Why Isolation Is Non-Negotiable for Predictable Bonding Success

Sometimes you've got these subgenital cases where you're trying to, you know, you see these pictures on Instagram, on Facebook of these people that do this like amazing rubber dams where they've got secondary clamps pushing the rubber dam deeper and floss ties and this amazing stuff. And, you know, sometimes you can accomplish it. And then sometimes you've got rubber dam kind of blocking a subgenital part of your prep. So sometimes that's nice with something like an... ISOVAC is that you can get a matrix band or a Toffelmeyer or something in a subgenital aspect without having to worry about the rubber dam getting in the way. Welcome to Austin, Texas, and welcome to the Phil Klein Dental Podcast. So let me begin with a few questions. When you're doing your bonding procedures, are you truly controlling your environment or just hoping for the best? What's really happening to your bond the moment saliva or blood enters the picture? Are newer isolation systems enough? Or is the rubber dam still the gold standard? And when contamination happens, inevitably it will at some time or another, do you actually know how to recover the bond predictably? To help us answer these questions, we're joined by Dr. Nate Lawson, a practicing general dentist. He holds a PhD in biomaterials and serves as director of the Division of Biomaterials at the University of Alabama at Birmingham School of Dentistry. He is a researcher who has published over 200 articles, abstracts, book chapters, and periodicals related to dental materials. Before we bring in our guest, I do want to say that if you're enjoying these episodes and want to support the show, please follow us on Apple Podcasts or Spotify. You'll be the first to know about our new releases, and our entire production team will really appreciate it. Dr. Lawson, pleasure to have you on the show. Thank you, Dr. Klein. I know how busy you are teaching, doing your research, and practicing dentistry at UAB, so we certainly appreciate your time today. So I think we've all seen a clear shift away from relying on mechanical retention through our prep design and moving towards advanced adhesive materials for both our direct and indirect restorations. With that evolution, tell us why meticulous isolation has become absolutely non-negotiable for achieving predictable, durable bonding outcomes in modern practice. Yeah, I mean, I think that, you know, it's funny that we think of composite resin being this great thing, but then... all looked into someone's mouth and then seen that album that was placed in World War I, and it's still holding up beautifully. And then the composite next to it is like... six months old and it's already staining and you think, well, what was this, what was the advantage of moving to this composite material, you know, aside from it being tooth colored, I would argue the biggest advantage to composite is just that you can do a lot more conservative prep where you don't have to prep for attention anymore. But like trying to think why is it that, you know, insurance companies let us replace composites every five years and why, you know, why do they have this, you know, lifetime in the insurance date of only being five to seven year old for, for large composites. And I, and I think a big part of it is. it down to technique. I mean, there's inherent disadvantage to composite, like it shrinks whenever you cure it with your curing light. So that's going to always be, you know, a problem with the margins and like amalgam. But I think that, you know, I mean, there's some technique involved with the placement of a, of a composite of like, you know, how long do you scrub the bonding agent? How long do you evaporate your solvent out and things like that? But I think that one huge factor is how well you're isolating before bonding. Yeah, there's no question. Isolation is so critical. Now, before I ask you a question about the rubber dam, I do want to ask you, is selective etch the most popular method now using that with universal adhesive materials? So you take care of the etch. of the enamel first and then you go in there with the universal adhesive for everything and then you get kind of a more controlled edge of the dentin but you do get those micro mechanical tags of the enamel so you have that covered with the phosphoric acid and then you use the self-etch component of the universal adhesive to take care of the dentin is that is that the most popular method now I mean, it's the method that I use. And I think that makes the most sense to me. We did a poll through our Instagram account, like probably just a couple of weeks ago. And I was surprised to find out, I mean, it's a pretty international following through our social media, but I was surprised to find out that more people were total etching. I mean, etching enamel and dentin than were self-etching based on our little poll. But yeah, I think for all the advantages you just mentioned, I think that it makes the most sense to do a selection. etch type of right so that so you're saying a lot of dentists are still doing the total etch where they're hitting the dentin also so aren't they like hyper demineralizing the dentin well some of the bond strength studies if like you look at dentin bonding i mean enamel bonding i think there's like no question enamel you gotta etch it a self-etch on enamel is just kind of not good weak but Weak, yeah. And then on the dentin, I think you could go either way. I mean, bond strength studies show relatively comparable bond strengths with a self-etch versus etch and rinse on dentin. In the studies that we've done at UAB, we actually, we show a slight... a better performance in a self-etch but there