Transcript for:
Understanding Impression Materials in Dentistry

hi everyone this is Miss O'Brien in this presentation we are going to go over chapter 15 of your DNA 110 textbook and this is the chapter on impression materials and our objectives for this presentation are to describe the purpose of an impression we're going to describe the three B basic types of Impressions and explain the importance of the Key properties of impression materials we're going to define the terms so and gel and describe these states as they occur with hydrocolloids we're going to explain why alginet is an irreversible hydroc coloid we're going to explain the difference between a hydrophobic and a hydrophilic impression material and describe the various types of elas elmir and explain why they are called elastomer additionally we're going to explain why PVS or polyvinyl soloxine impression material is so popular we're also going to compare the similarities and differences among the physical and mechanical properties of PVS and polyether impression materials we're going to discuss the advantages and disadvantages of using polye impression material for a crown impression and we're going to discuss acceptability factors for cord placement and gingival retraction we're going to explain the use of feric sulfate astringent to control gingival bleeding before making an impression and explain what a digital impression is we're also going to describe the advantages and disadvantages of digital impressions okay so let's talk about the purpose for dental Impressions impressions are used for a variety of things in the dental practice um basically they are a reproduction of the form of the teeth and the Arches and the hard and soft tissues and this helps when we're preparing uh teeth for restorative treatment um it help also helps with fabrication of removable prosthesis and appliances um this could be things like dentures or retainers or uh night guards bleaching trays those type of things um and also impressions are used for um molds of maxilla facial reconstruction um which is a little bit outside of well it's a lot outside of the um Standard General Dentistry uh that would be more like a maxilla facial surgeon would use those type of things um when treating patients for um you know trauma to facial structure caused by accidents or um congenital type of um deformities okay so an overview of Impressions um there's several different types of impression material there's lots and lots to choose from so when we select an impression material it's going to be influenced by what the impression material will be used for um is it going to be used for a final impression meaning we need a lot of detail um is it going to be used for a study model which means we don't need quite as much detail of each individual tooth so there's a lot that goes into deciding which material you're going to use for an impression um impression material must be moldable in a plastic State and able to adapt to the teeth and the tissues if it wasn't moldable or in this plastic state it wouldn't reshape itself around the tissues to allow us to see you know the shape of the teeth and the structures all that um impression material is loaded into a tray for support and we'll see pictures of the different types of trays and impression material can set to a semi-solid elastic or rigid State depending on the material elastic materials um are used more they Flex from tissue undercuts when removed um when you're removing the Impressions um you know the impression material needs to move back and forth a little bit to find its way out you know around the um the fatter parts of the teeth for instance um so it has to um Flex a little bit when we're removing it um Impressions form a negative reproduction and um from this negative reproduction we pour up a study model or a diagnostic cast using dentl Stone usually or plaster and this is our positive reproduction so we'll see pictures of that in just a second and a full mouth replica is a model or cast um that's what we pour up in Stone from the impression um or we can um create a Dye which is a replica of a single tooth and both of these are made from full mouth Impressions um the dye the single tooth model this allows a restoration to be made indirectly uh meaning it's made outside of the mouth not inside of the mouth okay so negative versus positive reproduction so this is your negative reproduction so this is um uh it looks like algen Impressions and alginate is one of the types of impression materials that we use um and you can see the impressions of all the you know the molers the premolar the canine the enzers um you see impressions of all of the teeth and then you also get an impression of the hard pallet or the roof of the mouth and the um you know the other structure within the mouth so um that's your negative reproduction which is your impression then we have um a positive reproduction and this is the replica or cast so the positive reproduction is this this uh this impression um Stone Dental stone is poured into this and it creates a model so this is your positive um uh reproduction which is your a cast or model and you can see here uh here's a little negative impression this is actually a bite registration um that guides the teeth together when this uh cast or model is on an articulator which is this piece of equipment and we'll get more into uh bite registrations and all that so here's a little chart that kind of sums things up um uh Caster model they're they're pretty similar um the cast is the definitive reproduction of prepared teeth used to fabricate a prosthesis and again a prosthesis can be like uh Dentures or bik guard or bleaching trays something like that um and sometimes the cast is called the master cast so it's got a little bit more uh detail than a model so you probably use more expensive materials that that provide more detail to make a cast um now from that cast they can cut out single teeth and then they can create um the center structure which is called a dye so a Dy is uh it's a highly accurate replica of a single tooth and this is generally used to make a crown or an inlay so they would make a crown um that would fit on top of uh the patient's tooth from the die um and then the model so so the study model um this doesn't need quite the detail that a mastercast would need um this is a replica used to observe a patient's oral structure so um orthodontists use these study models for instance to see um how the teeth olude or come together and the the structures of the mouth okay um so there's three basic types of Impressions we have preliminary Impressions final Impressions and bite registration or accusal Impressions and we will talk about all of those different different um types of Impressions and then the impression materials that we can use um for instance are um some of the impression materials are like alginet and we will be using that in our lab to take Impressions on each other um also silicone rubber um or polyvinyl soloxine is a very um very popular impression material it's got a high level of accuracy um polyether is is also used um and digital Impressions um I don't know if any of you guys have experience with um digital Impressions uh that you might do with like a Sak machine for instance um but digital impressions are kind of um they're they're really gaining popularity it's it's an expensive piece of equipment but more and more offices are making the um investment to do digital Impressions um and kind of get away from the old-fashioned impression materials but we have to learn how to do both because um you know a lot of offices are still using algid and polyvinyl saloan Impressions okay um so preliminary Impressions these are usually a precursor to another treatment um they're the initial Impressions not the final Impressions so casts that are made from preliminary Impressions these are used for things like stud models um maybe custom trays which we'll talk about uh provisional Restorations provisional means temporary um so not the permanent Restorations but just the temporary um and they can be used for pre- and post treatment records um like in orthodontic treatment for instance um now alginet is usually used for preliminary um Impressions and the reason for that is that alginet is fairly inexpensive and for these preliminary Impressions we really don't need a high level of detail and accuracy like we do if we're making um you know crown or dentures or something like that okay and then final Impressions um so in this picture here we've got um polyvinyl soloxine sometimes it's called vinyl poly soloxine it's the same thing um but this is um this is how you administer the the PBS which we'll see in a lot more slides um so final Impressions these are more accurate than preliminary Impressions we really need a much higher level of detail when we're doing final Impressions and and polyvinyl soloxine um or another material called polyether they really offer that versus you know alginet so um so final impressions are used when you're fabricating um crowns or Bridges or implants for instance um or partial or complete Dentures so we really need a high degree of accuracy and detail when we're taking final Impressions to to make these um protheses like uh Bridges and implants um so that the patient is comfortable and they have very functional um occlusion with these Restorations okay so bite registration um so this replicates the patient's bite and what what it does it establishes the proper relation uh between the restoration and the opposing teeth so so you can take um over here we have um our our cast I assume this is a master cast and um you know you have your your maxillary Arch uh you have your mandibular Arch the lower Arch well when you have these two things that's great but how do they fit together you don't know really how they fit together the two arches in the patient's mouth unless you have a bite registration so um so what we usually do after we take Impressions we take a bite registration so that we know how the teeth fit together um and then the dentist uh or the dental assistant might Mount these on an articulator um that's this piece of equipment to see how everything fits together um because you really need to see that before you make any sort of um you know restoration or prostheses that is going to go into the patient's mouth permanently um so the bite registration will establish the proper relation between the restoration and the opposing teeth um it's also used to help mount the diagnostic cast in their proper relationship on on an articulator um this is an articulator it holds the cast in place um so by registration um it can be taken with either wax um or polyvinyl soloxine um so wax is kind of easily distort it uh it can be a little bit thick so you might not get the patient's true bite or true occlusion um poly vinal sling that's what we see here and up here um is is just more accurate and it's a little bit of a thinner material so you can get a better idea of the patient's true occlusion okay um so the types of impression materials so there's actually a lot of different impression materials um some are in use today some have kind of Gone by the wayside as you know improved products come out um you know mostly today we use the elastic materials um those are are far superior to the old in elastic materials um so the elastic materials include the hydrocolloids um this is Ager and alginate um so alginate we use quite a bit Ager is kind of Fallen by the wayside because it's not a great material um polysulfides uh um you know that's another one that's kind of Fallen by the wayside because it's not a great material um silicone rubber materials like polyvinyl soloxine uh or PBS that's used quite a bit quite a bit for final Impressions so it's a really great material very popular um very expensive though uh polyethers uh are a good material not quite as good as PBS um so they're used maybe not quite as much as PVS but they they are in use um and then in 2000 around the year 2000 they came out with a hybrid of polyether and polyvinyl soloxine um which kind of takes uh the the great qualities of PBS and the the great qualities of polyethers and mixes them together to make a a superior product so um the polyether PBS hybrids are uh very good materials um I haven't seen them use quite as much as the PBS um but there you know there are a lot of um great reasons to use them which we'll talk about um then inelastic materials so these were the materials that were in use in dentistry before the elastic materials were invented you know or manufactured so this is things like um Dental compound impr pression plaster zinc oxide eugal or Zoe and impression wax and we will talk about those and you'll pretty quickly see why they're not in use today so they're really not great okay um so Key properties