OBJECTIVE: Periodontitis is one of the most common infectious diseases in the world causing a progressive loss of the tooth supporting tissues. In this study, we have focused on the evaluation of biological and mechanical properties of polycaprolactone (PCL) 3D-printed scaffolds with or without alumina toughened zirconia (ATZ) powder, as suitable substrate material for alveolar bone and periodontal ligament (PDL) regeneration.

MATERIALS AND METHODS: The ATZ was incorporated in PCL matrix by stirring agitation and dissolution in chloroform, with a solvent casting method. PCL/ATZ 80/20 w/w% and PCL/ATZ 60/40 w/w% composites and pure PCL were prepared. Then two different types of geometry were obtained through 3D-printing process: a scaffold with a standard porous and circular geometry, to perform different biological assays with ASC52 hTert cells line, and a rectangular geometry for tensile tests. A 24h adhesion test and a cell viability assay with three time-step, respectively at 3, 7 and 14 days was performed by CellTiter-Glo kit to quantify scaffold colonization by cells. Scaffolds were held in osteogenic medium for 2 months prior to quantify the genes expression of ALP, COLL1, OCN and RUNX2 with Real-Time PCR (RT-PCR). SEM micrographs of the 3 scaffolds were acquired along with EDX analysis to quantify the presence of calcium deposition. To assess the mechanical properties of the composite materials, tensile strength was measured by a dynamometer in tensile configuration.

RESULTS: All the scaffolds allowed ASC adhesion and growth, in particular PCL/ATZ 80/20 w/w% showed better biocompatibility on the long term, although the addition of ATZ to the PCL matrix reduced the osteoinductive capacity of the materials. Based on the RT-PCR, there were no significant differences on ALP and RUNX2 genes expression, while both COLL1 and OCN expressions were reduced in presence of ATZ filler in the polymer scaffolds. These results were consistent with SEM images and EDX quantification of calcium aggregates in the new bone tissue formation on the scaffolds. As far as the mechanical properties concern, we observed an increase of the Young’s modulus (E) in the composites compared to neat PCL; this improvement caused a noticeable reduction of the elongation at break (ε) in the composites with high amount of ATZ filler.
 

CONCLUSIONS: The presence of ATZ powder in PCL reduced the osteoinductivity of the scaffolds, while increased their strength. This behavior plays a relevant role in the final choice of the material to be used in PDL regeneration, as this could limit the possibility of tooth ankylosis. Future tests will be focused on the biological and mechanical properties of the scaffolds obtained by mixing PCL and ATZ powders through a different free-solvent process.