 Hello everyone welcome back to another session in dentistry and more today's topic in orthodontics is growth moments. So we have two basic kinds of skeletal moments take part in growth of craniofacial bonds which is known as drift and displacement. The displacement further divided into primary displacement and secondary displacement. So the first one is drift. The concept is simple. The drift is by resorption and deposition. It is by the osteogenic properties of the bone itself. One side will be resorbed and other side will be deposited and the position changes or the movement happens. Whereas the displacement is a movement of the bone to a new position as a whole cortical drift. It is a growth moment of an enlarging portion of a bone by the remodeling of its own osteogenic tissues. So the drift occurs due to the combination of deposition and resorption. So you can see this red area is resolved the green area is deposited. So this bold black line is the initial position of bone. This dotted black line is the final position. So this was the initial position. Now it is moved to the new position. So the movement happens due to the resorption deposition mechanism. Drift usually takes place in the direction of movement. So in which side it is getting deposited the displacement is happening towards the side of deposition. So in primary displacement movement can be either in the direction of bone deposition or in the direction of bone resorption. So both can happen and as a bone enlarges it is carried which is carried away from the bone. So the growth remodeling takes place to maintain contact such as the contail. So let's take an example of contail. The contail grows upwards contail grows. So this is a contail. So contail grows upward and backward. So upward and backward. So when the contail grows upward and backward what happens? Why it is going upward and backward? It is to maintain the contact with mandible or fossa. So the mandible is displaced downward. So this mandible is displaced downward. So that is why this is known as primary displacement. The same bone is causing the movement of the other part of bone. So this is going upward and backward to get in contact with a fossa that is mandibular fossa. The mandible moves downward. Whereas the secondary displacement so the increasing in size of middle cranial fossa which causes the maxilla to be displaced anteriorly and inferiorly. So when the middle cranial fossa is getting enlarged the maxilla goes anteriorly and inferiorly. So this is maxilla. When middle cranial fossa enlarges the maxilla moves anteriorly and inferiorly. So this is mainly due to the other bone not the maxilla itself. So this is the difference between primary and secondary displacement. Hope you understood the concept of drift that is by resorption and deposition by the osteogenic properties. Here also the properties are there. There is a resorption and this is happening. But the bone moves by the change in the movement of the other part of bone or the adjacent bone. That is the difference between primary and secondary. And the main difference is the movement of bone as a whole. This is not as a whole movement it is by the resorption and deposition action. So that is all about the growth movement, drift and displacement. So I hope you understood the concept of drift and displacement. I will come up with a new topic in orthodontics. Thank you.