are other studies that show more equivalent um but i think there's just takes a lot of technique sensitivity out of it because you don't have to wonder how long do you edge because if you don't if you ask for too long then you yeah you've demineralized too deep into the dentin and your adhesive can't can't penetrate deep enough and you don't have to worry about how much do you rinse off after you've uh etched the tooth technique sensitivity is taken out of the uh equation when you not all of it some of it's taken out but if they're using a total etch are they then using a universal adhesive on top of that so they're kind of etching the dent in again with the self-etch component of the universal yeah you know i guess universals that wasn't with their claim to fame is that you could decide whether or not you wanted a self-etch or total etch with them yeah because what concerns me about that is and i'm not a researcher and I don't have a PhD like you in materials, but what concerns me is that hyper demineralization and the MDP doesn't have as much substrate to work with because there's not enough inorganic material in the hybrid layer. Yeah, that's a great point. Yeah, you don't get to rely as much on the chemical bonding capabilities of some of these new monitors like MDP that are in our universal adhesive. So you're kind of like just then relying on the kind of traditional... Denton bonding mechanisms of, you know, resident infiltration. Yeah. And then tags and tubules and stuff. So yeah, that's a great point. So let's talk rubber dam. A lot of dentists still resist it. In fact, in most studies I've looked at, Dr. Lawson, only 20 to 30% of GPs say they are consistently using a rubber dam outside of endo. So what are they missing? What advantages are being underestimated when it comes to using the rubber dam for long-term bond predictability. Yeah. I mean, the, the advantage of rubber dam is that it controls not only just for saliva, but also for circular fluid and a lot of times blood, you know, as well. And it pushes tissue out of way to improve visibility. You know, there's other advantages like when you do things, I mean, it keeps things out of my patients. mouth. I mean, that's how I try to always sell it to my patients. Like I'm using the special sheet on your mouth to, you know, a lot of patients are now concerned about what chemicals they're consuming, you know, as you're removing things out of their mouth. So I'm using this rubber dam to help protect, keep things out of your mouth and your throat. You know, so that's, that's, that's one patient benefit and visualization, tissue retraction. Yeah, I mean, those are a lot of advantages. So why do you think so many dentists are not using it? Is it just the inconvenience of putting it on and they struggle with torn rubber dam? Only 40% to 45% said they used it for endo, which was really dangerous. Yeah, that's scary. What do you think the main reason why dentists are just not using it? Yeah, I mean, for the webinar that we did through Viva, we showed a study where 40% of dentists said they weren't using it for inconvenience. 28% thought it was unnecessary. 11% said patient refusal, which I don't totally believe because I've yet to have a patient refuse a rubber dam that I can remember. And 10% said time, 0% said cost. I guess inconvenience then was number one. I would say that like one of the things that really helped me becoming more compliant with rubber dams was really keeping our armamentarium in a single place so that I didn't have to, we used to have like the hole punch in one place and the frame and somewhere else. clamp somewhere else and we try i mean it's such a silly thing but we try to consolidate it so that it was easier to access everything together um also another thing that i think really helps is using the punch guide trying to place the holes yourself a lot of times you'll either get holes too close together or too far apart which can either mean you've got too much if they're too far apart too much material to try to floss in between teeth or too close together then it's stretching over the teeth and now you've got little voids in your rubber dam so Those are little tricks that help me become more compliant. So as a restorative dentist, we're not talking about endo now. How long do you think it should take a dentist to put a rubber dam on just for a typical composite? I mean, ballpark. God. Well, I'm not the fastest by any mean because I don't practice dentistry every day like many dentists. I'm pretty slow. I mean, I would guess it takes me maybe a couple of minutes. I mean, yeah, I'm also doing the one. punching all the holes and getting everything all ready and i mean once you get in a good groove i also work with different assistants almost every week and i'm teaching them how to do it so i think if i was in a groove everything was all ready for me i just had to be the one doing it i feel like i could get it done in like a minute um like get the the clamp on stretch the rubber dam over the clamp and then just start popping contacts so you place the clamp on first and then you go over the clamp with the rubber dam I do. I use a wingless clamp a lot when I'm doing restorative because oftentimes like I might be wanting like with a wing clamp, there's a little projection that pokes into the interproximal space mesial of where the clamp is. And sometimes that can prevent me from getting like a wedge or ring or matrix band on the mesial of the tooth that I've clamped or even on the distal of the tooth in front of it. So I'll use the wingless clamp and it gives me... It doesn't have that projection, so I can get equipment in there like, you know, matrix bands and stuff. Yeah, as an endodontist for my career, I