 Hello everyone, welcome back to a new session in dentistry and more. Today's session is about dentine. So we will be covering this under a few sessions. So the first session is about dentine, its formation, its structure and little details about the dentinal reviews. And second part is about various types of dentine and the last session will be covering about the theories relating the dentine transmission of nerve impulses. So let us see one by one. So dentine as we all know it is a tooth layer basically the second layer of tooth which provides the bulk and general form of the tooth and it begins to form slightly before the enamel. It determines the shape of crown including the cusp and ridges and also the number and size of the roots. So let us get into the details of dentine. So dentine the hard structure of tooth just like enamel which is physically and chemically it closely resembles bone and it is said to be a living tissue then enamel is not a living tissue it is mostly a vascular, a cellular. But dentine is a living tissue since tubules present in it contains processes of specialized cell which are odentoblast ok so odentoblast. So since it has odentoblast which is known as living tissue we can say that it is a living tissue unlike enamel. The main morphological difference between bone and dentine is that some of the osteoblast osteoblasts are the bone cells exist on the surface of the bone and when one of the cells become enclosed within its matrix it is called an osteocyte ok. But the odentoblast cell bodies remain external to dentine ok but their processes exist within the tubules in dentine but the cell bodies remain external to dentine the osteocyte is not there in odentoblast there is no odentocyte in osteocyte it is nothing but when the cell becomes enclosed within its matrix ok. But these odentoblast cell bodies remain external to dentine that is the basic difference between bone and dentine or we can say osteoblast and odentoblast we have osteocyte in bone which is enclosed within the matrix and stages of tooth development we have studied in detail the stages of tooth development in enamel it is almost same nothing is different only thing is the odentoblast which is giving rise to dentine first the inner enamel epithelium it influences the pulp to differentiate the odentoblast to form the first layer of dentine then dentine forms when dentine forms it in turn differentiate the amyloblast the inner enamel epithelium into amyloblast. So once this dentine pre-dentine is formed the nutritional supply to the inner enamel epithelium is cut and the nutritional will be taken from the dental sac. So this is the dentine which forms pre-dentine forms so it forms in the coronal part and even the root part so we have two types of dentine the coronal dentine and root dentine and this is a cervical loop so there will be proliferation at this area this will results in root formation and this is giving rise to hardwicks epithelial root sheath so all this we have covered in detail in the development of tooth and also in enamel chapter. So coronal part I mentioned in enamel chapter in detail so the root dentine when the root formation proceeds the epithelial cells from the the cervical loop which proliferates apically and influences the differentiation of odentoblast from the dental papillae as well as cementoblast from the follicle okay this is a follicle this is dental papillae so we differentiate the dental papillae to form the root dentine and it will differentiate the cells from the dental sac to form cementum so there will be deposition of root dentine and cementum. So that is about formation of odentoblast or dentine so the structure of dentine basically the dental matrix of collagen fibers are arranged in network so it is arranged in a network and as this dentine calcifies calcifies the hydroxyapatite crystal mass the collagen fibers so the bodies of odentoblast they are arranged in layer on the pulpal surface of the dentine okay so bodies are arranged in so these are arranged this is a pulpal surface so this is a pulp this red color so bodies are arranged this is a pulpal surface okay this is a pulpal surface so the body the odentoblast odentoblast will be like with a projection and will be like this so this is a tail and this is a head part so the bodies of odentoblast arranged in a layer on the pulpal surface so this will be arranged in the layer on the pulpal surface on the dentine and only their cytoplasmic processes are included in the tubules in the mineral matrix okay so each cell give rise to one process which travels the predentine and calcified dentine within one tubule and terminates in a branching network to the DEJ or CEJ so it goes starts from the pulpal surface and terminates here this is the enamel the outermost covering and it's it terminates at the DEJ or CEJ which is the root portion where cementum and dentine meets which is known as cemento dentinal junction in crown it meets with enamel which is known as dentino enamel junction okay now let's learn something about dental tubules which is basically the course of these tubules follow a gentle curve okay so the gentle curve so it is a double curvature and this is known as a S shaped curve so we have a S shaped curve this is like this S shaped curve and it starts at right ankle at the pulpal surface okay so this is a pulpal surface it starts at right ankle to the pulpal surface just like enamel it starts from right ankle to the dental surface so it starts right ankle at the pulpal surface and first convexity of this doubly curved course is directed