial compression and highly interconnected internal structure that supported primary neural cell viability and preserved cellular functionality. Therefore, polyurethane-based nerve guidance conduits can be manufactured by FDM, rendering high printability, favorable mechanical performance without compromising biocompatibility.

This study investigated the chemical, thermal, and mechanical properties of segmented polyurethanes (SPUs) synthesized using less common biodegradable polyester polyols, specifically poly(adipate) (PAD) and poly(sebacate) (PSC), to evaluate their potential as nerve guidance conduits (NGCs) in peripheral nerve regeneration. The synthesis of novel 4,4′ methylene-bis-cyclohexyl diisocyanate (HMDI) SPUs was conducted in a two-step process: prepolymer formation and chain extension with 1,4-butanediol (BO) or 1,4-butanediamine (BA). SPUs were synthesized with two molar ratios—polyol:HMDI:BA/BO at 1:2:1 and 1:3:2 for the PAD:HMDI:BA system—to optimize mechanical properties. 1HRMN analysis verified the expected chemical structure of SPUs, whereas Raman and IR spectroscopy confirmed successful polyurethane synthesis. X-ray diffractograms showed that PAD-based SPUs (SPUPAD) were amorphous while PSC-based SPUs (SPUPSC) exhibited semi-crystalline behavior. SPUPAD showed only one degradation stage by TGA, while DSC showed one thermal event. In contrast, SPUPSC exhibited two degradation stages and three thermal events that confirmed phase separation. The longitudinal tensile properties of an NGC fabricated from SPUA-PAD-2 (PAD:HMDI:BA (1:3:2)) after 30 days of immersion in water (25 °C) showed a lower modulus (4.46 ± 0.5 MPa) than native intact nerves (15.87 ± 2.21 MPa) but a similar modulus to extracted nerves (8.19 ± 7.27 MPa). This system exhibited a longitudinal tensile force of 11.1 ± 1.6 N, which is lower than that of peripheral nerves (19.85 ± 7.21 N) but higher than that of commercial collagen-based nerve guide conduits (6.89 ± 2.6 N). The observed properties suggest that PUA-PAD-2 has potential as a biomaterial for nerve regeneration applications.