 Hello everyone, welcome back to another session on dentistry and more today's topic is alveolar bone. So alveolar bone is one of the component of pyridontism. So pyridontism consists of two soft tissues and two hard tissues. So junjewa and pyridontal ligament are the soft tissues whereas the cement and alveolar bone are the hard tissues. So we finished junjewa, pyridontal ligament, cement and now we are moving on to alveolar bone. So I hope you understood all the three concepts, junjewa, cement and pyridontal ligament. So understanding pyridontium and its component requires a thorough knowledge of tooth formation and its stages. So bud stage, cap stage, bell stage, thorough knowledge would help you to understand all the other chapters and other concepts so easily. If you have a proper knowledge about the basic concepts, it will be very difficult for you to understand the further topics because all are interconnected because the tooth formation happens altogether in amyl dentine, pulp, root, pyridontal ligament, cement and junjewa. So all are forming as a unit. So you just cannot skip one unit and learn the other units. So you have to learn everything altogether. For that you need to have a very good knowledge about the beginning of tooth, bud, bell and cap stages and all the layers and the other components. So it will be very easy to understand all the remaining topics in oral cavity. So let's see the details of alveolar bone. So this session is about its composition, its classification and development. Alveolar bone is by definition part of the portion of maxillan mandible that forms and supports the tooth socket. So entire maxillan mandible we need to think about a portion which supports and forms the tooth socket, which supports the tooth roots or tooth so that a smaller part or comparatively smaller part of maxillan mandible that supports the root is alveolar bone. So it has a role in rapid remodeling like during the tooth eruption and functional demands. It continuously remodeled and it act as an attachment apparatus for cement and pyridontal membranes and alveolar bone. So it has got various functions, it provides attachment to the pyridontal ligament, it absorbs the occlusal pressure, it gives attachment to muscles, it provides framework for the marrow, it is a reservoir for ions especially calcium and it house the roots of tooth which is achieved by the insertion of sharpies fibers into alveolar bone proper. So there are various functions. Now we are seeing about the composition of alveolar bone. So alveolar bone is composed of inorganic and organic matter and two-third of total is inorganic matter and the remaining one-third is organic matter. So inorganic matter includes hydroxyapatite crystals and minerals such as calcium, phosphorus, carbonate, citrate, hydroxyl ions, magnesium, sodium, potassium, fluoride and very smaller quantity. Whereas inorganic matter it consists of both collagen and non-collagenous proteins. Percentage is non-collagenous protein such as osteocalcin, osteonectin, silo protein, phosphor protein and proteoglycans. So that is about composition of alveolar bone. And now we move on to the most critical part that is development. So alveolar process consists of bone which is formed both by cells from dental follicle that is alveolar bone proper and cells which are independent of tooth development that is brachial or mandibular arch because maxilla and mandible develops from first brachial arch or this is also known as mandibular arch. The maxilla forms within the maxillary process and mandible forms within the fused mandibular process of mandibular arch. And both jaw bones start as small centers of intramembraneous ossification around stromodium. So it is formed both by cells from the dental follicle, from dental follicle what forms alveolar bone proper and maxilla and mandible forms from the cells which is independent of tooth development that is first brachial or mandibular arch. Now let's see step by step process of alveolar bone formation. First what happens maxilla and mandible develops intramembranously and at 8 week of utero what happens alveolar process develops from the dental follicle during tooth eruption. So maxilla and mandible already is forming intramembranously and around 8 week in utero what happens the alveolar process develops from dental follicle. This is intramembranous development and dental follicle give rise to alveolar process that happens during the tooth eruption. So next in well stage the developing bone becomes closely related and the size of alveolar is dependent on the size of the growing tooth germ. So it is always closely related the size of tooth germ and the alveolar bone. When alveolar bone it develops in a resorption deposition fashion it resorps at the inner wall and it gets deposited on the outer wall so it grows. So these developing teeth which lie in a trough of bone which is known as tooth crypt. So after that what happens these teeth which separated from