Dahl Technique and ‘Maryland Bridges’ – GF001

Main Topic: So this is why, this is the first ever group function okay? So i’m calling this series group function because it’s us, you and i working as a group. You guys the listeners, myself, the previous guest of the podcast, the future guest podcast and those on the Protrusive D,ental community facebook group we’re going to ask questions, we’re going to answer questions. They’re going to share answers, we’re going to try and be i guess a fly on the wall when these helpful conversations happen. So for the first ever group function, someone messaged me yesterday with a question his name’s Aaron Raju. Aaron, thanks so much for the question and he gave his consent for this to be go on an ama so i can ask me anything but of course i’m calling this the group function. So what Aaron asks is to do with resin bonded bridges so aka maryland bridges you know i don’t like that term but anyway maryland bridges and using maryland bridges as part of the dahl technique. Now if you are totally unfamiliar with a dahl technique you need to end this episode now and go back to episode 16 and 17 where we are joined by Dr Tif Qureshi and we talk everything and anything about dahl, about how it works, the mechanisms, the indications, contraindications. So this is a really important background knowledge to have, to be able to answer this question and resin bonded bridges are something very dear to my heart. I’ve got a little mini series online on rbbmasterclass.com so i placed hundreds of resin bonded bridges. I’ve published on this technique in dental update. So Aaron thanks so much for the question basically i’ll read it out “Dr Gulati..” Well first you don’t need to call me Dr Gulat. I am Jaz, you know that. Hope you don’t mind answering quick query. I read your papers in dental update regarding resin bonded bridges. I have a case where a resin bonded bridge is used to replace an upper right five with the upper right six as an abutment with the wing overlying the palatal cusps and the palatal surface. This was no prep and the plan is to dahl to reestablish posterior occlusion long term. I realize there is also a potential to create an anterior open bite as a result of raising the occlusion posteriorly. Have you experienced any kind of potential issues in your experience? And to avoid this i was considering a minimal occlusal preparation in the future to leave the palatal and lingual surfaces untouched. Kind regards, Aaron. Aaron thanks so much for the question. Let me break that question down into his different components so we can answer each one. So it’s it’ll flow better. So firstly the situation is we have a resin bonded bridge, it’s a cantilever resin bonded bridge, it’s from a first molar as the abutment tooth and it’s replacing a second premolar so it’s a cantilever design and it’s resin bonded so it’s not a conventional bridge, it’s a resin bonded bridge. Now the question is when we over lay onto the occlusal surface so half of the occlusal let’s call it the palatal half of the occlusal surface. Now this is a good thing to do generally because you’re maximizing the surface area that you’re covering of the abutment which is really important for resin bonded bridge because innately they don’t have much retention form. They’re relying heavily on the bonding. So it’s a good thing to do and also the other benefit of covering over the half the occlusal surface is if you put any pressure or force down the long axis of the pontic so the upper right five pontic okay? You put some forces up the the tooth as you’re chewing some food okay? Then forces will be acting on the bridge abutment and what the occlusal element of the abutment brings is that it allows your cement lut to be in compression compared to if you didn’t cover the occlusal and he only had the palatal surface the wing classic used to see this design quite a bit and they were not so successful is because when the patient now chews and they’ve got a food bolus on their secondary molar and they bite together. Now what’s happening is that shear stress and tensile forces are acting on that cement loot and then eventually this can debond but by having the occlusal component, it’s allowing it to be in compressive stress which it can handle much better So it’s always a good thing to do where you can. Now the issue is if you’ve got someone with a perfectly well interlocking interdigitated posterior occlusion then you don’t have space right? So your options are A) you prep and you prep 0.7 millimeters so you definitely don’t want to get into dentine because that really reduces the bond strength but you should be able to do it but nowadays you want to be minimally invasive so this is why some people like to use the dahl technique i.e do not do any prep or very minimal prep and have your technician make the resin bonded bridge abutment in supra occlusion. So you bond it on, cement it on and now when the patient bites together because you didn’t make the space for it you’re open everywhere else, you’re not biting anywhere else except on to the abutment of the upper right six. So can this technique work? Yes it can. So i’m just gonna for those who people who are watching obviously those who are listening i’ll be able to describe it for those people who are watching i’m gonna put some still images from my resin bonded bridge online course and this will help to drive the the sort of vision home as well and the explanation will be clearer. Using the dahl technique as part of resin bonded bridge to replace a tooth is something i did a lot of in hospital both when i work at that guy’s hospital and at sheffield hospital on the restorative department for the young people post-orthodontic around about anywhere from age 15 16 up to you know even their 20s we did this a lot. We didn’t prep and we just bonded these resin bonded bridge in supraocclusion and they would sort themselves out okay