Stem Cell Dentistry: Revolutionizing Visits to the Dreaded Dentist’s Chair

Gummy Teeth. Credit: 'Sweets' by sophiea is license under CC BY 2.0, image modified by Sophie Arthur.

How does going to the dentist make you feel? A trip to that dreaded dentist’s chair makes many people extremely anxious and nervous. For some, the thought of it is just simply petrifying! Are you one of those people? What if there was a new scientific discovery that could one day help patients with their dentist-associated phobias?

 

Can you imagine a trip to the dentist to treat a cavity that didn’t involve a filling, a root canal or dentures? What if there was a way that we could encourage your teeth to repair themselves? ‘Stem cell dentistry’ could revolutionize your future trips to the dreaded dentist’s chair after recent scientific breakthroughs – regenerative stem cell fillings and growing new teeth from scratch using stem cells!

 

All living things are made up of cells. In fact, there are over 200 different types of cells throughout the organs and tissues of your body. But living amongst them are some incredibly special cells called stem cells. There are two key facts about stem cells that makes them special – they can make identical copies of themselves and they can turn into any type of cell in your body. This gives stem cells an amazing ability to be able to help build, repair and heal our bodies, and is the reason why researchers are fascinated by them and their potential in future medicine. Stem cells come in two different types called embryonic and adult. Embryonic stem cells can become any cell type in your body, whereas adult stem cells are slightly more restricted in the cell types they can turn into. For example, adult stem cells found in the heart can turn into all the cell types that you might find in the heart, but they can’t make bone cells, or any other cell types in fact, and vice versa! Embryonic stem cells, though, could make both heart and bone cells and more!

 

You can even find stem cells in your teeth! Teeth are divided into two anatomical parts – the crown which is the part covered in enamel and visible in your mouth, and the root which anchors your tooth to its bony socket and usually can’t be seen. Underneath the enamel, you find the dentine. This makes up the bulk of the tooth and is the reason for sensitivity if it becomes exposed as a result of tooth decay. Finally, right in the middle of your tooth is the pulp, which contains all the blood vessels and nerve endings that supplies the tooth. This is, also, where we find the tooth’s adult stem cells called dental pulp stem cells (DPSCs).

 

Basic structure of the tooth. Credit: K.D. Schroeder, Diagram of a healthy human molar showing the enamel, cementum, pulp, and dentin which make up the structure, as well as the surrounding tissues from Wikimedia Commons is licensed under CC-BY-SA 4.0, adapted by Sophie Arthur

Dentists fill millions of cavities every year as a result of tooth decay to protect the now exposed dentine from further harm, but sometimes fillings fail due to the loss of the connection between tooth and filling, which allows saliva and bacteria into the exposed dentine causing further damage, or because some decay still exists beneath the filling. If the decay is so bad that the pulp is exposed then dentists may need to perform a root canal. Dental pulp may be damaged by a bacterial infection from the bacteria found naturally in your saliva invading into the exposed pulp. The pulp begins to die which allows the bacteria to multiply and spread. So, in a root canal, your dentist needs to remove all the infected tissue from your dental pulp, which can be extremely painful as all your nerves and blood vessels are found in that layer. Once the infection is removed, the root canal is filled and sealed with a filling.

 

Fillings are, also, subjected to general ‘wear and tear’ and could fall out due to excessive pressure whilst eating something too hard for example, so often need to be replaced or refilled with the added expense of money and time, which is why we need to look for possible alternatives to root canals and fillings. Researchers from the University of Nottingham and Harvard University are trying to solve this problem by encouraging teeth to repair themselves. In a recent press release [1], University of Nottingham’s Dr Adam Celiz stated that ‘Existing dental fillings are toxic to cells and are therefore incompatible with pulp tissue inside the tooth. In cases of dental pulp disease and injury, a root canal is typically performed to remove the infected tissues. We have designed a synthetic biomaterial that can be used similarly to dental fillings but can be placed in direct contact with pulp tissue to stimulate the native stem cell population for repair and regeneration of pulp tissue and the surrounding dentin’.

 

Their newly developed biomaterial claims to allow a damaged tooth to generate a new protective layer of dentine by itself. The DPSCs found naturally within your tooth would be stimulated, by biologically active factors called growth factors released by the biomaterial, to grow and turn into new dental-specific cell types such as ameloblasts and odontoblasts which would create the new protective enamel and dentine layers. As described by David Mooney, Professor of Bioengineering at the John Paulson School of Engineering and Applied Science at Harvard [1], ‘these materials may provide an effective and practical approach to allow a patient to regenerate components of their own teeth’ and so, this biomaterial could help revolutionize the treatment of dental cavities by helping the tooth prevent infections and create integrated, natural, long-term fillings. This research has already impressed and was awarded second prize in the ‘Materials’ category of the Royal Society of Chemistry’s ‘Emerging Technologies Competition 2016’ [2].