towards apex of tooth okay so it will be like this so the first convexity towards the apex okay this is first convexity and this is second convexity so first convexity towards the apex of tooth and these tubules are perpendicular to DEJ and CEJ okay so DEJ will be on the crown and CEJ C not CEJ C DEJ that is cemento dental junction this will be in root and DEJ will be in crown and this is double curvature double convex and it has a shaped pattern so dental tubules are almost straight near the root tip at the root tip which will be almost straight and also straight at the incisal edges and cusps so dentin thickness ranges from 3 to 10 millimeter and the ratio between outer to inner dentin has 5 is to 1 that is outer has 5 tubules compared to the inner tubules ratio between outer to inner number of tubules 5 to 1 the more tubules are present in the outer portion of dentin that is which is closer to the enamel and number of tubules per square millimeter varies from 15,000 at DEJ but the number of tubules is lesser at DEJ and more at pulp that is around 15,000 at DEJ but 65,000 near the pulp surface so 5 is to 1 was the outer and inner dental surface ratio okay 5 is to 1 but this is number of tubules per square millimeter so number of tubules per square millimeter is very low or less than 50,000 or around 15,000 at DEJ but it is 65,000 at pulp whereas the outer and inner surface of dentin is about 5 is to 1 okay so outer dentin has 5 with respect to inner dentin 5 times bigger outer dentin compared to the inner dentin and next we have dental tubules and it has lateral branches throughout the dentin which is termed as canalicule or micro tubules and this enamel spindle we have learned in chapter enamel that is the odentoblast process okay so the odentoblastic processes which extends through the DEJ into enamel several millimeters which is known as enamel spindle actually enamel spindle is not an enamel structure which is actually a odentoblastic that is a related dentin which which transfers or which enter into this DEJ for few millimeter at it terminates in enamel that is why it is known as enamel spindle this is the odentoblast which extends from DEJ extends through DEJ into enamel okay so that is known as enamel spindle so next we have various types of dentin in next session we will be learning about types of dentin such as peritubular dentin, inter tubular dentin, pre dentin and odentoblastic processes primary dentin, secondary dentin, tertiary dentin so all will be dealt in next session okay thank you hello everyone let's continue our dentin sessions so today's video is about types of dentin so i'll be explaining all the types using this picture and we have some special features of dentin such as incremental lines of von Ebbner's lines and contour lines of oven and tombs granularly so let's get into details of all the types of dentin and other features so let's start with peritubular dentin so all these questions are very very important because these are commonly asked short notes in university exam so let it be peritubular dentin, inter tubular, pre dentin, odentoblastic process primary dentin, secondary dentin, tertiary dentin, mantel dentin, circum pulpal dentin, inter globular dentin and we have contour lines of oven, von Ebbner's lines and tombs granular layer so all our short 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 dentin so peritubular dentin the dentin 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 tube the dentin which is immediately surrounds the dentinal tubules this brown color dentin is known as peritubular dentin which is highly mineralized than the inter tubular dentin okay inter tubular dentin is between the tubules as the name suggests it is between the tubules it is more mineralized than the inter tubular dentin and it is twice as thick in the outer dentin than the inner dentin 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 dentin calcified tubule okay so that is peritubular dentin now we have the second one that is inter tubular dentin so inter tubular dentin which is located between the dentinal tubules okay so between the dentinal tubules we have inter tubular dentin which is less mineralized than the peritubular dentin 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 dentin so we know we have peritubular dentin here and here this is just two odentoblastic processes we have many odentoblastic process so between peritubular dentin we have odentoblastic sorry inter tubular dentin this violet color I mentioned the inter tubular sorry inter tubular dentin lots of confusing dentin is there so I am talking about inter tubular dentin which is between the peritubular dentin okay and the fibers the collagen fibers ranges from 0.5 to 0.2 micrometer and 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 dentin and it provides tensile strength to so strength to dentin that is its function now we have pre-dentin okay so next is pre-dentin this is pre-dentin so we finished peritubular dentin and inter tubular dentin now we have pre-dentin pre-dentin we know which is the first dentin 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 dentin which is known as pre-dentin and which is not mineralized and these the collagen fibers which undergo mineralization at the pre-dentin and the pre-dentin then becomes dentin and a new layer of pre-dentin forms circum pulpily okay so pre-dentin once it is mineralized it becomes dentin and then at the same time there will be new layer of dentin that is pre-dentin will be formed so pre-dentin is not mineralized one it is the first formed dentin