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750: The 15 Nightmares of Every Lab When You Scan – Dr. Christian Coachman

A scanner can do amazing things — if you know how to use it! If you don't, it leads to frustration for you, your patients, and your lab. To help you overcome the barriers and become a master at scanning, Kirk Behrendt brings back Dr. Christian Coachman, founder of Digital Smile Design, to reveal 15 scanning nightmares that you can learn to identify and avoid. To start improving your scans and have a better relationship with your lab, listen to Episode 750 of The Best Practices Show!

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Main Takeaways:

  • You need to be a great dentist before mastering the scanner.
  • Be upfront with your lab about limitations and challenges.
  • Always analyze your scans before sending it to the lab.
  • In the digital world, there is no excuse for bad scans.
  • Don't pretend like you don't see scanning problems.
  • Modernize your communication by utilizing AI.
  • Utilize your CAD software for the best scans.
  • Train your assistants in proper scanning.


“It's exciting to see how the scanner is going to help us with challenging aspects of diagnostics, treatment planning, case acceptance, and clinical execution. But we still need to be a great dentist before that. Scanners will not do any magic in terms of fixing our mistakes.” (6:40—7:03) -Dr. Coachman

“The majority of cases that are coming from dentists to labs, unfortunately, there are surveys showing that most of the preps going from dentists to labs shouldn't be accepted by the labs. Most of the impressions coming from dentists to labs shouldn't be accepted by the labs. If we draw on ethical, common sense, quality standard line, we will get to that conclusion. When it comes to preps, impressions, and bite registrations — I can even say from my own experience — around two-thirds of these bites, preps, and impressions are below the line of a decent standard of quality. Now, I'm not saying this as a technician to blame dentists for all of our problems. It’s just to realize that preps, impressions, and bite registrations are very challenging to be made and we underestimate how difficult these things are. We don't talk enough about it. We don't put enough effort to become better at it. We try to pretend that these three things are under control, and they're not.” (9:43—11:03) -Dr. Coachman

“The first [problem with scanning] is poor mesh resolution, the quality of the mesh itself. The quality of the mesh is basically the quality of the surface of the file, how clean, how precise, how complete, how many details that mesh is bringing or how many details the mesh is missing. Does the mesh have holes? Did artificial intelligence on the scanner try to fix those holes, kind of guessing those problems? That's a problem as well. If that guessing is on a critical area of the scan, you may be fooled and think that the scan is good when it's not.” (22:15—23:03) -Dr. Coachman

“The quality of the mesh depends on the quality of your scanner and the brand of your scanner. It depends on the quality of the scanning technique, the scanning strategy, as they call it. Every scanner has a slightly different scanning strategy, and you need to master the scanning strategy of the scanner that you're using. Also, the process of exporting and importing the files, downloading the files, you may lose quality there as well. Changing software, changing brand — so, the scanner from one brand, the CAD software from another, you may lose a little bit of quality on this movement as well if the scanner and the CAD software are not working well together.” (23:04—23:49) -Dr. Coachman

“Another big [problem] is scan distortion, interproximally. This is very common on veneers, on preps that are touching each other, or teeth that are touching each other. They call it bridging as well. So, if you don't follow the right strategy, you can create an area that is very blurry, or you can create artificial spikes on the scanner. As you zoom in, you see that this is completely not realistic — it's something that the software created. If you don't carefully separate the teeth slightly, the finishing line is very visible. This also happens on the junction between the prep and the gum, and you have areas that you have those spikes that you don't see where the prep is, where the gingiva is, and this is something that makes no sense. It makes no sense for a lab to be seeing this and the dentist didn't see this before, because this is something that the dentist needs to see chairside before sending the file. So, if you give yourself a few minutes to analyze your scan before you send it to the lab, you will identify it because it's the same file.” (24:20—25:47) -Dr. Coachman