of impression materials so when we look at impression materials we want to think about things like accuracy tear resistance and dimensional stability um so accuracy uh the material it has to closely adapt and flow over the surface of the tooth preparation and record very minute details um and the viscosity has to be a little bit of a lower viscosity um you don't want it to be uh a very thick material that won't flow um you know or high viscosity you need this material to flow into all the nooks and crannies of the tooth you know if you look at your tooth there's a lot of um little Fishers and and grooves and dips and things like that so we want something that will flow into all those areas so that we can see all the detail of the accusal or chewing surface of the tooth um so so we really need something that's a lower viscosity to get that level of accuracy of the reproduction um the material the impression material also has to be tear resistant so um it's very very disappointing when you go to all the trouble of making an impression and having it in the patient's mouth for five minutes or whatever you take it out and it tears you know and then you have to start all over again so um so we want a material that's that's tear resistant so it has to be kind of strong in that regard um and then dimensional stability so um the dimensions must remain consistent after the impression is removed um we don't want this uh impression to shrink or to swell um because this impacts the accuracy of of the positive reproduction or the Stone model that you're pouring up that you'll use to make the you know the restoration or the prosthesis so um so dimensional stability you know if you take your impression out and before you pour it up in stone it shrinks 15 or 20% or even 10% then is the the restoration that you make from that going to fit in the patient's mouth you know or or if it swells by 15 or 20% so so dimensional stability is is very very important and dimensional stability is often affected by um by moisture uh that the impression is exposed to or lack of moisture you know so it can either um kind of inbi water that it's left in and swell up or it can sit out in the air and and water evaporates off of it and it winds up shrinking so uh it's important to think about dimensional stability okay so impression trays um you can see here on the left we've got a couple of metal impression trays and these are perforated meaning that they have holes in them so when you put the impression material in the tray and you place it in the patient's mouth some of the algen or whatever impression material you use will flow through these little holes and kind of lock the alginate into the tray which is a good thing it keeps it in place so um so you can see these are two different trays one is for the top of the mouth or the maxillary Arch that would be this one so you can see it has the middle part to capture the detail of the um the roof of the mouth or the hard pallet excuse me and then we've got the mandibular tray or lower tray which is shaped like a horseshoe and the reason it shaped like that is because it leaves room for the tongue um we don't want to make an impression of the tongue so we want that part kind of cut out um so this is your maxillary tray and this is your mandibular impression tray um and these are non-disposable trays which means you can use them over and over again but you have have to clean them really really well after each use and you have to sterilize them um because they are going in the patient's mouth and they're being exposed to um uh you know just all kinds of um germs and things from the patient mouth okay so the impression trays are used to carry the impression material to the mouth and support it while it sets um and it's removed from the mouth and then poured into stone so what you do is you load up the impression material in the tray and then you place it in the patient's mouth and it supports that material while it's in the patient's mouth um then you remove it and it still holds the impression while you pour Stone into it um to to create your study model or cast um so these should be rigid um the metal ones are definitely rigid there's also plastic which maybe aren't quite as rigid but they they should be nonflexible um and this rigidness it prevents Distortion of the impression I mean imagine if one of these bent from the weight of the impression material you know if it was flexible then you'd have a distorted impression and then your restoration wouldn't be you know uh it might not fit or or be good so um and Trays can be made for dentalist or entalis arches so that means that you know you can use this on somebody that has teeth or somebody that is missing teeth okay sorry um so stock trays um these are pre-manufactured trays so so these are stock trays because they're pre-manufactured and then also these plastic trays are stock trays and these non-perforated metal trays are our stock trays as well so that just means that they're pre-manufactured they make stock trays for adults or children and they come in a variety of sizes so usually the sizes are colorcoded um there's no standard for the colors but you know usually the purples are larger than the yellows these might be large and the yellows might be medium um maybe the blues are small but you know check the packaging just to make sure um so the metal trays are reusable you can use them again and again but you do have to sterilize them and clean them in between patients obviously um they're a little bit more expensive because they you know are they do last longer um then they have these plastic trays these are disposable so after you use them once you you throw them away um then they have uh perforated trays these are the ones with holes in them like these plastic ones are perforated these metal ones are perforated or they have solid um Rim lock trays so these are the solid trays and you can see there's like a little bit of a lip up here to hold the material in um now it's important to note that with the solid trays you have to use some sort of adhesive um and usually it's just like um they have ones that are like aerosols it kind of looks like a little can of hairspray and you just spray it on the tray and that holds the algen it in now with the perforated trays uh the alginet will seep through the holes and lock in place but with the smooth trays there's no holes for it to seep through so you need to put some sort of adhesive on the tray before you um you know before you load it up okay um and then we have stock sectional trays um these are used for sectional Impressions meaning just one part of the mouth so you can see here this is a quadrant tray and if you look at these other trays um on the previous slide uh these are made for a whole Arch right these these cover the whole Arch but these only cover half of the arch so it's a quadrant tray it covers one quadrant of the mouth um they also make stock sectional trays for anterior segments meaning you know just the anterior teeth like the enzers and the k9's for instance um half mouth trays and they make trays for bite registrations as well so there's also sorts of um sectional trays which just means it's not the full Arch then we have something called a triple tray um you might hear this called a closed bite tray or a double bite or a dual Arch or a check bite tray there's lots of different names of them um but basically it's a type of stock sectional tray um and it makes impressions of the teeth being treated and the opposing teeth so what you do is you you load the impression material on the top of the tray then you flip it over and you load it on the other side of the tray so when you take the impression you're going to get both the upper teeth and the lower teeth on the impression whereas if you're using um you know one of these trays you're only getting the upper or lower teeth on the impression but with the uh triple trays you get both both the top and bottom trays so you're also getting a bite registration as well um so this captures the Centric occlusion or bite the patient you know that just means that we're getting a bite registration and the triple tray is a dual Arch impression tray so it means it's capturing um the the maxillary Arch teeth and the mandibular Arch teeth and how they come together so it gets the bite registration as well so it captures the um the bite registration the counter impression which means the the teeth that aren't being worked on and the master impression the teeth that are being worked on S simultaneously and um and these are usually sectional trays um and they can be made for the posterior teeth like this one or the anterior teeth uh like this one there's all kinds okay and then bite registration trays um essentially the triple trays are bite registration trays um but they also have these bite registration trays that are called that so um these are u-shaped plastic frames with thin fiber m St stra stretched over the frame so as you can see here um just like the triple tray and the material is placed on both sides of the tray just like the triple tray um and these can be a full Arch like this one and again it's going to get the maxillary teeth and the mandibular teeth um or it can be a anterior or posterior um here's a a posterior here's what they call a sideless posterior so again there's all kinds of um trays that are made and you choose them based on you know what your patients having done and what type of impression you need okay and then custom trays so we're actually going to be making these later in the semester and we'll talk a lot more about custom trays in chapter 177 um they're especially used for uh patients that that are dentalist that that don't have teeth um but they can be made for patients that do have teeth as well um so so sometimes these stock trays might not fit each patient well enough um you know the stock trays come in extra small small medium large extra large well your patient might be an extra extra large you know or they're they might have their third MERS and they need a longer tray for instance um you know there's or they might be between a medium and a large or something so um so there's a lot of times where where we need to make a custom tray because the stock trays just don't quite do it don't get the detail that we need um so uh the tray should conform to the length size and height of the arch the depth of the padle Vault and the position of the teeth so basically it just means that it fits all the structures it needs to um whereas a stock tray doesn't in this case um so so really for the best fit you might need to make a custom tray um so custom trays and and elastomeric materials these can create highly accurate working models um much more accurate than stock trays if they don't fit correctly um so again don't don't worry too much about custom trays we're going to be talking about them a lot more in chapter 17 um they're made out of resins which is a type of plastic and these can be full Arch or sectional just like the um the stock trays um but it's you know it's kind of fun to make them so we'll get to do that okay so hydrocolloids um the this is a type of impression material and um one of the impression materials that we're going to use and that we use quite often than the dental office is algen which is a type of hydroc coloid so um so colloids your books defines colloids as a glue like material composed of two or more substances um so basically with colloids one substance does not go into the solution but it's suspended within another substance so we we encounter colloids all the time in our daily life even though you might not know it um so examples of colloids in real life or things like um you know body creams or moisturizer uh toothpaste milk ice cream yogurt beer even bread is considered a colloid so your book calls it a glue-like substance but it doesn't always have that that stickiness of a glue you know so um and then hydrocolloids um hydrocolloids uh are what we use for pression materials and these are water-based colloids that function as elastic impression materials um so so there's two hydrocolloids that are used in dentistry um agar which is a reversible hydroc coloid and alginate which is irreversible um now in reality agar is really not used very much anymore um alginite is you know is used because it's a superior material um you guys might know what Ager is if you've ever had a science class where you worked with a petri dish like um microbiology for instance um the petri dish has that red kind of gel in the bottom of it um that's usually Agger so so that gives you an idea of what that's like so um for there's a um a term uh Soul so um this is a the definition of soul is a colloidal suspension um like Ager powder mixed with water um and it's like a gelatin or glue like suspension so we'll