Straight Up

Nov. 1, 2011
Invisalign has been around for years. Many doctors embraced it as a method to perform full orthodontic treatment using clear aligners ...

Paul Feuerstein, DMD

For more on this topic, go to and search using the following key words: impressions, clear aligners, orthodontics, stereolithography, Dr. Paul Feuerstein.

Invisalign has been around for years. Many doctors embraced it as a method to perform full orthodontic treatment using clear aligners instead of traditional brackets and wires. After basic training, it was possible to perform many cases in the GP office that were often referred to orthodontic specialists.

More complex cases required additional training, but the ease of merely changing aligners every few weeks was much simpler than bonding on a mouthful of brackets and changing wires many times during treatment. As simple as it sounds, there is more to this than taking a few impressions, sending them to Align, and getting a box of aligners.

With the new technology, the impressions are scanned and the models are created on the computer screen. All of the treatment step models are set up on the screen, and the individual aligners are then “printed” using stereolithography.

Since this is all digital, the turnaround times are greatly reduced. The ClinCheck can be returned to the office in 48 hours or less. All the aligners can actually be “printed” at the same time.

Align has continued to streamline and improve the process and increase the accuracy and fit of aligners. The company realized that, although VPS or PVS impressions were accurate, the detail of areas such as interproximal contours was not as great as hoped. This is critical, especially in the areas of the aligners that are used for rotation or precise tipping.

Most of these impressions are taken with “tray body” material, and the lighter wash used in traditional crown and bridge was not really practical — either as a full impression (too runny) or syringed directly on the teeth just prior to the full arch impression.

The advent of digital impressions intrigued Align. The company looked at many of the systems in the marketplace and realized a bonanza with Cadent. Earlier this year, Align acquired the company.

Not only did Cadent have a simple impression system, iTero — which could easily take full-arch impressions — it also did a formidable palatal soft-tissue copy. At this time, since no powder is necessary, soft-tissue images are quite possible.

Also, Cadent has been in the orthodontic business for many years with its OrthoCAD product. For years, orthodontists have used this system to allow use of digital impressions for case design and unlimited storage of old models. Of course, these are just files, and are easily retrievable.

The other feature of OrthoCAD is the ability to treatment plan a case on the computer screen and set up the exact positions of brackets. The computer generates a tray that holds the brackets in place for precise and easy placement by using current bonding systems.

At this time, the accuracy of digital impressions is excellent and rivals the traditional impressions used, especially in crown and bridge. Quadrant impressions can take as little as two minutes for upper, lower, and bite in many of the systems.

Orthodontics requires full upper and lower and, as mentioned, soft tissue. Although all of the digital systems can create these, most are done in small sections and ultimately “stitched” together for the full arches.

Success is due to the systems and to patient cooperation. The key is allowing the operator to start and stop without losing accuracy.

This can present an issue in the systems that use powder since areas have to be resprayed if a patient closes and swallows between steps. This is certainly not an obstacle but must be considered (at least now) with the current systems.

With OrthoCAD, a full upper and lower arch scan takes more than 10 minutes. The starting and stopping at will, though, makes it easier for patients.

There are other “simple” orthodontic systems in the marketplace, some using clear mouthpieces (ClearCorrect and DENTSPLY Essix) with varying amounts of computer intervention.

Others, such as Six Month Smiles, use traditional bracket and wires but have developed easy diagnostic and delivery systems. Dentists should look at all options and, as many have done, use several techniques for different situations. Check out the CE offerings of all, and do your homework.

Dr. Paul Feuerstein installed one of dentistry’s first computers in 1978. For more than 20 years, he has taught technology courses. A general practitioner in North Billerica, Mass., since 1973, Dr. Feuerstein maintains a website ( and can be reached at [email protected].

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