The Deposition and Interaction of Nanoparticles With Dentinal Tubules

Objectives: Nanoparticles may enter and occlude dentinal tubules but are prone to aggregation, which prevents them from entering into the opening. The addition of surfactants to the nanoparticles may avoid this occurrence. The aim of this project is to investigate the ability of silica nanoparticles with or without surfactants to enter dentine tubules using both artificial and human tooth models
Methods: Nanoparticles of spherical silica encapsulating tris-(2,2’-bipyridyl) ruthenium(II) dichloride were used with Zonyl FSA, Triton X-100, Tween20 surfactants. The nanoparticles were prepared as a 0.004% w/v and 0.04%w/v solutions by addition of deionised water, followed by ultrasonication for 5 minutes. The average diameter of the nanoparticles was 607nm (+165nm 1 SD). The particles were applied with no mechanical agitation to the surface of; (1) in vitro model of PET ThinCert cell culture inserts; (2) 0.1mm thick sections of human molar teeth - covered by the Human Tissue Act. Scanning electron microscopy was used to view the nanoparticles on both surfaces. NPs were applied both before and after splutter coating of the samples.
Results: Both PET inserts and dentine tooth slices were useful models for viewing the aggregation of the particles. It was found that higher concentrations of NPs were required to occlude the tubule openings 0.04% w/v. There was variation in nanoparticles aggregation, with the most tubule occlusion occurring with no surfactant and NP with Zonyl. High aggregation within the dentinal tubules was also increased by nanoparticle concentration.
Conclusions: The use of silica nanoparticles on hard dental tissues will be dependent on the modification of the surface chemistry of both the particle and the dentine prior to delivery. Further research on how to improve the interaction and movement of NPs on the dentine surface is merited.