A Review of Intraoral Scanning Technology

To understand clinical digital dentistry, one needs to understand how the technology works to build an accurate intraoral impression. There are many different non-contact optical acquisition technologies used by different IOS handheld cameras to produce precise 3-dimensional renderings of a patient's oral soft and hard tissues. Confocal microscopy is used by TRIOS^® 3 (3Shape; 3shape.com) and iTero^® (Align Technology; aligntech.com). TRIOS uses confocal microscopy and ultrafast optical scanning, and iTero uses laser light beams based on parallel confocal principles.^1,2 The Medit i500 Scanner (Medit Corp; medit.com) works based on 3D video technology, as does the True Definition Scanner^® (Midmark; midmark.com), which is a structured light scanner that uses pulsating visible blue light and the principle of active wavefront sampling, a 3D video technology.¹ The CS3600 (Carestream Dental; carestream.com) is an LED light scanner that also uses the principles of active speed 3D video. The Planmeca Emerald^™ (Planmeca USA; planmeca.com) uses a multicolor laser-based system. The Primescan (Dentsply Sirona; dentsplysirona.com) uses a Smart Pixel Sensor that processes more than 1 million 3D data points per second. GC America Inc., Straumann, 3DISC, and densys3D also have scanners on the market. Regardless of the specific acquisition technology used, all IOS scanner heads project light to record individual images or video that is then processed by software to identify points of interest (POIs) and render the 3D impression.³ Specifically, software algorithms define POIs, identify coincident POIs on different images, and stitch them together to generate the digital intraoral impression.³ The scan data is then processed and optimized to reduce file size while increasing detail and resolution in key areas previously indicated to the software as important. With open systems, the scan data can be easily exported as an STL file, while a closed-system IOS requires the scan to be used only within the manufacturer's proprietary CAD/CAM workflow.

A number of considerations come to mind when deciding which IOS is right for a specific practice or laboratory. The cost and return on investment are probably the most critical considerations for any business looking to get into digital dentistry. This is well understood by companies that have introduced lower-cost intraoral scanners to the market to make the adoption of this technology more palatable. Software capabilities must also be weighed because they determine how intuitive the scanning process is and how steep the learning curve is. The software also determines what workflows and treatments can be performed with a particular IOS. For example, same-day restorative solutions are capable when using the CEREC Primescan, TRIOS, and Planmeca Emerald scanners, whereas Invisalign proposals and treatments are streamlined with the iTero 2D scanner. Similarly, Primescan offers the possibility of capturing edentulous mucosa or soft tissue quickly and accurately, giving this IOS the potential to move into the denture space.⁴ Another factor larger offices may want to consider is if the IOS software allows for a client/server relationship, which is important as it permits the sharing of digital scans and cases throughout the entire office environment. Also critical is the accuracy of the resulting scans. One independent study evaluated six scanners and found that each produced clinically acceptable levels of accuracy for single-tooth scanning.⁵

Hardware should also be contemplated when evaluating an IOS. Specifically, some are more mobile than others, with cart design options that allow for easy transport between operatories, and there is at least one wireless solution. Almost all IOSs offer touchscreen capabilities with their cart options, and the need for powdering the teeth has been eliminated from most. When comparing IOS wands, some are much larger and heavier, while others have either a pen or pistol grip. Additionally, some IOSs, like the CS3600 and Planmeca Emerald S, have tips of varying sizes to allow for capture of harder-to-reach areas, like the distal of second molars. Among the hot, new innovations in intraoral scanning at the 2019 International Dental Show in Cologne, Germany, was the announcement of fluorescent scanning capabilities to aid in the diagnosis of caries with the iTero Element 5D and TRIOS 4 scanners. Another great introduction to aid in the detection of caries and cracks in their early stages is near-infrared imaging with the iTero Element 5D and Planmeca Emerald S and infrared transillumination with the TRIOS 4. These new features not only aid in monitoring patients but also serve as communication tools to visually demonstrate to patients which areas need to be watched and which need immediate treatment.

Dentists who have integrated intraoral scanning into everyday practice understand the tremendous benefits of digitizing their patients. Scanning every patient at recall visits and obtaining full-arch scans instead of shortened quadrant impressions help to build a digital patient library that can be observed over time and aid in restorations or the diagnosis of progressive diseases. It also provides valuable reference data for future treatment. For example, if a patient has a traumatic incident and loses tooth No. 9, previously captured digital records can be referenced to the laboratory to produce a seamless immediate provisional implant restoration.

However, if the goal is to digitize every patient, it is crucial to understand that this is sometimes achieved more predictably, accurately, and efficiently by capturing a conventional impression that the laboratory can scan. Understanding the limitations and challenges of intraoral scanning helps dentists recognize when a conventional impression may be preferred. For instance, an IOS can be used to produce a very well fitting distal extension RPD framework, which can in turn be used in a properly border-molded conventional impression to make an altered cast to process the final restoration.

An open-system IOS offers flexibility and freedom in digital workflows by offering customizable methods for offices and laboratories to coordinate and collaborate. For example, a restorative dentist with an IOS could obtain the surface scan and CBCT data needed for implant surgical planning; once the plan is approved, the laboratory could design the surgical guide and send the file directly to the surgeon or restorative dentist's 3D printer for in-office manufacture. Open-system intraoral scanning also allows the dentist to work with a design center; the same-day restorative workflow is streamlined by delegating the design portion to a technician, allowing the dentist more time to see patients. A laboratory could further aid with the IOS workflow by using desktop-sharing software in real time to evaluate a digital scan for completeness with the dentist prior to a patient being dismissed. Final digital scans could then be sent to the laboratory via a cloud-based portal for easy transfer and seamless collaboration. Advancements with these submission portals even allow some systems to send scans to the patient so they can take their unique office experience home with them to share with family and friends or even on social media.

As existing dental practices come to grips with the permanency of digital dentistry and new dental school graduates are trained in entirely digital environments, the adoption rates for IOS are sure to be at an inflection point. Future developments will focus on integration with artificial intelligence to make IOS more intuitive and accurate, further opening the door to all those looking to go digital.

Barbara and Alan Jurim receive financial reimbursement as consultants for 3Shape, Inc.

Barbara Jurim, DDS, and Alan Jurim, DDS, operate a private practice, integratedDENTAL, in Woodbury, New York.