over time you would get the posterior over-eruption or dental alveolar compensation so this image for those watching is that the teeth are apart it hasn’t settled but even as quick as four weeks later they do come back and everything is meeting quite nicely if not a hundred percent and maybe ninety percent of the way there and then with a further follow-up teeth are all into collusion, they’re all into static occlusion again and things are looking pretty good. So how does this work? Well the posteriors over-erupt or dental alveolar compensation happens there could be some anterior intrusion and also there could be a degree of condylar repositioning and all these and any of these things can be happening at the same time. So it does work but you have to pick your battles and as now you know, now work in private practice, I tell you i don’t do a lot of this anymore. I’m very very selective about which cases i do this for. So let’s talk about some contraindications. So the real world advice is firstly all the principles of dahl, you have to also apply it to doing dahl on a resin bonded bridge because dahl traditionally nowadays when we do it, we do some anterior bonding for someone who’s got localized anterior tooth wear and then we allow the several teeth contacting at the front only and then allowing dahl to work its magic condylar repositioning, anterior intrusion, posterior eruption and then eventually everything is settled right? And this is fairly predictable especially in a younger patient but with the resin bonded bridge unless you’re doing like a long span anterior resin bonded bridge like in the situation that Aaron just spoke about, with dahling of just one tooth okay? That’s pretty extreme right? So all of the patient’s contacts all the chewing will be on the upper right six everything else will be open is this a good thing to do? Well I think Aaron told me the patient’s about 27 so yes fairly young and that should be fine but are there any risks? Now before we come on to the risks there are some things that apply universally with dahl like for example avoid dahling anyone with an anterior open bite because hey if they were receptive or susceptible to anterior overruption and whatnot and an intrusion then their own anterior open bite would have sorted itself out already right through eruptive forces but it hasn’t. So avoid AOBs, avoid intracapsular disorders with tmj. Do it on people you like and trust because it’s kind of something that you may be seeing them over again for if it doesn’t go to plan. Avoid severe tooth wear because they probably need a full mouth rehabilitation as Tif says dahl is very much reserved for interceptive like when it’s not too late, when you can do some edge bonding and you can recycle these as you go along so every eight to ten years do it again and really it’s a great way to keep someone going but if they’ve lost too much tooth structure or if they’ve got posterior wear, significant posterior wear that’s not a dahl patient, that’s a rehab patient. You also want to avoid it in someone with a reduced periodontium so imagine this patient that Aaron spoke of obviously 27, unlikely to have severe perio problems but if the upper right six was periodontally compromised then really there’s a fine line between doing a dahl and and just putting something at increased risk of occlusal trauma. So you have to be careful with the reduced periodontium and of course age is significant. So the younger you are the more predictable it’s supposed to be and one more thing that if you ever do a dahl always think about the axial contacts like where are the contacts happening and if the opposing tooth is having the contact along the long axis or not so you don’t want teeth display and flare out you try and want to design everything in your wax up and you’re planning to allow all the forces go up the long axis of a tooth. So Aaron let’s actually answer your question, it’s totally okay to do this but i don’t do it so much because it’s annoying for the patient and if they’ve got a perfect in well interlocked interdigitated occlusion already a little bit of prep for them to have a new tooth is not the end of the world okay? And that you can still stay in enamel for that 0.7 millimeter thickness and a lot of these cases you have a look and actually in some areas you may need to prep a little bit and other areas may not need to prep so much. So actually a lot of these cases don’t need as much as 0.7 millimeters perhaps you can actually do a lot less as well. Are there any risks of creating an anterior open bite? Well this is a very broad question because when can an anterior open might happen in restorative density? Well in this case it would happen where if they potentially have a large slide between their MIP and their centric relation contact point then let’s say you now prop them open on their upper right first molar as part of the bridge abutment and then what happens their lateral pterygoid muscle relaxes and suddenly their mandible goes all the way back, it’s like they’ve completely forgotten how to bite together and now yes they could have an AOB how can you screen for this? Well you need to check where is their centric relation contact point position, have they got a large slide perhaps you could use a leaf gauge to check what their first point of contact is and that might be useful for you and of course if they’ve got a poor posterior stability then nothing’s going to help them to slot back into their mip. So these are all the other things that we look at to predict if someone’s going to be high risk. There’s loads of other things that go on as well because if anything changes in the temporoomandibular joint then that can obviously change the way that our teeth occlude. So i think it’s a low risk of doing it but it’s still a risk nonetheless and every patient’s different and you should screen for this and do your usual occlusal check.