see that term more um so you should know what it means um now Ager when chilled will become semi-solid kind of like Jell-O um you know that texture um but when it's heated it'll reverse back to that Sal state right so um so it's not going to keep its form necessarily uh so you could take an impression of the teeth with Ager and then you could heat that impression and it would reverse back to the Sal State and go back to no impression of the teeth you know it kind of be back to where it started just a puddle or whatever so so this is a reversible hydroc coloid right you can get it back to its starting point with heat now algen it is an irreversible hydroc coloid so it also forms that Sal that gels but it won't reverse back to the Sal State once it's set so once you have your impression and algen it even if it's exposed to heat it's not going to revert to that puddle like Ager it's going to keep its form so once once the form is set in the algen it it's there for good that is an irreversible hydroc coloid okay so reversible hydrocolloid this is our Ager right so this was the first elastic impression material used in dentistry which was great because prior to agar they had inelastic impression materials which were just not good at all but it's all they had so this was uh this was good once upon a time but not anymore so this was Superior to inelastic materials it was much more accurate than inelastic materials U but it's not very accurate by today standards um it was once used for crown and Bridge Impressions um and duplication of cast uh but used declined as better materials became available so it's you know you would be hardpressed to find somebody that's using this any longer honestly um now algen this is like kind of the go-to it's it's kind of a it's a basic material but it's good enough and it's not expensive so it's it's pretty widely used so um so remember alginet is an irreversible hydroc coloid material um so like I said it's inexpensive it's easy to manipulate um you don't need a lot of special equipment you just really need a bowl and a spatula and it's reasonably accurate it's not super accurate but it's good enough for a lot of things um so it's used for things like um diagnostic cast partial denture Frameworks um you can use it when you're repairing broken Dentures you can use it um when you need to make fluoride and bleaching trays sports guards uh preliminary impressions for entalis arches um removable orthodontic appliances like um retainers for instance so it has a lot of uses so what you would do you would um you know take the impression with algen it and you get a product something like this over on the left and uh then you would pour up your Stone model and from that you can make bleaching trays or fluoride trays or sports guards or whatever you need um so so again this is your your maxillary um Arch impression um you can tell because it's got that middle part where the hard pallet is and then your mandibular impression and you can tell because it's horseshoe shaped and it leaves uh space for the tongue um so again algen not accurate enough for final Impressions like for crowns Bridges implants Etc um because it just doesn't capture the the fine detail that an elastomere like polyvinyl soloxine would capture um so the final impressions are are made with more accurate materials like PBS polyvinyl sling or polyether okay next slide um so alginet um I don't know if you guys know this guy he's called sigmoid or Sigman the sea monster something like that he's popular when I was a kid anyway he's covered with seaweed because he's a sea monster um so algen it what's algen it made of where does it come from um well it's actually produced from seaweed derivatives so it comes from seaweed which is why I put this little sea monster guy over here so you can remember it um now the main active ingredient in uh alginate is potassium or sodium alginate and then alginet comes in fast regular and slow set so when you're using alanet you mix it with water you have to mix it up pretty fast you have to get it in the patient's mouth before it sets you know it's it's hard you know it's hard to master the skill um you can get better and better at it um but it does take you know it takes a while to get everything done um so you know so if you're inexperienced you might want to use the slow set or the regular set that gives you more time to get it mixed up and get it into the patient's mouth um if you're really good at it and you or you know got experience and everything you can use the fast set which means you might have like a minute less to get it mixed up and get it in the patient's mouth which doesn't sound like much but I promise you it's that's like forever in dentistry so um so it comes in these these different sets um they do have dustless formulations of alginite what they do they add glycols or glycerin to the alginate and it just keeps it from puffing up you know it's a very dusty material so you know you want to make sure you don't shake the container or anything right before you open it um and dust also contains silica um and this can be hazardous um if you inhale it it can actually injure the lungs so again you don't want to shake that container right before you open it and cause a big dust cloud um and you want to wear a mask you know when you're working with this alginite because you don't want to inhale it directly and possibly harm your lungs okay an alginate um sometimes it comes in a package like this like it looks like a sack of flour um but then sometimes it comes in a canister too so it just depends um now the algen setting reaction um when you add algen at powder you know you'll mix this with water and then it creates um the reaction creates calcium sulfite dihydrate and sodium alginate and then ultimately calcium alginate um so the calcium alginate is ultimately what you get when you mix the powder with the water and this is um insoluble um and it creates a Sal of the mixed powder and water and then that will gel as it sets so um so again this is irreversible so this chemical reaction it's it doesn't reverse back to the Sal state it can't be reversed it's not like agar with agar you heat it up it goes back to the you know the saw state um but algen it once once it's set um the Sal state is gone you can't re you know you can't melt it down or anything like that it's set um so the setting reaction it's actually a a pretty rapid reaction um they do make slow set and fast set and regular set um by adding other materials to it but um you know you don't have a a whole lot of time you have to work quickly um but they can add Tri sodium phosphate um this is a retardant that they can add to the um alginet and this makes it a slow set it slows things down then there's something called uh dious Earth which is added as a filler and this is used to create stiffness strength and prevent stickiness so we we do want the material to set and be somewhat stiff you know um and and have good tear strength and all that um and then pottassium sulfate this is add it to the alate to keep it from interfering with the set of the gypson products used for models so remember once we take this impression we don't just work with that impression we have to pour it up into a stone model and get that positive reproduction and then we're going to make whatever on the Stone model you know maybe it's bleaching trays maybe it's a night guard maybe it's a a crown or something like that so um so so the the algen it has to compatible with the dental Stone which is a gypson product um which we're ultimately going to pour into it and then some alate um products will change colors when it sets which is kind of nice um that you can just look at it and see if it changed colors that's a little more expensive so at school we're not going to be using that you can uh you can tell if it's set pretty easily if you just touch it with your finger um you know if there's some left over in the bowl you can touch that with your finger and feel if it's set you know it gets to a certain hardness and it's pretty easy to tell if it's set or not okay um so working time for alginet um working time is defined as uh the start of mixing two seeding uh the material in the mouth and the setting time that's um from when you start mixing the powder and the water to when it sets or hardens so you can actually lengthen the setting Time by using cold water instead of room temperature water um um although you know when you put cold water in somebody's mouth even if it's mixed with algen it it could cause tooth sensitivity so be careful using cold water um but if you need extra working time and you don't have any slow set you can add cold water um to your regular set um or you can shorten the working Time by using warm water so if you're a pro and you're really good at this and you say I don't have any fast set but I want to get this done quickly you can use warm water and the reactions will be speeded up so you can do it like that um but ordinarily you want to use room temperature water um if you want like the the reaction to proceed um at its normal Pace now you are going to be tempted to add extra water because it it always seems like there's not enough water to get the powder and the water mixed together and get it smooth and creamy substance so you're going to want to add more water but don't do that um you know follow the manufacturer's instructions and use exactly as much powder as they say and exactly as much water as they say um and then you just have to work hard and mix it up like this person on the right here um so regular set alginet you have about two to three minutes working time and two to five minutes set time and five minutes with something in your mouth like that that can be a long time for the patient so that's why people kind of like to use the fast set to make it more comfortable for the patient but again you have to have a certain amount of skill to be able to use the fast set um because it requires you to be very quick um so the fast set um you have about 1.25 to two minutes of working time and then one to two minutes of set time which is a lot nicer for the patient okay okay so algen properties permanent deformation um so something when something deforms it changes shape right so permanent deformation means it changes shape forever it doesn't go back to its original shape so this is something that we have to be careful of because we don't want our Impressions to change shapes we want them to accurately represent the teeth and the structures in the mouth so when you take an algen impression um when you you remove it if there's any undercuts and this is what we mean by undercuts um the the alginet is going to go under here right so this area is an undercut so when you remove it this part of the algen it's going to have to stretch out to get around this fat part of the tooth right so so it's going to compress or be kind of pushed together to get around that tooth right the same thing is going to happen here and here and like any tooth is going to almost any um anterior tooth is going to be a little thinner at the gingival margin or the gum you know the area where the gum is um you're going to have these undercuts so the algen it is going to be compressed when it's removed from there because it's going to have to push push out of the way to get around the fat part of the tooth right so the greater the compression the more likely it is to permanently deform so it's got to deform somewhat to get out of there to be pulled out of the mouth right but you don't want it to permanently deform so um so basically we need 2 to four millimeters of alunite between the the tray and the teeth or any undercut right so you have to have a layer of alginite that's about two to four millimeters thick um in order to get around this without the the impression deforming permanently um because if it's less than 2 millim is going to deform more easily and will be more likely to deform permanently in which case you would have to redo the impression which would be very unfortunate um so algen it should be removed with a rapid snap to prevent deformation so when you're removing the alginate you've got to like pop it off of the teeth right you have to do it very quickly and we'll be practicing um all of this in laap um so the impression uh deformation May recover if the depression sits for 8 to 10 minutes so what does that mean that means that when we remove the depression there's going to be some parts that are are pushed around because they had to you know squish together to get out around the fat part of the tooth right so um so once you take it out and let it sit it'll stretch back to its original um shape so so you don't want to pour up the impression right after you take it out of the mouth because it's probably not a true representation of the shape of the the