which is adjacent to dental pulp okay so that is pre-dentin 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 a enamel part okay yes because this is a DEJ so that is enamel spindle we learned in last session and laminalimentons was a organic layer of peritubular dentin so the odentoblast which resides in the peripheral pulp at the pulp pre-dentin border and their process extends into dental tubules okay so the process extends into dental tubules these odentoblast reside in the peripheral pulp and pulp pre-dentin border so we have pulp here so hope you can understand the concept we have pulp here this is the pulp okay this is enamel this portion is enamel so odentoblastic is between pulp and pre-dentin 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 dentin 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 dentin which is a dentin that is formed prior to eruption of tooth and which is secreted at relatively higher rate and which constitute major part of dentin in the tooth and mantel dentin is the first formed dentin in the crown underlying DEJ that is dentino enamel junction which is regular in structure dentin tubules form S shaped as a result of directional movement of odentoblast whereas the circum pulp dentin forms a remaining primary dentin or bulk of the tooth okay so mantel dentin and circum pulp dentin so the fibres are much smaller in diameter and are more closely packed together and the slightly more mineral content than in mantel dentin for circum pulp dentin okay so whereas a secondary dentin secondary dentin is formed after root completion and there is narrow band of dentin bordering the pulp which contain fewer tubules and primary dentin and there is usually a bend in the tubules where the primary and secondary dentin interface so since it is formed after eruption the odentoblast slightly changed directions which contributes to the bending of dentinal tubules so primary dentin is before primary dentin is before the eruption of tooth whereas a secondary dentin after completion of root okay now we have tertiary dentin tertiary dentin is what we are inducing dentin 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 dentin surface which is very close to pulp so after two or three weeks there will be dentin 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 dentin and there will be a layer of dentin formed a new dentin formed which seals off or which keep a boundary between the outer surface from the pulp so such type of dentin is known as tertiary or repetitive dentin 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 dentin is produced which are known as reactionary or regenerated dentin so killed odentoblasts are replaced by migration of undifferentiated cells arising in the deeper layer of pulp to the dentin interface so newly differentiated odentoblasts then begin deposition of repetitive dentin to seal off the zone of injury as a healing process initiated by pulp so there will be sealing of the ensuring so that is why it is known as repetitive dentin and now we have mantel dentin okay so already we've seen mantel dentin it is a first layer of primary dentin to be deposited and which is that is why it is the oldest dentin 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 dj okay whereas a circum-pulpile dentin which is formed after the layer of mantel dentin has been deposited and which constitute major part of primary and secondary dentin the hydroxyapatite crystals are deposited on the surface within the fibrils and continue to grow as mineralization proceeds which results in increased mineral content of dentin now we have incremental lines of worn ebner so the incremental lines of worn ebner or imbrications line appear as fine lines or striations in dentin so similar lines we have seen in enamel which are they the incremental lines of red cs okay so the similar line in dentin is known as worn ebner's line so these lines reflect the daily rhythmic recurrent deposition of dentin matrix as well as the 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 come continuous addition of minerals so those lines is known as worn ebner's line so this is in the dentin whereas in incremental lines of red cs in enamel okay so the course of these lines indicate the growth pattern of dentin and some of these incremental lines are accentuated because of the disturbance in the matrix and remanelization 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 a accentuated accentuated because of the disturbance in the matrix and remanelization process so accentuated incremental lines are known as contour lines of oven and we have another structure which is neonatal line where this is seen the deciduous teeth when the first permanent molar the prenatal and postnatal dentin is separated by an accentuated contour line which is known as neonatal line okay so with that we have seen in dentin also when the separation between the prenatal and postnatal enamel the similarly prenatal and postnatal dentin is separated by neonatal line this line reflects the abrupt change in environment that occurs at birth okay so the dentin matrix formed prior to birth is usually better quality than that formed after birth and now we have inter globular dentin okay inter globular dentin so before we have seen inter tubular dentin now we have inter globular dentin so inter globular dentin sometimes mineralization of dentin begins in small globular areas that failed to fuse into homogeneous mass so this results in zone of hypo mineralization between the globules so these zones are called as inter globular dentin which is forms