 So, symptom is a calcified avascular mesenchymal tissue that forms the outer covering of anatomic root ok not the clinical root anatomic root. So, it is forming the outer covering of anatomic root. This definition was given in Carranza and we have basically two main types such as cellular and cellular and it begins at the cervical portion of the tooth at the cemento enamel junction and continues to the apex ok. So, it starts here and it continues to the apex. So, it covers the root basically. So, what are the physical properties of the symptom? So, the hardness is compared comparatively lesser than dentine which is very yellow color which lack luster which is light yellow color and which lack luster and lighter in color than dentine. However, it may not be distinguished on base of color alone. So, the permeability of cellular symptom is greater than that of a cellular symptom. So, we will see in detail about these two. With age or the advanced age the permeability of symptom decreases and the symptom is thinnest at cemento enamel junction that is here cemento enamel junction and it is thickest towards the apex. So, at cemento enamel junction it is 20 to 50 micrometer whereas at the apex it is almost 3 or 4 times that is 150 to 200 micrometer. So, that is about the physical properties. Now, let us see the composition. So, the basic dry weight basis we can say 45 to 50 percentage of inorganic substances which consists of basically calcium phosphorous in the form of hydroxyapatite crystals that is an inorganic portion and whereas a 50 to 55 percentage of organic portions with organic material and water. So, organic matrix of cemento basically consists of type 1 collagen, type 3 collagen and other non-collagenous proteins whereas the type 1 collagen is the majority just like barodont ligament. If we say by volume we can say 45 percentage of inorganic matter, 30 percentage of organic matter and 20 percentage of water. The first one was dry weight basis and this is by volume. So, there are two types of or two sources of collagen fibers are present in cemento. One is sharpies fibers or extrinsic fibers which are embedded portion of the principal fibers of parodontal ligament formed by the fibroblast. So, we had studied the sharpie fibers in detail in parodontal ligament and the second one is fibers which belong to the cemento matrix they are intrinsic fibers and produced by cemento blast. So, extrinsic fibers are produced by parodontal ligament and fibroblast whereas the intrinsic cemento which is seen in the cemento matrix formed by the cemento blast. So, two types of collagen fibers. Which has highest fluoride content, so cemento has the highest fluoride content and it is readily decalcifies in the presence of acidic condition. So, it is easily recalcifiable and it has highest fluoride content because of its lower crystallinity of mineral component. Now, the non-collagenous parts we have proteins which play very important role in matrix deposition, initiation and control of mineralization and matrix remodeling. Basic non-collagenous proteins are bone silo protein, osteopointin, ternacin, fibro, nectin, osteocalcin, few of them we had seen in parodontal ligament and proteoglycans also we had seen congeotin sulfate, hyaluronic acid, hyparin sulfate. So, such proteoglycans are also seen in non-collagenous matter. So, collagen we were discussing extrinsic and intrinsic, so now I talked about non-collagenous matter and we have few growth factors and other cemento derived growth factors. Now, we will move on to the classification, this is very important a cellular and cellular type. So, a cellular type which is the term is little bit unfortunate because as a living tissue cells which are an integral part, so it is an integral part of a living tissue. Why a cellular? Because some of the layers do not contain the cells in its lacunae, so that is why it has got this name. Acellular cementum is the first one to be formed and sharpie fibers makes the most of its structures and it forms during root formation before the tooth reaches the occlusal plane and it covers the cervical one-third, cervical one-third or the coronal portion of the root. It does not contain any cell which is more calcified which the formation is slow and arrangement of collagen fibers are more organized, so it is the first one to be formed, mainly sharpie fibers, some layers do not incorporate the cell, one-third of the cervical or the coronal root portion, it is more calcified, formation is slow and our collagen fibers are more organized in nature. So, what about cellular cementum? Cellular cementum forms after the eruption of tooth once it reaches the occlusal plane. Okay, so its formation is also in response to the functional demand. So when there is a functional load, heavy load, there will be more cellular cementum deposition to bear the functional load and sharpie fibers occupy very small proportion, contains cementosides in lacunae, these cementosides is not present in a cellular, that is why it has