 Hello everyone, welcome back to another session in Dental Histology and more. Today's chapter is the development of tooth. It is a very basic chapter in dental histology or the basic concept of the foundation of dental histology. So all the remaining chapters, all the future chapters like enamel, dendain, pulp, alveolar bone. So everything is connected to this chapter because it is the embryonic stage from which all the other structures are. Developing. So understanding the basic chapter is very important. The terminologies, the concept in this chapter will give you a good idea or easy to for. It will be very easy for you to understand the future chapters if you have the firm grip on this concept. So let's see what is the various stages in tooth development from its embryonic state to a full function. Oral cavity. So this is the embryonic cavity. So we have future brain or developing forebrain. There is a mesenchym type of tissue which is covering the forebrain. And we have developing stomodium. This is a future oral cavity. This is a foregut. This is a pericardium future heart. So this is a embryonic cavity and the very early stage of gestation. So what happens is we have a structure which is known as primitive oral cavity or stomodium. Which is lined by stratified scamous epithelium known as oral ectodum. So we have a stomodium here. This is a future brain. This is a future heart pericardium. So in between, this is an embryonic cavity you might not be able to imagine exactly. So this is a very beginning embryonic stage in the first or second third week of gestation. So we have a primitive oral cavity which is known as stomodium and which is lined by oral ectodum. So what happens after that? This oral ectodum contacts the endoderma foregut. So this is a foregut. Foregut has endoderm here. So it contacts with endoderm of foregut which creating buccopharyngeal membrane. So buccopharyngeal membrane is there. It is formed by the endoderm of foregut and the primitive oral cavity that is stomodium. So what happens to the buccopharyngeal membrane is it ruptures. It ruptures around fourth week that is 27th day of gestation. It ruptures. So what happens after rupturing? Once it ruptures there will be a connection between oral cavity that is primitive oral cavity and foregut. So foregut and oral cavity a connection established. So that is happening at 27th day of gestation. So then what happens? So at around 3 to 4 weeks that is 27th day this buccopharyngeal membrane ruptures and connection established. And after 2 to 3 weeks, so around 6th week what happens? We have a structure formation which is known as primary epithelial band. Because this foregut and this connection we have a special type connective tissue here which is known as neural crestor ectomis and Gaiman origin. Which is creating a primary epithelial band around 6th week of intra uterine or life. It is happening after 3 weeks of buccopharyngeal membrane rupturing. So this is happening at 27th day. This is happening at 6th week that is a formation of primary epithelial band. Because it created from a connective tissue which is neural crest or ectomis and Gaiman origin. So what is the importance of this primary epithelial band? It is giving rise to dental lamina and vestibular lamina. So dental lamina is nothing but the future tooth are originating from dental lamina. So this primary epithelial band which has got 2 structures buccal process and lingual process. Lingual process is known as dental lamina, buccal process is vestibular lamina. So this connective tissue formation is not very equal in all the areas. So it has cell multiplication at few areas. So that few areas there will be rapid cell multiplication. So that is giving rise to epithelial band. So this epithelial band which invades the underlying ectomis and Gaiman along each of the horseshoe shaped future dental archers. So we have upper arch and lower arch. So this connective tissue proliferation which give rise to epithelial band which invades the horseshoe shaped upper arch and lower arch. And which give rise to future teeth. So that happens at the 6th week of intrauterine augestation life after 3 weeks of buccal pharyngeal membrane rupture. So after that what happens? It divides into dental lamina and vestibular lamina at around 7th week. So after 1 week it divides into dental lamina and vestibular lamina which is buccal and this is lingual process. So this dental lamina which is giving rise to the future all deciduous teeth. So all deciduous teeth arises from dental lamina and the permanent teeth will be arising from the lingual extension of this dental lamina. So there will be a lingual extension from which the future teeth arises and the molars that is permanent molars arise from the distal extension of this dental lamina. So dental lamina has all deciduous teeth but from the lingual extension the permanent teeth arises and distal extension the molars that is permanent molars arises. So the dental lamina is the most important structure which is giving rise to future tooth. So we have seen what is tomothium which is connecting with foregut by buccal pharyngeal membrane. It ruptures at 27th day