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Interview: "Nanoparticle irrigation: more than canal disinfection." Dr Anil Kishen

This interview in Endodontics covers Dr. Anil Kishen's vision for balancing clinical excellence and cutting-edge research. (Image: Dr. Anil Kishen)

Sat. 18 January 2025

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This month, Dental Tribune South Asia features an exclusive interview with Dr. Anil Kishen, a globally renowned endodontist and professor with expertise in endodontic microbiology, root canal disinfection, biomechanics, and tissue engineering. Based in Toronto, Canada, Dr. Kishen is a prolific researcher and author who focuses on innovative, minimally invasive solutions to improve endodontic outcomes.

Dr. Anil Kishen, can you share your journey in Endodontics and what motivated you to specialize in this field? What key moments shaped your career?

As a dentist, I often encounter patients who are hesitant to lose their natural teeth. To address this concern, I specialise in Endodontics and Conservative Dentistry, aiming to save natural teeth and alleviate dental pain for my patients. Pursuing my postgraduate programme (Master of Dental Surgery) at the Government Dental College in Chennai was a pivotal moment in my career. Dr Parameswaran, who was the Head of the Department at that time, recognised my potential for research and encouraged me to collaborate with professors in Biomedical Engineering at the Indian Institute of Technology, Madras (IIT-M). Engaging in research activities with colleagues from IIT-M was a transformative experience. It deepened my understanding of fundamental research and helped answer many questions I had as a clinician.

You’ve made significant contributions to the field of Endodontics. Could you elaborate on some of your most impactful research or clinical work?

My contributions to Endodontics may be divided into two main streams: basic science knowledge and clinical applications.

In the basic science stream, I have published research on dentin biomechanics, hydromechanics in dentin, and fracture resistance mechanisms in intact teeth. My lab was one of the first research groups to characterise Enterococcus faecalis biofilm, exploring its potential to mineralise and degrade dentin matrix. We were also the first to demonstrate that E. faecalis biofilm bacteria can internalise within macrophages and remain viable for extended periods. Recently, my lab has focused on developing multicellular tissue graft (or organoid-type) models to study cellular-level interactions in wound healing.

In the clinical application stream, I have contributed to antimicrobial photodynamic therapy and have published extensively on developing and applying bioactive engineered chitosan-based nanoparticles for endodontic use. I am currently interested in applying these concepts to heal other chronic wounds in the body. Over the past few years, we have conducted clinical trials and assessments of nanoparticles for wound healing, and the findings have been very promising and encouraging.

Your research into nanoparticle-based disinfection methods has garnered significant attention. Could you explain how nanoparticles, particularly silver nanoparticles, are changing the landscape of biofilm management in root canal treatments? What led you to explore this innovative approach?

Endodontic treatment presents several challenges. Instead of developing multiple strategies to address each issue, I began to question why we don't have a single treatment approach that can effectively tackle various problems.

One appealing aspect of the nanomaterial research in my lab is that these materials are tunable biomaterials, meaning their physical and chemical properties can be adjusted to enhance specific biological activities.

To date, we have created innovative products that range from providing rapid relief for dentin sensitivity to promoting the healing of chronic wounds.

Your research also focuses on the immune-modulatory effects of nanoparticles in dental tissues. How do you see these findings contributing to both preventive and regenerative strategies in Endodontics, particularly in complex cases like apical periodontitis?

The balance between pro-inflammatory and anti-inflammatory immune responses significantly influences the progression of diseases. This balance determines whether a condition is symptomatic or asymptomatic, whether it causes low or high levels of tissue damage, and whether it leads to regeneration or repair. The immune system protects host tissue from microbial threats, requiring an appropriate response to restore homeostasis without triggering excessive inflammation, which can impede normal wound healing.

Immune-modulatory materials play a crucial role in adjusting immune responses to enhance tissue repair and regeneration. Traditionally, our treatment strategy for apical periodontitis has focused on reducing microbial load to enable host cells to initiate wound healing. However, this healing process has been observed to be delayed and less predictable histologically. The use of immune-modulatory nanoparticles in treating apical periodontitis may not only help eliminate bacteria but also support more consistent histological wound healing. I believe these materials are ideal for regenerative endodontic procedures.