got this name and contain these cementosides which communicate each other with canalic So, there will be communication using canalicule and two-third of the apex part, so from this part to this part is cellular cementum and this to this cellular cementum, so this is the two-third of root portion, this is cellular and this little bit portion is cellular and its deposition is more rapid and collagen fibers are irregularly arranged. So, we have another classification that is Trotter and Page given, Page put forward this classification, it is based on the location morphology and histologic appearance. So, let us see these five classification, the first one is a cellular fibrillar cementum or AAC, a cellular extrinsic fiber cementum AEFC, cellular intrinsic fiber cementum CIFC, cellular mixed stratified cementum CMSC and intermediate cementum. So, it is based on the presence of cell that is a cellular, the first two component, first two types, the next two type is cellular and cellular, it has cells and where it is located few are intrinsic, few are extrinsic and one is mixed, so always study with connection based on the types of cell and based on the location and morphology, so it will be easy, do not just by heart this, so let us see one by one, so what is a cellular fibrillar cementum, okay, so this is formed at the most cervical enamel border, cervical enamel border following completion of pre-repti enamel maturation and sometimes also during tooth eruption, it is probably secreted by cementoblast, so it is formed here, okay, where it is formed most cervical enamel border after completion of pre-repti enamel maturation, there are two types of maturation, post-repti maturation and pre-repti maturation, so post-repti maturation takes longer period after the eruption, so the enamel will take up minerals from the saliva and GCF, that is post-repti maturation, pre-repti maturation before eruption, so it happens or it seen after following the completion of pre-repti maturation and sometimes also during the tooth eruption, that is cellular fibrillar without any cells, without any fibers, fine, now we have a cellular extrinsic fiber cementum, so it forms both pre-amp post-repti enamel, it is secreted by fibroblast, okay, this is secreted by cementoblast, secreted by fibroblast, on the apical portion of the root, it comprises a portion of the mixed fiber cementum, okay, so here it is comprised of mixed fiber cementum, otherwise it is a cellular extrinsic fiber cementum, now we have cellular intrinsic fiber cementum, so what is extrinsic, what is intrinsic, I talked here in the beginning, so hope you remember what is extrinsic and what is intrinsic, so cellular intrinsic fiber cementum is a third type, so it is formed both pre-amp post-repti, it is synthesized by cementoblast but does not contain extrinsic sharpies fiber, okay, hope you remember the extrinsic sharpie fibers, so whether is intrinsic is written, only intrinsic fiber extrinsic is about sharpies fiber, so without any sharpies fiber, so these are formed or synthesized by cementoblast just like a cellular a fibroblast cementum and it does not contain extrinsic sharpies fibers and the fourth one is cellular mixed stratified cementum which is formed by both cementoblast and fibroblast, okay, so it is combination of cellular intrinsic fiber cementum and cellular extrinsic fiber cementum and we have the fifth one also intermediate type, so intermediate type mostly CNET, cemento-dental junction, so we have the five types AAC, AEFC, CIFC, CMSC and intermediate type, so this cellular a fibroblast cementum there is no fibers, the cells are absent because it is a cellular no fibers formed by cementoblast location at coronal cementum, the cellular extrinsic fiber cementum densely packed sharpies fibers because extrinsic fibers, so sharpies fibers, there is no cell because it is a cellular formed by fibroblast and cementoblast, okay and location so vehicle third of fruit, cellular intrinsic fiber cementum, fibers are intrinsic cells are there present because it is cellular formed by cementoblast, location, resorption, lacunae and the next one CMSC, fibers extrinsic sharpies and intrinsic fibers, cells are present formed by fibroblast and cementoblast location apical one third of fruit and vocation, intermediate cells remnants of hardwigs, sheath and location cemento-dental junction, now let's move on to the cementogenesis, so formation of cementum is known as cementogenesis, so again I tell you if you don't know the bell stage in detail it is very difficult to understand the cementogenesis, so if you are studying gingiva, periodontal ligament, alveolar bond, cementum so whatever you are studying you need to have a very concrete base on the formation of tooth, so if you have a very good concept in formation of tooth it's very easy to understand all the formation the periodontal components, let it be periodontal ligament, cementum, alveolar bond or gingiva because it is all a single unit, so cementum formation takes place along