 Hello everyone, welcome back to new session on dentistry and more. So we have a continuation of fluoride topics. So today we have a very small topic that is prevention of dental caries by fluoride. So we have learned various fluoride mechanisms like systemic fluorides, topical fluorides and its gross mechanisms like systemic goes to the blood circulation. It enters to the mineralization stage and replaces hydroxyl ion and making it fluoro-apetite crystals. Whereas in topical fluorides the mechanism is different because it uses the posterior rective mineralization where this fluoride forms calcium fluoride by combining with the calcium of enamel and this fluoride will be available for further remanolization. So the mechanism is different where the systemic utilizes the pre-rective mineralization stage which is a majority that is 90 percentage of total mineralization and it has to be done before 6 to 7 years because most of the teeth get mineralized before 7 years and posterior rective mineralization will be utilized in topical fluorides where the 10 percentage of the mineralization will be used but that is very critical because it is lifelong remanolization and remanolization will be happening in our tooth because our teeth in oral cavity are subjected to various pH and various changes in day to day life. So basically what happens when a fluoride is incorporated into teeth we have learned already. So in today's video I will be explaining few mechanisms whereby fluoride prevents dental caries. The first mechanism is fluoride increases the enamel's resistance and acid solubility because it replaces hydroxyl ion in the enamel lattice because it is a hexagonal shape which has a central void where the hydroxyl ion is located. Since fluoride is very highly electronegative it replaces the hydroxyl ion both are negative ions so it replaces the hydroxyl ion and it fills the void which is present inside the enamel lattice and makes it very resistant to acid attack. So that is why it becomes resistant when there is acid challenge happens because it forms fluoropotate. You know enamel is a hydroxyapatite crystal so this hydroxy ions that is OH ions will be removed and it becomes fluoropotate. So this hydroxyl ion that is OH ions is less electronegative than this fluoride ion. So this will be replaced and this fluoropotate will crystal will be formed. So that is why it is becoming very resistant and it is making acid less soluble. Whereas the second mechanism is reminulization potential of fluoride. So if we add fluoride in our drinking water or if we keep fluoride in our topical or toothpaste or any solution gels forms varnish. What happens is fluoride will be present in the oral environment maybe in the gingival crevicella or saliva and it will be act as a reservoir to replenish the lost ions in the teeth. So today today we may lose so much of ions because of our acidic food taking and our brushing or many factors we lose day by day some ions. But if fluoride is present in the saliva or GCF it can easily replenish the lost ions. So reminulization will be favoured and there will be less caries chances. So topical fluoride also it has the advantages of presence of fluoride ions in the GCF and saliva. So it gives fluoride ions whenever there is a loss of ions from the tooth surface. So it always protects the tooth by providing fluorides whenever there is deminulization. So reminulization potential is very important because every day it act as a reservoir inside saliva or GCF. And fluoride also has antibacterial effect because it interferes with the bacterial cell growth because it has inhibitive effect on the enzymes which are essential for cell metabolism and growth. That is streptococcus bacterial enzymes are destroyed or inhibited by this fluoride and it reduces surface energy of tooth and it can strip off bacteria from hydroxyapatite because fluoride can bind more effectively to positively charged areas on the appetite itself than the bacteria. So obviously fluoride is beneficial. So if it attaches on the tooth surface and the bacteria has no place to be attached to there is no platformation and ultimately less caries. So this is the antibacterial effects. And the fourth point is increased rate of post eruptive maturation. So I told you already there are two phases of maturation of a particular tooth pre eruptive maturation that is happening before the tooth erupts into oral cavity and post eruptive maturation. And post eruptive maturation is critical because it is a lifelong process. Every day we have ion loss from the tooth surface and at the same time the ions are coming back to the tooth. So if the ion loss is becoming more compared to the replenishment then there is chance of caries. But the rate of post eruptive maturation is why it is important because this fluoride has a special capacity to remineralize the hypomineralized areas that is its biggest advantage. So wherever the tooth is not properly mineralized that areas will be soon or fastly remineralized by the help of fluoride. And the newly ruptured teeth we know the newly ruptured teeth are still need to get mineralized by 10 percentage. So these teeth can attract fluoride very easily. So we should apply fluoride always to the newly ruptured teeth. That's why fluorides are applied onto the newly ruptured teeth in nuts and stick we have seen. It is applied on 3, 7, 11, 13. So all the teeth are like deciduous molars, permanent molars and incisors, canines, primolars. So soon the tooth erupts into the oral cavity we should apply fluoride because this fluoride will soon be uptake, soon will be taken into the surface because these areas are hypomineralized. It get mineralized only after 3 years or 2 to 3 years. The complete mineralization happens, the post mineralization happens by after 2 to 3 years. And there will be a lifelong remineralization, remineralization cycle. So we have to use that potential once the tooth erupts into the oral cavity we should apply fluoride. That is why we are applying topical fluorides into the recently ruptured teeth. And the last mechanism is modification in tooth morphology. So it has seen that people who consumed fluoride water as changes in the diameter and custom depth compared to the people who have not taken fluoride water. So it reduces the occlusion depth and occlusion cavity will be lesser and lesser transverse of caries. Because of this improved morphology of occlusion surface can be attributed to the lesser amount of caries. So the diameter and custom depth are smaller if fluoride is present. So this is a very small topic, these mechanisms are the real reason why the fluoride prevents dental caries. So these were the mechanism, the first one was it increases enamel resistance to acid solubility. There will be less acid solubility enamel, then there will be remineralization, there is antibacterial effect and increase rate of, that is in hypo mineralized area, there is increased rate of posteroctymetration and there will be modification in tooth morphology. So about the mechanism of caries section of fluoride, so I will come up with fluoride toxicity and defluration in my next sessions.