teeth for instance so um so you want to let the impression sit for about 10 minutes before you pour it up and that'll let it you know kind of recover and stretch back out to you know to the the shape that is uh representative of the mouth um and deoration that does not recover is permanent deoration so if you see a big dent you know in the um in the impression then that could be permanent deformation you kind of have to look inside the mouth and compare it okay so another property is dimensional stability um algen it is very sensitive to moisture loss so if you leave it sitting out water's going to evaporate off of it and the whole thing's going to shrink right so that's dimensional stability when when your impressions shrink or swell they don't have good dimensional stability so alginet doesn't have a great deal of dimensional stability it's not terrible but at the same time it's not great so so after you take the impression you know after you snap it out of the mouth you want to rinse it and disinfect it okay because remember these materials are being exposed to saliva you know all kinds of germs microorganisms in the mouth um possibly blood so you definitely want to um rinse any debris off of them and then disinfect we'll talk about how to do that um then after you uh disinfect it if you can't pour up the impression right away what you want to do is you want to wrap it in a damp paper towel kind of like in this picture and then put it in a ziplock bag and this creates um uh sort of like a moisture chamber that way the um the impression won't um lose lose moisture or there won't be evaporation and water loss from the impression and that way it'll keep its true size it won't shrink um so cesis this is um this is the name for um contraction of the impression that results from losing water you know the shrinkage and the impression should be um it should be poured up after it's disinfected so again you want to give it about 10 minutes before you pour it up because um you know that any deoration that occurs when you remove it from the mouth you give it about 10 minutes for it to recover um then you pour it up after it's disinfected now a lot of times in the dental office you can't pour things up right away necessarily I mean it's just so busy um but you don't want to put it off for too long so um so if you can't pour it up right away what you can do is wrap the impression in a a damp paper towel not super wet because if you do that then the impression can suck up the water swell right so you want it in a damp paper towel and then put it in a Ziploc bag so it can contain the moisture and you should really should pour the impression up with stone um if you're using Alin it you shouldn't wait any more than about an hour to Pour It Up um the longer the pouring is delayed the more likely um that Distortion will occur and if Distortion of the impression occurs then your model is going to be distorted and your restoration or your prosthesis is also going to be distorted and it may not fit the patient correctly okay um tear strength so this is another um property of alginate and you can see here there's some tears in the impression so they probably have to redo it honestly um algen it when you mix it with too much water it's going to be weaker and more likely to tear when you remove it from your mouth so again I know you're going to be very tempted to add more water when you're mixing the powder and the water for the algen it but but don't you know stick with the the measurements that the manufacturer tells you to otherwise you're going to wind up with something like this that you're just going to have to start over and do it again um these thinner sections like the inner proximal areas um are more likely to tear obviously um and if you remove the impression slowly it's more likely to tear so you really have to do that snap and get it out of the mouth quickly um you do want to um leave the impression in the mouth for one extra minute after the material is set so your algen it sets and you kind of feel it and it feels hard so you can tell that it's set and what you want to do is look at the clock and just leave it in there an extra minute and that's going to increase the tear strength um that way when you snap it out of the mouth quickly it will be less likely to to tear because it had that extra time in the mouth to um you know to set even further okay um so the objective of making alginate Impressions um we want to reproduce the oral structures with acceptable accuracy while practicing good infection control and maintaining patient Comfort um so remember um you know good infection control is critical uh there's all kinds of you know disease and things floating around you know flu season uh you know covid seems to be all year long now bronchitis colds all that stuff you know people have all sorts of germs in their mouth so um you know so have them do a pre-procedural rinse um you know use like Listerine or chlorexidine which is um antibacterial rinse um that'll remove any debris from their mouth and lower the the load of microorganisms in their mouth um and of course going to be wearing PPE when you do these Impressions um so we want we want accuracy we want good infection control and we want to try to you know maintain patient comfort as much as possible um you know impressions are are not a lot of fun to get um but you know we we try to make it as nice for the patient as we can okay and then the clinician will need to prepare the patient dispense um and mix and load the algen it into tray so um you know we want to put the the bib on the patient we want to try in the tray to see what is the right size for the patient um you know make sure everything fits explain the procedure to the patient so they know what's going to happen it can be kind of scary when this algen it kind of goes down the back of your throat and you start gagging so you need to you know warn the patient about that um then of course you have to do everything very quickly you know mix up the alic get it into the trays get it into the mouth and hold it there um after removal of the impression the impression must be disinfected and properly handled prior to pouring gypson material so again you know when the impression comes out of the mouth it's going to be covered in saliva possibly blood you know definitely lots of germs um so we want to disinfect it um you know we don't want to leave it laying out where somebody else is exposed to the germs on it um you know so we'll talk about how to handle it and how to disinfect it okay um so tray selections um so 90 I would say in general dentistry like 95% of the time or more we wind up using stock trays um but sometimes you do have to make custom trays for um certain patients um stock trays um which this is one um these generally work well with alginet um you know there's room for the material the adequate thick the 2 to four millimeters um algen it must be uh tightly adapted to the tray or Distortion will occur so when you load the alginate into the tray you kind of really press down on it um perforated trays will allow the alginate to lock into place so this is perforated it has holes in it the algen it will squeeze through the holes and as it hardens it locks it into place which is what we want um if you're using one of those smooth trays whether it's plastic or metal then you're have to use some sort of adhesive right if you're using a non-perforated tray um which I don't really like that because it adds one more step to what you're doing um disposable plastic tray should be rigid so the metal ones are definitely rigid but the plastic ones should also be rigid because you don't want them to bend or anything like that because that will cause Distortion in your impression which means there will be Distortion in your model and whatever you're making probably won't fit the patient well um so the full Arch tray should cover all the teeth and extend into the facial and lingual vestibules so you know the cheek side of the teeth and the tongue side of the teeth um it should extend posteriorly to cover the retromolar area for mandibular trays and the hamular notch area for the maxillary tray so your retromolar area and your hamular Notch area those are just slightly behind your last Moler so um the tray needs to cover back to the last Moler whether that's your second Moler or your third Moler you know your wisdom teeth um but it needs to cover that area and then it needs to be deep enough to provide at least 2 millimeters of space for algen it beyond the incisal or accusal surfaces so you know you have to have at least a 2 millimeter layer of algen it on top of those chewing surfaces and then it needs to be wide enough to allow 5 millimeters of algen it between the sides of the trays in the tissue so on the outside of the teeth and the inside of the teeth the the Buckle and lingual uh vestibules you have to have that 5 millimeters um now utility wax can be used to create an extension so let's say somebody has kind of a larger mouth and they have their wisdom teeth in so they have their third molers um maybe the stock trays fit okay in every respect but they just don't go back far enough well what you can do in that case is you can take some of this is called utility wax and you just kind of add it onto the end of the tray and you make it a little bit longer that way you can have a you know a tray a stock tray but kind of customize it to fit somebody that needs that extra length in the tray because they have a third Moler um and then have patients rinse before taking the impression again it'll remove uh debris it'll bring down the bacterial load in the mouth so um you know so it's a win-win okay dispensing algen so this kind of looks like what we have at school we have these canisters and with the canisters you have a scoop um so usually you use uh two or three scoops and then you use you know one unit of water for each scoop so here's one that would be two three um so again don't monkey with the you know to keep the the ratio what it should be you don't want to you know mess around and and wind up with algen it that has poor tear strength because you put in too much water um so manufacturer Supply measures for powder and water make sure that your your measurer or you know um this thing came with the this canister because different manufacturers have different size Scoops right so make sure you're using the right one it here to recommend it proportions of powder and water you know don't add more water um do not change Scoops between products because they might not be the same size so you might not get the correct amount if you grabbed a scoop from another you know another canister that's another brand especially um powder may become packed tightly in storage okay so so this stuff kind of settles when it's in when it's just sitting in the closet so what you want to do before you use it is um take the container and turn it end over end um and this way U the you know it'll kind of fluff up that powder it'll decompress the powder and mix the ingredients now this isn't saying take it and shake it shake it shake it vigorously you don't want to do that you just want to gently you know turn it upside down end over end a few times and and then let it settle for a few minutes before you open it because again you don't want to open this and get this big blast of dust and breathe it in because that's not healthy for your lungs so wear a mask when dispensing and mixing the alginet because the dust may be um hazardous and this is mostly due to the silicone dioxide um but the dious Earth can also um cause issues for your lungs as well so again no shaking it just a very gentle end over endend to mix it up a little bit okay and this is what your mixed product looks like nice and smooth and shiny um and you have to work to get that you know you're going to be putting a lot of e into mixing this your arm will be tired so um so mixing algen it so um we would use uh usually three scoops of the powder for a moderate to large upper adult Arch okay or two scoops for a small adult um and then we would use two scoops for the adult lower arches so why are we using three for the maxillary Arch and two scoops for the mandibular Arch well remember with the axillary Arch it's a bigger tray right because the tray um encompasses the the hard pallet or the roof of the mouth whereas the mandibular tray is horseshoe shaped right and that area where the tongue is is cut out so you don't need quite as much material for the mandibular Impressions that you do for the maxillary Impressions so that's what the difference is there use one unit of water per scoop like I showed you on the previous slide um room temperature tap water is placed in the rubber bow and the powder is added to it so um so it's funny because in real life like I would say 99.9% of the