 hello everyone welcome back to another session in dentistry and more so we are continuing our topics in fixed partial denture so we finished pontix abutments bonding design and today we have retainers in fixed partial denture so it's a component of an fpd which takes support from an abutment tooth and provides retention to the processes so can see here we have four components one is the abutment then we have the connector which connects the pontix and retainer then the retainer and pontix so these are the four components connector retainer pontix and abutment so today we will be looking into the retainer in detail so the ideal requirements of retainer it should cause least amount of destruction to the abutment then it should not destroy the outline form of the tooth and the marginal line should be finished with great accuracy then it should be rigid that is ability to withstand the load that is occlusion force that is rigidity it should be having good marginal line with great accuracy the least destruction to the abutment then it should be in good functional adaptation and also it should protect the tooth against the fracture it should be cleansable it should be aesthetic and it should not cause any trauma while preparation should not cause any trauma to the pulp or the surrounding tissue and it should not create any kind of recurrence that is the secondary caries and so vehicle marginal ridge should not be destroyed so these are the ideal requirements of a retainer now we have the classification of retainers we have basically two types one is it is divided into extracoronal intracoronal and radical that is a position where the retainer is placed so in extracoronal we have complete crowns and partial veneer crowns complete crown it could be all metal all ceramic and the combination that is a metal ceramic whereas a partial veneer crown that is the three fourth crown the seven by eight crown or the medial half crown whereas the intracoronal we have inlays and onlays whereas the radicular we have the cast post and prefabricated post so the next classification is four types that is based on the first thing is based on the tooth coverage the same thing we are putting into a different perspective that is based on the tooth coverage then the location then the mode of retention and based on the material being used so we'll start with the tooth coverage that again can be divided as full coverage retainer partial coverage retainer the conservative retainer and telescopic retainer so the full coverage retainer as you see the picture here those retainers they cover all the five surfaces of the abutment teeth like visual distal the label or the buckle or lingual or palatal and the incisal or occlusion so the advantage of these full coverage retainer that is the contact area can be properly developed the empressure can be enhanced buckle contours can be correctly developed it can facilitate the occlusion plane modifications and this is indicated for endodontically treated abutment and it is also ideal for restoring edentulous area in patients with craniofacial abnormalities but the problem with our full coverage retainer is that we need to have extensive tooth preparation then the finish line should be kept in sub-jinjavel so there will be a tissue response and jinjavel decay is prevalent in these type of retainers only thing is metal crowns will be placed in posterior so still it is a concern of acidity so this is basically indicated there is a full crown indicated in short clinical crown or if patient with history of active caries and poor hygiene or in both vital and pulplice teeth or the metal ceramic crowns and all ceramic crowns are used in situations which require good cosmetic results with maximum resistance and retention requirements so we have many types of full crown that is the first one is metal crown full metal crown full metal crown is commonly used in posterior teeth so the metallic restoration used to cover the all surface of a clinical crown okay sometimes it can be a gold or stainless steel but the best part is it requires just minimal preparation it can be we can put into a partial or full veneer crown it requires minimum tooth reduction that is a advantage minimum tooth reduction unlike our porcelain and it is strong even in very thin section that is a rigidity part it is very strong even in its thinnest part and its thinnest part unlike our porcelain so always the preparation needs if it is in a centric cusp we need to reduce 1.5 mm or non-centric it's just one mm that is a occlusion reduction okay occlusion reduction so margins we can put a chamfer finish line with which allows around 0.5 mm thickness clearance so always we prefer chamfer for a metal crown and it is commonly indicated as a single crown or even as a bridge mostly for the posterior teeth and in patients with high KD syntax or just like andronically treated teeth or mal-aligned teeth or teeth with short glyphogen gel height but the problem with other disadvantage or contraindication is that it cannot be used in anterior teeth because of the obvious aesthetic reasons and in a situation where conservative preparations can be used when we can go for another type of conservative preparation this will not be opted and if we need less than maximum resistance and retention we can opt for another crown rather than metal if caries is extended gingively as that the finish line cannot be made we just cannot do a chamfer outline because there is gingival extension of caries we cannot perform a metal crown preparation and if there is uncontrolled caries it's better not go with the metal okay but the advantage is that it's good resistance form retention high strength good protection for the tooth to be restored modify the occlusion all those things are advantages but the disadvantage is it's aesthetics pulpo vitality is not good that is but pulpo vitality cannot be detected and incipient caries cannot be detected and extensive amount of tooth reduction but it is comparatively lesser than the ocelain now we have the metal ceramic