 Hello everyone, welcome back to another session in dentistry and mode. Today's topic in orthodontics is N-Loss V-Principle or Expanding V-Principle. So we were talking about the growth, the pattern of growth. So we discussed Scammon's growth curve, Cephalochordial gradient of growth and the pattern of growth that is drift and displacement. So this is a concept by Enlo. He says the expansion happening in the form of V that is expanding V. So it starts like this and it goes expanding. So the V expands. So that is the idea behind this. So the craniofacial bones or their parts it has a V shaped configuration or we can say funnel shape in three dimension. So it's all two dimensional pictures. So it is a funnel shaped bones in three dimensional picture. So Enlo point out that the bones grew by addition on the inner side of V and removal of bone or resorption from the outer side. So this concept of bone growth is known as V-Principle of Enlo. So according to this principle, bone deposition occurs on the inner side and the resorption takes place on the outer side and which leads to the widening of V. So on the inner side deposition happens, happens. So it slowly widens and becomes an expanded V just like this. So it is going like this. So the expanded V where the structure translates from its original position and moves towards the wide end of the V. So at beginning it was here and it translates to here. So the position changes. So it starts from the small V to the expanded V. So it translates to this position to this position. So this is just a diagrammatic explanation. So it is on the wider end of V. So wider end of V. So the most common bone is a palatal bone and the mandible also follows the V-Principle. So in palat, the heart palat viewed in the coronal section shows that the resorption occurring on the outer surface that is the nasal surface and the deposition on the inner surface that is palatal side. So the resorption on the nasal side and deposition on the palatal side which leads to the palatal remodeling and it follows the V-Principle whereas the mid-palatal suture and secondary displacement happens due to the growth of nasal bone which increases the width of palat and causes its vertical descent. Next one is the ramus. So the ramus, this is the ramus, this is from the topu and the side view. So ramus, the growth of the mandible also follows the V-Principle. When viewed from above, this picture, when viewed from above, the contile and the ramus expand in a posterior and lateral direction due to growth of the body ramus and the contile itself. So it expands backward and also laterally because of the growth of body ramus and contile itself. So growth is accompanied by progressive relocation of the entire ramus in a posterior direction. So this is the initial position and this is the final position. So you can see the V concept. It is getting expanded and translated to the wider ends of V. So the resorption occurs on the anterior edge with resultant lingual shift of the anterior part of ramus to become added to the body. So the resorption occurs on the lingual side and the deposition on the buckle side. So this pallet and this mandible follows the expanding V principle. So very simple principle. The addition is happening on the inner side, resorption on the outer side and the bone translates to the wider end of V and it is getting expanded. So that is all about Henlo's V principle. Henlo has put forward another principle along with his accepted V principle that is a counter part principle. So counter part principle says that the growth of any given facial or cranial part relates specifically to other structural and geometric counterparts in relation to it. So it says that there will be a counter part for most of the bones. So there are many structures in the craniofacial skeleton which can be considered as counterparts such as NISO maxillary complex and anterior cranial fossa, then middle cranial fossa and width of ramus, maxillary tuberosity and lingual tuberosity. So there will be always a balance. So to maintain the balance there will be a growth happens on both the bones simultaneously. So this theory or this principle had many shortcomings and it is rejected. So the Henlo V or expanding V principle is an accepted one from Henlo. So these are the two concepts put forward by Henlo. Henlo is expanding V principle and the counter part principle. So I will come up with a new topic in orthodontics. Thank you.