pop the clamp on and then, of course, drop the sheet, the rubber dam over the clamp, put the frame on. It was, you know, 15, 20 seconds. But again, we didn't have to worry about in a proximal. We're, you know, we're not making access anywhere other than the occlusal. So let's talk about. integrated isolation and evacuation systems. They're becoming more popular. Where do you see these fitting into everyday practice and can they realistically replace the rubber dam? So when you compare integrated systems with rubber dams, I think there's some advantages of integrated systems that rubber dams don't even have. So for example, something like an ISOVAC system, that's like a two-part system. You've got this hard plastic piece which goes in the high-volume evacuator and then a rubber mouthpiece that's disposable. The rubber mouthpiece has a bite block, which is something I often don't even think to use for my patients, but I know they all appreciate when I do use it. And then it's got two flaps, like one that does tongue retraction and one that does cheek retraction, and then it does suction. So one of the nice things is that extra bite block that goes on there. I guess other than that, the... Suction is something that the rubber dam doesn't have. You know, the retraction of the tissue is something that they both have. So another nice advantage is that, you know, with the rubber dam, even though it can protect against circular fluid and blood better than something like an Isovac, sometimes you've got these subgenital cases where you're trying to, you know, you see these pictures on Instagram, on Facebook of these people that do this like... rubber dams or they've got secondary clamps pushing the rubber dam deeper and floss ties and this amazing stuff and you know sometimes you can accomplish it and then sometimes you just have to be realistic that as hard as you trying you can't achieve that and so then you've got rubber dam kind of blocking a subgenital part of your prep so sometimes that's nice with something like an isovac is that you can get a matrix band or a toffelmeyer or something in a subgenital aspect without having to worry about the rubber dam getting in the way like i had an experience like that just I guess it was last week where I was trying to do some anterior composites. There was one tooth where it was pretty deep margins, and I had the rubber dam on there, and I got these matrices, these anterior matrices in there, and I take everything apart, and I realized that some of the rubber dam had slipped between my matrix and the tooth, and now I've got this little void there. And so I had all the best intentions, and then I had an unfortunate outcome. Yeah, so using these... isolation systems. And it used to be called Isolite. You mentioned IsoVac. Is that the same thing? It's the same thing. IsoVac is just the version that doesn't have a light associated with it. So the IsoVac system has got the hard plastic piece that it's just a kind of a very simple little plastic piece that goes right in your high volume evacuator. And the Isolite has a light as well attached to it. And what about sterilization? How does that work with this system? What do you sterilize each time? For the Isovac, you just sterilize the hard plastic piece, and then the rubber piece is disposable. I know that there's other... other systems and where you can have a reusable and autoclavable mouthpiece. I don't have any experience with that. The one I've used is disposable and the cost on it is actually not that much more than a rubber dam. So, you know, it's not like it's, I used to think that it was going to be really expensive for that rubber mouthpiece. And then when I saw the price on that, I said, oh, this is actually, you know, it's maybe, maybe 30, 40% more than a rubber dam. So the mouthpiece gets discorded? In the ISOVAC system? The mouthpiece gets discarded. Okay. And then what's the connection into your HVE? It's just this like plastic L -shaped piece. They're not unreasonably expensive. I mean, they're not. But you don't throw those out. Which is a great point because the first time I ever got one and I was working with an assistant, she said, oh, what do I do with the mouthpiece? I said, oh, throw that away. And then I came up the next day. I said, where's the hard plastic piece? She's like, I thought you said to throw it away. And so there's all through many dumpsters to try to find it and never found it. So that is an important point when you're communicating with staff. So how do you sterilize that hard plastic piece that connects the disposable mouthpiece to the actual HVE? Oh, we just put it in a autoclave. Okay. So that's autoclavable. So you need a bunch of those for the office. Yeah. Interesting. I'm in packs of threes and we've got, I think three in our clinic. So you work at the UAB clinic and our faculty practice. Yeah. We're not probably, we're not like a high, high production clinic. So we can get away with, you know, cause not every patient needs. restorative so it's you know three three of those connectors is it's fine for me right let me ask you this let's say we're using a universal bonding agent um let's let's focus on the dent in here dr lawson tell us what the ideal hybrid layer should look like under perfect isolation conditions and then contrast that to a hybrid layer the moment it becomes contaminated with saliva or cravicular fluid oh um so i mean the the hybrid layer essentially is going to look slightly different if you're using phosphoric acid on the dentin or without it if you use phosphoric acid on the dentin you're going to see about i mean you'll see where dental tubules are you should see little tags of resin going in there and about five microns of it almost