“You should ask your lab to make print screens of all the situations and areas that are not ideal. Let's sit down one day, go through these things, and let's discuss together what is acceptable or not. ‘What is acceptable? Every time you see a finishing line like this, this is acceptable. Go for it. Let's both consciously make that decision. But if we see this a little bigger here, let's stop. I'm going to do my best as a dentist to see this chairside. If I don't and you see it in the lab, just send me a message that we have to redo this. This is not acceptable.’ So, create your quality standards with your lab by looking at the images. It's very simple. I don't understand why people don't do that. Just tell your lab, ‘Even if you will accept my scan, everything that you don't like, make a quick print screen and share it on the chat with me. Just share it. I just want to be exposed. I want to look at it. I want to get better. I want to understand the problem.’ Many dentists don't even know how to evaluate their scans, and it's so easy. You learn with your lab because that's what labs do all the time. So, encourage your lab to show the areas that are not good so you can learn with them.” (26:39—28:04) -Dr. Coachman

“Problem number three is [having a] finishing line [that is not visible]. That's another thing that shouldn't be acceptable anymore in dentistry, unless it's a conscious decision and you say, ’This is not ideal, but we have to work with this,’ for any reason. But the amount of times that dentists are — it almost feels like dentists are pretending they are not seeing it. Like, ‘Doctor, I cannot see your margin here,’ and the doctor is like, ‘No? How come?’ They say, ‘Look, this is the exact same image that you looked at. So, let's look at this together. Where is the finishing line here? There is absolutely no finishing line. The prep and their gum are becoming one thing, completely blurry.’” (28:36—29:21) -Dr. Coachman

“If, for any reason — your patient has emotional issues, you already scanned the patient ten times — there are limitations beyond your control, just anticipate the problem. Don't pretend you don't see it. Don't put the scan aside and say, ‘I'm not going to even look at it. I know it's not good. Let's see if it's going to pass. Let's see if the lab is going to take it.’ Don't do that. Just say, ‘Look, on tooth number nine on the distal-mesial or distal-palatal area, there's an area there that we cannot see. I tried three times. Just work with it. Do this. Once you bring it to your CAD software, zoom in. Give me an image. I'm going to draw with my finger here where the most precise possible line is here.’ But I'm already telling you we cannot improve this area because of X, Y, Z. I'm anticipating the problem. Have the courage to do that, and it's going to be a much better communication. The lab is going to respect you much more, and it's going to create accountability. It's going to make the lab want to work better for you. It's going to make the lab complain less about you. Nobody is going to complain if you already anticipate it. ‘I had a problem here. This is not perfect.’ I'm already telling you that's how we're going to work around this and get this done. It’s much better. Much better.” (29:23—30:59) -Dr. Coachman

“You, as a dentist, need to put in a few minutes to analyze your preps, chairside, while your patient is still there. Make notes. Create a report. ‘Tooth number eight, there's a subgingival area where there's a challenge there. Tooth number nine, there's a part on the palatal-distal where it’s not visible, but we're going to work around that. Tooth number seven, the prep is X, Y, Z,’ and you go through this report. Nowadays, you have no excuse not to do that with AI.” (31:02—31:38) -Dr. Coachman

“Every time you scan a patient, you should do a quick report about the preps, the scans, the bites, the provisionals, and the facial information. So, specifically on the restorative workflow, if you want your lab to be able to do the best job, you need to get the best information about the preps, the scans, the bite, the face, and the provisional.” (33:49—34:14) -Dr. Coachman

“[Problem number] four is sharp angles. We struggle with sharp angles. Meaning, preps that the doctor didn't see — or pretended not to see — that there was a sharp angle there that is not good. It's not good for restorations, in general, to have a sharp angle in the prep. But it's even worse for CAD/CAM restorations because of the milling strategy. So, we want to make sure that the inside of the prep is smooth, without sharp angles. And chairside, you can see that.” (37:44—38:17) -Dr. Coachman

“We still identify too many sharp angles as we get here in the lab. And most of the time, we don't want to ask the dentist to reschedule the patient just because of a few sharp angles. So, what we do is, usually, we create some spacing there. That usually makes the restoration a little bit thinner in that area. Many times, it's not a big deal. Sometimes, it may be a big deal. And many times, when it is a big deal, we don't see it as a big deal and the restoration, instead of lasting 15 years, may break in five years and we don't know why. So, I would definitely evaluate, chairside, sharp angles. The scanner gives you the perfect condition because you can scan your preps, then you can put opaque color — not colored scan view, but the opaque that looks like a plaster model. That's the perfect view for you to see how the shape of the prep is, and smoothness, and if you have sharp angles or not.” (38:19—39:28) -Dr. Coachman