time in dental offices people are putting the powder in the bowl and then adding the water to it which is actually not the best way to do it I mean it works but it's not the best way to do it the best way to do it is put the water in the bowl first and then add the um powder to it you kind of sift the powder into the water and that the reason for that is fewer air bubbles are created so you get a better um you know you bet get a better uh Stone model when you're finished um or I mean ultimately you get a better model when you're finished um but you also get a better impression so um so remember water in the bowl first and then the powder but when you guys go out and work in dental offices I think everybody does it the opposite way so um so just remember the best way which is what we teach you always the best methods um so remember cold water will slow the set and warm water will accelerate the set so if you accidentally pour warm water in there you're going to have to work really really quickly okay um then we're going to stir the powder into the water until it's wet then once it's all wet then you start mixing it really really aggressively and you you push it against the sides of the bowl um with this wide spatula and I have a video of this in a minute and the reason we do that is because we want to force um any entrapped air out of there um because any entrapped air is going to create air bubbles and if the air bubbles are in the impression material then you could wind up with an impression that has a big air bubble on the accusal surface of a tooth you might be working on um and then that would show up in the model so you know we really can have that um now mechanical mixers may be used usually don't find those in regular dental offices um mostly you know the dental Labs will have the mechanical mixers for um for that but you never know you might get lucky um that would be nice um so usually it takes about 45 seconds of mixing for regular set and 30 SEC seconds of mixing for fast set alginet so you really have to work very very quickly you know you really have to be have everything ready to go and you know all your ducks in a row before you get started um and then ultimately it should have a creamy consistency kind of like this and not grainy if it if it looks grainy that means that the powder is not all completely mixed into the water okay so load the tray so this is what the tray looks like once you load it um what you're going to do is you're going to pick up the alginate on the spatula and you push it into the bottom or the depth of the tray and what this does is it forces out air and it's um prevents voids in the impression if you have air in the impression or air bubbles it can create little holes um in there which is what we call a void so um so load the alginate in large increments so take a Big Blob of it and push it into the tray and do that as quickly as possible and that reduces air you know from getting trapped into the impression material then you want to load the tray until the algen it is even with the top um of the sides of the tray uh so you can see that here it's kind of just level and then um what you can do if you want is use a wet gloved finger you know you're going to be wearing gloves when you do this of course um if you wet the finger of the glove and you run it along here along the top you can make a little kind of like a little trough or a shallow indentation for where the teeth are going to be you don't have to do that but some people like to do it um but make sure you only do that if your glove is wet if your glove is dry and you run it through here everything's going to stick to it and it's going to be real messy okay so so um I I suggest in your book suggest starting with the lower Arch um you know not everybody does this but the lower Arch is more tolerable for the patient so it's you know you're going to be a little more successful if you start there I think um and the lower Arch the the material the algen it doesn't really go down the back of the throat like it does with the max or the upper Arch so you know so the lower Arch is just a little more user friendly so after you load the tray what you're going to do is take some algen it from the bowl and you're going to wipe it on the accusal surfaces so on the chewing surfaces and you can also put it in the embrasures of the teeth you know any spaces between the teeth that might be showing and it'll Force air out of those spaces so you won't get those voids or air bubbles in the um final product so for the lower impression you're going to be standing in front of the patient um and if you're right-handed you're going to be at the seven o'clock position so you're going to be slightly to the patient's right and if you're left-handed you're going to be slightly to the patient's left at the 5:00 position so you're going to use the right side of the tray to retract the left corner of the mouth and then with the other side of the mouth you're going to use your finger to retract and then you're going to rotate rotate the tray into the mouth again we're going to see this in a video in a minute um you're going to seat the posterior first so seat the back of the tray first and then you know bring it to the front to seat the front so it's going to be kind of tilted a little bit backwards um when you start out it's covering the posterior teeth and then bring it down to cover the anterior teeth and then once you do that you're going to run your finger inside the lip and kind of pull the lip out around the tray um and then this will allow the algen it to flow into that VES in the anterior area um have the patient lift their tongue to the roof of the mouth and then relax it okay that way that it'll get the tongue out of that um out of the way of the alginet that's going to be kind of flowing through the tray um then stabilize the tray with the index and middle fingers of the right hand over the right and left sides of the arch um and if your hands are kind of on the smaller side that can be kind of difficult so so some people will use their two index Fingers um you know on the right and left hand stabilize it um some people can do it with one hand um it just depends on the size of your hands and the size of the patient's um mouth really okay and then for the upper Arch um so seating the tray on the maxillary or upper Arch you're going to be behind the patient so again you're going to do the same thing as with the maxillary or the mandibular you're going to load the tray um then take some alet from the bowl and wipe it on the accusal surfaces the chewing surfaces of the teeth and in any embur any spaces between the teeth to force the air out okay we don't want any air in there that's kind of the kiss of death for an impression um and then with the upper impression um you the clinician you're going to be standing behind the patient so if you're right-handed you're going to be behind the patient at the 11:00 position so you're going to be slightly to the right of the patient um if you're left-hand it you're going to be slightly to the left of the patient so you're going to retract the corner of the mouth with the side of the tray and um use your finger to retract the left corner and you're going to rotate the tray into the mouth you kind of have to turn it a little bit to get it in there then um again you're going to seat the posterior first and then gently seat towards the anterior and this way the algen is going to be flowing forward towards the anterior of the mou not back into the the pallet so this is especially important with this upper Arch um the patient should be seated upright to keep saliva and algen it from collecting in the back of their throat um you might want to have your suction in there to to collect any saliva and uh sweep away excess alginate from the posterior to prevent gagging so some people will slightly recline the patient kind of like in this um picture when they're putting the tray in um but once you get the tray in sit the patient upright because that reclining position can um you know can cause the patient to gag okay and then removing the tray um so like we said you want to remove it very very quickly you kind of want to snap it out um so what you can do um look at the you know usually there's some algen it left in the mixing bowl and you can kind of look at that and touch that to see if the algen it is set once it becomes hard you know you know it's set um so you actually want to after it's set you want to leave the impression in the patient's mouth for another minute and this will help it gain tear strength so it doesn't tear when you take it out um then when you're ready to remove the tray you're going to use a finger at the top of the side of the tray and you apply a little bit of pressure just enough to kind of break the seal like a vacuum seal forms and then um while pulling the tray uh quickly away from the teeth with a snap so you're going to break that seal at the same time you're going to snap it out so it's a very quick kind of movement um and again we'll be practicing all this in lab okay handling the impression so algen it again it can shrink it can swell you know so you have to be real careful with it um you want to rinse it underwater to remove the saliva once you remove it from the mouth then look at it and and evaluate it you know is it acceptable quality you know are this is there a lot of voids from Air um did you get all of the teeth you know especially the last Moler in each um quadrant um you know did you get all the structures you need to get so so look at it and see if it's acceptable if it's not acceptable you know redoing it while the patient is still in the chair is better than dismissing the patient and then saying oh wait a minute it's no good I have to bring them back so you know so valuate it right there and if necessary if you're not sure ask the dentist if it's okay um if it's not then you just start over you know at least the patient still there um so if it's acceptable you're going to hold the impression inside a plastic bag and spray it with disinfectant right so we keep it inside the bag so that you know the disinfectant isn't flying all over and people are inhaling it which you know again can be bad for your lungs so um so put it in a plastic bag and then spray it inside the bag then you can use a lab knife it's just kind of a Dull Knife um you guys will get them for your Labs um to remove excess alginate from the posterior of the tray but but again be careful that you don't remove anything you know that that's vital to getting a good um model um shake off excess moisture um you know again do this in a controlled manner don't be shaking it every which way you want to you know try to shake take it in a sink and just you know very keep it all controlled um and then you're going to place the um the impression in a zip blocked bag and a damp paper towel so again you don't want the paper towel to be dripping wet because if you do that then the alic can take that moisture and it swells up right so so it's just damp not dripping wet and then the impression should be poured within an hour any more than an hour the dimensions of the impression can change and um um and then you won't get the product that you need okay so this is a a not so great a not so great model okay you can see there's lots of you know there's voids there's bubbles there's all kinds of things and and the detail is really lost so um so that's not what we want um so the criteria for clinically acceptable alginite Impressions um again we evaluate the Impressions immediately after removal from the mouth and and rinsing the impression um the impression may need to be repeated you know that it happens you can't want them all um an acceptable impression will cover all areas of Interest so if you're missing the very back teeth you know something like that it's going to be a problem and structur should be recorded with sufficient detail um they they should not be grainy at all and um they should be um you know some you shouldn't have too many voids and that's caused by entrapped air um so you know a minimal amount of voids um and certainly none in critical areas like on the occlusion for instance um the alginite should be fully seated in the tray um and with perforated trays that's usually not a problem it's usually with the the non-perforated or smooth trays that um that can be an issue um they should be free of debris um and if you look at table 15.3 in your book um it's got some good suggestions for troubleshooting alanate Impressions so like some common issues with alate Impressions and how to correct those so um take a look at that when you get a minute okay and here's the video that I promised so let's watch this e for e e e okay so let me get out of here oops sorry okay okay sorry about that let me get back to