crown this session this session will be anyway a lengthier one we need to discuss all the crowns and all other classification so in metal ceramic crown this is a phasing of ceramic with a metal copying so it can be fabricated over the full veneer crown or partial veneer crown preparation we need to have two mm occlusion reduction and margins in facial side we need to keep a shoulder finish line then the lingual side we need to keep a chamfer and this shoulder must extend at least one mm lingual to the proximal contact area it can afford high force it can accommodate cast or soldered connectors and all those things the best part is it has got good strength of cast metal crown with the aesthetic of all ceramic crowns and it has got good retention but the problem it the preparation requires more tooth reduction and the facial margins for anterior teeth is often placed subjectively which can cause a periodontal problems and a frequent problem is the difficulty of accurate shade selection so that is a problem with metal ceramic crown now we have the third variety that is all ceramic crown so this is also called as jacket crown so it is used to cover all the surface of the clinical crown it is best to use in the anterior where the aesthetic is at most important so it gives good aesthetics but the problem is risk of reduced restoration longevity and there is potential for fracture so we need to keep a 90 degree angulation and margins and it is commonly indicated in anterior teeth which is not indicated in posterior teeth because of its reduced strength and in case of H2H or in case of overbite we don't prefer all ceramic crown and also tooth with short clinical crown also we don't prefer the all ceramic crown so advantages are the best thing is its aesthetics and comparatively strong but there is high chance of fracture because they are brittle in nature all ceramic crown so next we have the partial coverage retainer okay so this is coming under area first we studied the full coverage now we have the partial coverage retainer so the advantages are it is comparatively a conservative tooth preparation it guides for coronal condos emperation forms are pre-established marginal fit and complete seating of casting can be easily verified before and during cementation aesthetics are fine margin accessibility for finishing and cleaning is good but the problem they are not as retentive as complete retainers there is a limited display of metal then tooth preparation is difficult because only limited adjustment can be made in the path of placement so these are the disadvantages that are the path of placement the display of metal and average retention indicated an intact or minimal restored teeth or the normal anatomical clinical crown or teeth with adequate labia lingual thickness contraindicated teeth with short clinical crowns thin teeth with buckling hole dimension teeth are approximately bulbous poorly aligned teeth now people with bad oral hygiene and high caries index so we have basically three types that is the posterior three fourth crown anterior three fourth crown the three quarter crown posterior anterior and the pin modified three quarter crown that is pin modified so the three fourth crown it is indicated when there is carious or damaged tooth with intact facial surface okay there is intact facial surface and the rest part we are going to replace and we can use it for a splitting or long clinical crown but it is contraindicated in short clinical crown or damaged facial surface if there is a facial surface damage we just cannot go for three fourth crown because we are keeping only facial surfaces intact and the advantage is more conservative approach than the full metal crown and the more aesthetic because we are keeping facial surface intact and the pulp vitality test can be done and there is less ginger oil irritation but the disadvantages are it is less retentive it needs skill and there is mental display next we have half crown so it is a partial coverage restoration that restores the occlusion surface or incisal edge then the measles surface and a portion of the facial or lingual surface so this half crown is basically used in measly tilted tooth okay now we have the pin ledge pin ledge is nothing but which is a technique that employs parallel long pins prepared in the lingual or palatal surface of the clinical crown why we are preparing this pin in order to increase the retention of the restoration so we provide pins in the palatal or lingual surface to provide the retention so these restorations used both grooves and also the pins okay for the retention now we have the three four reverse crown three four crown we know this is three four reverse crown next we have the three fourth reversed crown so we know three fourth crown there the facial surface is intact this is reverse crown so this is nothing but a partial coverage restoration that restores the occlusion surface or incisal edge and three axial surfaces of the clinical crown but the lingual surface is not included okay in three fourth crown the facial is intact or facial is not included here the lingual is not included now we have one more one that is seven by eight crown so this is a partial coverage restoration that restores all surfaces of the crown except the meso buckle cusp so this is basically used for the first molar in upper so that is seven by eight crown so we have all the partial coverage once so we learned about the three fourth crown then the reverse three four crown the one half that is a not one half the half crown then the pin ledge three four reverse crown and the seven by eight crown so we started from complete coverage partial coverage now we have the conservative retainers conservative retainers we already discussed it requires minimal tooth reduction usually it is the resin bonded fbds so i have already uploaded one lecture video on the same topic i will put it here on the i button so you can have a look on the resin bonded fbd which comes under the conservative retainer after that we have a very important one