each other by the development of interdental septa. So interdental septa forms and these teeth are separated and then with the onset of root formation the interradicular bone develops in multi-rotor teeth. So we have seen interdental septum then there will be interradicular bone formation as root formation happens between the two roots of multi-rotor teeth. Whereas in case of deciduous teeth when a deciduous tooth shed its alveolar bone is automatically resorbs. So after that the alveolar process gradually getting incorporated into maxilla or mandibular body. Though it has separate origin finally it will be a one single bone. So permanent tooth moves into place developing its own alveolar bone from its own follicle. So the dental follicle give rise to pedodontal ligament, cementum and alveolar bone. So that's about development. So maxilla mandible forms through intramembraneous ossification in 8th week of utero alveolar process develops from dental follicle and it becomes closely related in bell stage. So it depends on the tooth size and resorption happens in a wall deposition on outer wall and it grows and these tooth lie in a trough of bone which is known as tooth crypt and these tooth separated by interdental septum and interradicular bone which separates the different roots of multi-rotor tooth and the deciduous tooth alveolar bone automatically resorbs and it slowly getting incorporated into the body of maxilla and mandible and will be a single bone. Now let's move on to the classification. We have many classification in alveolar bone. The one is based on the functional adaptation. So according to functional adaptation it can be classified as alveolar bone proper and supporting alveolar bone. So alveolar bone proper is just adjacent to the tooth root and the remaining part is supporting alveolar bone. And another classification is based on the histological characteristics. It can be divided into mature and immature bone. Mature again into compact bone and cancellous bone. Immature is woven bone. This is very important. Histological classification mature and immature. Mature into compact and cancellous bone and immature into woven bone. Compact means it is very densely compacted. Cancelous is not very densely compacted. Woven is a immature bone. And ultimately we can classify it is based on the gross morphology. So gross morphology we have basically only two types. One is basal bone and alveolar process. So alveolar process again it will be classified as alveolar bone proper, inner and outer cortical plates, trabecular bone, interdental septum and interradicular septum. So alveolar bone proper, inner and outer cortical plates, trabecular bone, interdental septum and interradicular septum. The alveolar bone proper which is again divided into bundle bone and lamellar bone. This is based on the gross morphology. This is based on the histology. This is functional adaptation. So let's see one by one. So first one is alveolar bone proper. So alveolar bone proper is a thin layer of compact bone. So before that we need to study what is compact bone and what is cancelous bone. And this is a alveolar bone. This part up to the root tip arbitrarily we can say that it is alveolar process and the remaining bone is a basal bone. So up to the root tip. There is an arbitrary point alveolar process and basal bone. So when we take a longitudinal section we get two layers of bone. The outer compact bone which is in pink color and the inner cancelous or spongy bone. Now we will start with alveolar bone proper. So alveolar bone proper is a thin layer of compact bone. So this is a compact bone the pink shaded and this black inner covering of the compact bone is known as alveolar bone proper. So it is continuous with the cortical plates and it forms the tooth socket. So it forms the tooth socket. So it is continuous with cortical plates and it forms the tooth socket. So it will be like this. So that is alveolar bone proper. It surrounds the root of the teeth and gives attachment to the principal fibres of periodontal ligament. So there will be principal fibres of periodontal ligament attached to the inner layer of cortical bone. So it is vascular canals and it is a double fibreler orientation. So this is very important in radiography because grippiform plate is anatomical landmark and lamina dura which we seen in radiograph which is covering the root is a radiographical term and we also call it as bundle bone. So bundle bone is a part of alveolar bone proper and it has lamellar portion also. So it is known as grippiform plate, lamina dura, bundle bone and alveolar bone proper. Lamina dura is a radiographic term, grippiform plate is anatomical term and bundle bone is a morphological and alveolar bone also morphological term. So it is around the teeth actually. Now we have inner and outer cortical plates. So alveolar process is continuous with the basal bone of maxilla and mandible. So this is the basal bone. So alveolar process is continuous with the