CEREC Dental Assistant Training - hands on crown design part 2 - positioning through milling

Okay, welcome back. We're going to talk now about what to do after you've got it positioned. So just a quick reminder of how we got to the positioning tool and the process we used to position that. Right click over the top of the restoration just about anywhere and you have your toolbar that shows up and this is the same toolbar here that shows up over on the right. So if you've closed out your toolbar you can always get to it by either going to the toolbar here on the right side of the screen or by right clicking over the restoration. So always start from big to small as we discussed in the previous video. Design based on big to small. So you want to position it first make sure that all of your contours are positioned nicely and then do all your final editing and precise manipulation after that's all done. So positioning first. Position it first. That's the very first thing you should do if it's needed after it is proposed by the computer. So let's just say we love this position. I love where it is and I have no concerns about the position and the location. Then I will go ahead and do the next step which for me normally is again right clicking to get my menu bar using the anatomical shape tool. So the anatomic shape tool is a very nice tool because it allows you to select big portions of the tooth or small portions of the tooth and it kind of snaps to each of those different areas in the tooth. So you can see as I hover over the tooth different areas are highlighting as I'm moving around. So here we've got the mesial facial cusp, distal facial cusp, distal lingual, palatal, the entire tooth, central groove, central groove, whole tooth, central groove. Now if we turn this up so I can see the facial surface down here and then up here you can see I'm grabbing different areas of the facial surface. Then if we go to the lingual it's same thing. I can grab the occlusal portion of the lingual or palatal part of the crown or we can grab the gingival or the main body portion of that. We can also grab the entire mesial portion. See I'm grabbing both cusps. So I could slide this inward, outward and I'll demonstrate that here in and out or you can do it on the distal. Same thing here. I'm moving the whole distal portion of the tooth. So I like to start by managing how everything lines up. First ignore the occlusal contacts. Ignore the colors that are going to show up when you get to the proposal section and you can see I've turned them off here. So I'm not worried about it at this point. First what I want to focus on is positioning that tooth ideally and then we will manage the occlusion after we've got it positioned ideally. So let's take a look. Look down the buccal corridor. That looks pretty darn well aligned right down the buccal corridor. That looks pretty good. Occlusally it looks pretty good for height wise with the exception of the marginal ridge here which looks like it's too tall. So I'm going to lower that a little bit but before we do that let's take a look at the lingual portion. Now you can see if I zoom out the palatal portion these where the gingival areas are more flat whereas this has a very rounded embrasure emergence profile from the gingiva. So I'm going to edit that so it matches the adjacent teeth. But first let's look at this marginal ridge. So there are a couple of ways I can adjust this. One way is to actually position the tooth. So when the tool comes on we now have this rotate feature where we can roll the tooth mesially or distally or buccal or lingual. So one way I can move that marginal ridge is to rotate the tooth. Now realizing when I'm rotating this area is going to go down and the distal is going to come up as it rotates around a line of axis here. So that's one way to do it and I'll demonstrate here. You just grab the arrow and you're rotating the whole tooth. So that's one way to do it and that may work just fine if it doesn't mess up your occlusion down the road. And again I've told you to ignore the occlusion for now. We're not going to check the occlusion until the very end. Now I do want to rotate just a little bit more here so those cusp tips line up a little better. But that's one way to alter that marginal ridge height. And one thing to focus on is we need to make sure that these heights are approximately even from the restoration we're designing to the adjacent tooth. Because if they're not even you're going to create a nice area for food to impact. So if we have this marginal ridge up too high every time the individual chews food's going to go down into that area. So manage your marginal ridges make them as even as possible. So let's look at another way to adjust that marginal ridge height. That's the circular shape tool. So the circular shape tool which is similar to the anatomic shape tool but it only grabs a definitive area. Based on how large the tool is. So you can see here with my right button I'm dragging up and down and it's changing the size of the tool. And I can also go over here and change the size this way. And this is a size based tool not an anatomic location based tool. So I'm going to change the size to it's fairly large. I'm going to lean it up so I can see where those marginal ridges are. And if I want to move the marginal ridge of the restoration downward I'm just going to grab and pull it down. Pull it down. And I want to make sure that I like where it is. If I want to edit it I'm going to edit it a little more. Pull it down. Now at this point it's important that we remember that we can undo any of these edits. You can either reverse what you did or you can actually go to undo. Click the undo button and watch what happens here. Boop! Moves it right back to where it was before I started using that tool. So each time you switch a tool you lose your undo ability so be careful. So I'm going to move that back down to where