 Hello everyone, welcome back to another session on dentistry and more. Today we have a topic from conservative dentistry that is bevels in dentistry. So bevels we need to apply in restorative dentistry in order to provide strength for the restoration. So there will be a weakest link in any restoration that is a tooth restoration joint or marginal peripheries. So we should make every effort in order to make these joints are most favorable so that it has good strength to withstand the occlusion forces. So this peripheral marginal anatomy of the preparation is called as circumferential type. So there is nothing but the joint or the junction between restoration and tooth. So what are the bevels? Bevels. So bevels are flexible extension of a cavity preparation which allows the inclusion of surface defects, supplementary grooves or other areas on tooth surface. So these are plain of a cavity wall or floor directed away from the cavity preparation. So earlier bevel was placed only on kevo surface margins and was defined as rounding of or kevo surface margin at an angle. So now they are placed at various surfaces of prepared teeth. Okay, before it was just placed on the kevo surface margin that is a junction between future junction between the restoration and tooth. But now it is placed at various surfaces of the prepared teeth and the bevel is defined as any abrupt incline between the two surfaces of prepared tooth or between the cavity wall and the kevo surface margin in the prepared cavity. So these bevels require minimum tooth involvement and do not sacrifice the resistance and retention of the restoration. So it should maintain resistance and retention for the restoration. So these bevels are part of this circumferential tie and are one of the major retention forms. Okay, major retention forms for a cast restoration. Okay, as it increases the possibility of a direct retentive frictional component between the casting and the tooth. So it is on the cast restoration it becomes a major retentive factor. So this makes it possible to decrease or eliminate the cement line by bringing the cast ally closer to the tooth surface. Now we will move on to the main topic that is types of bevels. So according to shape and types of tissue involvement they are divided into six types. Partial bevel, short bevel, long bevel, full bevel, counter bevel and hollow ground or concave bevel. So the types of bevel classified according to the surface they are placed. That is the surface. So that will be gin chival, gin chival bevel, crucial bevel, functional cuss bevel. Okay, the first one is partial bevel. So the partial bevel as you see the picture here, it involves a part of the enamel wall not exceeding two-third of its dimension. So this is not used in cast restoration except to trim weak enamel roads from the margin peripheries. Whereas a short bevel this includes the entire enamel wall but not dentin. You need to see the difference in partial bevel. We have just two-third of its length or the total dimension whereas a short bevel it involves entire enamel wall but there is no dentin. So this short bevel is indicated in class 1 alloys especially for the type 1 and type 2. Whereas a long bevel this includes all of the enamel wall one-half of the dentin, okay this is. So the short bevel involves the enamel whereas a partial bevel two-third of enamel, okay long bevel this includes all of the enamel wall and one-half of the dentin, okay. So this involves enamel plus one-half of dentin wall. So its major advantage is that the internal boxed up resistance and retention features are preserved in this bevel and it is indicated in first three classes of cast material. Next we have full bevel. This includes all of the dentinal and enamel walls of the cavity wall or floor, okay. This includes entire enamel and this is how it goes two-third of enamel complete enamel enamel plus half of the dentin complete enamel and dentin. So although it is well reproduced by all four classes of the cast, its use is avoid except in case where it is impossible to use any other form of bevel. So it is rarely used. Now we have the counter bevel. So you can see the picture when capping casts to protect and support them this type of bevel is used which is opposite to an axial cavity wall on the facial or lingual surface of the tooth. So which will have a gin travel inclination facility or lingualy. So that is counter bevel in order to protect the cusp. Next is the last one hollow ground or concave bevel. So this is the only form which is not in a flat plane form. So this allows more space for cast material bulk which is a design feature needed in special preparation to improve the materials castability retention and better resistance to stresses. So these bevels are idea 4 class 4 and class 5. So the buckle slopes of the lingual cusp and the lingual slopes of the buckle cusp should be hollow ground to a depth of at least 1 mm. You can see here in order to provide sufficient bulk of material on these surfaces and also to increase the resistance form. So we create the buckle slope of lingual cusp and lingual slope of buckle cusp in a hollow ground to a depth of 1 mm to provide a bulk. So one more we have that is reverse bevel. So this reverse bevel is placed at the dental portion of the cervical wall towards the axial gin travel line angle. So it is placed on the dental portion and towards the axial gin travel line angle. So this bevel at gin travel wall will prevent tipping moments and this hydrostatic pressure during cementing a cast restoration which can produce a rotational displacement of the casting with flat gin travel walls. So this effect is resisted by the reverse bevel resulting in even a better seating of the cast restoration. So in order to avoid the rotational displacement where we keep flat gin travel walls so we create a reverse bevel in order to prevent the tipping moments. So that was about the first classification based on the shape. Now we have the next classification is based on the surface it is being placed. So we will start with the first one that is gin travel bevel it is a weak enamel is removed can see the picture here bevel results in 30 degree angle at the gin travel margin that is burnishable because of its angular design. So a lap sliding fit is produced at the gin travel margin which help in improving the fit of casting in this region okay. So we create a 30 degree angle at the gin travel margin so that is gin travel finish I mean bevel so a lap sliding fit is produced at this gin travel margin. Now we have the occlusal bevel so occlusal bevel create a obtuse angle marginal to surface it create an obtuse angle that is angle which is greater than 90 degree okay so it will be like this more than 90 degree it will be more than 90 degree so which is the bulkiest and the strongest configuration of any marginal tooth anatomy which can resist stress. Next one is a functional cusp bevel it is additional removal of tooth structure in a cavity preparation okay. So a wide bevel placed on the functional cusp provides space for the adequate bulk of metal in an area of heavy occlusal contact when there is a chance if there is a functional cusp is there in order to provide additional bulk okay so we provide a bevel in the functional cusp. So functional cusp bevel increases the thickness of thin occlusal axial junction of the trestration so angleation always will be 45 degree so why it is very important because it provides additional thickness for the material which is necessary because these are the maximum large bearing areas because maximum occlusal forces are being placed on the functional cusp so if we provide a bevel on the functional cusp with a 45 degree angleation it gives more space for the material so the cast metal or the restoration or the newer material can withstand occlusal forces so large bevel is given which will help to bear the excess lot without fracture. So location it is prepared on the palatal cusp of maxillary teeth maxillary teeth and buckle cusp of mantibular teeth so very commonly asked question functional cusp bevel this bevel so this functional cusp bevel is a commonly a short note and this bevels itself it is a long instruction that is functional cusp is placed on the palatal cusp of maxillary teeth and buckle cusp of mantibular teeth on exam point of view it is very commonly asked question so any bevel can be asked as a short note or short essay so and the most common was the functional cusp bevel hope you understood this topic always draw picture of the bevel in order to get good marks because just writing the description will not give you marks because this is all about understanding the concept so you need to draw a cavity and the bevel okay so I will come with a new topic in industrial model thank you.