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Common digital scanning problems

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.

Scans not in occlusion

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. 

Why is this a problem?

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. 

What should I look out for?

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. 

Tips and Tricks

  1. Before beginning the scan, verify the patients bite so that both you and your patient have a better idea of what this looks and feels like during scanning
  2. To reduce artefacts, only start the scan when the true bite has been captured
  3. Capture as much of the mandible and maxilla as possible - allows more data points for the software to correctly interpret the bite. For this reason, and especially if the patient has a complex bite, it is best to take both buccal views
  4. Trialling different tips – some scanners have the option of changing the tips depending on which view is being captured and the size of the patient's mouth

Missing information (holes in the scan)

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.

Why is this a problem?

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.

What should I look out for?

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.

Tips and Tricks

  1. Practice makes perfect – capturing the correct angles is no easy feat and will only get easier with practice
  2. It’s worth building up a repertoire of different holds and positions as one technique may not be applicable for all cases. Several attempts might be needed and adjusting as you go to achieve the full scan

Inaccuracies caused by excess moisture

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.

Why is this a problem?

Like before, distortions will affect how the aligners fit the teeth and could stop treatment tracking correctly.

What should I look out for?

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

Tips and Tricks

  1. Before taking the scan, look at the patients mouth and ensure there has not been a build-up of saliva. Ask the patient to swallow, isolate the area with cotton rolls and suction fully before beginning
  2. Cotton roll placed in the buccal mucosa should help control moisture
  3. Ensure that the lens of the scanner is also dry and smudge free
  4. Depending on the patient’s tolerance, and if you continue to have problems, try keeping a saliva ejector in place

Not capturing the enough of the gingiva

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.

Why is this a problem?

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.

What should I look out for?

Again, it is important to review the 3D model after scanning. You should be aiming to capture around 1cm of the gingiva.

Tips and Tricks

  1. Ensure that soft tissue is not obscuring the gingiva by retracting the lip and tongue using your fingers and wand
  2. If problems continue, latex free lip and cheek retractors may help isolate and prevent soft tissue concealing the gingiva
  3. Reference the impression simulation during the scan to ensure all information is being captured, redo sections if necessary

How can I check my scans at home?

Visually double checking can be done using your scanners software, but by also using third party web tools such as Exocad webview ( 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.

Final Note

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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