that is very commonly asked telescopic crown so telescopic crown they are used when the path of insertion of the fbd does not coincide with the long axis of the abutment tooth so always the long axis long axis of the tooth should be parallel to the path of insertion of our retainer so if we don't have this by default in parallel position we need to opt a telescopic crown that is basically indicated for the tilted abutment so how do we plan telescopic crown the design involves the fabrication of two copings one over the other the primary coping uh the picture as you see here it functions to modify the morphology of the tooth and helps to change the path of insertion okay the first one helps to change the path of insertion and modify the morphology whereas the second coping it is designed to fit over the primary coping along the new path of insertion okay so that is how we tilt the uh path of insertion to parallel to the long axis okay so the tooth is there but we use two copings the first coping change the morphology and helps to change the path of insertion second one is fitted over the primary coping along the new path of insertion and the accurate parallelism of the coping is essential for successful telescopic crown so that was about the first classification based on the coverage now we have based on location okay so coverage we have full crown partial crown then the telescopic crown and all those things and also we have the resin bottom that is the minimal conservative preparation this is based on the location we have uh extra coronal then intra coronal intra radicular okay so extra coronal uh is like complete coverage or partial coverage whereas intra coronal is our inlay and only whereas intra radicular is nothing but post and core so intra coronal inlay and only we have inlay is nothing but a restoration which has been constructed out of the mouth from gold porcelain or other metal and then cemented into the prepared cavity of the tooth so it is prepared outside and it is cemented into the tooth okay it is its final position is inside the tooth and this is the most commonly used inlay whereas onlay it is essentially an inlay that covers one or more cusp and adjoining a crucial surface of the tooth it is retained by mechanical or adhesivine whereas the inlay has four four walls support okay so only is replacing cusp so it doesn't have a good retention just like inlay okay so only is replacing the cusp or adjoining a crucial surface so the retention is less for only compared to inlay you can see the picture here inlay and only you can easily make out this is inside the tooth which has good support from the remaining teeth this is coming over the tooth may be replacing the cusp and the occlusion surface okay so that is inlay and only so basically this inlay and only is indicated only in large restorations or enteronically treated teeth teeth at risk for fracture or dental rehabilitation with cast metal alloys we can use it for dastema closure and occlusal plane correction whereas this intracoronal inlay only are contraindicated in people with high curies varying patients and people who's having concerns of aesthetics and for small restorations we cannot use this one but the advantages the first thing is its strength by compatibility low wear and control of its contour but disadvantages if the process is very cumbersome like it needs to be done up to many appointments higher chair time temporary registration is required and obviously the high cost and the technically it's very sensitive and so that was about the intracoronal we have the intraradicular retainers so radicular retained radicular retained processes which consists of post or double okay so post or double with an attached core so there will be a double something like this and double with a core so core which obtains its retention and resistance to displacement from the prepared root portion of an interondically treated tooth so if you don't have much crown strength structure remaining after the interondic treatment in order to get the crown for a to receive a retainer we need to provide post and core for core buildup and more strength so while the root preparation retains the post so this is like so sorry this will be like this post this will go into the root canal then there will be a core or this our retainer will come so the core establish the retention and resistance for the complete veneer crown that restores a pulpless tooth to normal form and function so this is for extensively damaged tooth so the post or double and core may be custom made where the radicular retainer is fabricated to fit the root preparation or prefabricated where the root preparation is designed to fit a stock post and core is built up with silver amalgam or composite resin so we have various types custom made is there then prefabricated like taper serrated post threaded post or smooth post so that was about the intra-radicular post and core so this detached double crown and Richmond crown are two types of intra-radicular retainers now the third classification which is based on the mode of retention okay so we were talking about the retainers so the third main classification is based on the mode of retention so it is full coverage can be partial coverage can be pin ledge post in root canal or conservative restoration that is resin bonded all we have discussed already and the final one is the material material usage so based on the material usage that is all metal retainers the ceramic retainers then the resin bonded retainers all those things so that was about our retainers so we were discussing the various types of retainers that is based on the coverage based on the location based on the mode of retention and based on the material usage so this is very commonly asked question in prosaeronics the classification is important and you need to draw pictures for all the three fourth crown sand bait crown one half crown so hope you understood this topic of retainers next we have connectors in fpd so i'll come up with that topic in dentistry ammo thank you