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. 2022 Jul;11(14):e2200232.
doi: 10.1002/adhm.202200232. Epub 2022 May 4.

Mobile Nanobots for Prevention of Root Canal Treatment Failure

Debayan Dasgupta  1   2 , Shanmukh Peddi  1   2 , Deepak Kumar Saini  3   4 , Ambarish Ghosh  1   2   5
Affiliations

Mobile Nanobots for Prevention of Root Canal Treatment Failure

Debayan Dasgupta et al. Adv Healthc Mater. 2022 Jul.

Abstract

Millions of root canal treatments fail worldwide due to remnant bacteria deep in the dentinal tubules located within the dentine tissue of human teeth. The complex and narrow geometry of the tubules renders current techniques relying on passive diffusion of antibacterial agents ineffective. Here, the potential of actively maneuvered nanobots is investigated to disinfect dentinal tubules, which can be incorporated during a standard root canal procedure. It is demonstrated that magnetically driven nanobots can reach the depths of the tubules not possible with current clinical practices. Subtle alterations of the magnetic drive allow both deep implantations of the nanobots isotopically distributed throughout the dentine and spatially controlled recovery from selected regions, further supported by numerical simulations. Finally, the integration of bactericidal therapeutic modality with the nanobots is demonstrated, thereby validating the tremendous potential of nanobots in dentistry and nanomedicine in general.

Keywords: active matter; dentine; endodontic reinfection; nanobots; root canal.

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Conflict of interest statement

Conflict of Interest

DD, SS, and AG declare financial interests in Theranautilus. This biotechnology company is developing similar technology for medical applications. The remaining author declares no competing financial interests.

Figures

Figure 1
Figure 1
a) Schematic showing the anatomy of a typical human tooth. The pulp is cleared during the root canal treatment procedure, forming a cavity in the central canal and exposing the dentine tissue. The dotted lines represent the cross-section plane. b) (Upper panel) Image of a representative sample used in our experiments. Scale bar represents 5 mm. (Lower panel) Schematic representation (not to scale) of the cross-section of a human tooth. The central canal is shown in black and a model of a single dentinal tubule is shown. Persistent bacteria at the depths of the tubule are shown as green oval shapes.
Figure 2
Figure 2
a) Schematic showing a triaxial Helmholtz coil similar to the coil setup used for experiments. b) Various snapshots from a movie where the bot was maneuvered forward and backward through a dentinal tubule. The scale bar represents 10 μm. c) A longitudinal view of the dentine tissue where the nanobot was driven ≈1000 μm inside the depth of the tubules as measured from the entrance at the central canal.
Figure 3
Figure 3
a) Schematic showing the distribution of nanobots under an oscillating field. The direction of oscillation is perpendicular to the cross-section plane, as shown by the red cross and dot markers. b) Schematic showing the mechanism of motion of nanobots under the influence of oscillating field near a surface. c) Maximum intensity projection of 100 confocal slices showing the distribution of nanobots under an oscillating field. The scale bar represents 500 μm. d) Schematic showing the experimental procedure followed to demonstrate retrieval of nanobots. In Step 1, nanobots were subjected to an oscillating magnetic field to drive them randomly inside dentinal tubules. In Step 2, a rotating magnetic field was applied along a single direction to empty a sector of the tooth. e) Maximum intensity projection of 150 confocal slices showing the distribution of fluorescent nanobots. The empty space at the lower right corner shows the area from which nanobots were retrieved. The scale bar represents 500 μm.
Figure 4
Figure 4
a) Simulated distribution of nanobots traveling at different velocities through the dentine. The experimental value best matches the simulated velocity of 3.6 μm s−1. b) Spatial distribution of the nanobots after 8 min for experiment and simulation.
Figure 5
Figure 5
a) Series of images where dead bacteria (stained in red) are near nanobots, which act as a localized heat source when subjected to magnetic hyperthermia. Green indicates live bacteria, which express the green fluorescent protein. Scale bars represent 5 μm. b) Maximum intensity projection showing selectivity in bacterial death inside dentinal tubules. Bacteria were allowed to move inside tubules in all directions. Nanobots were driven along a single direction using a rotating field, following which the sample was subjected to magnetic hyperthermia. Bacterial death is observed along a band in the center where more bacteria were stained red. Scale bar represents 100 μm.
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