How to master intra-oral scanning

Dr Ahmad al-Hassiny

Wed. 6. December 2023

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Intra-oral scanning has taken the dental industry by storm. Over the past decade, we have watched traditional impression taking become completely disrupted by technology. It is well established both in the literature and by countless anecdotes by dentists worldwide that intra-oral scanning provides many benefits compared with taking a physical impression.^1,2 This includes offering better efficiency and comfort for the patient, being faster to carry out than traditional methods and being as accurate if not more accurate than physical impressions.^3–5

Fig. 2: An example of a clean and dry crown preparation with the gingiva retracted sufficiently ready for scanning.

The question now is not a matter of whether a clinic should digitise but when and—more importantly—how. We have seen the industry grow significantly over the past five years. Now, there are over 15 intra-oral scanners on the market. It can be difficult for clinicians to decide on an intra-oral scanner in the first place, but once they finally take the plunge and purchase one, they may not know how to use it.

Some distributors provide excellent training, while others will simply send the scanner to you and that is it.⁶ You are left to figure out the rest for yourself. Just like any new method or technology, there is undoubtedly required training for and practice using an intra-oral scanner. Although there are countless benefits of digitising, it is necessary to realise and appreciate that you need to train yourself on how to use the device proficiently. Thankfully, these days, it is much simpler to learn how to use an intra-oral scanner. Software employing artificial intelligence (AI) helps bridge the gap between new and experienced users, and generally, in my experience of training thousands of dentists on how to use these devices, it should not take more than a month of training to become confident in most day-to-day scanning indications.

In saying that, I have seen countless instances of dentists not using scanners correctly, because of either poor understanding of the technology or a lack of training. In this article, I will share some of my tips on how to become proficient in intra-oral scanning based on my personal experience in training dentists on how to take full-arch dentate scans easily within 45 seconds. My personal best is 18 seconds. This is doable for everyone reading; it is just a matter of training and practice. Intra-oral scanning will be the best thing that ever happened to your practice once you become confident in it. You will never look back.

The first piece of advice may be self-evident, but is important to mention. Scanners come in two forms, either carts (with built-in PCs), such as CEREC, 3Shape TRIOS MOVE and iTero, or scanners that are used with third party PCs or laptops that are either supplied by the distributor or purchased by the clinician separately (Fig. 1). This is the more common type of scanner configuration and includes 3Shape TRIOS, Medit scanners, Virtuo Vivo and almost every Chinese-made scanner.

Table 1

Fig. 3: An example of scanning a patient. Note that both my dental assistant and I are retracting the cheeks.

It is crucial to make sure that the computer you use with your scanner not just meets but exceeds the minimum requirements for the scanner of your choice (Table 1). If the computer is not powerful enough, you will have a buggy, laggy and generally frustrating experience with your scanner. Expect to spend anywhere between US$3,000 and US$5,000 on a good enough laptop, or ensure that your distributor is supplying you with one that is excellent.

The next piece of advice is to ensure proper fluid and soft-tissue control. Clinicians need to understand that intra-oral scanners are basically cameras. They project light in different forms, and this is reflected off the oral tissue and captured by a sensor. Based on this principle, therefore, if we are trying to accurately capture the teeth or gingiva, we need to ensure three main things: that there is nothing in the way, such as the tongue, lips or cheeks; that the area is sufficiently dry and clean, meaning that there is no blood or pools of saliva that will impact the light projection (Fig. 2); and that the tissue does not move when capturing. The last point mainly applies to edentulous scanning, which is part of the reason that this is much more difficult than scanning teeth.

The easiest way to achieve all of these things for a crown preparation scan, for example, is to simply look through your mirror at your preparation before scanning. If there is any bleeding or any crevicular fluid seeping, this needs to be controlled. If there is gingiva that is slumped over the margin, this needs to be controlled. In general in my practice, I routinely use retraction cord every time I scan, as it allows me to control all these factors with one technique. You can use any gingival retraction technique you like, as we all practise differently, but you must use retraction if scanning equigingival or subgingival preparations. It is vital to make sure that all soft tissue is controlled properly before scanning. Although your laboratory may accept the scans and produce the work, without proper gingival retraction, scans will not be accurate, especially around margins.