“Clearance is pretty obvious, a classic nightmare for technicians. The amount of times that a technician needs to call the dentist in their career and say, ‘Doctor, there's no space.’ After several years working as a technician, it does feel like putting the “F” in between — there is “no” and “space”. And between no and space, put an F there. Meaning, there is no fucking space here. How can I work with this scan? And even though it makes technicians angry, I used to really understand the dentist because I was also a dentist. It's hard to evaluate clearance in many situations. But with a digital workflow and a scanner, there's absolutely nobody to blame anymore but yourself. There's no excuse because the scanner is giving you exactly the clearance, chairside. So, having the lab manufacture a restoration without ideal clearance makes no sense. Not identifying that beforehand makes no sense. Not anticipating the problem makes no sense.” (39:30—40:49) -Dr. Coachman

“Today, with the digital workflow, we can see [the design and finishing line] in advance. We can simulate the prep and we can overlap with the design. We can simulate on the software where the finishing line should be. So, when you're prepping, you can be looking at these images in front of you to guide your preps. Then, some scanners even allow you to overlap the design, as you're prepping, with transparency. So, you're looking at the computer, you're looking at the screen of your scanner, and you can see your prep, your finishing line, and the future design already with transparency on top, showing you exactly where the problem is, allowing you to immediately go back to the mouth and change the finishing line, looking at the 3D image of the design and transparency over the prep. So, this is the perfect world. Nowadays, it makes no sense for the dentist not to leverage these tools to make sure that the finishing line of your prep is ideally positioned to allow us to design the restoration that you want, the restoration that your patient wants.” (43:04—44:14) -Dr. Coachman

“[Problem] number seven — another classic one — undercuts, path of insertion. Man, oh man. The amount of preps that we get that have undercuts and no path of insertion is still too big. And unfortunately, to get mad at dentists again, there's no excuse because the scanner screen is there for you to look at it. Some scanners even give you the colors. lt's almost like having an alarm. The scanner is like, ‘Don't send this to the lab! There's an undercut here, Doctor! Look at this!’ Orange towards red is an undercut. We get too many preps with undercuts. And, of course, as you know, if there is an undercut, we will either have extra spacing that will weaken the restoration, or, many times, the problem is that the undercut is close to the margin. So, it means that if we manufacture the restoration, the restoration will have a big, open margin on that area, creating leakage or creating a weak spot when it comes to longevity.” (44:21—45:32) -Dr. Coachman

“Still, today, we get too many preps that have undercuts — too many. It makes no sense. My question is, why? Why do you do this? Why do this? Why take this risk? The patient is right in front of you. The scanner screen is right in front of you. It takes one minute to make that evaluation. It takes a few more minutes for you to go back to the mouth and retouch those areas, and it takes a few more minutes to rescan those areas and stitch the information and solve the problem. So, let's work together and make this a problem of the past.” (46:57—47:32) -Dr. Coachman

“The eighth problem we get from scans is that we don't get the ideal soft tissue information, the gingiva. So, as I said, to make your lab the best possible version of themselves, to allow your lab to create the best possible restoration, we have those six components of information that we need. We need great information on the preps, on the scans, on the bite, on the face, on the provisional, and on the gingiva. So, the gingiva is obvious. A restoration needs to be in harmony with the gum. You have submergence profile, you have emergence profile, you have papilla shape, you have pontic areas, you have implant areas, and the restorations need to adapt beautifully to that tissue. So, we need that information in the lab. In an ideal world, that ideal integration between restoration and gum will be developed with the provisional from the dentist. So, in the ideal world, the dentist is putting energy into the provisional and shaping the provisional so finishing lines, pontic areas, black triangles are not there. Emergence profile, implant profile — everything is solved with the provisional. So, now, what we want is to leverage our scanner to copy/paste that information to the lab. It makes no sense for you to put energy into developing this ideal soft tissue with the provisional and not copy/pasting that into the lab and having the lab start from scratch or have the wrong reference.” (47:36—49:29) -Dr. Coachman