after 2 to 3 weeks. There will be continuous multiplication of connective tissue which is neurocaster ecto mesenchyme in origin which is giving rise to primary epithelial band which is not everywhere. It is proliferating certain areas which invades the whole shoe shape upper and lower arches which has got two processes lingual and vestibular. The dental lamina is a lingual process which is giving rise to deciduous teeth and the lingual extension giving rise to the permanent teeth and the distal extension of dental lamina giving rise to permanent molars. So this is the epithelial band. So I have two different pictures. This is from frontal view that is a friend view. So this is a maxillary or maxilla primitive maxilla and this is the primitive mandible. So we have whole shoe shaped arches and this is the epithelial band primary epithelial band from which the future teeth arises. Whereas this is a different view that is a lateral or side view. So you have the buckle portion that is a vestibular lamina of primary epithelial band and this is the lingual portion of primary epithelial band which is known as dental lamina from which the future teeth arises. So this is a side view and this is a friend view. So when you are looking at a person, so it looks like this the maxilla mandible or the future bones where the primary epithelial band is in the pink color. So visualizing this concept is little different because the pictures are not in 3D format. So this is a side view or lateral view and this is a friend view. So this is how primary epithelial band forms. It invades into the horseshoe shaped arches, maxilla mandible arches and creates epithelial proliferations thereby future dental lamina and vestibular lamina forms. So we have learned dental lamina and vestibular lamina are the lingual and buckle portion of primary epithelial band from dental lamina the future teeth arises. That is the lingual extension. So there will be a lingual extension. This is a single tooth so we have a set of teeth so the lingual extension will be set. So that lingual extension is also known as successional lamina because it produces or give rise to the successors teeth that is the permanent teeth. So lingual portion that is the dental lamina give rise to basically the deciduous teeth. So from that we need to get the permanent teeth so it arises from the successional lamina which is present in the lingual side of primary epithelial band. Okay we do not get confused dental lamina is a lingual part of epithelial band and lingual part of dental lamina successional lamina arises. And we know permanent molars which is coming from the distal extension because we have molars deciduous molars so deciduous molars successional lamina give rise to the permanent premolars. So we do not have any space for permanent molars in epithelial band so it arises from the distal extension of dental lamina that is the permanent molars for second and third molars. So what is the job of vestibular lamina which is a buckle portion of you cannot distinguish vestibular lamina and dental lamina here because this is a frontal view. So here you can distinguish this is a vestibular lamina and this is a dental lamina this is a lingual side this is a buckle side. Okay since it is a frontal view the anterior portion will be the buckle and the posterior part will be the dental lamina. Okay so vestibular lamina which is also known as lip furrow band it is a buckle portion of primary epithelial band. It give rise to the vestibule. Vestibule between the lips and cheeks and the tooth bearing area so the vestibule between the lips and cheeks and the alveolar bone which bears the teeth. Vestibular lamina becomes a lip furrow band between the alveolar bone and lips and cheeks. So what happens to this dental lamina so usually dental lamina has five year period or five year activity. So after five year activity it ruptures when the tooth forms the tooth allows us its connectivity the dental lamina and the remnants might be present in jaw or ginger. Okay so the remnants of dental lamina which is present in the jaw is known as epithelial pearls or islands or epithelial island or epithelial pearl. And the remnants of dental lamina which is present in the ginger is known as cell rest of sari. So this is very important what is epithelial pearl or island and what is cell rest of sari. It is the remnants of dental lamina after its activity the remnants might be present in jaw or ginger. The remnants in ginger is known as epithelial pearls or islands and the remnants in ginger is known as cell rest of sari. So this is dental lamina. Now we will look into the various stages of tooth formation. So before that you need to get this concept clear so it will be like this in future there will be formation of tooth bud from dental lamina. So before that this is how it forms the primary epithelial band. What is vestibular lamina what is dental lamina and what is lip furrow band what is epithelial pearls and what is cell rest of sari. So everything is very important short nods short essays long essays. So there are many questions been asked from this chapter. So now let's see the various tooth formation.