With its irregularities and anatomical complexities, the root canal system is one of the most clinically challenging spaces in the oral cavity. As a result, biofilm not completely removed from the nooks and crannies of canals remains a major cause of treatment failure and persistent endodontic infections, and the means to diagnose or assess the effectiveness of disinfection are limited. One day, clinicians may have a new tool to overcome these challenges in the form of microrobots.
In a proof-of-concept study, researchers from Penn Dental Medicine and its Center for Innovation & Precision Dentistry (CiPD) showed that microrobots can access hard-to-reach surfaces of the root canal with controlled precision, treating and disrupting biofilms and even retrieving samples for diagnosis, allowing for a more personalized treatment plan. The Penn team shared their findings on the use of two different microrobotic platforms for endodontic therapy in the August issue of Journal of Dental Research ; the work was selected for the cover of the issue.
“The technology could enable multimodal capabilities to achieve controlled and precise targeting of biofilms in hard-to-reach spaces, obtain microbiological samples, and perform targeted drug delivery,” says Dr. Alaa Babeer, author principal of the study and specialist at Penn Dental Medicine. Doctor of dental sciences (DScD) and graduate in endodontics, who is now in the laboratory of Dr Michel Koo, co-director of the CiPD.
In both platforms, the building blocks of the microrobots are iron oxide (NP) nanoparticles that have both catalytic and magnetic activity and have been approved by the FDA for other uses. In the first platform, a magnetic field is used to concentrate NPs into aggregated microswarms and magnetically control them in the apical area of the tooth to disrupt and recover biofilms through a catalytic reaction. The second platform uses 3D printing to create miniaturized propeller-shaped robots embedded with iron oxide NPs. These helicoids are guided by magnetic fields to move through the root canal, carrying bioactives or drugs that can be released in place.
“This technology has the potential to advance clinical care at various levels,” says Dr. Koo, co-corresponding author of the study with Dr. Edward Steager, principal investigator at Penn’s School of Engineering and Applied Science.
“An important aspect is the ability to have diagnostic and therapeutic applications. In the microswarm platform, we can not only remove the biofilm, but also recover it, allowing us to identify microorganisms that have caused the infection. Additionally, the ability to conform to tight, hard-to-reach spaces in the root canal allows for more effective disinfection compared to files and instrumentation techniques currently in use.”
A collaborative system
This microrobotics system is the culmination of years of collaborative work between Penn Dental Medicine and Penn Engineering. In a recent separate study, Dr. Koo and colleagues built the platform to electromagnetically control microrobots, in this case allowing microswarms of iron oxide NPs to adopt different configurations and release antimicrobials on the spot. to effectively treat and eliminate dental plaque.
“We see potential applications of microrobotics systems for oral care at home as well as in the dental office for more precise and efficient tools for clinicians,” says Dr. Koo.
To determine the effectiveness of endodontic microrobotic systems in disrupting and recovering root canal biofilm, researchers conducted experiments on vertically placed 3D printed tooth replicas in collaboration with Dr. Bekir Karabucak, Chairman of the Department of Endodontics at Penn Dental Medicine. A mixed biofilm containing endodontic bacteria (Streptococcus gordonii, Enterococcus faecalis, Nucleated Fusobacteriaand Actinomyces israelii ) was prepared inside the replica teeth and the NP suspension was introduced into the root canal. Using electromagnets, microswarms of NPs were created and precisely controlled to disrupt the biofilm. Upon analysis of the collected biofilm, they found that all four species were detected and, using a microscope, all nanoparticles appeared to have been removed from the root canal.
Break the mold
The second system tested exploits the flexibility of iron oxide NPs as building blocks and involves the creation of a molded robotic system. Flexible corkscrew molds in the shape of a helicoid (two helices wrapped around a central axis) were 3D printed and filled with an NP-embedded gel. Using a magnetic field, the helicoids were shown to move through the channel with high efficiency to achieve chemical and mechanical disruption of the biofilm. Of particular note is the added ability to load the helicoids with therapeutic agents for targeted drug delivery to the apical region of the root canal where the infection is in close proximity to surrounding tissue.
Additionally, the research team demonstrated the unique ability to track microrobots in real time using existing imaging technologies such as intraoral scanner, dental X-ray, and cone-beam computed tomography, capable of locate the helicoids in the intact dental canal. .
“Most importantly, we demonstrated in an ex vivo model that the robots could be controlled by the magnetic field without interruption by the soft and hard tissues surrounding the teeth. In addition, they showed tremendous maneuverability from the top to the bottom of the canal,” notes Dr. Karabucak, who explains that the magnetic field of the two endodontic systems tested would be generated by a small device in the oral cavity.
Besides the potential for improving endodontic treatment and tissue regeneration, researchers see this technology as something that could have broad applications in medicine and industry.
“From disinfecting medical devices like catheters to ensuring clean water lines, this technology has the potential to transform fields far beyond dentistry,” adds Dr. Koo. “This could disrupt current modalities across all disciplines.”