“Number two, you need to scan the provisional upside down, outside of the mouth, so you can capture the underneath information that the provisional was able to build. Because as soon as you take the provisional out of the mouth, the tissue will collapse. So, scanning the tissue in the mouth will not give you the whole, precise information. It needs to become part of your protocol to scan the provisionals. If you did a great job with the provisional scan, the provisionals upside down outside of the mouth, give the lab that extra information. Also, then put the retraction cords, open the margins, and then scan the preps. When you put the retraction cords, you remove the provisional, the pontic area is collapsing. The implant area tissue is collapsing. The emergence profile area is changing. You're putting the cords, you're retracting the gum, you're changing the shape of the papilla. What I'm trying to say is that the scan that you do of the preps and the implants is not the gingival scan. The gingiva is completely distorted there. That's the prep and implant scan. So, you need to do this other scan with the gingiva so we, in the lab, can use that information to design the restorations in harmony with the gingiva.” (50:03—51:20) -Dr. Coachman

“[Problem number nine is] the famous one, the bite. Wrong jaw relationship, wrong bite . . . they all [make me crazy]. But this is a tough one because it means that, in the lab, we're going to design a full arch. We're going to put all the energy scoping that full arch, adjusting that full arch, working with the digital articulator, adjusting excursive movements, protrusion, canine guidance. We're going to then manufacture these damn restorations. We're going to adjust them. We're going to make them look beautiful. We're going to layer them, stain and glaze. We're going to polish them. The occlusion will be beautiful. We're going to stain. We're going to make them look natural. We're going to put them in a beautiful box and send it to the dentist. And then, you put it in the mouth, and the bite is off. Then, you have two choices. One, destroy completely the occlusal surface and try to save the day by being a hero there and then destroying the glaze, destroying the surface, trying to polish, chairside, destroying the longevity of the restorations because you're increasing the chances of cracks and fractures because you're inserting fracture lines inside the materials. But you're still kind of nice to the lab because you're saving the whole mess by yourself. Or you're going to send back everything to the lab and say, ‘The bite is off.’ And we're going to say, ‘But that's the bite you gave us.’ So, that's the reason why it's important for us to balance the bite in the provisional phase, because then you can scan the bite with the provisionals as well on bigger cases.” (51:24—53:24) -Dr. Coachman

“[Problem number ten is], no provisional info, no scans and pictures of the provisional. I'm repeating this because this needs to become a key part of the workflow. You have to scan the provisionals and you have to take the facial pictures with the provisionals. The dentist may say, ‘But my provisional is not good. I did a provisional quickly. Don't take my provisional as a reference. Use the previous design as a reference.’ Say, ‘Doctor, that's not the point. We don't want your provisionals just to follow your provisionals on the design. We want your provisionals because the picture of your provisional and the scan of your provisional will allow us to stitch together the rest of the information.’ So, with the facial picture of your provisional, the patient smiling with the provisional, it will allow us to match the upper scan of your provisional to that picture. The upper scan of your provisional will have enough information that will allow us to overlap the scan of the preps in a much more precise way. And since the provisional scan has the perfect intercuspation with the lower in the bite registration, we will be able to have the prep scan in the ideal jaw relationship with the antagonist. That's how we stitch the information. Sometimes, we don't need to use it. Many times, we do need to use this information. So, don't even think. Just give the lab the information and allow the lab to stitch the information better together.” (56:31—58:12) -Dr. Coachman

“[Another problem] is, the doctor did send the scan of the provisional and the picture of the face of the patient with the provisional, but the picture is bad, and the scan is bad. That doesn't help much. So, we need a precise scan of the provisional and with as much soft tissue as possible. We need a reference. Scan the palate, always. You always need to scan the palate because you never know when you're going to need it to overlap the information to build the patient's avatar.” (58:20—58:51) -Dr. Coachman