looks like spaghetti noodle of collagen with resin in between it and that's the so-called um hybrid layer and That's if you use a total etch system. If you use an etch and rent system, your hybrid layer is going to basically still contain some of the smear layer from when you've ground on the tooth. That gets dissolved in your hybrid layer. Then you get about penetration of about one micron of half a micron to one micron of adhesive in between that surface layer of collagen. And then maybe a little bit can make it into dentinal tubules. With blood or saliva on there, I don't really know what it looks like under an SEM. I've never seen an image of saliva or blood -contaminated dentin with bonding agent on top of it. But I imagine blood and saliva are slightly different. Blood is going to have platelets. It'll have glycoproteins. It'll have different types of contaminants. And the reason why I'm asking the question is because we're all not perfect. There are cases when we try to do everything right and we get this contamination. But let's say we're using a universal adhesive. So it's a self-etched system and you're scrubbing in the adhesive and you've done your proper scrubbing. And then all of a sudden, and you thin out the solvent so that you get rid of all the ripples. You do everything according to IFU. And then their tongue just kind of goes right over the whole surface. You haven't cured it yet. What is that going to do? to the success of the bond. And what should the dentist do? Would you start over? Yeah, I mean, actually, I've got a little step-by-step for contamination at every level of bonding. In that particular case, I guess it depends if you've got... on top of wet bonding agent based on a little thing your best thing would be to rinse it off dry it off and reapply fresh bonding agent and then light cure the bonding agent so essentially start over you want to because you've contaminated the uncured adhesive at that point i guess in your example i forgot to ask if you are you self-etching yeah yeah i mentioned where we're using a universal adhesive so that you're basically self-etching Yeah, in that case, yeah, that isn't a form of starting over, yes. Okay, so if you're using a universal adhesive and the tongue makes contact with the surface and you haven't cured it yet, you want to take your air water syringe, wash everything off, and then what, dry it? Dry it and then reapply your bonding agent. Okay, then put the universal adhesive back. Now, if you're doing a total etch? If you're doing a total etch, you do the same thing. So basically you're- You wouldn't have to go back and re-etch it. That's, I mean, again, this is, I forgot to mention the beginning of the podcast. Like I, my personal bias in dentistry is like, I'm very tied to anything I could find in a lab study because based on those studies, if you're using universal adhesive, if it's extra rinse or total etch, I guess, I don't even know why I asked previously to clarify. In either case, you would go rinse off the wet contaminated bonding agent, dry it and reapply bonding agent. Now, what happens if you are using a universal adhesive? You've already done your selective etch. You put the universal adhesive down. You scrubbed it in. You thinned out the solvent. And then you light cured it, just like the IFU says to do. And then it's contaminated before you put your composite on. It's cured, but it's contaminated. Any problems there? The rinse dry and then just put composite directly on top of it. Okay, so you don't need to do any more adhesive on top of adhesive. No. And all these things are like the best thing to do in a bad situation. I mean, the best thing is always to go reprep. So all of these led to lower bond strengths, but it was the best thing. I mean, there was no, aside from like going back and reprepping a little, these were all, or sandblasting or something to refresh the surface. These were like the best thing to do in a bad situation. So why not just refresh the surface? I mean, they're in the dental chair and it doesn't take that long. If it was me, I would rather just not do the rescue protocol and go right back to what I was supposed to be doing in the first place. Is that... Just because of time or just because of time? Yeah, time. Or I suppose it's like maybe if you don't have great isolation. I mean, in your situation, the patient went over and did that annoying thing where patients like to lick your dentistry. But, you know, some of these situations, it's like you're just working and, you know, maybe it's a young kid or maybe it's, you know, really hard to isolate and you. That's the best you're going to get. This is the best I'm going to get. Yeah, I mean, if it's the lingual of number seven and they literally just wanted to go up there and look around and mess around with your prep and you feel like you could refresh it and do it again without any contamination, yeah, that would be the best. Yeah, so that would be the best situation to do it over. But if you're thinking this is going to happen anyway, over and over from now until kingdom come, we're going to... get this thing rescued and finish this job and get it done or eventually go to glass anomer right yeah that's another option glass anomer is amazing for some of these um you know really hard to isolate areas and i wish i would have I mean, I use glass ionomer so much in subjunctival caries because it's just so hard to isolate down there sometimes. Yeah, I mean, I talked to Brian Novy, Dr. Novy. You probably know him. And he is such a big advocate for glass ionomer. And when I talk to some local dentists around here in Austin, Texas, they'll say, no, I don't use it. It washes out. It doesn't have good wear resistance. It's not