Nanoparticle Guided Dentin Micro-tissue Engineering: Characterizing Fluid Dynamics for Delivery and Tissue Mechanical Response

Disease process and iatrogenic procedures compromised the mechanical integrity of remaining dentin, which in turn increased the susceptibility of endodontically treated teeth to vertical root fracture. Cracks and fracture of endodontically treated teeth diminished the treatment predictability. Micro-tissue engineering principles are applied to design tissues with improved mechanical and biological characteristics. Chitosan nanoparticles (CSnp) are bioactive biopolymers, when applied to dentin displayed antimicrobial and enhanced toughness characteristics. Crosslinking CSnp with dentin collagen provides additional stabilization towards efficient mechanical load-transfer and resistance to matrix degradation. However, effective transport of nanoparticles into root canal remains to be a challenge owing to the complex canal morphology and non-uniform stresses generated with the syringe-based delivery method. The objectives of this study were: (1) to characterize the stability of the nanoparticle dispersion and surface ultra-structure of micro-tissue engineered dentin, (2) to evaluate the fluid-dynamics and delivery efficacy associated with a novel strategy based on activated microbubbles to deliver nanoparticles into root canal, and (3) to examine the effect of micro-tissue engineering with crosslinked-CSnp on the mechanical characteristics of root dentin. CSnp dispersion of 1mg/ml concentration was selected based on the nanoparticle aggregation kinetics. This concentration sustained the stability with optimal charge density and dispersity. Crosslinking CSnp on dentin resulted in a denser/homogeneous coating with altered hardness and elastic modulus on dentin surfaces. Ultrasonically activated microbubbles induced fluid-dynamics with high velocity and inertial stress through intensified cavitational bubble dynamics but formed a coating of CSnp mixed with dentin smear layer on canal wall. Manually agitated microbubbles generated uniformly high viscous stress with increased particle flux facilitating homogeneous coating of CSnp on root canal dentin. Micro-tissue engineered root canal dentin with crosslinked-CSnp and water-soluble chitosan resulted in decreased strain distribution enhancing the stability of root under physiologically loads. There was an increase in the sustained load at fracture in specimens treated with photodynamically-crosslinked-CSnp. The findings from this study emphasized the advantage of manually activated microbubbles to deliver CSnp in root canal and the impact of micro-tissue engineering with crosslinking CSnp on dentin to enhance the mechanical characteristics of root. These outcomes have potential application in clinical practice.Ph.D.2019-11-19 00:00:0