we had it just a moment ago. We're going to edit that marginal ridge height to make sure it's approximately even. Once we've got the marginal ridge height approximately even the cusp height's even and this one looks a little too tall to me. So I can either use this tool the circular shape tool to move it up and down or I could go to my anatomic shape tool and just grab that one cusp here and move that up and down. Alternatively I could use the plus or minus on the remove but watch what happens when I hit remove. Now this doesn't change it in an anatomic way it just literally removes some of the material and that can make it look a little weird which I don't like. So let's practice our undo tool here bring it right back where it was. I would caution you don't use the plus or minus tool when you're altering anatomy. Only use this at the very end when we're altering when we're checking our occlusion as a final resort. I would caution you I'd recommend using these two tools most of the time after you've done your position and rotate. Use these two tools smooth any areas you need to smooth and then at the very end to make your occlusion just right use these tools sparingly. Let's move these cusps down which I like to use the circular shape tool. This mesial facial cusp it's a little too high. There we go that's looking better. Now pay attention to your arrows here. Personally I only ever use this two directional arrow. I hate the four directional this confuses me. Let me turn it on and I'll show you what happens here. So basically I now have the ability to move the tooth in any of four directions but for me I and this may work well for some and I you know I'm happy for you if it works well for you. Personally I don't like that much control. I like a more limited amount of control and this is great for some again and if you want to use it that way that's perfectly fine. Personally I prefer this two directional control maybe it's because I'm a two directional guy I don't know. Anyway so it's for me it's a little easier to adjust if I want to move things around a little bit. I like the control that the two direction gives me. Okay so once we've got our marginal ridges even the next thing I like to do after I've managed the cusp tip heights the marginal ridge heights is to evaluate my contact and then the occlusion. The occlusion I always do very very last. So check your contact point and then do your occlusion very very last. So a couple of ways to look at the contact we can go over here and trim the model which takes everything but the restoration away. So here's our restoration you can look and adjust this contact as needed with whatever tool you want to. So evaluating the contact point we have several ways of adjusting it. This is one way to get to it is by trimming the model on or off. One thing that I like to do so that I can see more accurately where that contact is hitting is by turning the jaw whichever arch we're working on making that more translucent by dragging the slider down. So that accomplishes the same thing as trimming the model but it allows us to see a ghost image of the adjacent teeth. So now I can see exactly where I'm editing. The nice thing about it is I can edit through the ghost teeth. So I can turn my tool on and here I've still got the the circular shape tool selected. I can turn my tool on and now I can edit this contact through the adjacent tooth. So I can see a little bit better where those contacts are. This is my preferred way of editing the tool or editing the contact because it gives me a little bit more visual reference as to where that contact point is how high how low and the size. Personally my preferred contact size depends on the tooth molars posterior teeth generally speaking should have a much larger contact not a point contact you want an area contact and I like to leave a little bit of yellow because I want to adjust that contact just a little bit in the mouth. So if there's a little bit of yellow after it's you know fired if you're firing it and polished you've still got a little extra contact to deal with so you can adjust it tapping it in the mouth. The computer based on our parameter discussion from before will propose that contact based on the number that we have set up in the restoration parameters. So that's only for proposal purposes. I could increase my settings in the parameters to propose a contact that is heavy heavy red if I wanted to or no contact whatsoever and then go back in and edit it. For me usually it gives me a little bit of green and I go in and increase the contact pressure. Certainly you could go in and change those parameters so that it gives you less of a contact or more of a contact depending on your preference and save a little time but I find after I position the tooth it almost always alters that contact so I just kind of ignore what it proposes and build or remove that contact to what I want it to be. So final double check make sure you like where the contact is buckle the lingual where the position is in relation to the contact and occlusal or gingival how high it is and then the size and always remember that molars and pre-molars should have contact areas not contact points. You want an area where the teeth are contacting because as we chew there's a lot more force and it's much easier to force that down in between the teeth. So at this point once I've finalized my design and if there are any areas that need to be smoothed sometimes you get a proposal from a biocopy sometimes you get areas that are rough go ahead and smooth them again right click give you your smooth tool same thing here I can change the size of the smooth tool over here with this slider or I can right click and drag up and down and that accomplishes the same thing. One other interesting tool nice tool that they have with our smooth our plus and our minus tool is the strength I usually leave mine at a hundred percent some docs like