Digital dentistry has come with its fair share of benefits – faster workflows, better comfort for the patient and moving away from impressions that are time consuming and prone to error. Although digital impressions solve a lot of the problems caused by conventional impressions, they bring their own complexities. Here we’ll outline the main problems and some tips to avoid them.
Digital impressions, include 3-4 main scans – upper arch, lower arch and either/both buccal views. Buccal scans are most prone to error simply due to working with a tighter space. Automatic alignment can be unsuccessful due to artefacts from the cheek, the patient having an abnormal bite or no distinctive shapes on the buccal side for the software to interpret the bite correctly.
Using scans with an incorrect occlusion at the beginning means there is no guarantee of how the bite will develop throughout treatment, which could result in unstable outcomes.
The error can be extremely obvious, and the patient may end up with what looks like a false overjet or class 2/3 malocclusion. The error can also be more subtle with the contact points only being slightly off. The best way to identify if the occlusion is off is by visually analysing the 3D simulation and verifying the contact points and intercuspation match that of the patients. Most scanners will allow you to manually adjust the scans which could prevent needing to rescan.
This happens when during scanning, not all of the dentition is captured which results in ‘holes’. Sometimes, it can be difficult to capture all the angles of the patient's mouth. Especially if the patient has considerable overcrowding or gaps between the teeth which may require a bit of playing around with angles and lighting to achieve a complete impression.
Although the design lab can try and fix the scans, there is no guarantee that they will be identical to the patient’s actual dentition. This can affect how the aligners sit in the patients mouth which could impact on how the teeth track.
The best way to check that the scans is by reviewing the 3D model during and after scanning. Some scanners will have scan verification processes built into their software that will flag any missing information. Although this is extremely useful, it isn’t 100% reliable and should not replace visually checking. It will also allow you to retake the scan if necessary while the patient is chair side.
These errors can be slightly harder to spot than the previous case of holes in the scans. Excess moisture from saliva and other fluids will cause reflections that the scanner is unable to identify which results in distortions.
Like before, distortions will affect how the aligners fit the teeth and could stop treatment tracking correctly.
Distortions caused by excess moisture will look like a build-up of material that isn’t there in real life. It can be an error in only one tooth but can also span across multiple with ranging severity
Equal attention should be given to the surrounding gingiva as capturing the teeth. This can be extremely tricky if the cheeks have not been retracted properly and made even more difficult if the patient has a small mouth.
Missing gingival information could have implications on the specialist’s ability to create the treatment plan. We also recommend that the trimline for aligners is straight and 2mm above the gingival zenith which is 4x more retentive than having a scalloped cut around the margin. The cut is dependent on there being enough gingiva captured.
Again, it is important to review the 3D model after scanning. You should be aiming to capture around 1cm of the gingiva.
Visually double checking can be done using your scanners software, but by also using third party web tools such as Exocad webview (https://webview.dental/). It is linked in your portal so scans can be visualised one last time before completing a submission. However, it would be best to pick up any anomalies during the scan to prevent a second trip for your patient.
The main delays we see in receiving treatment plans is due to new scans being required. It’s always worth double checking each scan prior to submitting in the same way as it is useful to review a study model.
We hope this information helps you identify problems, but if you do continue to struggle, remember that your scanner manufacturer will likely have many resources and in-depth user training if you require further assistance as well as dedicated personnel that can provide one to one instruction.
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