“[A problem with implant scans is] there's noise on the scan body region. This is something that you can see chairside as well. So, if you're doing an implant with the digital workflow, the quality of the image of the scan body that you capture is the key to overlap everything. Otherwise, you're going to place the implant in the wrong place. So, you need to make sure that the scan body image quality is great and sharp and there's no noise, meaning there are no things that look like whatever on top of it. It's a clean, precise image . . . The next one is wrong height of scan body, meaning picking the wrong scan body to scan. And the third one about the scan body is scan body wrongly scanned or placed, meaning that the scan body is not completely fitting in the implant, or is rotated, it's out of position, is the wrong size, or there is noise on top of the image. These are the most common mistakes or problems that we see with scan bodies.” (59:09—1:00:30) -Dr. Coachman

“[Another problem with implant scans is] poor choice of scan body. So, you need to learn from . . . the companies, from the lab, or from experienced digital clinicians what it means to choose the right scan body and what a poor choice of scan body means. There are different brands, different situations, different scenarios, and you need to understand that because that will dictate the quality of the whole work over implants if you do digital.” (1:00:35—1:01:08) -Dr. Coachman

“[Another problem with implant scans is] full-arch scan distortion. So, no passive fit on the restoration or on the passive fit test. We know this is a challenge. We know that this is a big topic on scanning. This is the ultimate challenge to overcome in scanning situations, scanning a full implant arch and having precision to fit a milled restoration with passive fit. So, that's a real problem. But we have different, great solutions for this today that makes us be able to scan any scenario, any situation, and do it fully digital. We don't need to do the old-school, analog, high-precision impressions of full-arch implants. And this is amazing because these high-precision impressions in the analog world were a nightmare. They were crazy, insane techniques to try to transfer the precise position of the implants to the lab. So many things could go wrong that being able to scan multiple implants with precision is huge. And today, you can. There are different strategies for it and we're going to show it in the course.” (1:01:11—1:02:36) -Dr. Coachman

“There's absolutely nothing on any of the seven levels of scanning that you say you need to be a dentist to understand how to do it — nothing. There's nothing about the scanning process that should [only] be done by a dentist because the dentist knows something that a hygienist or assistants or a technician wouldn't know.” (1:06:16—1:06:37) -Dr. Coachman


0:00 Introduction.

1:04 Why this is an important topic and about IOS-F1 Festival.

5:14 A scanner isn't a magic solution.

9:25 Two-thirds of cases sent to the lab should be rejected.

12:43 Master the process of creating a precise patient avatar.

14:29 Find the real problems that need to be solved.

21:13 Lab nightmares: Poor mesh resolution.

24:20 Lab nightmares: Interproximal scan distortion.

28:34 Lab nightmares: Finishing lines that are not visible.

31:00 Modernize your communication.

37:37 Lab nightmares: Sharp angles.

39:29 Lab nightmares: Clearance.

41:25 Lab nightmares: Prep margin designs.

44:19 Lab nightmares: Undercuts.

47:33 Lab nightmares: Not getting the ideal soft tissue information.

51:22 Lab nightmares: The bite.

56:29 Lab nightmares: No scans and pictures of the provisional.

58:13 Lab nightmares: The picture and scan of the provisional is bad.

58:54 Lab nightmares: Noise on the scan body region.

59:54 Lab nightmares: Wrong height of scan body.

1:00:05 Lab nightmares: Scan body is wrongly scanned or placed.

1:00:35 Lab nightmares: Poor choice of scan body.

1:01:09 Lab nightmares: Full-arch scan distortion.

1:02:42 Types of scans and teaching team members to scan.

1:06:39 The vision of IOS-F1 Festival and 2025 course dates.

Dr. Christian Coachman Bio:

Combining his advanced skills, experience, and technology solutions, Dr. Christian Coachman pioneered the Digital Smile Design methodology and founded Digital Smile Design company (DSD). Since its inception, thousands of dentists worldwide have attended DSD courses and workshops, such as the renowned DSD Residency program.

Dr. Coachman is the developer of worldwide, well-known concepts such as the Digital Smile Design, the Pink Hybrid Implant Restoration, the Digital Planning Center, Emotional Dentistry, Interdisciplinary Treatment Simulation, and Digital Smile Donator. He regularly consults for dental industry companies, developing products, implementing concepts, and marketing strategies, such as the Facially Driven Digital Orthodontic Workflow developed in collaboration with Invisalign, Align Technology.