okay get back to our slideshow so um so that was a pretty quick video you might want to watch it a couple more times just to um really kind of see the process again uh the only things that I kind of differ with from that video or your book kind of differs with um usually it's better to do the mandibular um you know the uh mandibular Impressions first they they chose to do the maxillary Impressions first um and then also um they didn't okay why is this here again okay and then one other thing they didn't do was um they uh they didn't um spray the uh the impression inside the bag um so you always want to um put the impression inside a bag and rinse it and and then spray it so um yeah so uh but it's pretty good you get to see the whole process and again when you um when you actually do this in lab you're going to learn so much more it's you know you just really have to have that Hands-On element to um to master this um and then there's um okay so also uh lastly with alginet they do have these two consistency alginet systems um you don't use these very often in general dentistry um maybe more in Specialties um but basically it's just two alinat that have different viscosities one's thicker one's thinner um you know you use the thinner portion for like the um detailed areas like the occlusion of the teeth for instance and then the um the thicker viscosity or the thicker um alginite would be the base you know that you put in the trays um so this can uh lead to improved accuracy and detail um it's useful for complete and partial denture Impressions um and with um you know the the higher viscosity materials resist flowing so the patient less likely to gag um so again you don't really see this too often in out in practice um but certain specialty practices may use um the two consistency alginate system um and it's kind of like um with the polyvinyl soloxine you have like heavy body light body um it it's kind of like that okay so now we're going to move on to elast mirors and these are another uh family of impression materials which are um a little bit newer than um the hydrocolloids like Ager and um alginet and they're a little bit more you know they're accurate they're actually a lot more accurate so elast are highly accurate um elastic and materials that have qualities similar to rubber like rubber materials and these are used for fabrication of things like metal castings um ceramic Restorations like crowns Bridges um implants uh partial denture Frameworks uh complete Dentures so so these impression materials are used for a lot of purposes um so the four types of elastomer that we have um poly sulfides which are a little bit of an older material um condensation silicones um which are not uh they've fallen out of favor as well for for various reasons um addition silicones um which is your polyvinyl soloxine or the PVS that's wildly popular um and then polyethers which um have some good features um but they're not quite as um great as the PBS not as popular so um so elmir um with elast mirors uh the two most widely used lass mirors are uh polyvinyl soloxine or PVS and polyether um they also made a hybrid of these two materials called V vinyl polyether and it just combines the best properties of each so um so again they both have some good properties and mixing them together kind of synergizes that um and then elastomers um they have a flexible Matrix and this contains fillers to reduce polymerization shrinkage so these elastomers they go through a polymerization reaction so what happens is the there's mon monomers um in the material and then uh when they go through the polymerization reaction all these monomers um connect together and make these long chains these polymers and in addition to being connected as a chain they also cross link so the chains connect together as well um so polymerization uh the reaction um results in a very good material but it also results in some shrinkage you know these monomers kind of get pulled together and condensed so so a little bit of shrinkage does occur um so they found that to counteract that um they you know they put a filler into the material um to kind of keep the shrinkage from being um significant so the cires they're not water-based like the hydrocolloids so they're not nearly as sensitive to uh water loss or imbibition which is you know swelling um as the um hydrocolloids so they're much more dimensionally stable and the shelf life for elas mirrors is uh 12 to 18 months and if you refrigerate them um the shelf life will lengthen a little bit if they're refrigerated um but you don't want to use them when they're refrigerated you want to take them out and let get to room temperature before you actually use them um and then adhesive so atast AMR they don't adhere well to solid metal or acrylic custom trays so you have to use an adhesive for the elastomers so remember we said that you have to use an uh an adhesive if you're using alginet with non-perforated trays and here's a tray adhesive that's for alginate um you can also use this one it looks like fingernail polish but most people use the the spray just because it's easier um so so with the alanet you only have to use the adhesive if you're using the smooth non-perforated trays but with the last of mirrors you always have to use some sort of adhesive because they don't adhere well to um the solid metal trays or custom trays so um but you want to make sure that you get an adhesive that's made for elastomere specifically you can't use alginate tray adhesive um if you're using uh PBS or another elastomere so um you have to place the adhesive in the tray to maintain the material in the tray and this prevents Distortion if the tray if the if the material doesn't adhere to the tray and it kind of spills out then it causes Distortion and your impression really isn't any good um so remember each type of elastomere whether it's PVS or polyether or whatever it has its own type of adhesive um so you can't use um you know algen adhesive for PVS or you can't use polyether adhesive for PVS there's no mixing and matching um and then you apply uh the tray adhesive in a thin layer and allow it to dry before placing the material so you spray it on and then you kind of just hold it for a few seconds it dries pretty quickly and then you're um good to go as far as loading it okay and elastic recovery so elastom are able to rebound due to their um rubbery nature which um reduces Distortion and and deformation so PVS actually has the best elastic recovery or B rebound of the elastic mirror so that's why PVS is so popular because it gives you a lot of detail and a very very accurate impression and over here on the left we can see um this is light body polyvinyl soloxine so light body means it's less viscous it's a thinner um type of material they also make um regular body they make heavy body so um you know so they make this um PVS and other elastomer in different thicknesses or viscosities and then usually um uh you can dispense it with a um it's the auto mixing tip here and then here's the cartridge it's got the Catalyst in the base um and then it's like kind of like a little gun and you kind of pull this part with your hand and um this this Auto tip mixes the Catalyst and the base and it comes out Mixed so that's kind of nice um you don't have the mixing like you do with algen it um they also make PVS as a putty so um so again you have a catalyst and a base and it's just like Play-Doh if you've ever played with that or Silly Putty and you just mix them together and obviously that's very um High viscosity you know it's a very thick material putty just like it sounds okay and so elast Amir wetability so we talked a little bit about wetability in I think chapter two previously um but you know it's got applications that's why we brought it up so um so hydrophobic material um when you see the word hydrophobic Hydro is water phobia or phobic is fear so hydrophobic material it doesn't like water doesn't necessarily fear it per se but it it doesn't get along with water it doesn't really mix well um so hydrophobic material generally does not wet well with water so so poor wetting means you're going to have a high contact angle between the material and the um water molecule so it's kind of like um water beating up on your car right after you waxed it that's that's a high contact angle or po wetting so most alasmr have po wet ility for a wedding and they'll have a high contact angle um there is one exception polyethers so um so last mirors they generally need a dry field for accurate Impressions so that means that you have to dry off the teeth and the tissues really really well to get accurate Impressions but that's kind of hard when you're working inside the mouth right so you know so it's they they do have drawbacks so um so water forms a high contact Ang angle and beads on the surface and this can affect the impression believe it or not even something that little um the one El last mirror that's a little more hydrophilic meaning it it does uh wet well with water is polyethers so polyethers are the most hydrophilic elastomere um they're wettable so they have more of this low contact angle so they don't have issues when taking the impression in you know a wet Fe field versus a dry field and this is why they they got the idea to mix polyethers and PBS because one's hydrophobic the other's hydrophilic so wet ability also influences how well wet gyps and materials like the dental Stone how well it flows into the impressions for detail so um so something with poor wet ability is not going to get as good a flow of the gypson material into all the little nooks and crannies of the accusal surfaces of the teeth right so um so you want something that's a little more wable for a better product okay um so polysulfides these are actually the oldest of the elastomer um sometimes they're called rubber base and um they're more accurate and dimensionally stable than hydrocolloids like um alginet is a hydroc coloid but they're not as accurate as other elas air they're one of the older elastomer um these were previously used for crown and Bridge impression and partial complete denture Impressions but they're not really used that much now um they they have to be hand mixed there's no autum mixing you have have to push these out onto a mixing pad and mix them together by hand and then um and they they they smell bad they have a sulfur odor which is like um you know like rotten egg kind of odor which you know is not very pleasant and they're real messy like this this dark um material stains uh can stain your your clothes and things like that so um it's not real desirable um so sometimes it's still used for complete denture Impressions but it's they they've really fallen out of favor because they're just not you know great material now silicone rubber impression materials these are also elastomer um there's two types of silicone impression materials there's condensation silicone and addition silicone so condensation silicone This was um developed in the 1960s and this is an alternative to that messy smelly polysulfide so they were Step Up um and these were usually used for crown and Bridge um Impressions um it's easier to mix there's a pleasant taste there's no odor um there's shorter working and setting times and poly cides but the problem is with cond condensation silicone um it sets through a condensation reaction and condensation um what it produces in this material is um a byproduct alcohol um ethyl alcohol as a byproduct so what happens um you know when the condensation reaction occurs and the um the this material loses the ethyl alcohol it evaporates what happens is the impression shrinks so so there not you know there shrinkage and so there's not a lot of dimensional stability so um so condensation silicon they were an improvement over poly sulfides but they had other issues so so they were replaced by addition silicon and the addition silicone that replace them is polyvinyl soloxine or PVS so that's kind of really the best impression material on the market um unless you consider the the PB polyether hybrid so um so addition silicone this was introduced in the 1970s and again it was definitely an improvement over the condensation silicone as far as the um dimensional stability it didn't shrink as much um so this had greater dimensional stability and accuracy um it's clean easy to use no foul odor or taste um this is right now the most popular material for crown and Bridge um procedures for the impressions but it's also the most expensive impression material um which is a bit of an issue you know it's or can be I guess um so again polyvinyl soloxine or PBS this is an ex uh an addition silicone impression material um which is an elastomere um so here is the um here's how you administer um the the PVS um you know you have this cartridge which has two sides it's got