[Music] hello everyone assalamu alaikum welcome back to dr teeth now this is my first dr teeth note can you see that is it nice i'm really liking it anyway i know i have to improve a lot but uh let's start with this video today we are going to learn about the direct retainers in the cast partial dentures or the removable partial denture now these notes will be available on our website i'll share the link to download these notes in the description box of this video and also in the upcoming videos i will try that each video has notes with it so that it gets easy for you to you know revise it right because you cannot always come back to the video and watch it again right so first we need to understand what are direct retainers so it is the component of the removable partial denture that engage abutment and resist the dislodging forces right so let us suppose this is our abutment teeth what is an abutment teeth it is any teeth from which we are going to take support for our prosthesis right so that is called the abutment tooth okay so the direct retainers is that component which will engage the abutment and why we need to engage the abutment because we want to resist the dislodging forces now these direct retainers they are of two types we have the intra coronal and the extra kernel so we have two types of direct retainers the intra-coronal and the extra kernel okay so as the name suggests what do you mean by intra intra means within and coronal means the crown so the intra coronal retainers they lie within the confines or you can say within the limit of the crown so let us suppose this is our crown okay so the intra coronal retainer what they will do they will just lie within the confines or within the boundaries of the crown okay but what about this extra coronal so they will lie outside the crown so you can imagine that it could be a it could be a class or it could be something else and that's something else we'll see right i'm not going to complicate it right now so just understand that extra coronal is outside the crown right now this intra coronal it is of two types we have the precision attachment and the semi precision attachment now what do you understand by the term precision precision means it's very precise now how can something be precise if you have manufactured it very well the manufacturing process is very precise there is a precision attachment and that is why we have given this name to it so if the components are made in metal using high precision manufacturing techniques we get precision attachment and what are semi precision attachment now semi precision attachment they are not very precise they are semi precise you can see how because first we make a wax pattern or a plastic pattern and then we subsequently cast it in metal so that process of making it it is not very precise so the result is also not precise like if you are not putting your hundred percent in your study you cannot expect a hundred percent result right so similarly we have a semi precision attachment here so intra coronal is of two types precision and semi precision now the extra coronal direct retainer they are of two types also we have extra coronal attachments and retentive class assemblies so let's begin with the intra-coronal direct retainer okay now the intra coronal direct retainer it was introduced by hermann e s i leave this pronunciation to you in 1906 if that is important and we have seen that these retainers lie within the confines of the tooth okay so as you can see here we have two parts of this retainer we have a patrick's and we have a matrix so this matrix it is contained within the contours of the crown as you can see here right and this matrix this is a extension that will go and fit into the matrix okay so you can remember patrick's with papa and matrix with mama so always papa has to go to mama when she gets angry so patrick's goes to the matrix right and it obviously fits there now this intra-coronal direct retainer it can be precision or non-precision as we have already seen now coming to this diagram right here here now this diagram here i've tried to show the parallelism of different tooth if you have multiple tooth okay like if you have to place multiple intra coronal attachment to many teeth it is very necessary that we have parallel preparations okay so the matrix and the patrick's has to be parallel when we have multiple tooth that will have them so why should they be parallel because when we have parallel walls we will have well defined path of insertion and removal okay and also such parallel walls they will help in mechanical binding okay because of friction and that is called as the binding phenomena okay so i'm just going to highlight this now let's talk about the precision versus non-precision we have already discussed this but let's do it once more so precision is made by high precision manufacturing but in the non precision first we have a wax or plastic pattern and then we cast it in metal so because of the manufacturing process this one is very precise okay but this is less precise okay also these attachments they have long parallel walls and they have a very you know very amazing surface adaptation and here we have a slight tapering wall now let's move on to the extra coronal direct retainer as you can see here it is lying outside the confines of the tooth okay this you can imagine either buckley or lingually not within the tooth right and this is obviously not within the tooth so it is extra coronal okay lies outside the tooth and we have seen that it is of two types extra coronal attachment and the retentive clasp assemblies now this is also of two types we have the supra bulge and we have the infra bulge we will see what that means so first we will talk about the retentive clasp assembly so this is just about the different types of clasp about which you might have you know heard about or you know seen but we will see that okay one thing i forgot to mention is that the extra coronal attachment was introduced by henry r boos or boss i'm sorry 1900 in 1900 right i thought i should mention it because i have mentioned about the previous one the intra-coronal one okay so this right here it represents a clasp now the clasp can be divided into three parts we have now let us suppose we have a tooth right here okay this looks like a starbucks coffee anyway so let us suppose this is our clasp okay so it can be divided into three