in crowns of teeth in the circum pulpal dentin just below the mantel dentin okay just below the mantel dentin we can see inter globular dentin so this is a circum pulpal dentin this is a mantel dentin just below the mantel dentin we can see in circum pulpal dentin the inter globular dentin which is seen just below mantel dentin 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 dentin 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 dental tubules that is tom's granular layer don't get confused tom's process in enamel tom's granular layer in dentin so that is all about various structures various types of dentin so we have covered peritubular dentin which is adjacent to tubules inter tubular dentin between the peritubular dentin pre-dentin which is first formed dentin and under the plastic process which is cytoplasmic extension primary dentin and secondary dentin which is the mandrel dentin secondary dentin and the tertiary dentin which is repetitive dentin on process pathological or operative procedures mandel and circumpulpal dentin mandrel dentin is adjacent to dg and the remaining portion as it is circumpulpal dentin because it has towards a pulpal site okay and inter tubular dentin and we have incremental lines which is similar to incremental lines of radius 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's all about the various types of dentin next we have a few theories of the innovation of dentin and some of the physical and chemical properties and innovation part of dentin i'll come up with so i'll come up with innovations and physical and other properties of dentin in my next video thank you hello everyone let's continue our sessions in dentin so this third part will be covering more about physical and chemical properties and organic and inorganic content of dentin and the innovation various theories of innovation and the functional changes that is age and functional changes which are detracts sclerotic or transparent dentin and affected and infected dentin so let's see the details of these theories innovation and functional changes dentin is light yellowish color and it becomes darker with age which is harder than bond but considerably softer than enamel which has lower content of mineral salts which renders it more radio lucent than enamel okay radio lucent it appears more blacker okay radiopec means more whiter in radiography so it appears more radio lucent than enamel because of the lower content of mineral salt now it is a chemical composition which has 70 percentage of inorganic content whereas in enamel it was 96 percentage and the 20 percentage is organic matter and the remaining 10 percentage is water in organic substance it has basically type 1 collagenous fibers and minor amount of type 5 collagenous fibers non-collagenous proteins includes dentin phosphor proteins dentin matrix protein dentin silo protein bone silo protein osteopontin osteocalcin etc and other proteoglycans phospholipids and some of the growth factors inorganic substance basically calcium hydroxyapatite crystals so type 1 collagen is a principal type of collagen found in dentin and inorganic crystals are plate shaped and are much similar than hydroxy apatite crystals in enamel and dentin also contains small amounts of phosphates carbonates and sulfonates okay now we are moving on to the innovation part so this is the part of dentin which has nerve endings so nerve fibers were shown to accompany 30 to 70 percentage of the odendoblastic processes and these are referred to as intra tubular nerves so it has intra tubular nerves so which carries the sensation okay so intra tubular nerves so these nerves and the terminals are found in close association with odendoblast process within the tubule so we have various theories of pain transmission through dentin so this is the theories of pain transmission the first one is direct neural stimulation transduction theory modulation theory gait control or vibration theory and hydrodynamic theory so let's see one by one the first one is direct neural stimulation this is according to which nerves in the dentin get stimulated but the main drawbacks is the nerves in dentin tubules are not commonly seen and even if they are present they do not extend beyond the inner dentin so topical application of local anesthetic agents do not abolish sensitivity hence this theory is not accepted okay so the direct neural stimulation is not well accepted theory as per this theory they say is the nerves are present on the dentin so if it is present on the dentin that topical application of local anesthetic agents should abolish sensitivity but it is not happening so it is not well accepted next one is transduction theory which is the odendoblast process is the primary structure excited by the stimulus this is the odendoblastic process and that the impulses transmitted to the nerve endings in inner dentin okay so drawbacks is the non-neurotransmitter vesicles in the odendoblast process to facilitate the synapse or synaptic specialization so according to transduction theory there is no presence of any type of neurotransmitter vesicles in the odendoblast so that theory also not well accepted now we have the third theory that is modulation theory so according to which nerve impulses in the pulp are modulated through the liberation of polypeptides from the odendoblast when injury or something happens so these substances may selectively alter the permeability of odendoblastic cell membrane through hyperpolarization so that the pulp neurons are more prone to discharge upon receipt of subsequent stimuli that is