Understanding Embryological Tooth Development

Hey guys, my name is Minas and today we're going to be talking about the embryological development of the teeth and this is a video that moves on from my previous video embryology of the face. You know I would recommend you watch that video. It is linked to the development of the teeth. but I've made this video in a way so that you don't really have to do that if you don't want to so as usual have broken it down made it very simple so that any beginner to embryology first-year medical dental student will be able to understand it even if you don't know what embryology is and we're gonna We begin at the beginning at the blastula. A blastula is a ball of cells that's a result of fertilization. Where the sperm fertilizes the egg, that ball of cells moves through the uterine tube into the uterus and it'll implant into the uterine wall. And once it does that, a process of gastrulation will form these three germ layers, which is the ectoderm, mesoderm, and the endoderm. And this is pretty much what you were in the beginning. You have three layers, flat as a pancake, the mums uterine wall. This is an oversimplification for this where it's a cross-section of that pancake looking at it down or up it's a cross-section so you have in blue the ectoderm and in solid blue there is other neural crest cells in red we have the mesoderm which end up being muscle kidneys gonad other connective tissue and in the endoderm which becomes the primitive gut etc So what happens is that this flat pancake will fold eventually and the neural crest cells with the ectoderm in between will pinch off from the other parts of the ectoderm and form a neural tube. And in solid blue here we have these neural crest cells and they migrate and they have help to make lots of different structures in the body. Regards to the development of the tooth, this is important. So keep that in mind with the neural crest cells. Over here we have the mesoderm, it has three three parts the paraxial which has which makes the somites muscles the intermediate kidneys and gonads and then the lateral plates and again we have the endoderm which eventually becomes the tube in itself okay let's start talking about the development of the teeth so in the previous video with the embryology of the face we talked about how the air sinus sinuses contribute to the shape of the face so does the jaw of the the bones of the jaw so the max axilla and the mandible. And these jaw bones accommodate the development of the teeth. So initially, if we have a look over here, around week eight, the first formation of the tooth begins at the bud. So what happens is that the epithelium of the oral cavity will actually proliferate and form a dental lamina. overlying the jaw bone and this is around week 8 this occurs in the upper and lower jaws and a couple of weeks pass around week 10 and there is an evagination of the dental buds around a dental papilla which will become its cap stage and this initial dental papilla will be from the first baby teeth so the milk teeth the decidual teeth and a bit lingual to the dental bud is the permanent tooth bud. Okay so just to quickly recap week eight we have the oral epithelium making the dental lamina over the jawbone. This evagination is the dental bud and further invaginations will lead to the cap stage of teeth development. There are 10 in each jaw, 10 on the top and 10 on the bottom. This cap consists additionally of an inner and an outer dental epithelium. So again, this evagination, it consists of an outer and an inner dental epithelial layer. So, where does this dental papilla come from? Remember the neural crest cells? These interact with mesenchyme, surrounding mesenchyme, which is just tissue, to make the dental papilla. So it's an interaction of this ectoderm with some... mesenchymal tissue that will actually lead to the formation of this dental papilla. So from week 10 at the cap stage the cap grows and will become a bell stage because the tooth will start looking like a bell and as the tooth grows there are cells that are differentiating and we have the beginnings of ameloblasts and odontoblasts. Ameloblasts are enamel secreting cells and odontoblasts secrete dentin. And dentin is just a calcified tissue which makes up a major component of teeth. So the odontoblasts actually differentiate from mesenchyme near the inner dental epithelium. So in red here we have the odontoblasts and this inner epithelium which was at first the surrounding area of epithelium from this dental papilla will actually differentiate into amelioblasts and odontoblasts. Okay, the rest of the dental papilla cells this middle part will become the dental pulp and the dental pulp is essentially the inner components of loosely connected tissue of the two teeth eventually will house blood vessels and nerves among other things now I've left these four images here of the embryology of the face video to outline a very quick point. If you had seen the video you'll know that these bits in orange are the medial nasal prominences and they'll eventually become the philtrum as well as the crest and the tip of the nose. However they also have an internal component and the internal component will contribute to the four incisors. These four teeth will be originated from medial nasal prominence. And that's all I wanted to talk about with the embryology of the face. So from the bell stage, we have now at four months, the tooth has still not erupted, the baby is not yet born, but we can see now that there is a thick layer of enamel that is the result of ameloblasts. In addition, the dental pulp will start to be invaded by blood vessels. And all the way in the bottom here, we have the root sheath. Again, which is the result of the underlying mesenchyme. So the dental epithelium will move into the underlying mesenchyme, forming the epithelial root sheath. And this is at week 24. Okay, let's have a look now at what it looks like before birth. It still hasn't been erupted. We can see our dentin and enamel, which is the result of the odontoblasts and ameloblasts. Both the ameloblasts and the ameloblasts are still erupted. blasts and odontoblasts as their products thicken will gradually regress and become much thinner and assimilated into the upper surrounding tissues however we have now some cementoblasts and cementum So the mesenchyme in contact with the dentin in blue, so the surrounding tissue, it becomes cementoblasts and they produce cementum. So cementoblasts in orange produce this color-coded in purple cementum. And this is a very bony substance, which essentially does what its name says. It keeps the tooth in there cemented. On the outside of the cement layer, we have a connective tissue growth called the periodontal ligament. And this ligament holds the tooth in place and also acts as a shock absorber. Eventually, with further narrowing of the root, the crown gets pushed into the cavity. And we will have the eruption of the tooth. This occurs. at around six months to two years after birth. So we see here, if this is the oral cavity, we have the enamel, and a large part of the dentin, as well as where used to be the dental pulp, is now filled with blood vessels and nerves. In green we have the periodontal ligament which holds everything into place and also acts as a shock absorber. And here we have the tooth inside its socket bone. And this is essentially the end of the video. I've broken it down and made it very simple so that any beginner to embryology should understand this video. And so let's quickly talk about what happens after birth with the teeth. So the decidual teeth or the milk teeth, the baby teeth, grow out. from six months to 24 months and will actually be expelled from the teeth once the permanent teeth start growing and what happens is from the permanent tooth bud its actual growth if this if the tooth was up here and we have the permanent tooth bud here growth of the permanent tooth will help expel the baby tooth And it'll grow in its place. And the previous... Milk tooth root will actually be broken down by osteoclasts. And that's the end of the video. I hope that this helped you and you enjoyed it. If you liked it, please subscribe and like the video. You can follow me on Facebook and also you can follow me on Instagram. Leave a message or a comment below. I read them all. And if you want to send me a message on Facebook, I reply to every message as well. So thank you.