the root okay, so this is a root portion, so it takes place along the entire root, so at the advancing root edge hardwigs epithelial root sheath or herce herce, so it is a approximated, so advance bell stage collapsing of the stratum intermedium happens on the both outer enamel epithelium and inner enamel epithelium, it approximated and it is becoming a hardwigs epithelial root sheath, so along the root side it forming a sheath which is derived from extension of inner and outer enamel epithelium and this is possibly sends an inductive message to the ecto mesenchymal cells of pulp okay, so the pulp of ecto mesenchymal cells now differentiate into ordentoblast okay and produce a layer of pre-dentane along the thinner aspect of herce, so when this herce induct a message here the dental pulp will produce ordentoblast along the inner aspect of hardwigs epithelial root sheath okay, so this is hardwigs epithelial root sheath, this is the advance bell stage I just made a small portion of it, so once the dentin is for dentin formation is underway which breaks the hardwigs epithelial root sheath, so it is now known as epithelial wrist of melasis, so we have seen the same scenario in perodontal ligament after the dental pad dental sac it is giving rise to more collagen fibers and forming the perodontal ligament, so what happens here is the inner layer of dental follicle comes in contact with the pre-dentane, so dental follicle is here dental papilla is here, so we hope you remember that bell stage inside dental papilla outside dental follicular dental sac, so after the hardwigs epithelial root sheath breaks on it become epithelial wrist of melasis the follicle which is present outside it will come in contact with the pre-dentane, so this is the dental papilla it will come in contact with pre-dentane, so once it contact with the pre-dentane what happens the cells of dental follicle now differentiate into cementor blast which are the main cells responsible for cement formation, so the cementor will be formed here cementor blast okay, so that is how it forms hardwigs epithelial root sheath was there when pre-dentane is formed from the dental papilla that is inside okay, symptom is outside and dentane is inside formed the hardwigs epithelial root sheath breaks, so that through that breakage the dental papilla enters and it differentiates into cementor blast and the cementor will be laid, so cementor blast synthesize organic matrix which is uncalcified and called as cementoid tissue or pre-cementum, so that is the uncalcified first part or the first form of cementum which is being laid out, so this is the cementoid tissue or pre-cementum, so it is uncalcified it has the name pre-cementum but it is uncalcified it is also known as cementoid okay it might be because asked for a shock not cementoid tissue or pre-cementum, so that is about the cementogenesis hope you understood what is the concept, now we move on to the mineralization, mineralization begins at the depth of pre-cementum, so hydroxyapatite crystals are deposited first between and then within the collagen fibrils by a process that is identical to the mineralization of bond tissue it is same as a bond mineralization, you know actually the width of this pre-cementum is around 3 to 5 micrometer and this process of establishing an appropriate condition for crystallization and growth of the individual crystals in cementum which is normally are extremely slow process and it extend over a period of several months, so it is a very slow process mineralization, so the development of cementum has been subdivided into two stage one is pre-functional and the functional stage, so pre-functional portion of cementum is formed during the root development and is extremely long lasting process okay the pre-functional, so functional is starts when the tooth is about to reach the occlusion level and is associated with the attachment of root to the surrounding bone and it continues throughout the life, this mainly happening it is during the stage of adaptive and reparative process, so when there is functional changes there is a lot of functional load will be there for the masticatory function and other functions, so the functional development is a continuous process and there will be continuous adaptive and reparative processes the cellular cementum we have seen based on the functional limit, cellular cementum will be response to the biological changes or biological or functional demands of the cementum, so that is about the first part I have finished the basic features physical characteristics the basic type cellular and cellular the differences and the shorter classification five types and the cementogenesis hope you remember the hard wicks epithelial root sheath and how it is formed and the pre-cementum and cementoid tissue and the mineralization we have two stages pre-functional and functional, now the next part I will be covering about the cells mainly cementoblast and cementocytes, cemento enamel junction and basic functions of cementum