parts we have one that is the proximal one third this is the middle one third and this is the terminal one third so this terminal one third it is somewhat flexible and why this flexibility helps because so let us suppose this is the greatest curvature of this tooth means from here it is very bulky now when we have to insert this clasp or say insert our cpd or rpd onto the tooth what will happen since this is flexible this will easily pass through the greatest curvature okay it will change its shape little bit and then when it reaches a pikely it will again come back to its original and it will sit here passively i hope i made it clear now let's have a look at this diagram now here in green you can see we have a survey line and this is our class now we have seen that the clasp is somewhat flexible now when we place this prosthesis here what will happen now as you can see here this terminal portion this clasp terminus it is contacting the abutment apical to the height of contour so because of this the dislodgement will be prevented and also note that at this position the clasp is now passive means once our prosthesis is fully seated this clasp will not apply any unwanted forces on the abutment teeth which is a very good thing now let's talk about something that is protherous cone theory what is that so prothero was a name of a person and he introduced this theory so in his theory he said that the crown is you know made by nature in such a way that it resembles two cones which are placed by their base facing towards each other as you can see here so this is the height of the contour of the tooth means here you will have a greatest dimension of our tooth it will be very bulky here you can imagine okay and above it and below it the above it portion is the supra bulge okay and the portion below the height of contour is known as the infra bulge so here you can see this right here this cone is the suprabulge and this cone represents the infrabulge now this height of contour it is the junction of the occlusion and the cervical convergence now when you see this tooth from the occlusal view let us suppose this is the crucial view and we have the anatomy right so this greatest diameter this greatest diameter of the crown is the height of contour and why are we seeing it from top because that is the proposed path of insertion right you will place the prosthesis from top so it is very logical to understand that whenever we have a clasp terminus here right below the height of contour since the diameter here is more than the diameter here obviously it will not be able to lift very easily because it is a metal after all right so it cannot easily change its shape and lift that is why we are getting a retention because we are engaging in undercut on the abutment and based on these two terms only we have the supra bulge and the infra bulge clasp the clasp which engages the tooth from the superior side that is the suprabulge and the ones that engages from the apical portion or infra means below right so that is the intravault so with this we come to the types of the clasp we have the suprabulge and the infrabulge the supra bolt is also known as the eckers clasp after dr paul e eckers or circumferential class based on its design and the second type is the infrabult also called as the roach clasp after dr f ewing wrote or the bar clasp now let's see the types of the suprabulge clasp let me zoom out so here we have some designs we have the simple circlet reverse circulate because you can see this is reverse of it and we have the c clasp we have the embrasure clasp because it is engaging the embrasure and then we have the only clasp because it is kind of like an only right you must have learnt about the english and unless so this is the only class we'll learn about them you know in detail in subsequent videos but in this video we're just going to see an overview okay so we have some more we have the multiple circulate as you can see okay so this is the buckle view this is the buckle view this is the lingual view and when you see it properly means lingual view it will look something like this okay and we have the ring class okay it is like a ring so those were the supra bulge clasp now we have to talk about the infra bulge okay as you can see here it is approaching the tooth from the inferior side right below the height of contour so these are the infrabulge we have the eye clasp it resembles an eye we have the modified t you can say half t and this is the full t so that is the t class now a question is what is clasp assembly okay in school i remember the first time i heard assembly and also you might have heard it for the first time there as well so assembly is kind of a group okay so what is a clasp assembly so it must be a group of something right so clasp assembly is actually made up of these things we have the rest we have the retentive arm reciprocal arm minor connector okay and also we have some specific design features like approach arm so these approach arm you will find this in the intra bulge clasp not in the supra bulge okay so clasp assembly is a combination of rest retentive arm reciprocal arm and the minor connector so let us see the clasp assembly of the supra bulge clasp as you can see this is the rest so in the batman tooth we prepare some depression or you can say a pit sort of thing that is called as the rest seat okay and within the rest seat the rest of the clasp will engage it will fit in here in the depression that we create while doing mouth preparation so that is the rest and it provides the vertical support to the prosthesis okay i'll just mention it here vertical support i think i have mentioned it in the note somewhere i'll see but anyway i'll just mention it here so it provides vertical support and generally rest is located on the occlusal surface of molars premolars or if it is a canine it will be located at the cingulum of the canine okay and also on the incisal edges of mandible incisors in some cases okay so that is about the rest so the rest provides vertical support so it will not allow the prosthesis to sink inside because we have a you know stop here it creates a stop here okay so it will resist the displacement of the prosthesis towards the supporting tissues okay and also it will transmit the functional forces parallel to this abutment tooth or any abutment tooth okay on which we have pasted it it will but it will do it will