but I've made this video in a way so that you don't really have to do that if you don't want to so as usual have broken it down made it very simple so that any beginner to embryology first-year medical dental student will be able to understand it even if you don't know what embryology is and we're gonna We begin at the beginning at the blastula. A blastula is a ball of cells that's a result of fertilization. Where the sperm fertilizes the egg, that ball of cells moves through the uterine tube into the uterus and it'll implant into the uterine wall. And once it does that, a process of gastrulation will form these three germ layers, which is the ectoderm, mesoderm, and the endoderm. And this is pretty much what you were in the beginning.

You have three layers, flat as a pancake, the mums uterine wall. This is an oversimplification for this where it's a cross-section of that pancake looking at it down or up it's a cross-section so you have in blue the ectoderm and in solid blue there is other neural crest cells in red we have the mesoderm which end up being muscle kidneys gonad other connective tissue and in the endoderm which becomes the primitive gut etc So what happens is that this flat pancake will fold eventually and the neural crest cells with the ectoderm in between will pinch off from the other parts of the ectoderm and form a neural tube. And in solid blue here we have these neural crest cells and they migrate and they have help to make lots of different structures in the body.

Regards to the development of the tooth, this is important. So keep that in mind with the neural crest cells. Over here we have the mesoderm, it has three three parts the paraxial which has which makes the somites muscles the intermediate kidneys and gonads and then the lateral plates and again we have the endoderm which eventually becomes the tube in itself okay let's start talking about the development of the teeth so in the previous video with the embryology of the face we talked about how the air sinus sinuses contribute to the shape of the face so does the jaw of the the bones of the jaw so the max axilla and the mandible.

And these jaw bones accommodate the development of the teeth. So initially, if we have a look over here, around week eight, the first formation of the tooth begins at the bud. So what happens is that the epithelium of the oral cavity will actually proliferate and form a dental lamina. overlying the jaw bone and this is around week 8 this occurs in the upper and lower jaws and a couple of weeks pass around week 10 and there is an evagination of the dental buds around a dental papilla which will become its cap stage and this initial dental papilla will be from the first baby teeth so the milk teeth the decidual teeth and a bit lingual to the dental bud is the permanent tooth bud.