basal bone. So arbitrarily as I mentioned the root tip keeps the alveolar process away from basal bone but it is a continuous we can keep an arbitrary point and we can divide the entire one into alveolar process and basal bone and alveolar bone proper is known as bundle bone as numerous bundles of sharpies fibers pass into it from the periodontal ligament okay. So that is why it is known as bundle bone lamina dura is because of its appearance it is a radio opaque area and grippiform plate because it has numerous sieve like appearance the vascular channels. So the alveolar bone proper has bundle bone lamina dura and grippiform plate synonyms. So it appears as a radio opaque or white line radiograph which breaks in continuity and if it is break in continuity of lamina dura at proximal aspect of crust of inter dental septum this is a inter dental septum and at the crust of inter dental septum if the breakages of lamina dura is visible then it is considered as the earliest radiographic change in periodontitis. So if the inter dental septum if the covering that is a lamina dura is not continuous then we can say that that part of bone is associated with some of the inflammatory process and which is indicating of periodontal disease at the earlier stage. Now we will see the cancerless bone okay. Cancerless bone is also known as spongy bone which is anatomic nerve, trabecular bone which is a radiographic nerve and cancerless bone is a historical name okay. So spongy bone cancerless bone and trabecular bone are same, grippiform plate lamina dura bundle bone and alveolar bone are same. So spongy bone or cancerless bone or trabecular bone which is a presence of trabeculae and closing irregular marrow spaces lined with a layer of thin flattened endosteal cells. This metric consists of irregularly arranged lamellae separated by incremental and resorption lines. So this is a lamellar part okay so the alveolar bone proper has bundle bone and lamellar bone. So matrix consists of irregular arranged lamellae and it is got basically two types type one and type two type one the interdental and inter-radicular trabeculae are regular and horizontal in a ladder like arrangement whereas a type two shows irregular arranged delicate interdental and inter-radicular pattern. So inter-dental septa or inter-dental bone is between the roots of two teeth whereas inter-radicular is between the roots of multi-rooted teeth okay this is inter-dental between the teeth this is inter-radicular between the roots. So the cortical bone and spongy bone so this is the cortical bone which is comeback bone and the spongy bone inside okay. So cortical bone is another name of comeback bone. So cortical bone is around see 85 percentage the spongy bone is 15 percentage cortical bone is having less turnover than spongy this is having high turnover and remodeling is around 3 percentage in cortical or compact bone and this is remodeled at 25 percentage and spongy bone is mainly of metabolic function this is of mechanical and protective role. So the layer of compact bone or cortical plate as known as alveolar bone okay and then said this is spongy bone this is alveolar process and this part is basal bone. Now we have inter-dental septum inter-dental septum is a bony partition that separates the adjacent alveoli. Coronally septa is thin and consists of only fused inner cortical plates. Coronally it will be thin and meso-distal angulation of meso-distal angulation of inter-dental septum is parallel to the line drawn between CEJ and approximating teeth and if inter-dental septum is narrow the septum may consist only cribriform plate. If the roots are too close together an irregular window can appear in the bone between the adjacent tooth. So it is a alveolar bone which is present between the teeth that is inter-dental septum and the shape of inter-dental bone is a function of tooth form and embrasure width the more taper the tooth the more pyramidal in the bony form the wider the embrasure more flattened the inter-dental bone will be. Alveolar crest is a tip of inter-dental bone where the inner and outer cortical plate meets the margin will be thin and knife edged in vestibular surfaces of anterior and rounded posterior teeth most prominent border of inter-dental septum. Okay so this is a crest of alveolar outer and outer and inner cortical plates this is a crest of inter-dental septum in one way. Inter-radicular septum is a bone between the roots of multi-rooted teeth. So basal bone, basal bone it is a OSHA's tissue of the mandible and maxilla except the alveolar process. Okay so alveolar process is up to the root and it is a OSHA's tissue that mandible and maxilla without alveolar process. So part of mandible and maxilla without alveolar process is basal bone. So this is a alveolar bone this is a basal bone. Okay and anatomically we cannot say that there is a distinct boundary that exists between maxilla mandible alveolar process and basal bone. This is just an arbitrary line. So