3D Tissue Models and Novel Approaches for Dental Tissue Infection Management and Repair

The 2024 Edward Leo Sheridan Memorial Lecture was delivered to the RCSI Faculty of Dentistry’s Annual Scientific Meeting by Professor Alastair Sloan of the University of Melbourne.

Professor Sloan obtained his BSc (Hons) in Biomedical Sciences from the University of Wales in 1993 and his PhD in Oral Biology and Pathology from The University of Birmingham, UK in 1997 in the Faculty of Medicine and Dentistry. Following postdoctoral research, he was appointed to a Lectureship in Oral Biology at the School of Dentistry in The University of Birmingham in 2000.

In 2005, he moved to the School of Dentistry, Cardiff University and was awarded his personal chair in 2012. He was Head of Oral and Biomedical Sciences at the School of Dentistry between 2010-2015, Director of International (2012-2015) and Director of Research (2015-2017). Between 2015-2017 he was Chair/Director of the Cardiff Institute for Tissue Engineering and Repair (CITER), a cross-University research network.

Professor Sloan was appointed Head of School in 2017, a post which he held until January 2020 when he relocated to The University of Melbourne to take up his present role as Head of School of the Melbourne Dental School.

He is a Fellow of the Higher Education Academy and a Fellow of the Royal Society of Biology (FRSB). In 2020 he was elected Honorary Fellow of the International College of Dentists (FICD) and in 2021 awarded an Ad Eundem Fellowship of the Faculty of Dentistry Royal College of Surgeons, Ireland in recognition of his contribution to dental education and research. He was the recipient of the 2021 International Association for Dental Research Distinguished Scientist Award, The Isaac Schour Memorial Award for his research programmes in tissue engineering and stem cells.

Professor Sloan’s research is multi-disciplinary and in the broad field of mineralised connective tissues. He is interested in the reparative potential and behaviour of the dentine-pulp complex and bone, specifically the potential therapeutic manipulation of the dental pulp stem cells (DPSCs) and the cellular and molecular responses of these cells to natural biomatrices and compromised biological environments to understand their functional behaviour during tissue injury.

Complimentary to this work he is also interested understanding the heterogeneity within dental pulp progenitor populations and their function in 3D environments in vitro. In addition, he is interested in the potential therapeutic roles of these DPSCs
in the wider context of regenerative biology.

His research is also focused on understanding the dentinogenic and osteo-inductive properties of dentine and bone matrices to facilitate novel tissue engineering methodologies and natural regenerative processes and is related to the development of novel clinical therapies and methods in relation to dentistry and orthopaedics regarding tissue regeneration and repair. Directly related to this, his research is also focused on understanding bacterial invasion and attachment in dental and bone infections and development of novel antimicrobial carriers/restorative materials for clinical endodontics and orthopaedics.

His group have established liposomal nanocarriers for antimicrobial delivery and prototype restorative materials and model systems to better understand the nature of the bacterial / pulp environment during pulpal infection. He also has a long standing interest in developing novel in vitro/ex vivo organ 3D culture model systems for mineralising tissues to provide innovative models for tissue regeneration/engineering and testing of novel therapeutic agents and advancing the 3Rs (reduction, replacement refinement)
in biomedical research and bioengineering.

Read Professor Sloan’s lecture in full here:

Thank you very much indeed and thank you for the honour of delivering this very prestigious lecture. I hope to be able to have a very clear conversation with you despite 23 and a half hours of traveling, despite the very best challenges of modern travel, it still takes quite a long time to get from Melbourne to London and then on to Dublin. But I’m delighted to be here, and it’s an honour to be able to speak at this lecture. Before we start, I better just tell you a little bit about what my lab does. What do I do? Because, as your dean mentioned, I’m a I’m a bio engineer, a tissue engineer by background, with a PhD in that subject from the Faculty of Dentistry at the University of Birmingham in the UK. And my lab does a number of different things. We work in a whole range of different areas. And we work in in areas of tissue repair, tissue regeneration. We work with a number of different tissues, hard tissues, dermal skin tissues, mucosal tissues, stem cells, and of course, working with our colleagues in oral surgery, but also in orthopaedics, working with implants and biomaterials, always being led by the next need for clinical need, but also what patients and our surgical colleagues actually want us to look at.