You must control the soft tissue too. Retraction is imperative. Most of us work with a dental assistant, so train your assistant to retract the soft tissue properly when you are scanning. I use my finger or mirror to retract the cheeks. My dental assistant also retracts the tongue and cheeks while we move across the arch (Fig. 3). If your scanner keeps starting and stopping, commonly it is because the scan keeps being interrupted by the cheeks or lips as they slump over the teeth. Proper retraction will no doubt make your scans much more efficient.

“The question now is not a matter of whether a clinic should digitise but when and—more importantly—how.”

The next tip concerns how you actually scan. How to hold an intra-oral scanner properly is something that is overlooked, and all clinicians seem to do it slightly differently. Generally, scanners are held in a pen grip and the index finger is over the scanner button to be able to start and stop the scanner within the mouth (Fig. 4). One basic tip is to never start scanning before moving the scanner into the mouth and having it in position. The reason for this is simple: once you press the scanning button, the software will immediately start capturing images, so if you start this process outside the mouth and then move into position, you will likely capture an artefact like the lips as you move into position.

The next tip is scanning strategy. A scanning strategy refers to how you move the scanner around the mouth to take a scan. The pathway is almost always the same when followed properly. Although AI software makes it easier to take a full-arch scan and is more forgiving, following a scanning strategy still has multiple benefits, including ensuring high accuracy and efficiency. Current literature shows that full-arch dental impressions can have extremely high accuracy if adequate scanning strategies are used.⁷ The typical scanning strategy is as follows: starting on the occlusal surface of the terminal molar and moving across the occlusal surfaces to the opposite side (Fig. 5).

Fig. 4: How to hold an intra-oral scanner in a pen grip.

Fig. 5: Standard scanning strategy when using an intra-oral scanner to take a full-arch scan.

Fig. 6: An example of double images at the incisal edges.

“Current literature shows that full-arch dental impressions can have extremely high accuracy if adequate scanning strategies are used.”

A vital piece of advice is to tilt the scanner facially while moving across the incisors to ensure that you capture the incisal edges in their entirety to prevent double images and inaccuracies in this part of the scan (Fig. 6). Once on the occlusal surface of the opposite molar, you simply tilt your scanner lingually/palatally and then continue to capture the tooth surfaces, moving back to the original point you started at, finally tilting over to the facial surface and capturing the last remaining data. When using most intra-oral scanners, it is not critical whether you capture facial or lingual/palatal surfaces after carrying out the occlusal aspect scan of a full-arch scan strategy. Rather a smooth and steady motion is much more important.

Carrying out this scanning strategy requires practice and muscle memory. There are no shortcuts. At first you will feel uncomfortable and likely lose your spot many times. With time and repetition, you will be able to do this without looking into the mouth, but rather watching the computer screen to see exactly what you are capturing. Once you feel confident with intra-oral scanning, you should be able to take a full-arch scan easily within 45 seconds. I highly recommend to all clinicians to practise as much as possible when they first acquire a scanner. Practise on models, your staff or even your spouse. You will not get better at intra-oral scanning by keeping the scanner in a cupboard.

In summary, these are some of the tricks and tips I teach our associates and the thousands of dentists we train at the Institute of Digital Dentistry, both in our live courses and online. We also have an entire library of online content in which I demonstrate these tips and tricks which you can find on the institute’s website.

The first step to becoming proficient in scanning is to accept that this is the best way to take an impression. If you do not believe in the technology, you will not bother learning it. Digital dentistry is the future of dentistry, and you do not want to fall behind. It does take practice, and learning to use a scanner can be frustrating at times, but with perseverance, there is no doubt that you will be fully confident in taking scans within a few weeks of proper training and practice.

Editorial note:

This article was published in digital—international magazine of digital dentistry vol. 4, issue 3/2023. The list of references can be found here.