we have covered our classification and the formation of bone the process of alveolar bone formation and classification in detail and about composition. Now the second part of alveolar bone will be covering the histology that is various cells and matrix components. So I'll come up with the second part the cells of alveolar bone basically the histology. So alveolar bone part 2. In this session we will be dealing about cells and matrix component of alveolar bone. So we have basically two types of cell that is osteogenic and osteoplastic. Osteogenic as the name suggests it is creating cells and osteoclastic it is destroying cells. Osteogenic cells are osteoblasts, osteocyte, bone lining cells and bone progenitor cells whereas the osteoclastic basically just the osteoclasts and in matrix component we have inorganic and organic. In inorganic we have calcium hydroxyapatite crystals. In organic we have collagen matrix and non-collagenous proteins. In non-collagenous proteins we have osteocalcin, osteopontin and bone silo protein, osteonectin, proteoglycans, etc. So the commonly asked questions are osteoclast, osteoblast. So we'll start with osteoblast. So during embryonic development the intram-embrane is born of the maxilla and mandible. Initially forms from osteoblast arising from condensing mesenchym in the facial region. So it is the most active secretory cells in bone. So it has basophilic cuboidal elongated cells which is rich in synthetic and secretory organelles such as rough endoplasmic reticulum, Golgi apparatus, granules, microtubules and it produces basically typhon collagen and non-cancelous bone proteins like silo protein, osteopontin, osteonectin and also growth factors also it will produce which express and release alkaline phosphatase. So alkaline phosphatase is very much important in bone formation. Alkaline phosphatase. So alkaline phosphatase activity has been recognized as a reliable indicator of osteoblast function. And osteocytes. So I'll just give you a cycle of formation. This is osteoprogenyta cell which is a very primitive one. Then osteoblast, later osteocyte and finally osteoclast. So these three are osteogenic cell but this is osteoclastic cell. So osteocyte is nothing but cells which is entrapped like osteoblast which is entrapped within bone are known as osteocytes. So the entrapped osteoblast. So osteoblast we learned. So the entrapped osteoblast is known as osteocyte. So if this osteoblast is entrapped within bone that is osteocyte which will be having canalicule and they occupy in spaces known as lacunae in bone and defined as cells surrounded by bone matrix. Now we have bone lining cells, bone lining cells. When bone surface are neither in the formative nor in the resorptive phase the surface is completely lined by a layer of flattened cell which is known as bone lining cell which is regarded as post proliferative osteoblast. So these bone lining cells are present when osteoblast and osteoclast activities are not there on the bone surface. Now the osteoprogenyta these are actually cells which produces osteoblast. So they are fibroblasts like cells with an elongated nucleus and few organelles. Whereas osteoclast we have learned this in detail about osteoclast in our previous sessions. So osteoclast originate from hematopoietic tissue fusion of mono-nucleus cells to form a multi-nucleated giant cell. This is a multi-nucleated giant cell. I have told you about this is a ruffled border and there will be a clear zone. So it is very large. It can have 5 to 50 nuclei which is active on less than 1 percentage of bone surface. It lie in house ships lacunae, acedophilic cytoplasm and there will be ruffled border. Okay so there will be ruffled border phasing the bone because hydrolytic enzymes are secreted and it has increased surface area. So wherever this resorption happens the border will be in this shape ruffled border and multi-nucleated giant cell will be there and there will be a clear zone apart from it. So that is osteoclast. Osteoclast is a commonly as short note. Osteoclast and osteoblast can be osteocyte and osteoprogenyta cell also can be a short note. So osteoclast at the periphery of ruffled border the plasma membrane is smooth and closely opposed to bone surface and the adjacent cytoplasm is devoid of cell organelles which is rich in actin and talin proteins associated with cell adhesion. This region is known as clear zone. Okay so this is a ruffled border and this is a clear zone. So clear zone is a adjacent cytoplasm which is not having any cell organelles. So this clear zone creates an isolated micro environment in which resorption can take place. So clear zone is also important. So severe osteoclast excavating a large area of bone which is the leading edge of resorption is termed as cutting con okay and released cytokines stimulates stem cells to differentiate into osteoblast. So these osteoblasts secrete osteoid which is known as filling con. So cutting con and filling con are the cutting