a modulation theory when it gets modulated okay that is also not well accepted the next one is gate control or vibration theory this theory states that the pain is a function of balance between information traveling into the spinal cord through large nerve fiber and information traveling through small nerve fiber so large nerve fiber carry non-nose-subtive information and small fibers carries nose-subtive information okay that is a gate control or vibration theory it is between the large and small nerve fibers so according to this theory a beta fibers which transmit information from vibration receptors which stimulate inhibitory neurons in the spinal cord which in turn act to reduce the amount of pain signal transmitted from a delta and c fibers across the midline of spinal cord and from there to bring there is a gate control vibration it is basically the types of fibers it is highlighting a beta a delta and c fibers so whereas the modulation is different one modulation is the permeability change in odendoblastic cell membrane by hyperpolarization transduction is different one it is odendoblast process which is excited by the stimulus and the last one which is the most accepted theory which is the hydrodynamic theory so various stimuli such as heat cold air blast or mechanical or osmotic pressure which affects the fluid movements and the dental tubules okay so hydrodynamics so hydromines water dynamics is changed so the fluid moments is the most accepted concept of pain transmission so this is a fluid moment either inward or outward stimulate the pain mechanism in the tubules by mechanical disturbance of the nerve closely associated with odendoblast and its process so it is all about moment of the fluid inward and outward the odendoblastic process so these endings may act as a mechanoreceptors as they are affected by mechanical displacement of tubular fluid so this is all highlighting about the moment of fluid and it is the most accepted one okay so age and functional changes we are moving to the last part which is age and functional changes so the vitality of dentine due to physiological and pathological stimuli there will be always a change in vitality of dentine and secondary dentine will be continuously deposited and the pulpal layer as a dentine is removed so removed by the changes and such as dental caries abrasion attrition and such process there will be formation of structures like dead tracks, sclerosis and in addition to the secondary dentine or reparative dentine okay so reparative dentine we already seen in our session 2 now let's see what is dead tracks so dead tracks is nothing but odendoblastic processes which disintegrate and empty tubules are filled with air so it disintegrates and it fills with air okay so the it looks like black or dead tracks which is very black in color when transmitted light and white in reflected light okay so dead tracks appear as black in transmitted light and white in reflected light so this degeneration is often observed in areas of narrow pulp on because of crowding of odendoblast and these empty areas demonstrate decreased sensitivity and dead tracks are probably the initial step in the formation of sclerotic dentine okay so this is the track which is giving sclerotic or transparent dentine this sclerotic or transparent dentine when caries attrition abrasion erosion or cavity preparation causes collagen fibers and appetite crystals to begin appear in the dentinal tubules so this blocking of tubules may be considered as a defensive reaction of dentine so these appetite crystals are initially only sporadic in dental tubule but gradually fill it with a fine mesh work of crystals so that is transparent dentine so as this continues the tubule human is obliterated with minerals which appears very much like peritubular dentine it looks like peritubular dentine so the refractive indices of dentine in such areas become transparent and transparent and transmitted and dark in reflected light so there is decreased permeability of dentine okay so that is why these caries attrition abrasion in such cases the collagen fibers and appetite crystals to begin appear in the dentinal tubules so the dentinal tubules will be blocked and the refractive index of this dentine will be similar as the adjacent peritubular dentine and it will look like transparent and and transmitted and dark in reflected light so the last one is affected and infected dentine so the infected dentine is that part of dentine which is contaminated and contains microorganisms and the toxins and demineralized dentine whereas the affected dentine is not occupied by microorganism it just contains the toxins produced by microorganism of infected dentine and also there is demineralization okay so the collagen fibers are D natural D natural in infected dentine while in affected dentine the collagen fibers demonstrated cross banding and is physiologically remineralizable so that's all about dentine we have finished dentine so we have finished in three sessions the first part was the basic dentine formation and the second part was various structures and the third part we mainly focused on the theories of innovation okay so the lots of questions will be asked lots of short notes we had seen primary dentine secondary dentine tertiary dentine then the one-abness lines then we have detracts sclerotic or transparent dentine oven lines of oven and the mandrel dentine circumpal dentine peritubular inter tubular inter globular dentine predentine so everything might be asked as short note so I'll come up with a pulp in my next session thank you