 So, good morning everyone. So today we are seeing Keri's activity test So Keri's activity test is nothing but measuring the activulations over a stated period of time in a person It is a speed of progression of Keri's solution. How fast a person will develop Keri's That is what Keri's activity test is all about So we have seen the Keri's risk assessment that is assessing the risk of a person and This Keri's activity It is assessing the speed of progression both are different. Oh one or the same it is Indicating the same thing that is risk and the Keri's development and the other one is Keri's progression speed okay both are indicating the Formation of Keri's but in a two different aspect So we don't go much Into the details. We just have to see the ideal Recusets of any Keri's activity test. So as we all know it should give a good correlation between predicted and actual Keri's and there should be reliability Validity and it should be simple and it should be rapidly giving the results and It should also Be very inexpensive non-invasive procedure and easy to evaluate. So these all are the ideal Rekusets of Keri's activity test So we have n number of Keri's activity test, but we will be studying only the colorimetric Colorimetric Snyder test So we have many tests you can just remember the names like Saliva flow test, Lactobacillus test, Swab, Albans, Salivary Reductive test for our test And Foci-T Calcium Dissolution test. So we'll be seeing the colorimetric Snyder test So flow test and this buffering test. It's all checking the flow rate and buffering capacity So the basic procedure is same for everything and Lactobacillus Colony test is also checking the count of Lactobacillus bacteria. So the basic procedure is like this. We take Saliva We incubate it. We check for bacteria or we check for any change in the Saliva So in Snyder test as its name suggests it is a colorimetric Test. So something is there linked with color So what we are checking here and Snyder test is the change in color Okay, the change in color will indicate something that we will learn just given by Snyder in 1951 So there is a principle behind this test that has formation of organic acids by Acidogenic and aciduric microorganisms in a carbohydrate medium So as we all know dental caries is formed by the presence of Streptococcus bacteria acting upon the carbohydrate resulting in Lactic acid. So the formation of Lactic acid ultimately Causes deminulization and leads to cavity formation So this is what the principle of Snyder test. So what We are doing in Snyder test is we are collecting amount of Saliva and we are adding with The substrate that is glucose agar medium And we are incubating it at 37 degree Celsius. Incubation means multiplication of bacteria in order to have a better Amount to get it checked. Okay, so if we have very low amount of bacteria, we will not be get the clear picture of Saliva details. So we usually in Microbiological specimens will incubate it. So we do incubation always at body temperature that is 37 degree Celsius So we incubate it maximum of 70 tours and we'll check for the color change in Saliva. So how to the change in color occurs at Saliva So what happens is we are Adding glucose material So there will be bacteria in this saliva. So that is what we are checking the amount of bacteria in Saliva. More amount of bacteria means The patient has more caries susceptibility. Less amount means less susceptibility So more bacteria means it produces more amount of acid So more amount of acid means the saliva will go to less pH That is more acidic If there is less amount of bacteria less amount of acid the pH will not change much So the basic pH is what we are taking is 5.4. The normal pH is around 6 So, how do we get the idea? The pH change so there the comes The Bromocosal Green dye which is an indicator dye which helps us to Identify the change in color According to the pH it gives green color at 5.4 pH and it gives yellow color at 3.8 pH So yellow means more acidic green means least acidic So that is why we are adding this particular dye Into this material. Otherwise, we won't be knowing the pH change how the pH is changing. We will be seeing just saliva We will not get an idea of pH And which gives Very clear indication visible indication that pH has gone to a lower level by adding this particular Dye so don't forget the name Bromocosal Green which is an indicator dye Which changes the color of saliva based on the pH So what happens is when it is 24 hours? We check the bottles So if it has become yellow that means if it is pH is 3.8 We can say that the particular person has very marked susceptibility of carries If still it is green we continue to incubate and observe at 48 hours And if it is becoming yellow at 48 hours, we can say that there is definite carries susceptibility marked means very high Definite means it comes in between But if it is still green we are incubating at 72 hours. So it is becoming Yellow at 72 hours. We can say that there is a limited carries susceptibility carries susceptibility is very less because the organisms could produce The yellow color that is pH change has happened over a period of three days So the amount of bacteria will be less. So there will be less carry susceptibility If still it has become green and there is no color change. We can say that that person has no carries Susceptibility or no carries activity. So that is the basic principle will incubate Up to 72 hours after 72 hours, there is no point of testing Because the bacteria won't survive beyond 72 hours. So after that We'll get an idea the patients carries susceptibility. Okay, so this is what it the color change will look like the Question number one is green and the five is yellow So this is 3.8 Sorry, this is 5.4 pH and this is 3.4 3.8 Yeah, 3.8 So there is many advantages and disadvantages. We don't need to Use multiple serial dilutions. We can use only one tube And it is very simple to carry out disadvantages are just time-consuming and the color changes are not very precise And there are two modifications of Snyder test. One is Albin's test and one is Swap test. In Albin's test We use a less agar in the medium Because usually when we apply agar it needs to be melted So if we use less agar there is no need of melting and in Swap test We are using buckle surface swaps Using a cotton applicator Okay, so these two are the modification of Snyder test So we have many other Examples of carries activity that is four stick calcium dissolution test Checking the streptococcus by using toothpick tongue blade and Dipslide method and reductase test aura test, which is a new invention the recent one So that's all about carries activity test We need to study only Snyder test, which has been commonly asked for our exam. Okay. Thank you