 Welcome back to a new session on dentistry and more, today's topic is window of infectivity. As we all know dental caries is caused by bacteria streptococcus mutants and dental caries is a bacterial infectious disease which causing destruction of tooth by acting upon sucrose and producing lactic acid which ultimately leads to cavitation. So window of infectivity is nothing but the initial colonization of streptococcus mutants in a child that happens during 19 to 31 months and on a mean value 26 months. So this colonization is important because till that period, so till around 2 years the colonization is negligibly low because of the protective effect of mothers milk and its antibodies. Once the baby is getting devoid of this protective effects and the eruption of molars happening there is high chances of bacterial colonization. When the baby born there is no bacteria in the baby's mouth. The baby getting bacteria from the mother or the first caregiver or primary caregiver. So the baby gets bacteria and its initial colonization starts during this period. That is exactly we can say during 19 to 31. This is an idealistic condition it can vary. So if the window of infectivity is earlier the child has more risk care for to develop and progression of caries. So window of infectivity is to be taken care well otherwise there will be lots of caries in future because during that period the molars are erupting and soon after eruption the teeth will be very much prone to dental caries because of the demonized enamel structure. So it has to be taken care well. So window of infectivities of clinical importance and always we should take care of babies oral cavity during this period. And the second window of infectivity is seen between 6 to 12 years. At this period the patient's or the child's mouth is undergoing mixed dentition period. There are lots of teeth, deciduous and permanent teeth and there is transient malacryptus phase. So the bacteria has lots of favorable conditions to get colonized. So colonization is always happening on the plaque. So plaque is on the teeth. So when the molars erupts so this plaque gets a surface to get attached. So the bacteria has a colonization surface. So bacteria utilizes substrate from the plaque and it get internally rearranged and reorganized and hard surface that is teeth. So colonization is associated with formation of dental caries. So window of infectivity is nothing but the initial colonization of stuctococcus mutants in a child's mouth that is happening between 19 months to 31 month. If you put this in a graph format birth to 5 years during this period and the mean value we can say that 26 months that is exactly 2 years and 2 months. So during that period the initial colonization happens. So colonization will anyway happen. So we should always take care of baby's teeth during this period. So we can avoid a lot of dental caries. So this is a short note being asked from University exam many times what is window of infectivities. Nothing but colonization, initial colonization of stuctococcus mutants in bacteria and these are the factors. If high maternal infection is there there is high chances of colonization and can be earlier colonization if that is high sucrose content also there is earlier chances of colonization. Earlier it is more riskier and the protective effect of breast milk is giving protection or delaying of this colonization. So that's all about window of infectivity and stuctococcus mutants causing dental caries in a child's mouth and second window of infectivity during 6 to 12 years. So I will come up with a new session on dentistry M.O. Thank you.