 Hello everyone, welcome back to another session in dentistry and more so we are continuing our fpd sessions topic for today's finish lines in fpd and last session I was talking about the principles of tooth preparation In that we have marginal integrity. So this comes under marginal integrity. So this is a Small topic, but it should be included in the marginal integrity since it is a little confusing. I'm taking it as a separate topic So finish line is nothing but the axial wall means the ginger wall where the final part or the Ginger part of the retainer will be placed. So it has got importance in aesthetics and preservation of tooth structure So a finish line should be following few characteristics that is shallow bevels which are parallel to the cavo surface should be avoided because the restoration will be too thin at this area and May chip easily. So That is the discrepancy decreases with the increasing in angulation of the bevel and few points to be noted while doing the finish line one thing is the Bevel should not produce a very acute margin which can lead to fracture of the wax pattern during removal You can see here should not create any acute margins So the shallow cavo surface bevels may lead to chipping of the restoration and also The tooth should not be reduced more than half of the width of the diamond bar because our reduction may lead to the formation of a lip of Unsupported enamel which is known as lip pink. So we should not create lip pink or chipping while doing our final preparation now let's start with a few Finish line designs. The first one is Shampoo then we have shoulder knife edge feather edge. Then we have modification radial shoulder heavy Shampoo So all these differs in angulation. Okay, angulation of the axial wall to the Junchail wall So Shampoo is nothing but finish line possess a curved slop from the axial wall till the margin This is the axial wall till the margin. There is a curved slop So this is the axial wall this black one and this is a gentle wall. So there is a curved Slop, this is a slop. Okay, just like this Whereas a shoulder, there is a acute angle. Sorry. There is 90 degree angle not acute angle 90 degree angle between the axial wall and the Junchail wall So that is a difference between chamfer and shoulder whereas a knife edge. There is no such angulation Okay, it is almost straight line So in chamfer it can be produced using a topid or diamond point and This is commonly used in Cast metal crowns or metal only portion of P.F.M. Crowns. This is very distinct. It can be easily identified It has got very least stress So only half of the diamond tip will be placed not completely just a half of the diamond The burr which we use for marginal preparation just half we keep at the margin. So that is about the chamfer So it has got least stress and good success rate. Whereas a heavy chamfer what it does is It changes the angulation. This is a small one. So heavy chamfer the cavo surface margin will be large Okay So it will produce a 90 degree cavo surface ankle with the large round radius So that was about chamfer and heavy chamfer Where the heavy chamfer is indicated for all ceramic crowns. Okay, all ceramic crowns This was indicated in cast metal Restoration this is for all ceramic crowns Which has got better than conventional chamfer properties Bevel is added if we want a bevel can be added to use for metal restoration bevel. It's nothing but at the end We just keep a bevel. Okay We are placing a bevel here this just Like this Now we have the shoulder. So shoulder is Having a 90 degree angulation, which is for again all ceramic crown and it has got good resistance to occlusion force because this spot is good enough to withstand the occlusion forces and there is no chipping and It minimizes the stress which leads to fracture post-lane. So there is lead stress here We use a flat end tapered but not so this flat end of tapered where we use and This is healthy contour and it improves aesthetics Just got good aesthetics So there is 90 degree sharp internal line angle. So this is the internal line angle sharp 90 degree internal line angle But it cannot be used for cast metal restoration because there will be concentration of stress on tooth So there will be 90 degree angle. So this is not suitable for cast metal restoration because there is stress and chances of coronal fracture because the stress is concentrating on the tooth Next we have the sloped shoulder Okay, the modification of shoulder this 90 degree will become 120 degree. This is 120 degree nothing Much changes just the angulation changes and it becomes 120 degree. So facial margins of a metal ceramic crown Can be used with a sloped shoulder. There is no unsupported enamel So we have sufficient bulk to allow thinning of the metal framework to a knife edged or acceptable aesthetics The radial shoulder is different one. It is a modified type of on shoulder with cavosurface angle 90 degree and Which is having a shoulder with lessened with rounded internal angles Next is a shoulder with a bevel. Okay shoulder with a bevel So shoulder with a bevel nothing, but with a 90 degree cavosurface angle with a bevel, okay So this is how it is 90 degree cavosurface angle with a bevel so that is shoulder with bevel it is Indicated in proximal walks for inlays and onlays or occlusion shoulder of onlays and mandula 3 4th crown and Facial finish line of metal ceramic restoration where the ginger well aesthetics is not very critical And situations where a shoulder is already present. So all these areas we can just provide a bevel So it is not like a slopping shoulder. That is 120 degree. Okay. This is like 90 degree with a bevel. Okay, so don't get confused. This is slopping shoulder. We have 120 degree. This is Shoulder with a bevel. Okay after having this 90 degree we put a bevel Knife edge is Which permits acute margin of metal. There is no much angulation between the axle wall engine travel wall and This thin margin which is maybe difficult for waxing and casting and this is also Susceptible for distortion, but which is indicated in mandula posterior teeth with very convex axial surface and lingually tilted lower molars So next we have one more thing that is a feather edge, which is also known as Shoulder less Preparation. Okay. So this is similar to knife edge preparation, but is marginally very thinner There's the same disadvantages as knife edge preparation So chisel edge preparations are similar to feather edge margin, but it is marginally thicker. That was chisel edge Okay chisel edges Similar to the feather edge, but it is marginally thicker. Okay, so that was about our preparations various finished lines So we learned basically The very common chamfer and shoulder only thing is the angulation. This is almost like So shoulder we have radial shoulders lopping shoulder shoulder with a bevel chamfer We have heavy chamfer then we have the knife fetched feather edge Which is also my shoulder less also chisel edge. So that was all about the finish lines and FVD So I'll come over the new topic in prosthodontics. Thank you