Digital Impressions (Cadent iTero, 3M™ ESPE™ Lava™ Chairside Oral Scanner (C.O.S.) Brontes 3D)

Tens of millions of impressions are taken each year for the production of crowns, bridges, and partial dentures. Dentists seem to be taking a number of these time-consuming, “patient-hating” procedures daily. New systems are now available that create digital impressions of a patient’s teeth, both prepared and unprepared. These systems provide a way to dispense of trays and impression materials. These methods should lead to increased patient satisfaction and their accuracy should create better-fitting crowns and bridges.

The 3M™ ESPE™ Lava™ Chairside Oral Scanner (C.O.S.)is a combination of unique hardware and software with a design based on the research of Professor Doug Hart and Dr. Janos Rohaly, originally at MIT, as well as development during the last three years by Brontes Technologies. Research and development has led to a sophisticated method for capturing images called “Active Wavefront Sampling.” This method enables “3-D Video in Motion” - a breakthrough in image capturing technology in which the system efficiently captures broad anatomy from the mouth.

The Cadent iTero™ system comprises an intraoral scanner, a CAD workstation at the dental lab, and central production support by Cadent. There are no special techniques required since the dentist preps the teeth being restored and attends to normal clinical matters, such as tissue and moisture management. The case proceeds with the dentist or dental assistant completing the digital Rx. iTero then instantly develops a customized scanning sequence for that specific case. Guided by visual and audible prompts, the dentist - or more often the assistant - proceeds through the scanning sequence. During this time, the system stitches together the scans of the target area, the adjacent teeth, and the bite into a real-time digital model. This magnified digital model is presented on a flat panel display along with real-time analytical tools, which bring attention to areas that may need adjustment - for example, occlusal clearance. All of this occurs in just three to four minutes. Adjustments may be made and additional scans taken after which the digital file is transmitted to a participating dental lab. The lab completes the computer-aided design (CAD) and uploads that design to Cadent. The models, removable dies, and copings - if requested - then are produced at Cadent’s production center in New Jersey and delivered to the dental lab for completion of the restoration.

Brontes Technologies offers dentists and laboratories a technology that would enable a range of restorations that a user could prescribe, both conventional and CAD/CAM. The unique technology used in the 3M ESPE imaging device allows the user to move freely throughout the mouth capturing data of all surfaces of the dentition and tissue. This eliminates the potential inaccuracies caused by the extrapolation of data.

iTero does not feature an in-practice milling system. So the capital expense with iTero is modest without any limitations on either restorative materials or clinical indications. As such, iTero can serve as a digital front end to any type of restorative system - conventional or CAD/CAM. This includes the current standard of care, porcelain fused to metal. Cadent is positioning iTero as open architecture. This means the digital file also can be sent to in-lab CAM systems, too.

When it comes to investigating digital impression technologies such as cadent iTero or 3M™ ESPE™ Lava™ Chairside Oral Scanner (C.O.S.) clinicians will encounter terms like confocal, triangulation, reflective coatings, stereolithographics, and active wavefront sampling. Simple definitions of terms that clinicians soon will be seeing:

The imaging technology used in the 3M™ ESPE™ Lava™ Chairside Oral Scanner (C.O.S.) is Active Wavefront Sampling (AWS). AWS is a new technique for capturing three-dimensional data that enables a 3-D video in motion approach to scanning. This technology was born from research done at MIT. Unlike triangulation and laser methodologies, AWS does not rely on the warping of a laser or light pattern on an object to determine 3-D data. These more traditional 3-D methods suffer from distortion, optical illusion, and are comparatively slow. AWS allows a user to capture 3-D data in a video sequence and model this data in real time. It is highly accurate and extremely fast.

The imaging technolology used in the Cadent iTero is not based on triangulation while also being telecentric. As a result, no reflective coating is required. The probe can be placed directly on the surface. This promotes ease of use and patient comfort. The parallel confocal design also promotes exceptional accuracy. The iTero system expands upon this concept by simultaneously projecting 100,000 beams of parallel red light rays with each individual scan.

- Triangulation: The majority of optical scanning systems are based on some form of triangulation. There are three common elements to all such systems: (1) a light source that (2) illuminates the object, which is positioned at an angle to (3) a detector. This triangulation of light leads to compromised accuracy when scanning two types of surfaces:

- Curved surfaces because the angle of reflection reduces the viewing area
- Surfaces that do not reflect light evenly, such as natural dentition vs. amalgam

To cope with this second problem, systems based upon triangulation require dental surfaces to be coated with an opaque, reflective coating. An uneven coating or environmental changes during scanning - such as saliva, contact with scanner probe or the tongue - might further compromise the accuracy of these systems.

- Parallel confocal: Confocal is a principle by which light is filtered by passing it through a small pinhole. Only the light reflected from the object at the proper focal distance will pass through the pinhole. Therefore, only those rays that are in focus will return through the filtering device.

- Telecentric: A telecentric system maintains the same field of view, the area being scanned, regardless of distance from the object that is being imaged. As a result, there is no need to compensate for different levels of magnification and no need for the user to hover above the object.

- Steriolithography: The digital files from these systems are transmitted into CAD systems, then to various CAM production systems. Steriolithography is just one of many additive CAM approaches that build up materials. On the other hand, milling-based CAM systems are subtractive in nature.