 So, this video is basically about the surface structures such as 100 sugar bands, incremental lines of rhesus and various surface structures such as pericameter, prismulus, enamel, nasmith membrane which is enamel cuticle, enamel lamellae, enamel teffs, dentino enamel junction, enamel spindle and enamel rod ends. So, these are the structures which you see in surface reaches and other type which is the junction of dentine and enamel which is a scallop structure and enamel spindle and organoblastic process. Okay, so let us see the surface structures and these are in detail. 100 sugar bands. 100 sugar bands, it is a regular change in direction of roads responsible for the appearance of alternating dark and light strips of varying width. So there will be dark and light, this is not possible to show it here, so there will be black and white appearance in when we take sections of teeth, we can see the dark and light lines. So these changes is due to the change in direction of enamel rods. Okay, so this alternating dark and light strips of varying width is known as under sugar bands. So this is most commonly seen in longitudinal ground section. Okay, so when we take longitudinal ground section, we can see 100 sugar bands. So they originate from DEJ and which pass outwards ending in some distance from outer enamel surface. So it originates from DEJ and it end from little distance from outer enamel surface. So this could be due to, there are many things, it could be due to the change in calcification process. Calcification will not happen very regularly, so sometimes the change in will be rhythmic matter but in various frequency. So that change in calcification process could be the reason for under sugar bands and they may not be an optical phenomena but they are composed of alternate zones having slightly different permeability and different content of organic material. Nulled enamel is an optical appearance of interwind bundles of rods at incisal and incisal edge and cuspel tape whereas 100 sugar bands it is alternate white and dark bands or strips at various width which could be which is not an optical phenomena but they are composed of alternate zones having slightly different permeability. So slight different permeability with different content of organic matter. So that is why it is seen as white and black alternating bands. So that is 100 sugar bands which is very important. Now we have incremental line of red Cs. Next we have incremental lines of red Cs. So these are brownish bands which is seen in ground sections of enamel that illustrate successive apposition of layers of enamel during formation of the crown which are known as incremental lines of red Cs. It is nothing but we know in enamel mineralization will happen layer by layer the minerals will be deposited. So this particular rhythmic pattern of apposition this mineral deposition by layer by layer. So in the crown section it is reflected in ground section as particular lines. So these lines are nothing but indicative of mineralization, rhythmic mineralization pattern. So that is known as incremental lines of red Cs. So 100 sugar bands is another type of reflection and oblique light that is also another pattern of optical appearance that is white, alternating white and black bands in oblique light when we take a longitudinal section. So similarly incremental lines of red Cs is also a brownish band and which is seen in ground sections of enamel which is indicative of mineral apposition. So these longitudinal sections which surround the tip of tentane from DJ in cervical parts which from oblique deviates to occlusion side. So we can see at the tip of tentane which surrounds the tip of tentane which surrounds the tip. It is not easy to show in this type of board. So in transverse section so they appear as concentric circle it has been attributed to the periodic bending of enamel roots. So it is due to the periodic bending of enamel roots and there will be physiologic calcification happening. So why it is important because this broadening of incremental lines may reflect the metabolic disturbance at the time of matrix formation. So if something happens so if it is broader then there will be some disturbances happened in matrix formation. So my metabolic disturbances is causing this change so we can make out that something happened during the matrix formation. So that is the importance of this incremental lines of radius. So that is about incremental lines of radius. Now we have surface structures, various surface structures such as enamel, cuticle, enamel, enamel types. We have cracks, road and peri-chaimata. We have also peri-chaimata also as a surface structure. So we are going in detail about the surface structure. So we have various surface structures. The first one is prismless enamel. So we have prismless enamel, peri-chaimata. Road ends, enamel cracks, enamel cuticle, enamel lamellae, enamel tufts. So let us see what is prismless enamel which is present in 70% of permanent teeth and all deciduous teeth which found least over the cusp tip and commonly in the cervical area which is least in cusp tip and commonly in cervical areas and which will not be visible and all the epithelial crystals are parallel to one another. And they are perpendicular to stria of radius. So they are more mineralized than the bulk of enamel which is present beneath that. So that is structure less or prismless enamel. So that is about prismless enamel. Now we have peri-chaimata. Peri-chaimata, these are the transverse wave-like grooves believed to be the external manifestation of stria of radius. So stria of radius which is externally manifested as peri-chaimata. So there will be 30 peri-chaimata per millimetre in the region of cemento enamel junction and their concentration gradually decreases near occlusal or incisal surface at 10. So here it will be 30 per mm and at the occlusal or incisal edge it will be 10 per mm. So it is the external manifestation of incremental line of radius or stria of radius and enamel road ends. So we have enamel road. So we have another structure which is a surface structure which is enamel road ends. So these are concave and very in depth they are shallow, surveyically and deep occlusally. And bits of about 1 to 1.5 micrometer in diameter and small elevations which are known as enamel caps. So we are talking about enamel road ends, enamel road ends. If it is between 10 to 15 micrometer which is known as enamel caps and if it is very larger enamel elevations which is known as enamel broads, enamel broads and enamel caps. That is enamel road ends. Now we have enamel cracks. They are actually outer edges of lamellae. They originate from incisal edge and extend to varying distance in enamel in perpendicular direction towards dentino enamel reaction. So if any crack is present here it will be starts from here towards DEJ. So mostly it will be 1 mm in length. So these are known as enamel cracks. Neonataline we have neonataline in surface structure of enamel. They are like deciduous teeth when they develop partly before and partly after birth. So the boundary between these two portions in enamel is