Who were the key mentors or figures that have influenced your career, and how have they shaped your philosophy and approach to Endodontics?

Several mentors have contributed to my education and career over the last three decades. I will list some of the very significant people.

The first person is Professor Parameswaran from the Madras Dental College. He was the first person to identify my academic and research potential. He gave me a lot of freedom to participate in research activities in collaboration with the Indian Institute of Technology Madras (IIT-M). Balancing six days of busy outpatients in Madras Dental College, significant clinical lab work, and didactic activities with research at IIT-M was challenging during those days. Dr Parameswaran's unwavering support and encouragement were pivotal during the formative stages of my career.

The next person is Professor Asundi from Nanyang Technological University. I believe I was the first dentist and endodontist to receive an offer for a PhD scholarship at the School of Mechanical and Production Engineering, which is now known as the School of Mechanical and Aerospace Engineering. I am grateful for the trust placed in my abilities and for the belief in my determination to succeed. It was not an easy step for someone with a dentistry background to conduct doctoral-level research and pass graduate-level engineering courses at Nanyang Technological University. Professor Asundi's faith in my abilities to pursue an intense PhD in Biomedical Engineering was crucial at that stage of my career.

The third person on the list is Dr Shimon Friedman and Dr Calvin Torneck. I was invited for the first time to lecture at the Dentsply Key Opinion Leaders Forum in 2007. Dr Friedman met me for the first time at that meeting. After a long conversation, he invited me to the University of Toronto to lecture for his residents; the rest is history. At the University of Toronto, Dr Friedman granted me the freedom to teach in graduate programs, undergraduate programs, and clinics. He recognised my strength in endodontic literature and assigned me several graduate-level seminars, asking me to serve as the course director for some graduate-level courses. I must mention that my research contributions are increasingly aligned with clinical Endodontics, primarily due to Dr Friedman’s influence. Dr Torneck is one of the few clinicians who have an extremely sound biological understanding of microbiology and disease processes. I have had numerous sessions of long hours of scientific discussions with him.

I must acknowledge Dr Gunnar Bergenholtz, Dr Craig Baumgartner, and Dr Sergio Kuttler. Their profound impact on my academic and personal growth has been invaluable, particularly during pivotal moments in my journey.

In your work on fracture predilection in endodontically treated teeth, you highlighted key structural vulnerabilities. What are some of the latest advancements in biomaterials that address these risks, and how do you envision these developments improving long-term treatment outcomes?

When restoring endodontically treated teeth, it is essential to recognize that their biomechanical response to functional forces differs significantly from that of intact teeth with vital pulp. However, clinically, we rely on restorative materials to enhance the mechanical integrity of root-filled teeth. As highlighted in some of my previous articles, various risk factors are associated with the dentin of endodontically treated teeth, which require attention.

In recent years, researchers have been exploring innovative biomaterial-based strategies to improve the mechanical integrity of dentin, an area known as dentin microtissue engineering. My lab has been at the forefront of this field. We are utilizing combinations of engineered nanoparticles in two phases, during disinfection and before obturation, to enhance the mechanical properties of the remaining dentin in root-filled teeth.

What is your vision for the future of Endodontics? How do you foresee the field evolving over the next decade, especially with advancements in technology and research?

Predicting the future is challenging, but I foresee significant advancements in the field. We can expect continued development in instruments, disinfection technologies, and biomaterials for pulp regeneration. Additionally, there will be a greater emphasis on minimally invasive endodontic treatments supported by advanced biomaterials. Artificial intelligence will contribute to diagnosis, case selection, prognosis determination, and improving treatment precision and efficiency. However, one of the main challenges will be making these advanced technologies cost-effective while securing regulatory approval.

Dr. Anil Kishen, could you share your detailed irrigation and disinfection protocol step-by-step for root canals with our readers? Given your extensive research into nanoparticle-based irrigants and biofilm management, it would be insightful to know how you integrate these advanced technologies into your clinical practice. Your insights into combining cutting-edge research with practical clinical applications would provide valuable knowledge for clinicians worldwide.

Irrigation with a 6% sodium hypochlorite solution typically begins once an instrument is placed in the pulp space. I recommend applying 1 ml of irrigant into the canal each time the instrument advances 3–4 mm. After completing the canal instrumentation, perform a final irrigation of at least 5 ml using a syringe needle.