But most of my career has been looking at the tooth, because it’s a remarkable organ. It is one of the few organs that has the capacity for almost direct tissue repair and tissue regeneration, something we’ve known about for about 30 years now, since I started my PhD back in the early 1990s we know that the tooth itself, whatever might happen, whether that be disease or trauma or what you as clinicians might do, has a direct response from the living part of that tooth, which, of course, is the dental pulp. Now, if you’ve got a mild stimulus. It could be a disease. It could be something that you’re doing. What happens quite naturally are the cells, the adult blast cells right at the periphery of that pulp, will that regulate its behaviour. They will start to secrete more dentine tissue, and they’ll do that in a very localized environment. And that is what is very unique about this organ and about the reparative capacity. It isn’t random, it isn’t uncontrolled. It is highly controlled and highly regulated into a very specific area. But if we have a stronger stimulus, so significant caries, for example, significant trauma, what we do know now, which we didn’t know back when I started my PhD back in the University of Birmingham with Tony Smith, was that we get death of these adult blast cells. They’re post mitotic, which means they don’t just keep dividing. Once they’re adult blast they are there. They are fixed. They are killed by inflammation, by bacteria, by surgical procedures, they are gone, but we now know that we get a generation of new cells. We call them adult blast like cells or new odontoblasts.

And these come from a population of dental pulp stem cells that we find within that pulp, but again, that repair that they will drive is highly specific. It is highly focused. And that’s been an area of research for me that’s kept me going for the near part of 30 years, because it’s quite fascinating about how this happens quite naturally. Because unlike aspects of orthopaedic surgery, aspects of cardiovascular surgery, you can tap into this very carefully as clinicians to try and drive this response if we understand the underpinning biology. If you look at the historical photograph here, it gives you indication of what goes on in such a compromised environment, you can clearly see the care is Densen here, and the dark strains of the microbes that are in those dentinal tubules. And you can see here that I’m pointing to this swathe of reparative dentine, this new densing. And then you’ve got these new odontoblasts cells at the bottom here. If you look at the extent of that disease that is a highly compromised tissue, significant oxidative stress, significant inflammation. You still got bacterial cells marauding down those tubules, but you have got a cell type here, a tissue that is resisting that infection and providing a barrier system between the infection and the pulp. And when we look at it, we see that it doesn’t look like normal density.

It used to be termed, 40 years ago, osteogeneses by the histologists of the day, and it probably is the best mark and the best name for it, but it’s very a tubular, very dysplastic. And that’s not a coincidence, because that dysplastic, a tubular dentine, prevents those bacterial cells progressing any further, very easily. They have to demineralize that dentine. So this reparative barrier is very specifically produced to prevent further infection and protect that living part of the tooth. Now if we understand what controls that, as a bio engineer, I can provide ways of trying to drive that clinically, whether that with new materials or new therapies, something for you all to work with.

But to do that, we need models. And I developed so many, many years ago as part of my PhD, and we’ve kept this work going for the last 30 years. 3d tissue models, organotypic culture models. Before the word organotypic was in vogue, of how we could grow dental tissue in the laboratory. And what we actually can do is we were doing this with we have here a rodent. We can take slices of the mandible, and we can grow slices of dental tissue in the laboratory. There we go. And this is what it looks like when you grow it. And we can keep these dental tissues living those cell.

The tissue itself, living for up to 28 days in the laboratory. That gives us time to do things to it. Gives us time to manipulate, time to add things to it. Time to understand what’s going on biologically within that pulp.

So I work backwards from where we started, because when we started has gone full circle, but one of the things I was very interested in was actually understanding the process of pulpits of infection in that pulp, because it’s not your classic infection where you get a lawn of bacteria growing onto a tissue. It’s a very controlled diseased process. And what we could do with our model system is we could actually inoculate and seed on our two slides on the tissue we’re growing in the lab, bacteria, bacteria of known pulpal disease, members of the strep anginosus group. If you seed strep anginosus and other family members of this bacterial species onto living pulp, you don’t get this broad spread of bacteria you just get bacteria growing as if your cultures have become infected. But when you seed the bacteria, what you can see is the bacteria invade the tissue.