con wherever this resorption happens is cutting con and when the deposition happens that is filling con. So always bone formation is a continuous process resorption and deposition will occur in a bone that's how it is remodeled throughout the life. So cutting con is a osteoclastic activity creating a edge is resolved and the other side when cytokines are released and there will be osteoid deposition which is known as filling con. So cutting con and filling con cutting con filling con. So cutting con there will be osteoclast activity and filling con there will be osteoblast activity. So that's about osteoclast and osteoblast. So two more things we need to learn is reversal line and resting line. So these are important what is reversal line and what is resting line. So this all can be asked as short note. So reversal line or also known as cementing line. So reversal line or cementing line which is a site of change from bone resorption to bone deposition is represented by a scalloped outline which is rich in silo protein and osteopontin. So reversal line you can say it is corresponding with filling con where the osteoblast deposit the new bone osteoid. So this is known as reversal line or cementing line that is the site of change from bone resorption to bone deposition. So before it was bone resorbed area so new bones will be added. So bone resorbed area will be like this ruffled border. So when there is bone deposition it will be shallow instead of ruffled border. So that is known as reversal line or cementing line. So the change of bone resorption to bone deposition. Now what is resting line resting line is rhythmic deposition of bone with periods of relative inactivity seen as parallel vertical lines. So there will be parallel vertical lines in bones when we take ground section of bone we can see parallel vertical lines. So there will be rhythmic deposition of bone it will be added layer by layer but in between there will be a relative inactive phase which is seen as vertical parallel line that is known as resting line and reversal line is when deposition and resorption deposition happens the previously resorbed area gives a scalloped area which is known as reversal or cementing line. So we have few age changes in bone just like any heart tissue we have seen that in a symptom the age changes and also we have seen in PDL also. So any tissue any living tissue will go through the age changes. So in bones it is similar to like what is occurring in skeletal system there will be osteoporosis with aging there will be decreased vascularity reduction and metabolic rate and healing capacity. So bone resorption may be increased and more irregular periodontal surface will be seen and few variations in normal bone are fenestration, dysense, exostosis, buttressing, bone formation or it is also known as slipping. So fenestration and dysense are removal of bone that is facial surface more involved fenestration is isolated loss of bone and dysense is a complete loss of facial bone. So it is anterior tooth or more involved and frequently bilateral sometimes due to malposition and root prominence or labelled protrusion. So etiology could be excessive occlusion force so this fenestration and dysense could be a sharp note. So next thing is exostosis. Exostosis are outgrowth of bone of varied size and shape they can occur as small nodules large nodules maybe sharp ridge or spike leg projection or any combination of the above that is nodule small or large ridges or spike leg projections and buttressing bone formation or liping is nothing but sometimes what happens is bone formation occurs in an attempt to buttress bony trabeculae which is weakened by resorption okay. So when it occurs within the jaw which is termed as central buttressing bone formation and when it is on the external surface which is known as peripheral buttressing bone formation. So this peripheral buttressing bone formation will cause bulging of the bone contour which is known as liping okay. So that is attempt to buttress a bony trabeculae which is weakened by resorption. So that is bone buttressing so that is all about normal variations and we have bone deformities horizontal and vertical. So vertical will be an angular bone loss horizontal will be evenly distributed means your means your distal direction. So we are not going much into those things so idea was to give a proper introduction about alveolar bone the types of alveolar bone its formation its composition and little bit about its variation bone deformities and age changes. So we finished our pyridontism that is djinncheva pyridontal ligament or the soft tissues and cementum and alveolar bone are the heart tissues. So pyridontism is nothing but which supports and surrounds the tooth. So djinncheva pyridontal ligament, cementum, alveolar bone are supporting structures of tooth. So we have many more topics coming up we have to finish enamel, dentine and pulp. So I will come up with these topics in my next sessions thank you.