Okay so just to quickly recap week eight we have the oral epithelium making the dental lamina over the jawbone. This evagination is the dental bud and further invaginations will lead to the cap stage of teeth development. There are 10 in each jaw, 10 on the top and 10 on the bottom. This cap consists additionally of an inner and an outer dental epithelium.

So again, this evagination, it consists of an outer and an inner dental epithelial layer. So, where does this dental papilla come from? Remember the neural crest cells?

These interact with mesenchyme, surrounding mesenchyme, which is just tissue, to make the dental papilla. So it's an interaction of this ectoderm with some... mesenchymal tissue that will actually lead to the formation of this dental papilla. So from week 10 at the cap stage the cap grows and will become a bell stage because the tooth will start looking like a bell and as the tooth grows there are cells that are differentiating and we have the beginnings of ameloblasts and odontoblasts.

Ameloblasts are enamel secreting cells and odontoblasts secrete dentin. And dentin is just a calcified tissue which makes up a major component of teeth. So the odontoblasts actually differentiate from mesenchyme near the inner dental epithelium. So in red here we have the odontoblasts and this inner epithelium which was at first the surrounding area of epithelium from this dental papilla will actually differentiate into amelioblasts and odontoblasts.

Okay, the rest of the dental papilla cells this middle part will become the dental pulp and the dental pulp is essentially the inner components of loosely connected tissue of the two teeth eventually will house blood vessels and nerves among other things now I've left these four images here of the embryology of the face video to outline a very quick point. If you had seen the video you'll know that these bits in orange are the medial nasal prominences and they'll eventually become the philtrum as well as the crest and the tip of the nose. However they also have an internal component and the internal component will contribute to the four incisors. These four teeth will be originated from medial nasal prominence. And that's all I wanted to talk about with the embryology of the face.

So from the bell stage, we have now at four months, the tooth has still not erupted, the baby is not yet born, but we can see now that there is a thick layer of enamel that is the result of ameloblasts. In addition, the dental pulp will start to be invaded by blood vessels. And all the way in the bottom here, we have the root sheath. Again, which is the result of the underlying mesenchyme.

So the dental epithelium will move into the underlying mesenchyme, forming the epithelial root sheath. And this is at week 24. Okay, let's have a look now at what it looks like before birth. It still hasn't been erupted. We can see our dentin and enamel, which is the result of the odontoblasts and ameloblasts.

Both the ameloblasts and the ameloblasts are still erupted. blasts and odontoblasts as their products thicken will gradually regress and become much thinner and assimilated into the upper surrounding tissues however we have now some cementoblasts and cementum So the mesenchyme in contact with the dentin in blue, so the surrounding tissue, it becomes cementoblasts and they produce cementum. So cementoblasts in orange produce this color-coded in purple cementum.

And this is a very bony substance, which essentially does what its name says. It keeps the tooth in there cemented. On the outside of the cement layer, we have a connective tissue growth called the periodontal ligament.

And this ligament holds the tooth in place and also acts as a shock absorber. Eventually, with further narrowing of the root, the crown gets pushed into the cavity. And we will have the eruption of the tooth. This occurs.

at around six months to two years after birth. So we see here, if this is the oral cavity, we have the enamel, and a large part of the dentin, as well as where used to be the dental pulp, is now filled with blood vessels and nerves. In green we have the periodontal ligament which holds everything into place and also acts as a shock absorber.

And here we have the tooth inside its socket bone. And this is essentially the end of the video. I've broken it down and made it very simple so that any beginner to embryology should understand this video. And so let's quickly talk about what happens after birth with the teeth. So the decidual teeth or the milk teeth, the baby teeth, grow out.

from six months to 24 months and will actually be expelled from the teeth once the permanent teeth start growing and what happens is from the permanent tooth bud its actual growth if this if the tooth was up here and we have the permanent tooth bud here growth of the permanent tooth will help expel the baby tooth And it'll grow in its place. And the previous... Milk tooth root will actually be broken down by osteoclasts. And that's the end of the video. I hope that this helped you and you enjoyed it.

If you liked it, please subscribe and like the video. You can follow me on Facebook and also you can follow me on Instagram. Leave a message or a comment below. I read them all. And if you want to send me a message on Facebook, I reply to every message as well.

So thank you.

Transcript for:Understanding Embryological Tooth Development

Transcript for:
Understanding Embryological Tooth Development