 Hello everyone, welcome back to another session in the industry and more today's topic in Tronsodontics, the survey lines. So survey topic is already covered, so survey is nothing but procedure to determine the form and position of a given entity by taking linear and angular measurements or surveying as an analysis and comparison of the prominence of intraoral condos associated with the fabrication of a dental processes. So similarly, survey lines are lines drawn on a tooth or teeth of a cast by means of a surveyor for the purpose of determining the various parts of a clasp. Okay, so when we are doing danger fabrication we need to attach clasp to the processes so where exactly the clasp to be kept depends upon the angulation and the orientation of the tooth. So to determine the position of the clasp is done by surveyor and that particular line or the imaginary line is known as survey lines. So we have basically four types of survey lines which was given by Blatterfein. Blatterfein classified as high survey line, medium survey line, low survey line and diagonal survey line. So the first one is high survey line. It is found near the occlusion surface of a tooth. Okay, so it can see the line is near to the occlusion surface of a tooth and it is often parallel to the ginger margin. So this is the ginger margin. So it is parallel to the ginger margin. It results basically from the abnormal inclination of the teeth. So when there is a tilted tooth, abnormally inclined tooth, we need to keep a high survey line. So it is mostly on the lingual surface of lower teeth and the buckle surface of upper teeth. So lingual surface of lower teeth and buckle surface of upper teeth. And we need to use Rottweier clasp for high survey line. Whereas the medium survey line, it is situated across the center of the tooth. Okay, so before that we need to understand what is near zone and what is far zone. So zone which is adjacent to the idangela space is near zone and which is away from the idangela space is far zone. Okay, so coming back to the medium survey line which is situated across the center. Okay, so this is not towards the occlusion, not to a cervical, it is across the center but it exhibits a slight occlusion, ginger well inclined from the near zone to the far zone. So let it be this, be the near zone, this be the far zone. Okay, so this is the area idangela area and this will be near zone. So I drawn this is reverse but anyway the part of the tooth which is coming towards the near to the idangela area is near zone. Okay, so this has a slight occlusion ginger well inclination from near zone to far zone. So you can see a slight inclination towards the far zone and we need to use a curse or Rottweier clasp for medium survey line. Whereas a low survey line which is situated close to and parallel to the ginger well margin. So I can say which is more or less near to the ginger well margin which is close to or parallel to the ginger well margin. It frequently occurs as a result of marked inclination of the tooth and may also occur on conically shaped tooth. So when there is marked inclination or a conical tooth you need to keep a low survey line and the clasp used is modified T clasp and the last one is diagonal survey line. It travels diagonally from the near occlusion surface in the near zone to the ginger well and the far zone. Okay, so if it is near zone and if it is far zone just starting from the occlusion line to ginger well line. So we need to use reverse circulate clasp for diagonal survey line. So it's very simple the high survey line, medium survey line, low survey line, diagonal survey line compared to the occlusion ginger well height. One more classification we have needs classification. It classified it as class 1, class 2 and class 3. The class 1 is the survey line runs diagonally across the tooth surface. Okay, so it is going diagonally and the type of clasp indicated is occlusionally approaching. So we need to give a occlusionally approaching class with terminal third engaging the undercut. Okay, terminal third is engaging the undercut and the class 2 where the survey line also runs diagonally across the tooth surface but it is the mirror image of class 1. So class 1 is going like this. This is like this. So this is a mirror image of class 1. Okay, so you know how we appear in a mirror. So if the line is here in the mirror it will be from left to right. So here the ginger welly approaching clasp arm is suggested. So we can think of a clasp like this and the last one is class 3 where the survey line is parallel to the occlusional surface and lies just below it. So can do a clasp like this. This is a clasp. So here the survey line is parallel to the occlusional surface and lies just below the occlusional surface. So it is another classification of survey lines given by need. So these are the two classifications for survey lines. Blatter in classification and needs classification. So it is a simple concept of clasp where to kept depending upon the angulation and orientation of tooth. So survey lines are this one high, medium, low, diagonal, class 1, class 2 and class 3. Hope you understood this concept. We will come up with a new topic in cross-around X. Thank you.