At this stage, it is crucial to ensure the needle's location is appropriate relative to the apical terminus of the root canal. In total, this process usually involves about 10 ml of irrigant per canal. Following the initial irrigation, it is important to use a pressure-based method for supplementary irrigation. Options for this may include ultrasonic or sonic-assisted irrigation, apical negative pressure, or manual dynamic irrigation. It is essential to consider and adjust your supplementary irrigation strategy according to the root and root canal morphology.

The nanoparticle-based treatment for endodontics aims to achieve several objectives beyond just disinfecting the root canal. These nanoparticles are designed to provide an antibiofilm effect in the uninstrumented areas of the root canal, enhance the fracture resistance of dentine, improve the interface between the tricalcium silicate sealer and dentine, and facilitate proper root canal obturation.

In a clinical setting, this application involves a two-step procedure: first, applying solutions containing nanoparticles and activating them along the entire length during root canal disinfection, followed by conditioning the root dentine prior to the obturation process.

How do you manage the balance between your clinical, research, and teaching responsibilities? What role does each aspect play in your overall professional fulfilment?

I chose to pursue an academic career because I find great joy in teaching clinical students, and I am deeply passionate about my research. These two goals beautifully complement each other and are vital for my fulfilment. While balancing these aspirations over the years has required many sacrifices and adjustments, I consider myself very fortunate to have embarked on this fulfilling journey.

To conduct high-quality studies, I require adequate infrastructure, including a laboratory, funding, and dedicated research students who share my enthusiasm. I have been fortunate to work with exceptional PhD students who have made significant contributions to my research objectives. I believe that high-quality research enhances my effectiveness as a teacher. It enables me to facilitate inquiry-based learning for my students and helps me break down complex concepts into simpler ideas for teaching.

In today’s fast-paced environment, it is essential for academics to continually update their knowledge. Therefore, being both a teacher and a funded principal investigator (PI) demands a significant time commitment.

I take pride in my ability to effectively plan my work schedule and allocate time for my tasks.

I categorise my goals into short-term and long-term objectives. One helpful tool I learned several years ago is the Eisenhower Matrix, which I find particularly useful for managing additional administrative responsibilities.

Can you share with us a bit about your family and how they have supported or influenced your professional journey?

I am married to Arunthathi, who manages to keep our home together while balancing her work responsibilities. I truly appreciate all she does. We’re proud parents of two sons. Our elder son, Abinav, has just graduated from university and has entered the workforce, which is a big step for him. Our younger son, Aaryan, is currently navigating the challenges of secondary school. It’s a busy time for all of us, and we’re doing our best to support each other along the way.

What advice would you give to young and aspiring Endodontists who wish to make meaningful contributions to both clinical practice and academic research?

In my opinion, aspiring endodontists should concentrate on five key areas to make significant contributions to both clinical practice and academic research:

  1. Establish a strong research foundation. Begin by building a solid understanding of research principles and methodologies.
  2. Select an effective mentor. Choose a mentor who can guide you and provide valuable insights throughout your career.
  3. Cultivate a network of collaborators. Building relationships with fellow professionals can enhance your opportunities for collaboration and growth.
  4. Balance clinical practice and academia. It’s important to find a suitable equilibrium between your work in clinical practice and your academic pursuits.
  5. Maintain your passion. Stay passionate about your field, as enthusiasm will drive your commitment.

Your top 3 journal recommendations in Endodontics?

  • Journal of Endodontics
  • International Endodontic Journal
  • Dental Traumatology

Your top 3 book recommendations in Endodontics?

  • Pathways of the Pulp
  • Ingle’s Endodontics
  • Endodontic Advances and Evidence-Based Clinical Guidelines

If you could leave one lasting message for Endodontists around the world, particularly those in emerging regions like South Asia, what would that be?

I encourage early development of independent research skills in their careers, as this will help them balance clinical practice with academia. Collaborating with other researchers and clinicians can provide fresh perspectives and enhance their clinical skills. Additionally, sharing their work by publishing in reputable journals and presenting at conferences is an excellent way to build their reputation and connect with others in the field.

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