 Hello everyone. Let's continue our dentine sessions. So today's video is about types of dentine. So I will be explaining all the types using this picture and we have some special features of dentine such as incremental lines of oneabner's lines and contour lines of oven and tombs granularly. So let's get into details of all the types of dentine and other features. So let's start with peritubular dentine. So all these questions are very very important because these are commonly asked shock notes in university exam. So let it be peritubular dentine, intertubular, pre-dentine, all-in-low-blastic process, primary dentine, secondary dentine, tertiary dentine, mantle dentine, circum-pulpal dentine, inter-globular dentine and we have contour lines of oven, oneabner's lines and tombs granular layer. So all our shock notes and it's quite easy to understand from this picture. So always try to understand the concept with a picture in your mind. So it will be easy to reproduce the same into your answer sheets. So let's start with peritubular dentine. So peritubular dentine, the dentine that immediately surrounds the dentinal tubules. So hope you can see this brown color which immediately surrounds. This is the dentinal tubule and this is the odentoblast, this is a dentinal tubule, odentoblastic, the processes and the dentine which is immediately surrounds the dentinal tubules. This brown color dentine is known as peritubular dentine which is highly mineralized than the intertubular dentine. Okay, intertubular dentine is between the tubules. As a name suggests it is between the tubules. It is more mineralized than the intertubular dentine and it is twice as thick in the outer dentine than the inner dentine and this calcified tubules wall has an inner organic lining which is known as lamina limitants. Okay, lamina limitants which is the lamina limitants which is the inner organic lining of peritubular dentine calcified tubule. Okay, so that is peritubular dentine. Now we have the second one that is intertubular dentine. So intertubular dentine which is located between the dentinal tubules. Okay, so between the dentinal tubules we have intertubular dentine which is less mineralized than the peritubular dentine which is just adjacent or just surrounding the tubules. So one half of its volume is organic matrix especially collagen fibers and this is seen between the zones of peritubular dentine. So we know we have peritubular dentine here and here. This is just two orientoblastic processes. We have many orientoblastic processes. So between peritubular dentine we have orientoblastic, sorry intertubular dentine. This violet color I mentioned the intertubular dentine. Lots of confusing dentine is there. So I am talking about intertubular dentine which is between the peritubular dentine. Okay. And the fibers, the collagen fibers ranges from 0.5 to 0.2 micrometer in diameter. So hydroxy apatite crystals are formed along the fibers with their long axis oriented parallel to the collagen fibers. So that is how hydroxy apatite crystals are formed through this fibers. So it is well mineralized but not up to peritubular dentine and it provides tensile strength to, so strength to dentine. That is its function. Now we have pre-dentine. Okay. So next is pre-dentine. This is pre-dentine. So we finished peritubular dentine and intertubular dentine. Now we have pre-dentine. Pre-dentine we know which is the first dentine to be formed which is located adjacent to pulp where the dental papilla or the future pulp will be giving rise to the first layer of dentine which is known as pre-dentine and which is not mineralized and these the collagen fibers which undergo mineralization at the pre-dentine and the pre-dentine then becomes dentine and a new layer of pre-dentine forms circumpulpally. Okay. So pre-dentine once it is mineralized it becomes dentine and then at the same time there will be new layer of dentine that is pre-dentine will be formed. So pre-dentine is not mineralized one. It is the first formed dentine which is adjacent to dental pulp. Okay. So that is pre-dentine. Now we have odentoblastic processes. So odentoblastic process is the cytoplasmic extension of odentoblast. This is the odentoblastic process. So we know odentoblastic process which is entering into enamel which was known as enamel spindle. Hope you remember what is enamel spindle. So enamel spindle is odentoblastic process which cross the DEJ and which end ups in enamel. So this is enamel part. Okay. Yes. Because this is a DEJ. So that is enamel spindle we learned in last session and laminalimentines was a organic layer of peritubular dentine. So the odentoblast which resides in the peripheral pulp at the pulp pre-dentine border and the process extends into dentinal tubules. Okay. So the process extends into dentinal tubules. These odentoblast reside in the peripheral pulp and pulp pre-dentine border. So we have pulp here. Hope you can understand the concept. We have pulp here. This is a pulp. Okay. This is enamel. This portion is enamel. So odentoblast is between pulp and pre-dentine border and this process is cytoplasmic extension. And the process are largest in diameter near the pulp. Here it is the largest and it goes thinner as it moves towards the dentine. And the cell bodies are 7 micrometer in diameter and 40 micrometer in length. So that was about odentoblastic process. The next one is primary dentine which is dentine that is formed prior to eruption of tooth and which is secreted at relatively higher rate and which constitute major part of dentine in the tooth. And mantel dentine is the first formed dentine in the crown underlying DEJ. That is dentino enamel junction which is regular in structure. Dentine tubules form S-shaped as a result of directional movement of odentoblast. Whereas the circum pulp dentine forms a remaining primary dentine or bulk of the tooth. Okay. So mantel dentine and circum pulp dentine. So the fibres are much smaller in diameter and are more closely packed together and the slightly more mineral content than in mantel dentine for circum pulp dentine. Okay. So whereas a secondary dentine, secondary dentine is formed after root completion and there is narrow band of dentine bordering the pulp which contain fewer tubules and primary dentine and there is usually a bend in the tubules where the primary and secondary dentine interface. So since it is formed after eruption the odentoblast slightly change directions which contributes to the bending of dentinal tubules. So primary dentine is before primary dentine is before the eruption of tooth whereas a secondary dentine after completion of root. Okay. Now we have tertiary dentine. Tertiary dentine is what we