What we have here are a chunk of H and E stain slides where we’ve actually got a control with no infection four hours post infection eight and 24 hours, and below, we’re looking actually at a UV light at fluorescent images of the same bacteria. So we’ve taken two slices. They’re both in the same sample, one looking at under a microscope, one we’re looking at under under a confocal and they’re snapshots of the confocal images, and we stain the bacteria before seeding with a fluorescent dye, fluorescent diacetate. That’s what FDA stands for. And what you can see are these bacteria form small, discrete, micro colonies, and they invade into the pulpal tissue that’s not the surface of the tooth that is about a millimetre and a half into that living tooth slice. So rather than growing randomly or forming a lawn as an infection would do in a lab, these bacterial species are anchoring onto something, and they are invading deep into the tissue.

We looked more closely when working with E FACA, which is the classic species that you will recover, usually from failed root endodontic procedures, and then the abscesses that you find there. What we noticed, and we went back to look at the strep anginosus, is that these bacteria, when you inoculate them on the tooth slice, have a very strong affinity to the pulpal vasculature when you’re preparing that slice of tissue for culture, what you have is a blood vessel system still in there. You may not have blood flow. You can mimic that with other bioengineering and bio culture ways of driving and mimicking that blood flow, but the blood vessels are still there, and what we tended to find is that those bacterial species would interact and have an affinity and an anchoring point with those blood vessels, and they would use those blood vessels to track down into the pulp.

So, we think we now understand the process of how this infection becomes highly controlled. We get initial seeding of the bacteria. There’s affinity with the blood cells and an affinity with the endothelial cells, and they use those blood vessels to invade and track down deeper into the pulpal tissue.

We also wondered, though this understanding of this could provide us the new way of treating a pulpal infection without having to go through a partial or a full pulpotomy. Could you deliver an agent? Could you deliver a nano material, or a nano agent that could actually drive at the point of infection, an anti-microbial response that could remove that infection to allow you to drive and practice more vital pulp therapy.

To do that, we just picked an exemplar, not one that we would move forward with. In fact, we’re not, but we used triclosan as an exemplar of an agent, because we knew from previous work that zinc, which up until recently, was an active constituent in Colgate toothpastes, has a very strong antimicrobial effect.

At the same time, I had a research fellow who’d just moved from the School of Pharmacy in Cardiff to join my group in the dental school, who’d been working with liposomes, sort of nano scale vesicles, where he was encapsulating in those vesicles gentamicin to actually create a more anti-microbial bone cement for orthopaedic surgery. And he just published his wonderful work with our colleagues in the School of Pharmacy, where you could take gentamicin, which you tend to find in the world of orthopaedics, comes with the actual cement. You mix it together to prevent infection at the point of cementing of a hip, but it creates voids in the cement, so you get non infective osteolysis, and you get essentially loosening of the joint. But if you put the actual gentamicin in a liposome, and you modify the surface of that phospholipid bilayer that makes up the liposome, you actually can get delivery of the antimicrobial without creating the voids.

So, we wondered whether we could use the same approach in our treatment of pulpitis. Now, liposomes aren’t anything new. They were developed some 25 years or so ago for delivery of chemotherapeutic agents in cancer. They went out of vogue, and about 10 years ago, came back into vogue, sometimes aligning with the work with this ongoing in the stem cell field around exercise, the vesicles. These are essentially synthetic vesicles. They’re about 10 to anywhere between 10 to 100 nanometres in size. We can make them in the laboratory quite comfortably. We can synthesize them. We can load them with a cargo of choice. We can deliver them pretty easily. And in this case, what we were doing were delivering liposomes to our two slice, the infected two slice.

The reason I were doing that was to see two effects. One, could we actually kill the bacteria? But also, could we mediate a host inflammatory response? Because when you infect the actual tooth tissue, if you look at the graph here, this is just a gene expression of some key markers. If you actually look at the expression of two strong cytokines here, TNF alpha and il one beta, when you infect our tooth slice with the bacteria, you get this really cracking host response, where we get up regulation in these inflammatory cytokines. And you can see we’ve got the actual bacteria growing in the two slice. If you had triclosan as a liquid, you don’t really get much of an effect. You get diffusion of the liquid through the two slice. You don’t get any dilution. You get a long you get a large dilution effect. You don’t get much antimicrobial efficiency, and you don’t get any knockdown of the inflammatory responses. But if you deliver the tricoz in our liposomal vehicles, we were seeing almost 100% bactericidal response of the bacteria growing on the two slice but a knock down almost to baseline levels of that host inflammatory response.

