Digital Scan vs Traditional Impressions — Which Does Your Orthodontist Use?

What orthodontic models are used for

Before treatment begins, your orthodontist needs accurate three-dimensional records of your teeth and bite. These records serve several purposes: they form the basis of the treatment plan, allow monitoring of progress during treatment, are used by laboratories to fabricate appliances such as retainers and aligners, and provide a legal record of your dental anatomy before treatment started. Historically, plaster models cast from impressions were stored physically for years. Today, digital files serve the same purpose and can be archived, shared with laboratories digitally, and used directly by aligner planning software such as ClinCheck for Invisalign or Dental Monitoring. The quality and accuracy of these records directly affects treatment planning, so the method used matters clinically as well as for patient comfort.

Traditional alginate impressions — the process, pros and cons

Traditional impressions use alginate — a seaweed-derived powder mixed with water to form a thick paste — loaded into a horseshoe-shaped tray that is pressed against the teeth and held in place for two to three minutes while the material sets. The resulting negative impression is then filled with plaster or stone to produce a positive model. The process is straightforward and inexpensive, and the equipment requires no significant investment. However, many patients find it uncomfortable: the material can trigger a gag reflex, the tray can feel large, and the experience of having a setting material in the mouth for several minutes is unpleasant for some. Alginate is also technique-sensitive — bubbles, distortion on removal, or delays between taking the impression and pouring the model can compromise accuracy. Some practices still use polyvinylsiloxane (PVS) impression materials, which are more dimensionally stable but share the same experience drawbacks.

Intraoral digital scanners — how they work, comfort, and accuracy

Intraoral scanners use a small wand fitted with a camera and light source that is moved around the mouth, capturing thousands of images per second. Software stitches these images together in real time to produce a highly accurate three-dimensional digital model visible on screen as the scan proceeds. The process typically takes five to ten minutes per arch for an experienced operator. There is no material in the mouth — just the scanner wand — which eliminates the gag reflex trigger and the sensation of setting material. Accuracy studies consistently show intraoral scanners are equivalent to or superior to alginate impressions for most orthodontic applications, with the added benefit of immediate digital output. The digital file can be sent electronically to aligner manufacturers or laboratories within minutes, avoiding postal delays. Patient satisfaction scores consistently favour digital scanning over traditional impressions.

iTero Element — Invisalign's native scanner

The iTero Element scanner, produced by Align Technology (the maker of Invisalign), is the most widely deployed intraoral scanner in UK orthodontic practices offering clear aligner treatment. It produces the scan files used directly by the ClinCheck treatment planning software, which creates the virtual tooth movement simulation shown to patients before treatment begins. iTero scanners are present in a high proportion of Invisalign Premier and Diamond practices. iTero also offers an Outcome Simulator that allows patients to see a projected result on screen during the records appointment. While iTero can be used for fixed appliance records as well, its native integration with the Invisalign workflow is its primary clinical advantage. The scanner uses structured white light rather than powder, meaning no preparation of the teeth is needed before scanning.

3Shape TRIOS and other systems

3Shape TRIOS is a widely used competitor to iTero, particularly popular in practices that use multiple aligner systems or offer a range of dental treatments beyond orthodontics. TRIOS integrates with multiple aligner brands including SureSmile and SparkAligners, as well as restorative and implant workflows. Other scanners used in UK practices include the Dentsply Primescan, the Carestream CS 3600, and the Medit i700. Each has slightly different ergonomics and software ecosystems, but the clinical output — an accurate digital model — is comparable across systems. The choice of scanner in a practice is typically driven by the aligner brands it works with and the software ecosystem the practice uses for wider digital dentistry. From a patient perspective, the experience across modern intraoral scanners is broadly similar.

Which is better — the evidence on accuracy and patient preference

Systematic reviews comparing intraoral scanners with traditional impressions consistently find that digital scans achieve clinically acceptable accuracy for orthodontic treatment planning and appliance fabrication. For full-arch scanning in orthodontics — as opposed to restorative work requiring sub-millimetre marginal fits — intraoral scanners perform at least as well as alginate impressions, with some studies showing marginal superiority in the anterior segment. Patient preference studies strongly favour digital scanning: reported discomfort and anxiety are significantly lower, and the visual feedback of seeing a 3D model on screen in real time tends to increase engagement. The main practical advantage of traditional impressions is cost — alginate is cheap, the tray is reusable, and no capital investment is required. For practices that have invested in a scanner, digital records also eliminate the cost and delay of model storage and postage.

Useful related pages

This guide is for general information only. It is not a diagnosis, treatment plan, or substitute for advice from a registered dentist or orthodontist.