 

Unfortunately, it’s not as simply as it sounds! The introduction of biomaterials into clinical practice would require a lot of technical care after lots of time-consuming clinical trials to rule out any side effects for example, and is a highly regulated process as adding an unnatural compound into the human body requires ethical approval and also requires regulations defining the storage and use of these biomaterials. Yet, Mooney’s team claims to have created another technique that could streamline this process and produce a clinically viable option much more quickly by using lasers to stimulate the DPSCs. The study published in the journal Science Translational Medicine [3] describes drilling holes into a rat model’s molars to mimic tooth decay. DPSCs were applied to the exposed pulp and a laser was used to activate the growth factors and therefore the stem cells, much like in the biomaterial. Teeth were sealed with a temporary cap for the next 12 weeks and follow-up x-rays showed the dentine layer had started to grow back in response to the stem cell/laser treatment.

 

Mooney stated that the ‘treatment does not introduce anything new to the body, and lasers are routinely used in medicine and dentistry, so the barriers to clinical translation are low’ [4]. Regenerating teeth instead of replacing them could see an incredible advance in the dentistry field, where human trials for this restorative dentistry hope to start soon. Although the stem cell/laser treatment could be seen in the dentist’s surgery much sooner than the biomaterial, there is still no evidence of the long-term effects of either of these options, so it might be that we have to wait that bit longer to see biomaterials in the clinic if there are greater long-term benefits.

 

But what if the problem is more serious and your tooth has to be removed completely? At the moment your only option would be to get dentures or implants right? These options come with their own drawbacks where dentures could become loose causing discomfort, difficulty chewing and even infections, whereas patients needing dental implants require surgery, regular maintenance and dentist’s appointments which just gets more and more expensive! A team of scientists from Columbia University’s College of Dental Medicine may have introduced an alternative option – one which eliminates those disadvantages. Dr. Jeremy Mao and his colleagues at Columbia’s Tissue Engineering and Regenerative Medicine Laboratory have pioneered a new technique that involves attaching a 3D bioprinted scaffold infused with those stimulating growth factors again to the empty tooth socket. Using the same scientific basis of using growth factors to stimulate stem cells to turn into dentine cells, this techniques draws stem cells towards the scaffold and can yield an anatomically correct tooth that is the perfect fit for each patient in as little as nine weeks after implantation into the mouth, which is a huge improvement over regular implants which could take as long as 18 months from start to finish – but at the moment these implants have not been tested in humans [5]. In addition to growing a naturally compatible tooth, this new method eliminates the need to harvest the stem cells or grow the implant in the lab and then implant a fully formed tooth, as your body does all the work for you, together making a more effective, cheaper and natural tooth replacement!

3-D printed scaffold used to attract stem cells and grow replacement teeth. Credit: Dr. J. Mao, Columbia University Medical Center, permission to re-use granted from Columbia University Medical Center Media Relations team on November 1, 2016

Gone could be the days of fillings, painful root canals, irritating dentures and agonizing implants with these new technological advances, all thanks to the promise of stem cells. These less invasive procedures could reduce recovery times and reduce dental treatment costs, whilst making your experience at the dentist that little bit more relaxing!

 

Can you imagine a trip to the dentist to treat a cavity that didn’t involve a filling, a root canal or dentures now? While it’s highly likely that these treatments won’t be available to you for a while yet, stem cell dentistry could one day be the answer to your fears of the dreaded dentist’s chair.

 

Sophie Arthur
Twitter: @SophArthur
Website: https://sophtalksscience.wordpress.com/
Guest Contributor, Signal to Noise Magazine
PhD student, Stem Cell Metabolism, University of Southampton

 

References:

[1] Cass, L. Fillings that heal your teeth – how regenerative medicine could change your visit to the dentist, https://www.nottingham.ac.uk/news/pressreleases/2016/july/fillings-that-heal-your-teeth.aspx (2016).

[2] Emerging technologies competition: Previous winners, http://www.rsc.org/competitions/emerging-technologies/previous-winners/#2016-winners (2016).

[3] Arany, P. R. et al. Photoactivation of endogenous latent transforming growth factor–β1 directs dental stem cell differentiation for regeneration. Sci Transl Med 6 (238), doi:  10.1126/scitranslmed.3008234 (2014).

[4] Kusek, K. Researchers use light to coax stem cells to repair teeth, http://www.seas.harvard.edu/news/2014/05/researchers-use-light-to-coax-stem-cells-to-repair-teeth (2014).

[5] Kim, K., Lee, CH., Kim, B. K. & Mao, J. J. Anatomically shaped tooth and periodontal regeneration by cell homing. JDR 89 (8), 842-847, doi: 10.1177/0022034510370803 (2010).