So we had a view then that we think we can modify or produce nano scale materials to put into either cements or into novel materials for clinical use that can control the infection and remove the infection in a dental pop to pave the way for what I would like to see, which is more vital pulp therapy and less endodontic work and root canal therapy. Apologies to those who may be endodontists in the audience and for a bit of fun, would you think, could we actually incorporate these liposomes into dental cements. And this was one quick look with a glass Ionomer, along with also looking at MTA. And the answer is, you can, you can mess about with the phospholipid bilayer at the liposome. You can alter the chemistry of that little bit to get dispersion in a glass Ionomer. And we can see that we can have a prototype antimicrobial glass Ionomer cement. That work, though, triggered more interest with colleagues, both in Cardiff, and then actually, when I moved down to Melbourne with our colleagues in engineering and bioengineering, because they were actually quite interested in the actual concept of taking extracellular vesicles, liposomes, or otherwise, for delivery at a point of infection, so targeted delivery of an antimicrobial peptide to control infection,

working with colleagues in the School of Chemistry at Cardiff, that’s continued since then, was to say, making antimicrobial cements is interesting. But what about things that can go into that pulp chamber, can go into that tooth and maybe also be injected into other areas, other joints, other parts of the body where you get targeted biofilms and targeted infection. So we were working with a thermos-responsive hydrogel as a carrier for our liposomes.

Things that you can form together that are safe for the body. Metha silos is our gel. When you inject it, it is a liquid. And when it hits 37 degrees, it becomes semi solid. And working with these gels, and this is just some graphs showing the properties of those gels, what you see is when you work with the gel, you add liposomes, liposomes with a cargo, liposomes without cargo.

You don’t really damage or alter any of the natural properties of the gel. It will still shear thin. You inject it. It becomes runny. You leave it at 37 degrees. It becomes more semi solid. And more importantly, it releases its cargo, and it releases its cargo up close and personal to the bacteria that comes into contact with it. And when looking at the actual antimicrobial effect against e faecalis or anginosus, we could see that we have liposomes with triclosan as our exemplar in our gel, and what we could see was release and a wonderful antimicrobial effect of the liposomes in the gel, compared to simply the liposomes on their own. So the carrier gives you the ability to target where the infection might be, and a very crude root biofilm, sort of culture system that we developed where we prepped human teeth and then cultured them in a broth with an infection of E for Carlis to mimic a failed root canal, you could see the biofilm forming quite quickly, but when you actually apply liposomes in our hydrogel, we see a remarkable bactericidal effect of those bacterial species. So on one hand, with the model systems we’ve got and understanding how the bacteria grow, we have an approach we think to control infection, because if you can control the infection and leave in place significant amounts of pulp tissue, you can regenerate that pulp. You can regenerate that tooth.

You’ve been doing it as clinicians for well over 80 to 100 years, especially if you were using calcium hydroxide many, many years ago, widely used, way back when I started my PhD for treatment of purple exposure, you were getting this dentine bridge formation. It was a wonderful classic regenerative biology response. Clinically had immense success, but nobody within us had the mode of action. Did it irritate the pulp? Did it cause a superficial necrotic layer? How did it stimulate that repair?

The answer the first two questions is no and no, it doesn’t cause a superficial necrotic layer, no matter you might have been told whether you are in practice or whether you’re at dental school back in the day, it absolutely does not, and it doesn’t irritate the pulp that much, much easier either. What it does is it solubilizes and releases growth factors, bioactive proteins that are actually trapped within the Densen that surround the pulp cavity, and it’s those growth factors that you find in dentine that stimulates the regenerative response.

Same happens in bone. Bone is also chock full of a cocktail of growth factors, and when you actually fracture your fracture your leg or your arm and you leave it alone, it will repair quite naturally, because those growth factors become released. The same happens in density and repair.

So, working with Leili Sadaghiani., now director of the BDS programme at Cardiff University, we were looking to say, if you used cavity echoes that you would normally use clinically, does that stimulate the release of growth factors? And the answer is, it does. We looked at three classic ones, CGF, beta, BMP, two and VEGF, why those three? Veg FX, it stimulates blood supply. You need a viable blood supply for any reparative process. TVF, beta, because it actually stimulates migration and proliferation of the dental pulp stem cell population. And BMP two, because BMP two will stimulate differentiation of the stem cells into in some depending on where you are in that pulp into a pulpal cell or into a mineralizing phenotype that can form more density. But what we found, and what lady found some years ago, was if you act for some ridiculous amount of time, you get release of growth factors and. At the right level of concentration, you would normally see if you’re actually doing this and looking at this clinically.

