 Hello everyone, welcome back to another session on Dentistry and More. So today's topic is Wall Slow. Wall Slow is a very interesting topic. It says about the bone trajectories based on the functional forces, the changes in trabecular arrangement of the bone based on the forces. So before that we need to understand what is a bone and what is a trajectorial theory. Then we will move to the wall slow. So let's see what is inside wall slow. So wall slow should be in accordance with bone and trajectorial theory. Then only we will understand the concept of wall slow. First we will see what is bone. We know that there has two parts of bone and one is the outer and very thicker part which is known as compact bone and the other part is cancellous bone which is inside of a bone which is a very spongy and has a mesh work of trawaculate. So cancellous bone and compact bone. So the next thing is trajectorial theory. So trajectorial theory is by a scientist mayor. It says that the line of orientation of the bone in trawaculate follow the pathway of maximal pressure and tension. So I have drawn a picture of a bone and you can see these lines, the dark lines. These are the bone in trawaculate line of orientation. Also we can say that trabecular arrangement. So the load is happening here and maximum tension and pressure on both sides. So there is lot of stress happening here. So trajectorial theory says the line of orientation of the bone in trawaculate follow the pathway of maximal pressure and tension. So this is the pathway where is the maximal pressure and tension is happening because of the load here. So there is maximal pressure and tension. So the bone in trawaculate follows this pathway. So maximal pressure and tension pathway. So when there is maximum stress there will be thicker trawaculate. So thicker trawaculate is found in areas of maximal stress. So the alignment of trawaculate in spongy bone follow the trawaculate line like a mechanical structure. So it follows just like a mechanical structure. When there is force there is change in this direction. The bone in trawaculate direction it goes with maximal pressure and tension. So these trabecular lines are lines of maximal stress within the bone. So these are the lines, trabecular lines. These are the lines of maximal stress. So we can see that maximal stress. And these tragic trees grows at right angle to resist the manifold stress on the bone. So you can see it is not very clear but you can see these tragic trees cross each other at 90 degree. You can see the 90 degree. Why it is so? Because it can resist manifold stress on the bone. So it can resist stress on bone. So this is what trajectorial theory says that is the line of orientation. It is following the maximal pressure and tension. And these are the lines of maximal stress within the bone. And this alignment follow a maximum stress just like a mechanical structure. Now we will move on to the wall slope. I hope you understood what is the trabecular line and the stress and other concept. So wall slope is just an extension of this trajectorial theory. It is just explaining the reason for this maximal stress and tension. So wall slope was given by Julius Wolf in 1870. So what he was saying? The reason for arrangement of trabecular pattern. So the reason for arrangement of trabecular pattern is functional forces. So trabecular arrangement is due to functional forces. That is what wall slope is emphasizing on. So wall slope of transformation of bone is the change in direction or magnitude of force could produce change in internal structure and external form of that particular bone. That is wall slope transformation of bone. So what is the functional forces? The forces happening in the body. That is the functional forces. If we change that functional force in direction or magnitude, it can result in change in the internal structure and the external form of that particular body. So that is the wall slope. It is nothing but the explanation of this trabecular theory. So trajectorial theory is not mentioning about the functional forces. So if there is increased function, the bone is having more density. Or wherever the function is high, the bone will produce more density. Because it has to withstand that particular maximum load. And if the function is decreased or minimal function, the density also will eventually or automatically decreases. So the stress of tension or pressure will result in change in bone. That is a simple theory. That is if there is stress of tension or pressure, the bone will be changed. Because it has effect on the internal structure and external form. So that is all about wall slope. It is connected with trajectorial theory. So it is emphasizing on the functional forces and how functional force could change the internal structure and external form. So let's wind up this wall slope. We have seen bone trajectorial theory and the details. So I will come up with a new topic in my next video. If you have any doubts, please mention in the comment box or any more videos you would like to have lectures on. Please mention that too. Thank you.