Scanning long span edentulous is a very likely culprit with rendering dimensionally accurate models because to the software and camera, the geometric shapes are too identical across the ridge.
The more we can disrupt the symmetry with large, short, non-reflective and asymmetric scanbodies, the more likely we are to keep the models accurate. This video presentation address some of those issues and how to overcome them.
Much like conventional impressions, digital impressions can render ill-fitting restorations. It is imperative to figure out the source of the problem and to understand if it is a scanning or manufacturing issue. We have compiled the top reasons for such errors in this article:
- If the restoration is manufactured on printed models, you should be alarmed! There are so many variables that can be introduced in additive manufacturing process that can lead to less than desired results. Printed models should only be used after restorations are milled to assess contacts or to dial back bulky material to the margin on they die.
- Translucent / transparent enamel can lead to inaccurate scans. This is most magnified when we work on conservative preparations made on enamel. See this article to understand the troubles that can be introduced while scanning glass. aa
3. We highly recommend that the clinician places his or her margins as soon as they image the preparation. Oftentimes, labs only work with STL models instead of color models and this leaves a lot of room for open interpretation and errors. Labs can then print the models to finish work like contacts and reducing margins they have bulked out to protect the material whilst milling.
The overhead light source can distort your models and impressions. This particular doctor had excellent preparations and retraction but the light source kept flooding the dentition resulting in ill-fitting restorations. Our crew at CAD-Ray remotely logged in through teamviewer and was able to review the logged video while scanning and instantly noted the source of the error.
The Medit software and scanner have a setting that can warn you if there is too much excessive ligthing.
Here are fundamental principles every dentist should understand about intra-oral scanners, how we can introduce errors, how to manage them, follow proper scan strategies, maintain accuracy across the arch and lots of other nuggets
Every ios hates moving parts (tongue and cheek)
Every ios hates dark areas like the oropharynx, black triangles, etc…
Every ios hates liquids (blood on the margins)
Every ios can “get off track” and form double images
Every ios struggles with highly reflective surfaces like emax, zirconia, and shinny metal.
The principles shown in the video address every one of these factors and how you can control them and get accurate arch scans in just a minute with the medit i500
I have tried virtually every ios out there and they all struggle with my mouth full of emax. the focal length of the medit from -1.5 mm to 17 mm is the largest variation on the market, and the way the medit handles highly reflective surfaces also outperforms every other ios.
In January, it will be in turbo boost mode when new software is released.
This case shows a full arch imaging where the model starts to go “off track”. To keep the explanation simple, the further away you get from multiple planes / heights of immobile structures, and the more you image in flat areas, you can inadvertently introduce errors in your models. You can see a sample case here in the video.
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There is a very simple solution, as you can see in this video. It entails consistently moving back to reliable landmarks to stitch new information to exisitng correctly. If you notice how we start imaging on the occlusal of the premolars and the molars, then we roll to the facial of the molars and the back around to the palatal of the molars. Then we sweep over soft tissue on the palate. But we don’t continue in that direction. We immediately return to the molar area so the software has landmarks it can recognize.
We then move the camera forward, image the palatal of the premolars, and then sweep back across the palatal midline. We repeat this back and forth movement to maintain a proper path for the software to recognize landmarks that do not move, in the equation. With this technique, you can scan a whole upper arch in just a couple of minutes and capture great details of the dentition and the soft tissue on the palate
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Here, you can see how the software rendered a perfectly accurate and detailed upper arch with the palatal vault captured without any errors.