But more recently, in Melbourne, what we’ve done is to try and make that a little bit more clinically appealing. Can you act for 30 seconds and still see a release of these growth factors, effective release of these growth factors? And the answer is, we think we can. If you act for 30 seconds, 40 seconds a minute, you’re getting release of TDF, beta, VEGF and BMP two. You’re getting release of growth factors that will drive a reparative response in that dentine pulp. You don’t get any damage to the actual you still get the effect you want of etching of the density, which you can see on the SEL images here, but we get release of those growth factors.

And those growth factors that have been released also drives differentiation of your dental pulp stem cells into a more mineralizing phenotype, if you so wish. And that dentine matrix is powerful, and it’s there for you to work with. We can produce buckets of this with bucket chemistry. We can collect teeth under ethics, which we do from the clinics in Melbourne. And we can extract all these growth factors. We can create this dentine matrix preparation some 350, 380, different proteins in density, all of which modulates each other’s activity to drive the ideal reparative response. Hence, the photograph I showed at the start of that dentine, that reparative dentine being formed. But we can produce large amounts of this in the lab. We use it to dry and drive our experiments, but we can also do some very interesting things with it. It’s very powerful at very low concentrations. You don’t need that much of it if you to actually seed dentine matrix proteins in a collagen gel and then place stem cells in an insert.

It attracts those cells through into the gel. It’s really strong chemotactic process. It drives it through. So, the cells migrate from the insert into the gel. And if you leave it there for time, those cells will start to differentiate. So, we know the matrix has very strong chemotactic and differentiation potential, very biologically active.

We concede tissue engineering scaffolds with it. This was work done with our colleagues in Bergen, which is very interesting, where we’re taking silk spun scaffolds and pegylated scaffolds, so scaffolds that you would make in the lab for other aspects of bioengineering, creating a 3d structure with silk or with different polymers, and then we were coating that with dentine matrix proteins and seeding cells on that. Now, why would we do that? Well, if you want to put a scaffold into a piece of tissue to try and drive more repair, you want to know how those cells function, and we’re doing it because our colleagues in Bergen were more interested, actually, in craniofacial tissue repair and the dentine pulp stem cells are an easily accessible source of mesenchymal stem cells that are really important for driving bone repair. But when you put dentine matrix on these scaffolds, when you seed cells on there, the cells stop proliferating.

They stop doing what they were doing. They then start to differentiate, and they’ll start to secrete new proteins associated with mineralizing tissue. They will secrete anti-inflammatory cytokines. And you’ll start to see mineralizing tissue forming, which we can see on the stain here, on these scaffolds that we have on that figure there.

So actually, we can functionalise bio-engineered, or electro spun or these tissue engineering scaffolds that can be placed in different aspects of the body to drive a tissue repair. We can also place them in our liposomes. This was more for a bit of fun than a translational experiment, but you can actually have your cargo here in the middle of this, micelle. Here’s a phospholipid bilayer of your liposome. This is the middle of it. That’s where the density matrix proteins are solubilized. And when you actually place these in a cell culture, what you see is formation of mineralised tissue and mineralizing nodules, demonstrating the release of the proteins driving the cell differentiation. You can also see that the liposomes themselves had a chemotactic event. They attracted the cells to them very effectively.

So what you have clinically at your hands is a biological tissue that you can work with that will drive repair. And that means we need new materials that can work with that as well. And over the last few months, we’ve been developing a really strong relation.

Relationship with our colleagues in mechanical engineering, the Department of Mechanical Engineering, where we want to understand how new cements and new materials really work. Because if we understand that better, we can make materials that are far more biologically favourable to work with the biological systems that we have at our hands as well. So, in this case, we’ve started a long piece of work with SDI limited. SDI are a large dental materials company in Australia, based in Melbourne, where we are looking at chemistry informed computational modelling of how resin composites will function and perform so molecular dynamics is a simulation technique that’s very powerful. It accounts the chemistry of any sort of material that you’re working with. It also allows you to calculate the macroscopic and the microscopic properties of a material. It solves essentially some very hard sums, but it allows you to form equations to understand how a material will cure in situ and how it will function.

So, it allows the calculation of both statistical and dynamic behaviour aspects of a material, so such as a mechanical response, for example, mechanical response to a variety of loading types how it might interact with a biological material, such as dentine. And so what we’re doing, and you can see what this was, this figure here is showing is that the molecular dynamic simulation of a curing process in situ will allow us to predict how that material will function.

