 Hello everyone, welcome back to a new session on dentistry and more. So today we have phases of mixed dentition. So we know mixed dentition that is between 6 to 12 to 30 years where the tooth is inclusive of both the seduces and permanent dentition. So mixed dentition period is basically divided into first transitional period, inter-transitional period and second transitional period. So today's session we will be seeing about first transitional period. So what are the changes happening in first transitional period and the occlusional changes in other tooth erection and the exchange of the seduces tooth by permanent tooth. Let's move on to the topic that is first transitional period. So the first thing what happens is the erection of first permanent molars. So that is 6666. So first permanent molars are erupted during the first transitional period and it actually depends on the distal surface relationship of second deciduous molars. So that is second deciduous molars upper and lower relationship that we will be seeing in occlusional changes. So first molar erupts during the first transitional period and depends on the distal surface relationship of upper and lower second deciduous molars. So that is the molar emergence. And the second thing happens during the first transitional period is the exchange of primary incisors with permanent incisors. So this air represents the primary incisors and the one represents the permanent incisors. So this primary incisors is replaced by permanent incisors. So let's move on to the occlusion. So what happens with the occlusion during first transitional period? So the deciduous teeth occlusion is three types that is flesh terminal plane, mesial step and distal step. So I have given a picture that is flesh terminal plane, mesial step and distal step. So flesh terminal plane is mostly give rise to class 1 or class 2 or end to end relationship. Class 1 is utilizing the late mesial shift. So mesial shift, early and late mesial shift will be dealing in the next session. So that is flesh terminal plane and the second one mesial step. So mesial step most commonly gives to class 1 in permanent dentition or it gives rise to class 3 and distal step will always leads to class 2. So let's see flesh terminal plane. So flesh terminal plane is this one. So it can give rise to class 1 or class 2 or end to end relationship in the permanent dentition when the molas erupts whereas mesial step it can give rise to class 3 or class 1. So class 1 is the most desirable one and the distal step is always will gives to class 2 relationship in the permanent dentition. So that's about first transition period. So I repeat what happens is the emergence of molas and replacement of the deciduous central incisors with permanent incisors and changes in occlusion what happens is the three types of occlusion that is flesh terminal plane, mesial step and distal step. So flesh terminal plane will leads to class 1, class 2 or end to end relationship. Class 1 utilizing the late mesial shift and mesial step leads to class 1 or class 3 most commonly the class 1 and the distal step will always give rise to class 2 relationship occlusion relationship or molas relationship in permanent dentition. So that's all about the first transitional phase. So I will come up with the inter transitional and second transitional phase in my next video. Thank you.