are inducing dentine formation when there is a pathological cavity which is very close to pulp where the normal restoration is not possible. So what we do is we place a medicament on the dentine surface which is very close to pulp. So after 2 or 3 weeks there will be dentine formation which we are inducing from the underlying pulp the mesenchymal cells which induce cells the cells of this mesenchymal cells which produces odentoblast and dentine and there will be a layer of dentine formed a new dentine formed which seals off or which keep a boundary between the outer surface from the pulp. So such type of dentine is known as tertiary or reparative dentine. Okay. So when pathologic process or operative procedures when these odentoblasts are cut these undergo survival or sometimes these odentoblasts will die depending upon the extent of injury. So if they survive this dentine is produced which are known as reactionary or regenerated dentine. So killed odentoblasts are replaced by migration of undifferentiated cells arising in the deeper layer of pulp to the dentine interface. So newly differentiated odentoblasts then begin deposition of reparative dentine to seal off the zone of injury as a healing process initiated by pulp. So there will be sealing of the injury. So that is why it is known as reparative dentine. And now we have mantel dentine. Okay. So already we've seen mantel dentine. It is the first layer of primary dentine to be deposited and which is that is why it is the oldest dentine and produced adjacent to enamel in the crown which can be recognized by characteristic thick fan shaped collagen fibers and these fibers run perpendicular to DEJ. Okay. Whereas a circum pulp dentine which is formed after the layer of mantel dentine has been deposited and which constitute major part of primary and secondary dentine. The hydroxy appetite crystals are deposited on the surface within the fibrils and continue to grow as mineralization proceeds which results in increased mineral content of dentine. Now we have incremental lines of worn ebner. So the incremental lines of worn ebner or implications line appear as fine lines or striations in dentine. So similar lines we have seen in enamel which are they the incremental lines of red CS. Okay. So the similar line in dentine is known as worn ebner's line. So these lines reflect the daily rhythmic recurrent deposition of dentine matrix as well as a hesitation and the daily formative process. So this is the incremental lines the deposition when this mineralization happens. There will be minerals deposited as additive method. It cannot grow itself. There should be continuous addition of minerals. So those lines is known as worn ebner's line. So this is in the dentine whereas in incremental lines of red CS in enamel. Okay. So the course of these lines indicate the growth pattern of dentine and some of these incremental lines are accentuated because of the disturbance in the matrix and remandalization process. Such lines are known as contour lines of oven. So these lines represent hypo calcified bands. So why it is different from worn ebner's? This is an accentuated because of the disturbance in the matrix and remandalization process. So accentuated incremental lines are known as contour lines of oven. And we have another structure which is neonatal line where this is in the deciduous teeth when the first permanent molar the prenatal and postnatal dentine is separated by an accentuated contour line which is known as neonatal line. Okay. So with that we have seen in dentine also when the separation between the prenatal and postnatal enamel. Similarly prenatal and postnatal dentine is separated by neonatal line. This line reflects the abrupt change in environment that occurs at birth. Okay. So the dentine matrix formed prior to birth is usually better quality than that formed after birth. And now we have inter globular dentine. Okay. Inter globular dentine. So before we have seen inter tubular dentine. Now we have inter globular dentine. So inter globular dentine sometimes mineralization of dentine begins in small globular areas that failed to fuse into homogenous mass. So this results in zone of hypomineralization between the globules. So these zones are called as inter globular dentine which is forms in crowns of teeth in the circum pulple dentine just below the mandrel dentine. Okay. Just below the mandrel dentine we can see inter globular dentine. So this is the circum pulple dentine. This is the mandrel dentine just below the mandrel dentine. We can see in circum pulple dentine the inter globular dentine which is seen just below mandrel dentine. Next we have tom's granular layer which is different from tom's process. Tom's process was seen in enamel formation the ameloblastic processes which is involved in the production of tooth enamel. But this is tom's granular layer. So there is a zone which is adjacent to cementum that appears granular. Okay. So near to cementum. Okay. So when in the root dentine when it is near to cementum we have a granular layer which is known as tom's granular layer which is likely increases in amount from cemento enamel junction to the root apex. Okay. So it changes it increases from cemento enamel junction from the seizure to root apex. It is caused by coalescing and looping of the terminal portions of terminal portions of dentinal tubules that is tom's granular layer. Don't get confused tom's process in enamel tom's granular layer in dentine. So that is all about various structures various types of dentine. So we have covered peritubular dentine which is adjacent to tubules inter tubular dentine between the peritubular dentine pre dentine which is a first formed dentine and or endoblastic process which is cytoplasmic extension primary dentine and secondary dentine which is the mandrel dentine secondary dentine and the tertiary dentine which is the reparative dentine on process pathological or operative procedures mandel and circum pulpult dentine mandrel dentine is adjacent to deger and the remaining portion as it is circum pulpult dentine because it has towards a pulpal site. Okay. And endoblubular dentine and we have incremental lines which is similar to incremental lines of raxias in enamel contour lines of oven which is accentuated lines of incremental lines and tom's granular layer which is adjacent to cement there will be a granular layer. So that is all about the various types of dentine. Next we have a few theories of the innovation of dentine and some of the physical and chemical properties and innovation part of dentine. I will come up with so I will come up with innovations and physical and other properties of dentine in my next video. Thank you.