And this work has just started in Melbourne, where we are taking this through some very simple aspects of computational modelling all the way through to a design a modified generation two and three of the materials our industrial collaborator are producing, it provides, for the first time, the ability to understand, in real time, the chemical modifications that go on as you cure a material. And that’s important because you’re putting it into a living system, and the things that respond to that living system are the stem cells. I’ll leave you with three slides dental stem cells were not known when I started my career back in 1993 as a PhD student, they were first identified by Pam Roby and the team at NIH in 2000 but what they are a very powerful source of mesenchymal stem cells. We can extract those cells and grow them in the lab quite comfortably. We use a method where we seed them on a protein. And those stem cells are really quite interesting. And we asked ourselves once, what happens if you put them back into a pulp? How do you understand that reparative response that I spoke about at the very start of this lecture?

The cells behave differently because of their environment. Now direct your attention to A and A prime B and B prime A and B. This is 24 hours a snapshot of a confocal image, 24 hours after we have micro injected dental pulp stem cells into living pulpal tissue, a prime and B prime is seven days later. A and A prime, the cells are just into the pulp subsurface, hardly into that pulp at all. Pulps quite broken, quite open, not very dense, not a lot going on, not many blood vessels subsurface. Whereas B and B prime, the cells are deep into that pulp, high network of collagen, blood vessels, nerve fibres, cells.

The cells fluoresce green because they come from an animal that has a green report, a GFP, a green fluorescent protein tagged to a gene, a gene that when a cell dies, you lose a signal. You can follow the cells. What you can see here, you have 24 hours. The cells are sort of randomly moving around. And we can count each cell using MATLAB, a nice computer program, and each dot represents a cell. And that’s probably this area here is where the pulp dentine interfaces. And you can see these cells are migrating. After seven days, they’ve gone completely bananas, lots of proliferation of these cells, not what you would expect of a stem cell in the tissue, but when you put these cells deep into the pulp, what you find is those cells do not migrate very often or very far. Nor do they proliferate to the same extent. They’re not dying.

That tissue is not hypoxic in that area, but these cells are remaining quiescent, as they would do in a living pulp. So, when you are drilling, when you are prepared. Airing cavities when you’re going deep. My aim is to say, can you go deep into a cavity that allows the pulp to remain healthy, those stem cells to do its job, to produce more denting, to protect the pulp, and have a material that can fit into a deep cavity, the properties of which you know will respond well to the mechanical forces that we’ve got,

but the stem cells themselves can be useful for a range of other applications. They’re very resistant to oxidative stress. Think back to that image in my second slide of the reparative dentine process. Think about how carous that dentine was think about how compromised that pulp is going to be. Those cells still operate and function in that compromised environment, and they do so because, actually, they are very resistant to oxidative stress. They will resist within the culture here, so you collect them in hydrogen peroxide, and they will grow and grow and grow quite comfortably. And they will differentiate in that environment, their environment as well. And they produce a fair range of different oxidation sod, sod one, sod three, and a range of actual proteins that drive that oxidative stress resistance.

But also, they’re very resistant to infection. These cells can be very useful for broad aspects of craniofacial tissue repair. If you grow dental pulp stem cells with pigeon javalis, you grow any cell with pigeon javalis, pigeon to virus kills those cells, but not dental pulp stem cells. We can see here, but this is dental pop stem cells grown with and without P gin, Giovanni’s, and there’s no difference in cell viability or cell proliferation.

Why is that? This is just initial data that’s come from our lab in the last couple of weeks. But we look at the secretor and what the cells produce? And look at the whole cell lysate, and look at the different proteins being produced, we see that these stem cells produce a range of different proteins, network proteins that are very anti-microbial, but also drive the survival of that stem cell population. So, the secretum the cells produce drive a phenomenally important role in this response to the presence of bacteria. Which means these cells ccould be very useful as a stem cell source for driving tissue repair in the craniofacial complex, predominantly in around implants and in and around Peri patients. So dental stem cell population, when you look at the literature, I would ignore about 90% of it, but the 10% of it suggests very strongly these are very powerful mesenchymal stem cells that have significant use in clinical bioengineering.

I must thank the people that make the work, because I don’t do the work myself anymore. Thank the past students and post docs whose work I presented, and the great body of funders that have funded me for about 26 years now. And thank you for your attention.