Morphological Analysis and Resin Infiltration of Novel Nanogel-modified Adhesive-dentine Interfaces Using 2-photon Microscopy

Objectives: The integrity of a dental restoration relies on the extent of resin infiltration into demineralised dentine and sealing of tubules from resin- hydrolysing pulpal fluid. Combining resins with internally cross-linked, surfacefunctionalised nanogels offers control of their hydrophobic character, improvements in mechanical properties and reduced shrinkage stress¹. The study i) examined the infiltration and sealing capacity of a nanogel-modified adhesive and ii) monitored the movement of such adhesives through a demineralised dentine matrix in real time using two-photon microscopy.
Methods: i) A model BisGMA/HEMA 40:60 wt% adhesive was prepared. Nanogels comprised of HEMA and BisGMA were labeled with a Polyfluor 570 fluorescent probe and added to the resin at 40wt%. Human molars were restored using nanogel-modified and nanogel-free resins, and 2-photon microscopy revealed detailed morphology of the interfaces. ii) Dentine discs were demineralised in EDTA for 2 weeks. 100ul nanogel-modified resin was deposited onto the disc surface and 2-photon microscopy was used to monitor fluorescent signals at the disc undersurface.
Results:
The modification of the resin with nanogels had a dramatic positive impact on its tubule-sealing properties. The modified resins fully permeated demineralised dentine, the visualisation and quantification of which was achieved using 2-photon microscopy.
Conclusions: This study substantiates a previous study that shows the use of the amphiphilic nanogel additives based on HEMA and BisGMA improves dentine bond strength, even after storage (unpublished data). The infiltration of fluorescently- labeled adhesives through dentine is easily monitored using 2-photon microscopy.

1. R.R. Morães et al., J. Dent. Res. 91(2012) 179–184. doi:10.1177/0022034511426573 .
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