a base and a um catalyst in it and um and it goes through this mixing tip and the base and the Catalyst mixed together and it comes at the end so what you're doing is you're pulling this trigger with your hand or your finger and this plunger is used to you know you pull it back and you um place the cartridge there and when you pull the cartridge it presses the material out so so this is definitely um you know it's it's nicer than having to mix the algen it with the bowl and you know pressing it against the side of the bowl and everything um but your hand can get tired you know after you press this for a while so um they do have mechanical mixers for this which are are kind of nice um but this is the automixing uh equipment and materials so you have different different classes of the material like you have putty here um putty always comes in these canisters you know one has the base and one has the Catalyst and then the um the heavy body medium body light body uh they come in um these cartridges and again there's two sides the Catalyst and the basee and it goes through these mixing tips and there's a little swirly part in there and it mixes the the materials together um in the perfect uh proportions so um so here's a a heavy body light body um so what you do is you you use the light body on the accusal surfaces where there's a lot of detail right um and it it flows into all those little Fishers and grooves and things um and then the heavy body uh you would put into the tray and that kind of like um holds everything in place um so that's you know a lot of times they mix um the the various um bodies heavy body light body whatever um and then here's the the putty when you open up these canisters um you take the putty out in these little measuring spoons and and mix them together with your hands okay so PBS polyvinyl soloxine sometimes you'll see it um as vinyl polyoxin or VPS um it's the same thing uh this is an addition silicone impression material and again it's an elastomer um it undergos polymerization reaction which means a whole bunch of monomers are put together chained together to become a polymer um so it's polymer uh polymerization reaction of chain lengthening it's an addition reaction um and then there's Crosslink uh and vinyl groups and this produces a stable silicone rubber um it doesn't produce a byproduct like the condensation silicone and PVS has the smallest dimensional change on setting of The elastom and hydrocolloid so that's huge you know if you have very small dimensional change you're going to get a better more accurate product okay and it also has high elastic recovery and resists tearing so the high elastic recovery remember there's got to be a little give in this material so that it can get out of the mouth around those wide parts of the teeth it's got to be able to stretch and then go back to its normal you know to its original shape um so you know so it's not permanently deformed so that high elastic recovery is is a very desirable thing and then here's an impression where they used uh light body and heavy body they used a a combin ation so they you know they put the light body on the surfaces of the teeth and then the heavy body in the impression and then they they take the impression um you know to create the restoration or prosthesis or whatever um so PBS it's um it's a great material but there is a secondary reaction um it produces hydrogen gas as a secondary reaction and this gas can release for up to two hours from the impression and what that's going to do it can create PB uh Bubbles and a poor surface and a cast if it's poured too soon so so basically you have to wait two hours before you pour it or you could potentially have bubbles in your your study model which can you know lead to a loss of detail and you know if you're trying to make a restoration um if there's a bubble that's that's a huge issue so um so some manufacturers add Palladium powder to um to counteract the hydrogen gas release but you know it's best to wait a little while before you pour these up just to make sure that the gas release is complete um so PVS Impressions um they can be poured in stone several times and are dimensionally stable for at least a week so um so remember with the alginet you have to pour that up kind of like within an hour um ideally or else there can be dimensional changes that you know render the impression inaccurate um and you can only pour up an alate impression once you know so PVS is that's huge that you can pour up you know several Stone models in the one impression um and that is stable for a week so a lot of times what what happens is these PVS Impressions they're usually the final impression for a restoration so they send them off to the lab um and you know the lab pours them up and takes care of everything um but you know obviously if you're sending it off to a lab it has to be dimensionally stable for at least several days so this is good and then in um again they're they're highly accurate Impressions so so really it's the material of choice now unless you're using digital Impressions okay so hydrophobic versus hydrophilic we we discussed that um PVS has a hydrophobic nature unfortunately so it's not that's kind of one of the drawbacks that in the hydrogen gas thing um so it must be used on a dry field because it can't displace moisture so what happens is the moisture stays on the tooth and it impacts the impression so um so you have to dry the area uh when you're taking the impression so moisture on a a prep tooth will result in loss of detail um they can add an ingredient called staract and um to make the the PVS more hydrophilic a little more able to tolerate moisture so so that can help a bit um so PVS viscosi of the material so it's manufactured in um Light extra light regular and heavy viscosity so heavy viscosity is the thickest and extra light is the thinnest um and then monophase that's just the regular viscosity it's kind of like the medium and monophase can be used is a tray or Ainge material so when we say tray versus syringe um you know you can put it material that you put in an impression tray that's tray material right um syringe material is material that you put directly on the surface of the tooth basically and you'll do that and a lot of times you'll you'll mix syringe and tray material you know you'll put like a light body um uh on the tooth and then a heavy body body in the tray and then put the tray on the tooth with the light body on it so you can mix the two together um to get the detail plus the stability um so you know so that happens a lot but it's important to know what we mean by using something as a tray material versus a syringe material uh syringe material means we put it directly on the tooth with no tray and then PVS also is available in two-part putty form which I showed you on the previous slide um and that's you know you just take scoops of the Catalyst and base and you kind of squeeze it together and it's kind of fun actually to um to you know get that ready and then you kind of roll it into a hot dog shape and put it in the impression tray okay and then here's a um this is a very very complex uh final impression uh but you can see this has got like one two three four um four different colors which means there's four different viscosities in this impression and you can see in the description it says that um so this is an impression for uh for dentures so they have to have a lot of detail so in the maxillary impression they wound up using Four viscosities to capture the detail of the different structures and in the um mandibular they just use it looks like uh it says they use three viscosities I only see two but I guess there the dark blue is in there as well so um so PVS surface detail um the accuracy of an impression mat material it's measured by how well it captures the surface detail of a structure and there's a lot of detail on oral structures you know the teeth and the the tissues and everything um much more than you might think you know until you get to dentist you don't really see it um so to capture detail material must wet and flow over surfaces well so you know PVS is a little bit hydrophobic but they've added in surfactant you know to kind of help with that um so um so low viscosity materials these are your syringe materials low viscosity means it's thinner and it flows better um these wet and flow better than high viscosity uh materials which are the materials you put in the tray or like the heavy body materials um putty is super high viscosity you know it's very solid almost um but the low viscosity materials they're more like um you know not like the consistency of maybe a thin glue or something like that um so the low viscosity materials they can get into you know flow into all those nooks and crannies so obviously they capture a lot more detail than the high viscosity materials okay and then the PVS dispensing system so again if it's if it's a by hand system you're going to have a a little gun like this so um so the most popular dispensing system for PVS involves uh a cartridge this is your cartridge and it's got two Chambers um The Catalyst and then the base on the other side and then the mixing tip right and the mixing tips are disposable you just use them once so the dispenser um can be hand or motor operated so this one is hand operated and it pushes um when you push this trigger it it pushes The material through here and then out through the mixing tip right and as it goes through the mixing tip it's going through these Spirals and the Catalyst and the Bas is mixing together um so the mixing uh tips and the devices ensure that the proper ratio of the Catalyst and the the base without any voids or B bubbles is produced right with hand mixing we get a lot of uh Bubbles and a lot of air trapped in there this kind of eliminates that um there's also a little tiny package of extra light body um sometimes they call the the light body or extra light body a wash material um and that's called a digit so you might hear that that term sometimes um and a digit is just like a little like a single serving kind of thing single dose um so before you put this Auto mixing tip on the end of here what you need to do there's a cap that goes on the cartridges you take that off and then you're going to put the the mixing tip on there but before you do that uh take the cap off and then um Express a little bit you know squirt out a little bit of the material materal so that you know it can come out before you put the mixing tip on um that just ensures that it's working before you you know um waste a mixing tip if it doesn't Okay so PVS working and setting time so the working time um is about two minutes so once it comes out of the the gun the automixer you have about two minutes of working time um and then the setting time um and two minutes is plenty of working time uh really because you're not mixing it up during that time you're just placing it where it needs to be placed um and then setting time this is the the start of the mix until the material hardens and can be removed from the mouth and that's about two minutes for fast set or six minutes for a regular set and again it depends on the manufacturer um you know who's making it so working in setting times are affected by things like uh temperature you know warmer material set faster and refrigerated materials set slow so ideally you want to take this out of the refrigerator and have it at room temperature before you start using it on a patient okay and then here's the putty so you get the the two scoops of putty the blue and the white um and you shouldn't be doing this with bare hands you you should totally be wearing gloves because this is going to go in someone's mouth um so you mix it up real well until the color is uniform through out um so you mix the white and blue for 40 to 60 seconds and then you roll the putty into a hot dog hot dog shape and um again it's kind of fun and then you place it in the the tray and cover it evenly so you know you're manipulating it a little bit more with your fingers um than with like a spatula or something um so so there is something called a PBS uh putty wash technique so um so the putty is used for the tray material and then you use a light body uh wash material again it's also PVS and you syringe that around the prepared teeth so um so the putty kind of holds everything solidly in the tray but around the tooth that you prepared for the crown you put on this much lighter material that can flow into all the nooks and crannies and produce a great deal of uh detail so um so the combination uh of the putty and the wash material it's going to force that wash material into the ginger sulcus um and it captures the the margins of the impr impression so especially when you're making a a bridge or a crown you really need to get an impression a good