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PHILADELPHIA, US: New developments in small-scale robotics and nanotechnology offer previously unimagined opportunities for new diagnostic and therapeutic approaches. In testing the use of microrobots for endodontic applications, researchers from the School of Dental Medicine at the University of Pennsylvania and from its Center for Innovation and Precision Dentistry have found that the robots were able to access difficult-to-reach root canal surfaces, disrupt biofilm, retrieve samples for diagnosis and even deliver drugs.
The main cause of endodontic treatment failure is incomplete root canal disinfection, resulting in endodontic infections and periodontitis. One of the reasons for this is the complex anatomy of the root canal system, making effective biofilm removal difficult, and up until now, means of diagnosing and evaluating disinfection efficiency have been limited.
The microrobotic system used in the current study is the result of an ongoing collaboration between the dental school and the university’s School of Engineering and Applied Science. In a previous study, the collaboration produced a microrobotic system consisting of nanoparticles that can not only brush but also floss and rinse teeth in a single step, helping to effectively eliminate biofilm from teeth.
Effective and precise guidance of microrobots
The researchers developed and tested two different microrobotic platforms in their recent study. For both, they used iron oxide nanoparticles (IONPs), which share catalytic and magnetic properties, as building blocks for the microrobots.
When asked about the biocompatibility and safety concerns for patients, co-author Prof. Hyun Michel Koo of the Department of Orthodontics at Penn Dental Medicine, replied: “IONPs are widely used in nanomedicine due to their minimal cytotoxicity, excellent physicochemical properties, stability in aqueous solutions and biocompatibility. Several IONP formulations have already been approved by the US Food and Drug Administration (FDA) for parenteral administration as treatment of iron deficiency anaemia.”
He added, “Our previous histopathological analysis of gingival, mucosal and other tissues, including major organs such as the liver and kidney, showed no signs of harmful effects, indicating high histocompatibility of both in-house and FDA-approved IONP formulations.”
To evaluate the effectiveness of the endodontic microrobotic platforms, the researchers conducted experiments using 3D-printed tooth replicas prepared with a biofilm containing four different endodontic bacterial species.
For the first platform, using electromagnets, the research team concentrated the IONPs in micro-swarms and magnetically controlled them to disrupt and retrieve the biofilm. Analysis of the collected sample found all four bacterial species. In addition, under the microscope, all nanoparticles appeared to have been removed from the root canal.
For the second platform, the research team 3D-printed miniaturised helix-shaped robots and filled them with an IONP-embedded gel. They then guided the robots within the root canal using magnetic fields and observed that they disrupted the biofilm chemically and mechanically with high efficiency. Especially noteworthy is the possibility of loading the helix-shaped robots with therapeutics for targeted drug delivery at the apical region of the root canal, where infection is in close proximity to the surrounding tissue.
“The key limitations of current endodontic strategies are threefold: lack of precision in targeting biofilms infecting the apical region and anatomical complexities of the root canal, as well as the difficulty of retrieving biofilm samples for diagnosis. To the best of our knowledge, there does not exist an approach capable of simultaneous sample retrieval and antimicrobial treatment in endodontics,” commented lead author Dr Alaa Babeer from Penn Dental Medicine, on the relevance of the study findings for endodontic treatments.
“Our findings demonstrate the feasibility of using the versatility of microrobotics to access difficult-to-reach endodontic surfaces to perform biofilm killing, removal and retrieval for microbial detection in real time. Furthermore, we demonstrate the feasibility of robot tracking inside the canal using current clinical imaging modalities,” he continued.
Future fields of application and further research
The researchers envision a broad range of application for the microrobots in dentistry and general medicine. According to Prof. Koo, IONP microrobots could combine several functionalities in dentistry. These include automated, hands-free brushing and flossing for effective removal of dental biofilms, which can be helpful for persons with disabilities or lacking manual dexterity to perform good oral hygiene, he said.
Based on the results of the current study findings, Prof. Koo expects microrobotic platforms “to allow precision-guided therapies to disrupt biofilms in difficult-to-reach spaces and promote soft-tissue and bone regeneration”. He added that microrobots could perform delivery of drugs or living cells in different oral and craniofacial sites, ranging from deep periodontal pockets and the apical region of the root canal to temporomandibular spaces to promote healing.
For biomedical applications, Prof. Koo noted that “magnetically controlled microrobots have shown diverse applications, including anti-cancer therapy, targeted drug, gene and stem cell delivery, and minimally invasive surgery”.
The study authors stated that future research may expand the possibilities for robotic application even further to the detection, treatment and removal of biofilms associated with other infectious diseases and biofouling of dental and medical devices or implants.
The study, titled “Microrobotics for precision biofilm diagnostics and treatment”, was published in the August 2022 issue of the Journal of Dental Research.