Digital impressions with an intraoral scanner: how they work and what they are for

Digital impressions in a nutshell

A digital impression is a three-dimensional copy of your teeth and gums, recorded with a small camera that the dentist moves around your mouth: the intraoral scanner. In most situations it replaces the tray filled with putty that you had to hold in your mouth for several minutes. The model appears on screen straight away and is then used to design a crown, an inlay, a veneer, a splint or a treatment plan.

For patients, the difference usually comes down to this: no taste of putty, less gagging, and the chance to see your own teeth on screen while the dentist explains what they are looking at.

How an intraoral scanner works

The scanner tip shines light onto the teeth and captures thousands of images of small areas at high speed. Software stitches these images together in real time into one continuous 3D surface, much like the pieces of a panoramic photo. Depending on the model, the technology uses structured light or confocal imaging, but for you the principle is the same: no X-rays are involved, only visible light.

A typical scan goes like this:

• the area is dried and, if needed, the gum is gently retracted around the prepared tooth;
• the dentist scans the upper arch, then the lower arch, tooth by tooth;
• you close in your normal bite so the scanner can record your occlusion, in other words how your teeth meet;
• the software flags any missing areas, which are filled in within seconds without starting again.

The final file, often in STL format, can be worked on in the practice or sent to the dental laboratory.

Some scanners also offer an indicative shade reading. The final choice of colour is still made by eye, in daylight, often supported by photographs sent to the technician. For a prepared tooth, the dentist above all checks that the margin between the tooth and the future crown is perfectly clear on the model, because that margin determines how well the restoration will fit.

Is it as accurate as a conventional impression?

This is the most common question, and the answer is nuanced. For single restorations (a crown, an inlay, a veneer) and short bridges, published comparative studies show accuracy similar to the best conventional impressions. For a full arch, especially on several implants, stitching images over a long distance remains more demanding, and accuracy depends more on the device, the software and the scanning strategy.

Some conditions make recording harder whatever the method:

• a preparation margin placed deep below the gum;
• bleeding or a lot of saliva in the area;
• limited mouth opening;
• very shiny or reflective surfaces.

In these cases the dentist prepares the area carefully, or occasionally chooses a conventional impression. One often overlooked advantage: the scan is checked on screen before you leave, whereas a putty impression sometimes reveals its flaws only once it reaches the laboratory.

What digital impressions are used for

The intraoral scanner is part of many treatments:

• Fixed restorations: crowns, inlays and onlays, bridges, veneers. The digital model feeds directly into computer-aided design.
• Implant dentistry: a small locating cylinder screwed onto the implant (a scan body) records the exact implant position so the crown can be made. Scans are also used to plan guided surgery.
• Clear aligner orthodontics: the starting position of the teeth is the basis for the simulation and for making the aligners.
• Splints and trays: night guards for grinding, retainers after orthodontics, whitening trays.
• Monitoring: two scans taken months apart can be superimposed to track wear, tooth movement or changes in the gums.

Scans are also a great teaching tool: seeing your cracked tooth magnified on screen often makes it much easier to understand why a treatment is being recommended.

Benefits and limits, without the hype

The real benefits for patients:

• Comfort: no putty, no bulky tray, and you can pause at any time.
• Fewer retakes: a poorly captured area is simply rescanned on the spot.
• A faster workflow: the file travels without courier and without any risk of a plaster model distorting.
• Records: the model is kept and can serve as a reference if a splint breaks or is lost.

The limits worth knowing:

• the scanner only sees surfaces: it does not replace a clinical examination or an X-ray, which shows the inside of the teeth and the bone;
• some situations (very deep margins, long spans on implants, complete removable dentures for people without teeth) may still call for a conventional or combined technique;
• the final quality depends as much on the tooth preparation and the team's skill as on the machine itself.

A word on hygiene: there is no impression tray or plaster model to disinfect and transport, and the scanner tip is disinfected or replaced between patients.

In short, digital workflows improve the experience and the reliability of the process, but the scanner remains a tool that serves a diagnosis.

Preparing for a scan and questions to ask

No special preparation is needed. Brushing before your appointment makes scanning easier, and it helps to mention painful mouth opening or a strong gag reflex. Because the tip is slim, most sensitive patients cope well, especially with short breaks.

Children and teenagers, for example before clear aligner treatment, usually accept a scan far more easily than putty, which makes the first step of treatment calmer.

Useful questions to ask your dentist:

• Will the scan be used to make the restoration in the practice or in a laboratory?
• Does my situation (a margin under the gum, several implants) allow a fully digital impression?
• Can I see the model and the area to be treated on screen?
• Is the file kept for future follow-up?

To learn more about materials for your future tooth, read our article on dental crowns, steps and materials, or find out how a ceramic crown can be made in a single visit.

Digital impressions at German Dental Clinic in Agdal

Dr Fenjero Walid's practice, on the corner of avenue de France and avenue Ibn Sina, uses an intraoral scanner for crown and bridge, implant and aligner impressions. Combined with the in-house milling unit (CAD/CAM), it allows certain restorations to be designed and made on site when the situation is suitable.

During the consultation, the dentist examines your teeth, takes an X-ray if needed, and then shows you on screen what the scan reveals and which options are open to you. If you live in Rabat and dread traditional impressions, you can book an appointment to talk it through.