impression of the margins of the crown um so that you have a well fitting crown and this combination of putty and wash can help do that um so there's one step or two-step method um I've seen mostly the one-step method used um the two-step method is a little bit complex but with the one-step method the putty is mixed and it's loaded into the tray then you make a little indent for the prepared um uh tooth and then you syringe the material around the prepared tooth and then you put the tray in on top of it and when you put the tray in that kind of forces some of the material down deeper into the the gingerb salus or around the tooth so um and then you guys can read about the two-step method it's um it's a little more complex okay and then removing the set PBS impression so um so first of all you want to make sure impression materials materials are fully set if you remove them prematurely it's going to ruin the impression it causes Distortion and then you have to redo it so um so after you seat the impression remember you're not mixing this in a bowl so you don't have a lot of material left over um you know so after you seat the impression you take a small amount just squirt a little bit of the PVS material on the bracket table where you're working and then you can check that for setting you can see when it starts to get hard or feel it with your finger um and then you remove the impression quickly to minimize deformation so again just like with the alginite you're going to you know snap this out um but remember it's going to take a few minutes for the deformation to recover um with PVS especially it will rebound it will recover from that temporary deformation um but you should really wait uh you know 20 to 30 minutes before pouring it um I would wait even longer because that hydrogen gas that's being um set off of the the impression um and that can take up to two hours so um usually the PVS impressions are sent to a lab and not poured for a couple of days um so you know it's usually not a worry okay and then bite registration um PVS is used a lot for bite registration um you can use either uh elasta mirrors like PVS or wax but wax is not as good um PVS is used for bite registration due to its accuracy stability and ease of use it offers no resistance to biting down so it gets a really really accurate um record of your bite whereas wax feels kind of thick I never feel like I'm biting right with wax you know it's just too it's kind of harder and thicker but PBS is great you feel like you can get your true bite with that um so you can inject material from the auto mixing tip um directly onto the surfaces of the mandibular teeth and have the patient bite down so you just put it right on the teeth no tray required and have the patient bite down right um or you can use a tray you can use a bite tray or a triple tray um and you know put the material on both sides of the tray put it in and then have the patient um bite down so the tray supports the bite registration better than without using it but I've worked with a lot of dentists that just don't use any tray at all and do the bite registration that way um so there's a rapid setting time of 1 to two minutes um and again it'll remain dimensionally stable for at least one week which is great um there's another material another elastomere called polyether and that can also be used for bite registration as well okay and then the wax bite again wax bites are just not great I don't think um the one good thing is that they're not very expensive but you have to you know you can get these horseshoe shaped waxes um or you can buy by waxes that are just in squares and then kind of soften it by Heating and make it into a horseshoe shape but um these things always feel kind of thick um you know I've done a lot of these in in classes that I teach and stuff and they just always feel kind of thick and I never feel like my bite is quite right with the wax bites um like like with the PVS so um but you may encounter um somewhere where you do use it um usually it's just academic institutions where we're just practicing okay so PVS versus algen you know who wins well PVS is definitely more accurate and detailed um you know you don't have to store PVS Impressions and wet paper towels um they can be poured several times so you can use them to make stone models a lot of times with alginate you get one shot if you mess it up you have to take a new alginate impression you can't use the impression to make two models right um PVS impressions are more Di Nally stable they don't swell or Shrink like alginet um they have higher tear strength but um but you know there's a price tag to all of this they're definitely way way more expensive PVS is way more expensive than algen it so so yeah PVS is is the winner I would say the guy left standing is PBS and alginet been knocked out but you know but each of them have their place in the dental practice for now until everybody goes digital which is you know currently underway so all right and then poly so um imperum is one of the very popular um polyether Brands that's by 3M um this is a an elastic impression material so it's an elasa mirror it's in that family um and it's rather old it came to Market in 1965 so um so it's it's a good material it's got good flow and tear strength um the one good really really notable thing about polyethers what makes them Stand Out is that it's hydrophilic or more hydrophilic than PVS so it can tolerate moisture and that's important when you're working inside the mouth especially when you're you're making a crown and it has to go under the gums right it has to go subgingivally um it can be really hard to get a dry field um to get an impression of that so um so the polyethers are very useful for that they have good wedding properties um they don't release hydrogen like PVS so you can pour them up immediately with Gip some products without you know like dentl stone or plaster without having to worry about Bubbles from the the hydrogen gas and they have good elastic recovery um and they do not shrink so so they're not quite as accurate um as as PBS but but there are some some good things about um the polyethers um and then here's uh here's some polyether up here and um you can see that you know you've got a catalyst and a b um polyether um it also comes in light medium and heavy body viscosities so you have those options um you dispense equal lengths of materials from two unequal size tubes so you know you need more base than catalyst so the base is a that or tube but you dispense the same length um onto a mixing pad um uh and then mix it up or you can they do have cartridges with automixing tips so you know you don't have to go the the hand mixing route um The Catalyst contains aromatic sulfonic acid um and that might irritate the skin and tissue so so be very careful with the um with the Catalyst because it contains acid and if you get that on your hand or something um then it can cause an acid burn and you must mix the Catalyst and base thoroughly um and it sets very quickly so okay and if you're lucky you might one of these mechanical mixers in your practice um that's really nice you can have this with polyether or polyvinyl soloxine um but it just you know you don't have the automixing tips you don't have to use the gun and and you know your hand gets kind of crampy after a while this you just push a button and you've got these large cartridges or pouches and it mixes and it comes right out and it's just so so nice so much nicer makes your job easier so um so you know the um you have these pouches or or cartridges of catalyst and base and then you put it in the mechanical mixer you just press a button and it delivers it right into the tray then you go place it in the patient's mouth so it's a lot more um economical you know you have to pay for the machine but it works out in the end so okay and then polyether um properties so the original polyethers were really really stiff um compared to the other Rubber and pression materi material so they could be difficult to remove which is kind of scary when you're doing impressions you know you go to take it out and you're like oh is it stuck you know so so it's you know so it's kind of disconcerting to the patient and the operator so it's nice to have um you know that they've developed it a little more where it's not so stiff um so the newer formulations are more flexible they have a more pleasant taste um it's easier to remove from the mouth and to separate from the cast um because when you make the the cast when you pour up the stone in the model if it doesn't separate easily you can wind up with broken teeth or broken structures on the cast which is not fun okay and then with the polyethers um you really need to um block out undercuts uh with utility wax um as much as you can and and embase spaces you know you can put wax in these spaces between the teeth because if the material goes through here and locks then you'll never get that impression out without tearing it so you know so it's good to um block out undercuts and and bra your spaces as much as you can um you know this uh by blocking these things out with utility wax this will um prevent the impression material from flowing under and locking the tray in the mouth um and if that happens then the tray has to be cut out with burrs if they get locked into the mouth so um obviously that wouldn't be a great um patient experience okay um so polyether the working and setting times um it's comparable to polyvinyl soloxine uh the regular set working time is 2 to three minutes setting Time 5 to six um so it's just a little bit longer and then the fast set working time is one minute with a setting time of four minutes um so something else that's unique about polyether is that it has a snap set um what'll happen is it remains very very discus for that whole working time and then all of a sudden you get to the end of the working time and boom it gradually hardens um it changes rapidly so it doesn't gradually get a little harder a little harder a little harder it's just you know kind of gooey gooey gooey gooey boom it's hard so um so that's what we call a snap set okay and then here's another impression where they mixed viscosities um so they probably used the purple's probably a heavy body green probably a light body um so they do that so they can get stability but they can also get um good detail of the teeth um so polyether hydrophilic nature um again PVS is hydrophobic polyether is hydrophilic um so permanent deformation is low compared with poly sulfides but not as low as um the Silicon so so permanent deformation doesn't occur a whole lot with polyether but it occurs more with polyether than with PVS um the one advantage is with polyether it can tolerate more moisture than PVS because it's hydrophilic uh it must not be stored in water or disinfecting solution because it will swell um so since it's hydrophilic it actually can take water in it can imbibe water and and swell up and then change the dimensions um Impressions may be poured uh repeatedly for up to one week so that's kind of like PBS you can pour Impressions more than once they last a week um it may be shipped and will remain dimensionally stable for 14 days which is quite a long time um you do not need to um spray it with surfactant before being poured into stone because it's hydrophilic um with PVS um depending on the the manufacturer um it may need to be sprayed with Sur surfact in um before pouring gyps and products into it okay and then um somebody had the great idea of combining these two really good materials so they came up with um a vinyl polyether silicone hybrid so this is a polymer hybrid of PVS and polyether to get the best features of both and this was done around the year 2000 um so the the material is hydrophilic like polyether so it's great for those um Impressions where you need to get sub jingal margins where you can't really get a dry field um but they have the dimensional stability of PVS they they don't embibe water and swell up so that's good um it flows well it has has high tear strength and it comes in regular and fast sets with five viscosities but again this is a very um expensive uh product okay so um so I'm splitting this uh presentation into two parts just because it's such a long chapter um yeah it's just really really long so um so table 15.4 in your dental materials textbook uh this is um the has the features of the elastic impression materials it's a good summary to look at so so go ahead and look over that and then I'm going to end this presentation here and I'm going to um pick up in part two on on this slide um that talks about the um retraction chords so we'll get into that into part two um so thank you for listening and I will see you guys in class and please if you have any questions uh write them down and let me know thank you