transmit the functional forces parallel to the long axis of the abutment then we have the retentive arm we have talked about it a while ago this is the portion of the clasp that goes a cycle to the height of contour and these retentive arms they can be either suprabulge or infrabold so it depends on the approach either it is approaching from top to bottom or it is approaching from bottom to top means applicable to occlusion right so this is the retentive arm now this right here is our minor connector okay and as you can see from the minor connector the clasp is originating so this portion right here this is the portion of the minor connector from which the clasp is originating okay that is known as the shoulder right so the portion of the clasp that will arise from the minor connector right that is known as the shoulder so this shoulder this is rigid i'll just mention it here i have not mentioned it this shoulder is rigid okay now this mid section is somewhat flexible why you can see here that from here to here we have a tapering means it is getting thinner and thinner as we move downward okay so because this is thinner compared to this one it will have somewhat flexible nature now coming to this portion this is the terminus we have talked about it remember so it has even more smaller cross section compared to this one and it has the greatest flexibility so this has the greatest flexibility now coming to the infra bulge class as you can see here we have the rest so i have color coded this to make it easy let me know in the comment section below if you find this type of drawing helpful i tried my best though i'm not a good artist but still so this is the rest right here green then we have the retentive clasp this is the clasp terminus okay and then this right here this is the reciprocal element okay this is the horizontal approach arm because as you can see it is kind of horizontal right and then this is the vertical one okay this is the vertical one and then we have this this is the minor connector okay so as you can see here we have the horizontal approach arm and vertical approach arm and addition so these are specific design considerations right and if i have not talked about this term this is the reciprocal arm so as the name suggests it is just the opposite of the retentive arm it was lying below the height of contour but this lies at or or closer to the height of contour it will lie above the height of contour or at the height of contour and what it does during the placement and removal of the prosthesis this reciprocal arm it will brace the abutment okay it will kind of hug the abutment the presence of reciprocal arm is very important so while inserting the prosthesis if we just have this retentive arm okay so whenever it will try to pass through the height of contour we have seen that it will flex a bit okay because it has to pass through a greatest diameter right it will flex means it will change its shape a little bit and then it will come here and then it will come back to its original you know shape and engage here but when it was flexing when it was changing the shape because of the diameter this will apply lateral stresses onto this tooth okay so to counteract that lateral stress we need the reciprocal arm if you have the lateral stress the abutment will you know it will have detrimental impact on the abutment that is why we are placing the reciprocal arm just opposite to the retentive arm and also the position is or closure to the greatest height of contour or at the greatest height of contour i hope i made it clear i'm not using animations because it already took me lot of time to make these notes and and if i just sit down to edit this i don't think i'll be able to post a video even in two weeks so i'm really sorry for that hope you understood let me know in the comment section below please if you feel that you are able to understand this way also compared to my previous animation i'll try to put animations also in the upcoming videos let's see how it goes if i have time i'm just now focusing on the notes so fingers crossed also i would like to mention here that during the insertion of our prosthesis this reciprocal arm it should contact the abutment slightly before this retentive arm contacts the so before this could contact the abutment this should contact the abutment when we insert the prosthesis and while our attentive arm is passing through the greatest height of contour all throughout this reciprocal arm should contact the abutment that is how it will prevent the lateral stresses so always make sure that the retentive arm should never contact the tooth before the reciprocal arm by because if this happens there will be non-axial forces on this abutment tooth and that will be damaging so this is kind of a summary rest provides the vertical support the retentive clasp it contacts the abutment or bicycle to the height of contour right and the terminus of the clasp it contacts the undercut the reciprocal arm it contacts the abutment during prosthesis insertion and removal and it is above the height of contour okay then we have the horizontal and the vertical approach arm and the minor connectors now for minor connectors let's keep in mind that they have to be rigid and they may have different functions based on different cases like in some cases it can act as a guiding plate see when we have see let us suppose we have two tooths right here okay and we have a edentulous space here we prepare or you can say we grind little bit of the tooth abutment tooth and we place our minor connector here okay along with the prosthesis right so this act as a guiding plate it helps in the insertion and the removal of the prosthesis it may also act as a reciprocal element to balance the forces and also it may act as horizontal approach arm and vertical approach in case of the infrabulge clasp okay so that was all about the direct retainers in the next video we will study about all these you know clasp in detail and the notes of this video will be available in the link below so you can go there and download it and also please let me know in the comment section below if you find this study method helpful i will be only able to improve if i have your feedback and also if you're new here please consider subscribing and also share my work to help support the channel and this platform i'll see you in the next video take care all halfways [Music] oh