Photo stitching in 2D, where individual photos are connected to make wider angle shot.<\/figcaption><\/figure>\nSo let’s go back to our upper- and lower-arch scans. If they are sufficiently deformed, then it is not a surprise that software has a hard time superimposing a third, buccal scan and trying to figure out what the “best-fit” is. This deformation is the crux of the issue in the report from CERECDoctors, where they investigated the reasoning behind unreliable bite registration in full-mouth scans.<\/p>\n
Results from the study<\/h2>\n The first observation that the report made was that\u00a0where<\/em> you scan the buccal bite matters. Given the same patient (or typodont), if you scan the bite registration on the right side, the software gives you heavier occlusion on the right; similarly, a left buccal scan gives heavy occlusion on the left. This is obviously not ideal, and given what we know about deformations now, how do we get around this issue?<\/p>\nWithout a systematic approach to full-arch scanning, different buccal scans result in different occlusal patterns. Not exactly what we want. SOURCE: CERECDoctors.com<\/strong><\/figcaption><\/figure>\nIn the previous example, the full-mouth model was scanned\u00a0in an\u00a0arbitrary\u00a0<\/em>method with no predetermined pathway. From our experience at our training center, most first-time users naturally and understandably subscribe to this sort of random movement of the scanner head. Unfortunately, this has been shown to result in more stitching errors and therefore more deformation.<\/p>\nIn the CERECDoctors report, they recommend a different method of scanning called a\u00a0Linear Scan<\/em>. The idea was adopted from the CEREC Ortho software, which was designed specifically for orthodontic full-mouth scanning.<\/p>\nBasically, in Linear Scanning<\/em>\u00a0the full-arch is scanned in three continuous and linear scans, followed by several rolling scans that\u00a0“tie” the linear scans together. With no backtracking during the linear scans, the software seems to be able to produce a model with minimal deformation. Therefore, it no longer matters where the buccal scan is, the final occlusion of the full-arch models is the same (see figure below).<\/p>\nWith proper scanning, the bite registration is stable no matter where you take the buccal scan. SOURCE: CERECDoctors.com<\/strong><\/figcaption><\/figure>\nPutting numbers to the deformation<\/h2>\n This deformation problem is not new, and at the CEREC Asia training facility we have been advocating the Framework Scan <\/em>method\u00a0(our version of the\u00a0Linear Scan<\/em>)\u00a0for more than a year. In order to prove to ourselves that doing a Framework Scan<\/em> is actually beneficial, we decided to perform a small study to quantify the deformation.<\/p>\nOne way to simplify the calculation of full-arch deformation is by taking the linear error between two reference points. The assumption here is that with greater error, more deformation has occurred. Therefore, by comparing different methods of scanning, we can determine if there are significant discrepancies in accuracy.<\/p>\n
Method<\/h2>\n First we fixed an easily-discernible physical marker on a typodont in the 18 and 28 location, and made a stone reproduction so that there are no movable parts. Then we tested four different methods of using the CEREC Omnicam, and compared their results against a desktop scanner (InEos X5). To do this, we use a computer software to measure the linear distance between our markers on each model (see figure below), and then calculate the differences between them.<\/p>\nMeasurement of linear distance using GOM Inspect. All\u00a0five scanning methods were repeated 10 times to produce 10 digital models each (n=10), and the linear measurements were repeated 3 times on each model.<\/figcaption><\/figure>\nResults<\/h2>\n Here are the results to our test:<\/p>\nThe numbers under each bar indicate the difference in linear distance compared to InEos X5. The units are in microns. The making of this chart took way longer time than I’m willing to admit…<\/figcaption><\/figure>\nSo the five scanning methods that we tested were:<\/p>\n
\nDesktop Scanner:<\/strong> InEos X5<\/li>\nIOS:<\/strong> Following the CEREC Ortho guided scanning procedure<\/li>\nIOS:<\/strong> Using a method adopted from CEREC Ortho that we call Framework Scan<\/em> (or Linear Scan<\/em> from CERECDoctors.com)<\/li>\nIOS:<\/strong> Following recommended scanning guidelines from Dentsply Sirona in 2014<\/li>\nIOS:<\/strong> Following an updated 2016 guideline from Dentsply Sirona<\/li>\n<\/ol>\nIn short, our results show that CEREC Ortho, Framework Scans<\/em> and the InEos X5 desktop scanner show similar cross-arch stability. Since it is rather difficult to categorize an arbitrary scanning method due to its randomness, we decided to compare to the official guidelines from Dentsply-Sirona instead. Even there, statistically significant differences can be observed. Though it should be noted that these guidelines were not intended for full-arch scanning.<\/p>\np values for those who are statistically inclined. Asterisks indicate statistical significance.<\/figcaption><\/figure>\nConclusion<\/h2>\n\nUsing the Framework Scan<\/em> method can produce cross-arch stability comparable to the InEos X5 desktop scanner.<\/li>\nBoth Framework Scanning<\/em> and CEREC Ortho produces better cross-arch stability than the official guidelines, which were not intended for full-arch scanning.<\/li>\nFor full-arch scanning, Framework Scanning<\/em> (CERECDoctor.com’s Linear Scanning<\/em>) can produce more reliable results.<\/li>\n<\/ul>\nIn summary, while the quality of the tool matters, it’s equally important to use it properly. If you have any questions, feel free to comment below, or join our discussion over at the Facebook group. We are constantly looking for ways to improve, and would love to hear about your personal experience with any intraoral scanner regarding full-arch accuracy.<\/p>\n
Anyway… what’s up with the 2016 guidelines getting its ass whooped it by an older guideline?<\/p>\n
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<\/p>\n","protected":false},"excerpt":{"rendered":"
A quick study to show that the tool is only as good as the user.<\/p>\n","protected":false},"author":1,"featured_media":1436,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"generate_page_header":"","footnotes":"","_jetpack_memberships_contains_paid_content":false},"categories":[35,37],"tags":[59],"yoast_head":"\n
Not All Scans Are Equal - CEREC Digest<\/title>\n \n \n \n \n \n \n \n \n \n \n \n\t \n\t \n\t \n \n \n \n\t \n\t \n\t \n