to adjust this down depending on what you're doing how sensitive the area you're adjusting is you may want to decrease the sensitivity so that you don't crazy you know adjust it in a crazy way but always remember if you make a mistake you can undo it before you move to the next tool so don't hesitate to do what you need to do if you do it wrong undo before you move to the next tool all right okay so let's go ahead and talk about adjusting the occlusion I think I already mentioned it to you in one of the last videos we always want to adjust the occlusion so that it matches or is slightly less than depending on your indication the adjacent teeth that we're working with so you can see here in this particular model we don't have any occlusal marks forward of the first molar so we're just going to focus on this pre-existing first molar to manage our occlusal contact strength here now it's important that you understand what each of these colors means blue means we're approaching contact green means we have positive contact yellow means we're pushing beyond the surface and red means we're pushing way beyond the surface so positive contact is indicated with a green yellow is a is too much positive contact and red is way too much positive contact now I'm going to step back and correct that because all those colors are relative based on the adjacent teeth so all of these colors are based on number one how good your contact point is your contact information is which is all based on your scanning capability and the image quality that you have from your scanning and then number two how heavy the adjacent tooth structure contacts are so I could have red red red red contacts on all my adjacent tooth structure based on how hard the patient was biting or how the machine stitched those models together during the buccal scan and if I have red red red here to match that red red red here then it's okay on the other hand if I have a little bit of yellow here and a bunch of red here then obviously this tooth has a lot heavier contact than it should because it'll be in hyper occlusion once we're done now taking a step back remembering our restoration parameters there's that occlusal milling offset step choice parameter that we can change and that compensates to some extent for some of these contact points so if you've got the milling offset set at a negative 200 microns that means that after the crown is milled or after the crown is designed before it's milled the computer is going to calculate a 200 millimeter 200 micron offset downward so it's going to make that crown shorter by 200 microns if you have a positive offset then it's going to make it taller by whatever that offset number is so we could compensate for occlusal contact strength a bit with our restoration parameter setting occlusal milling offset but you want to be very cautious when you do that you want to make sure that you manage those numbers very clearly and that you're not doing anything that's going to create challenges for you in the adjustment after you've inserted the crown in the adjustment phase so I think I mentioned before the tools that I usually use very first and foremost start big to small position at this point if you've designed it you like everything but all your contact points are on an incline move the tooth if you don't like how tall it is how short it is move the tooth with your position rotate tool all right then you can use your shape tools circular and anatomic to alter the contact points as needed here we've got three three yellows to one yellow here so I'm going to adjust these a little bit and I'm going to use my preferred tool this is the one I prefer to use the vast majority of the time is the circular shape tool and I'm going to make that tool a little smaller I'm going to drag a couple of these yellows down maybe all three of them I'd like this contact to be a little lighter all these greens than the adjacent yellow all right so always remember that contact strength is relative based on what you have on the adjacent natural unaltered teeth and then to some extent how well your models are imaged and designed and stitched together by the computer if you've got really poor quality images chances are pretty good the inclusion is not going to be quite right so you got to manage that well all right so that's the contact adjustment portion next up would be a final quality assurance check and then sending the restoration to the milling machine so let's go ahead and move forward to the actual milling preview you need a click mill here or a click mill up there now we're going to get a preview and my experience is usually if you've turned it off up to this point the minimal thickness indicator here which we discussed in the previous video will pop on for you so it shows you where those areas that may be too thin are going to show up you can see most of these are around the the circumference the girth of the restoration which we have set at one millimeter one thousand microns so in my mind with little bit of blue small amount of blue in certain areas around the circumference of the restoration it's not a big deal if we had blue all over the place here based on the parameter settings that we had looked at previously 1.5 millimeters depending on the material we're using then it may be a cause for concern so let's talk about block size generally speaking my experience is almost every single restoration will mill in a 12 millimeter block that's we're talking about routine crowns veneers inlays and onlays bridges of course probably not into a 12 maybe a 14 depending on the design but almost everything else will mill in a 12 millimeter block with the exception of implant crowns which require their own unique special block so i i would recommend that you have most of your blocks in 12 millimeter blocks usually they're cheaper but if they're not cheaper one of the significant benefits is it's less wear and tear on