marked by accentuated incremental lines of red seaus which is known as neonataline. So neonataline is nothing but accentuated red seaus, line of red seaus which is showing the demarcation of the portion which is formed before and after the birth. So some teeth which partly develop before birth and after some portion after birth. So these are the line which is differentiating these two are known as neonataline or ring. So these results from abrupt change in the environment and nutrition of newborn infants. So prenatal enamel is better developed than postnatal enamel and pericameta are absent in prenatal enamel. So that was about enamel neonataline. Now we move on to enamel cuticle. Enamel cuticle they are delicate membrane covers the crown of newly erupted tooth which is known as Nasmith membrane which is very important Nasmith membrane is nothing but covering of newly erupted tooth. So these Nasmith membrane are delicate membrane which covers the crown of newly erupted tooth or which is also known as primary enamel cuticle. So Nasmith membrane is enamel cuticle. This is secreted after the epithelial enamel organ retracts from the cervical region during tooth development. It protects the surface of enamel from resorptive activity of adjacent vascular tissue. So the primary enamel cuticle or Nasmith membrane's job is to protect the tooth from adjacent resorptive activity. So we have primary enamel cuticle and secondary enamel cuticle. So primary enamel cuticle which covers the entire crown of newly erupted tooth which is removed by mastication which is secreted by post ameloblast whereas the secondary enamel cuticle which covers the cervical area of enamel thickness up to 10 micrometer which is continuous with cementum which is probably mesodermal origin and that is the difference between primary enamel cuticle and secondary enamel cuticle. So these all are short notes enamel cuticle, hander, sugar bands, incremental lines of red seaus, ferricahimata, enamel roads, Nasmith membrane, enamel cuticle. Now we have enamel lamellae, these are leaf-like structures, enamel lamellae are leaf-like structures so it will be like leaf-like structures that extends from enamel surface towards DEJ. So this is external surface, so this is DEJ, so it starts from here towards DEJ. And which is basically organic and a little bit of mineral composition which originates in develop in planes of tension when road, the enamel road cross such a plane they may not fully calcify. So when tension is there there will not be proper calcification. So that places a crack may develop. So this crack is filled either by surrounding cells if it has occur in unerupted tooth or by organic material if it has occurred after eruption. So the tension happens, so during such planes if tension is happening while eruption what happens they will not completely calcify and if the disturbance is very severe there will be a crack formation and if it is before the tooth eruption the crack is filled by surrounding cells and if it has occurred after then there will be organic content. So that is known as enamel lamellae. Basically it has three types, type A, type B and type C. Type A is restricted to enamel so this is enamel, this is enamel and this is dentine, this is dentine, this is enamel so this is dentino enamel junction. So type A is restricted to enamel so this will be here so it starts from outer enamel surface it will be here that is type A. Type B may reach up to dentine so if it starts it may reach till here enamel lamellae and it is mostly degenerating cells. So type C is containing organic material and it may invade, it may cross this one, dentino enamel junction that is type C. So the significance is it is a site of weakness in tooth and may form a road of entry of bacteria and initiate dental caries because it is poorly calcified. There is no proper calcification happens here and the next structure is enamel tufts. So enamel lamellae if you finish enamel tuft is thin ribbon like structure which is resembling a tuft or grass similar to enamel lamellae so this is like tufts or grass which is created by examining such area under low magnification of ground section. So we can observe it when we check it under low magnification in ground section. So these consist of basically hypo-calcified enamel rods and inteprismatic substances. So that is enamel tufts. So they arise from DEJ. So enamel lamellae which is erased from outer surface but this enamel tufts arise from DEJ. Enamel lamellae arise from outer surface enamel to towards DEJ. So enamel tufts arise from DEJ and it reach up to one fifth to one third of its thickness and their presence and their development are consequences of an adaptation to spatial condition of enamel that is a adaptation mechanism. So it basically significance of enamel tufts it prevents enamel fracture. So next we have dentino enamel junction. So this particular blue line is dentino enamel junction which is basically scalloped structure. So surface of dentine at dentino enamel junction is pitted and shallow depression of dentine which fit round at projection of enamel. It appears scalloped due to the mixing of crystals of dentine and enamel each other. So there will be mixing of enamel and dentino crystals. So it creates a scalloped structure that is dentino enamel junction. So enamel spindles we have enamel spindles. Next enamel spindles are odentoblastic processes which pass across DEJ into enamel. So their end is known as enamel spindles. So sometimes odentoblastic process starts from dentine and it crosses the DEJ and reach up to enamel with a thickened end and they have been termed as enamel spindles. So this direction of spindles and rods are divergent as rods are formed at right ankle to ameloblast and spindles are parallel to ameloblast. So enamel spindle is always parallel, enamel spindle which is parallel to ameloblast whereas enamel rods are right ankle to ameloblast. So that is about enamel spindles. So we have covered the structure, surface structures and other structures of enamel. So we are finishing our part one. Second part is amelogenesis, the formation of enamel. So we will be checking in detail already we know how enamel forms in our tooth formation stages. Anyway let's wind up the session one of enamel. So we have learned about thickness, color, hardness, solubility, permeability, translucency, chemical properties, various proteins and various structures. So structures are rods, road sheath, interprismatic substances, more about striations, more about direction of rods and hunter sugar bands, incremental lines of red sea and various surface structures such as pericameter, presemblest structure, enamel cuticle, enamel amelae, enamel tufts or entoblastic crosses and enamel spindle, dentino enamel junction, enamel cuticle which is also known as nasmitz membrane, enamel rod ends, enamel caps and enamel brush. So all are various structures which is present in enamel. So it can be asked as a short note, a short essay and a long essay. So it's a very, very important session. So I'll come up with enamel formation or amelogenesis in my next video of enamel. Thank you.