as aesthetic as I want. It's not as strong. But then when I talk to researchers like you and Novy and... bunch of others, they swear by glastonomer. I'd say about a third of the fillings they do are with glastonomer because I see a lot of high carers as patients. I like that kind of patient. So isolation becomes not as critical. It's still important, right? We don't want to put glastonomer on a tooth that's full of saliva and blood. but we've done some studies with resin modified glass on them are cements and we've like bonded cements in just a pool of saliva and the bond was unaffected um you know there's a there's a set there's Fewer studies than you think about bonding and presence of contamination, but there's one from this Japanese group, Shimazu, from 2020, where they showed glass on them and resin-modified glass on them were unaffected by either what they called, they called it some saliva or very scientifically lots of saliva. In both of those cases, They were unaffected by the presence of saliva. That's really impressive information, especially on those patients where you just know you're not going to get good isolation instead of fighting with it. But composite is very, very sensitive to isolation, right? If you don't have a good field, that bond ain't going to work, right? I mean, it's as simple as that. Yeah, for some reasons, dentin more than enamel. is more, more affected, but yeah, yeah, it's very, it is very affected. So let me ask you this, Dr. Lawson about blood. We talked about saliva contaminating the area and what we could do to rescue it or possibly do it over. What about blood contamination? Blood's hard because with blood, there's just been such fewer studies. And it's probably because like when we do research, we've done a lot of studies on saliva contamination. I don't know if any of them have ever been published, but we've done a lot of them at the school. It's really easy. You just spit into a little test tube and you've got all your saliva. Like letting blood to do a research study is much less popular thing to ask a graduate student to do. So there's just like very few studies that have been done on it. The few studies I could find. had talked about using EDTA to clean off blood. That's the same thing that they recommend to clean off contamination from ferric sulfate. So all these iron containing things, I guess. EDTA is an effective cleaner. You know, honestly, in the lack of good evidence, I've kind of just thought of blood like saliva. I don't know if that's, if it's going to perform the same. So any protocol I would use, you know, the protocols we just talked about for like, you know, removing saliva, I just think of using the same thing for blood. And I don't know, it's probably not, that's not evidence-based, but I just don't think we have the evidence for the best way to clean blood. What about sodium hypochlorite on a cotton pledge and just, wiping the tooth with that that's the endodontist in you coming out yeah i mean that's exactly right yeah that's exactly right nate dr lawson yeah that's the endodontist speaking i mean sodium hypochlorite solves everything for me as an endodontist but no seriously what would that help It's funny because in the restorative dentistry world, there's always this fear about bleach prior to bonding because of the peroxides, like carbamide peroxide and releasing oxygen, which inhibits the... polymerization of our composites. And so I think people sometimes lump together hydrogen peroxides with sodium hypochlorite bleach. And so, you know, I always think, you know, you guys in the endo field will all the time will do, you know, those endodonts that like to do their own posts. I mean, they'll bleach out a canal and then place a post in there. And, you know, the research on dentin bonding after sodium hypochlorite is not like the research about hydrogen peroxide and carbamide peroxide. I mean, there's, I remember compiling this list for one of our social media. accounts was showing different, there've been several studies that show that sodium hypochlorite doesn't affect dentin bonding like the carbamide peroxide. Right. I mean, we use sodium hypochlorite all day long and I did post and cores with bonding in the canal and bonding the core material to the tooth and never had problems at all with that. So it seems to me that sodium hypochlorite would be good for dissolving blood cells because it just denatures these proteins. Yeah, yeah. That's probably more accessible than EDTA to most of us. But that seems reasonable to me. So I think we can all agree that there's several variables that determine the outcomes, the clinical predictability of our bonding procedures. And certainly isolation is one of them. That's something we can really hone in on, whether it's using the rubber dam or using integrated systems like ISOVAC. But try different things. And I'm talking to the audience now. Look up. different systems, talk to your colleagues, and see what works for you. Obviously, it's very important to the procedure of adhesive dentistry to maintain a good field. Any final thoughts, Dr. Lawson? Yeah, like I said, we kind of let it off. I think it's one of the big reasons why composites just don't have the clinical lifetime of amalgams is I think isolation is a big part of it. If I had a guess, that would probably be... I don't know. I don't know if I'd say that's number one or shrinkage or the composite is number one or poor technique of the adhesive. I might guess isolation as being maybe even at the top. Dr. Lawson, thanks for being with us today. Really appreciate your input. And we definitely want to have you on future podcast episodes. Thanks so much. All right. Thank you, Dr. Klein. Thanks, everyone, for listening.