the machine number one and number two they tend to mill a lot faster you know without clinking fast mill they still know faster because there's less ceramic for the machine to mill through so i would suggest using 12 millimeter blocks as much as is possible because they mill faster and it's less wear and tear on the machine so let's take a look at 12 millimeter block here so you'll notice sometimes i'm going to edit this and i'll explain what i'm doing here in just a second sometimes when you put it in a 12 millimeter block the machine will not like your positioning and here it's it fits no matter what orientation so so one thing i'll caution you to do is always evaluate there's a because if you have a 12 millimeter block loaded and the machine defaults to 12 or defaults to the last one if you have a 12 selected and a 12 and a 12 millimeter block loaded and you get to this this milling stage and you have red sticking out that's the area that's not going to mill obviously so we have to reposition we have to move the restoration in the block all right two ways to do that all right we can use our tools again so a couple of ways to move the restoration in the block first way would be to get your tools over here and select whichever tool you wanted to either the position move tool or you can right click over the restoration and get that same tool all right so what we need to do is make sure the crown or whatever restoration we're doing fits in the block so it's obvious we need to move the block a little bit all right so we can move the block around the restoration all right so what i'd suggest is try to get it as close to the edge as possible without any red sticking out now watch what i'm going to do i'm going to actually move the sprue and it should pop that red to within the block you'll notice that the machine automatically moved the block when i rotated the sprue all right and there's no red hanging out of there so position it adjust the sprue and most of the time it'll actually match where the uh the end of the block is so but if you get that proposal rotate usually it's rotate the crown because if you notice the mesial to distal width is narrower than the buccal lingual width right so almost always and it's not every case but almost always and i'd say in my experience about 95 percent of the time 95 percent of the time a large crown first molar crown will still fit in a 12 millimeter block now if you've got a really tall restoration based on you know giant teeth or lots of recession then you'll probably need a 14 or even a larger block but again going back to what we just talked about 12 millimeter blocks tend to be cheaper they know faster and it's less wear and tear on the machine so there's a lot of benefit to having a large stock of 12 millimeter blocks which you draw from regularly now if you need to go to a 14 because of the size that's perfectly fine but i would suggest and encourage you to always try and fit your restorations into a 12 millimeter block because it will tend to save you money down the road because of the less wear and tear the time it takes to mill the restoration and the fact that they're a little cheaper in the long run all right so assuming we like the positioning the next thing we're going to hit is start milling let's talk about this over here so fast mill in my experience yields a less accurate restoration oftentimes we will default to the fast mill meaning the doctor who's milling or designing or doing the crown or restoration will select fast mill primarily because they feel like it goes faster than it does but the the way that it goes faster is by pushing harder on the the restoration on the the block the ceramic block so that gives you a couple of things number one is it's less precise because effectively the burr as it's spinning has less time to drill that ceramic away because it's moving faster right and number two it will tend to wear out your burrs much much much faster which also translates to more wear on the the burr assemblies on either side so in the long run is it worth running all of your restoration through fast mill i don't think so i think the the drawbacks to fast mill all day every day are significant even though it's going to save you a minute or two or three or four or five with each restoration i don't think it's worth it in the end unless you're in a pinch you're in a bind and you have you have to save four or five minutes i think you're better off in the long run running everything on fine mill because it's more precise the machine is not stressing the burrs or the burr assemblies the motors and in the end the restoration is a little more precise so i would encourage you to always mill on fine no matter what you're doing except in those few circumstances where you don't have enough time and there's somebody who's waiting on the milling machine or the patient has to leave then you can run it on fast but there are just a lot of benefits to leaving it on fine even though it's going to take you a few more minutes my experience over the past decade especially with a 4.0 software update is that when you mill it on fast you tend to have to do into you know intaglio surface adjustments either that or adjusting edges in the crown on the tooth itself before you're bonding the crown i feel like fine mill tends to to yield a better prepared intaglio surface of the crown all right so that is milling in another video i talk about some of the restoration the material choices and depending on what material you're using that will dictate how fast the machine mills it's all pre-calculated inside the machine and how precise the machine can be with regard to the milling process so choose your materials wisely make sure you do your research and make sure you know pluses and minuses of all those materials if you have any questions please email me send me a message either through the youtube or directly through facebook all right thanks