 Hello everyone. Let's continue our sessions in Dantine. So, this third part will be covering more about physical and chemical properties and organic and inorganic content of Dantine and the innovation, various theories of innovation and the functional changes that is age and functional changes which are detracts, sclerotic or transparent Dantine and affected and infected Dantine. So, let's see the details of these theories, innovation and functional changes. Dantine is light yellowish color and it becomes darker with age which is harder than born but considerably softer than enamel which has lower content of mineral salts which renders it more radio-lucent than enamel. Radio-lucent, it appears more blacker. Radio opaque means more whiter in radiography. So, it appears more radio-lucent than enamel because of the lower content of mineral salt. Now, it is chemical composition which has 70% of inorganic content whereas in enamel it was 96% and the 20% is organic matter and the remaining 10% is water. In organic substance it has basically type 1 collagenous fibers and minor amount of type 5 collagenous fibers. Non-collagenous proteins includes Dantine, phosphor proteins, Dantine, matrix protein, Dantine, silo protein, bone silo protein, osteopantine, 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 Dantine and inorganic crystals are plate shaped and are much similar than hydroxyapatite crystals in enamel and Dantine also contains small amounts of phosphates, carbonates and sulfonates. Now, we are moving on to the innovation part. So, this is the part of Dantine which has no endings. So, nerve fibers were shown to accompany 30 to 70% of the odendoblastic processes and these are referred to as intratubular nerves. So, it has intratubular nerves which carries the sensation. So, intratubular 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 Dantine. So, this is the theories of pain transmission. The first one is direct neural stimulation, transduction theory, modulation theory, gate 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 Dantine get stimulated. But the main drawbacks is the nerves in Dantine tubules are not commonly seen and even if they are present they do not extend beyond the inner Dantine. So, topical application of local anesthetic agents do not abolish sensitivity. Hence, this theory is not accepted. So, the direct neural stimulation is not a well accepted theory. As per this theory, they say the nerves are present on the Dantine. So, if it is present on the Dantine, 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 odendoblast process and that the impulses transmitted to the nerve endings in inner Dantine. 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 odendoblast 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-nososceptic information and small fibers carry nososceptic 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 brain. That is a gate control vibration. It is basically the types of fibers. It is highlighting A beta, A delta and C fibers. So, whereas a 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 moments and the dental tubules. Okay. So, hydrodynamics. So, hydromains, water dynamics is change. 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 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 two. 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, it looks like black or dead tracks which is very black in color when transmitted light and white in reflected like. 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 dental 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 tubules 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 dental tubules. So, the dental 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 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 is all about dentine. We have finished dentine. So, we have finished in three sessions. The first part was a 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 have seen primary dentine, secondary dentine, tertiary dentine, then the one-ibness lines then we have detracts, sclerotic or transparent dentine lines of oven and the mandrel dentine, circumpal dentine, peritubular, intertubular, interglobular dentine, predentine. So, everything might be asked as a short note. So, I will come up with a pulp in my next session. Thank you.