Poster BB2 - Angulation of engineered periodontal ligaments for functioning restoration in the canine model

Introduction: Angular principal fiber bundles (periodontal ligaments; PDLs) generate various functional responses to effectively optimize positional stabilities of teeth, transmit biomechanical stresses, or promote tissue remodeling. However, periodontitis, highly prevalent inflammatory disease, could induce destruction of PDLs including periodontia and dental prosthetics would be required to replace natural teeth. Recently, tissue engineering strategies have been developed to promote periodontal complex formation, but it is still challenging to regulate specific orientations of regenerated PDLs for restoration for tooth-supportive functions. In this study, spatial microarchitectures promote PDL orientations with limited bone formations in the canine model.

Materials and

Methods: After extractions of the 2nd premolar tooth (P2) and the P4, the alveolar bone was naturally regenerated to fill tooth-extraction socket defects in 12 weeks. Then, the periodontal 2-wall defect was surgically created mesial and distal roots of the P3 tooth and tooth-root cementum was physically removed by a dental chisel with the specific dimension (approximately 4.5mm width and 5.0mm height). Polycaprolactone (PCL)-based scaffold was designed with two compartments: microgroove-patterned PDL architectures and bone region with connective pores. The additive manufacturing could create microgroove patterns by the slicing procedure and the specific topographies could be utilized as the guiding platforms to angularly orient PDLs. After PCL scaffolds were manufactured and transplanted into 2-wall periodontal defects in the canine model, bone formation was quantified by micro-computed tomographic (micro-CT) for mineralized tissue formation and PDL formations were analyzed with histology including immunohistochemistry for biological/pathological assessments.

Results, Conclusions, and Discussions: Although the 4-week time-point was relatively short to completely regenerate alveolar bone tissues in defects in the canine model, scaffold transplantation defect sties interestingly showed statistical significance with bone parameters, qualitatively and quantitatively. Compared with no transplantation group, scaffolds could spatiotemporally contribute bone tissue formation in quantitative assessments, which showed statistically increased bone volume fraction (BVF) and bone mineral density (BMD) at the defect sites in scaffold transplantation group with significant difference. Histologically, fibrous connective tissues were analyzed for PDL regenerations with the perpendicular orientation by designed microgroove patterns of PDL-guiding architectures as well as PDL functioning restorations . By H&E and Picrosirius red stainings, PDL collagenous fiber bundle formations were determined morphologically and biologically. Following the microgroove patterns, PDL fibrous tissues were perpendicularly aligned to the tooth-root surface but, the no scaffold transplantation group had random or parallel orientations of PDL along the tooth-roots. The functioning of PDLs at 4 weeks after treatments were indirectly evaluated by immunohistochemical biomarkers; periostin and decorin (DCN) molecules. In the results, aligned fibrous tissues in the transplantation group qualitatively displayed with higher expression levels of biomarkers than the no transplantation group, which showed random organization of fibrous tissues and epithelial downgrowth.

In conclusion, there was the critical time limitation in canine tissue regeneration, but this pilot investigation could demonstrate that PDL-guiding architectures with designable and manufacturable microgroove patterns could regulate fibrous tissue orientations and limited bone formation with predictability and controllability of spatial tissue formations. Therefore, the single perio-complex scaffolds can provide spatial compartmentalization for oriented PDL regeneration in PDL regions and bone formation.

Acknowledgements (Optional):