Traditional impression materials have served dentists and their patients quite well for decades. Does it make sense to replace the goop with microchips? Is the new technology better? Will the added expense be more cost effective in managing the continued pressure on dental fees?
Manufacturers and distributors all believe intraoral scanners should be in every practice. Of course, that’s their job. But dentists who have adopted the technology are universally pleased, reporting better accuracy, faster seat times, and in some cases, lower lab fees. But, let’s be clear. Those are subjective opinions. Below are some of the facts about intra oral scanners and their advantages.
One way to measure the advantages is accuracy. Intraoral scanning is consistently better when it comes to accuracy than are impression materials. That is not because PVS and poly ether aren’t good materials. They are. It is because intraoral scans are more consistently accurate in quadrants by eliminating the variables inherent to traditional impressions. Using strict research protocol, good impression materials provide errors of about 35 microns. In contrast, Pradies et al, reported scan results in 2015, showing “an average error of 18 – 30 μm for a single tooth and less than 40 to 60 μm error measured over the restoration and neighboring teeth and pontic areas, up to 7 units.” They also found that for a 4 unit bridge, the length error was less than 100 microns. However, accuracy declines when scanning a full arch. Testing showed that mean error for a full arch was 100 – 140 μm, indicating a good measure of unreliability.
There are many intraoral scanners to choose from. Deciding on which one might be as simple as feel, newly updated advances, ease of use, or ancillary costs. However, based on research, accuracy shouldn’t be a differential in most cases. Researchers at the University of Ohio tested three intra-oral scanners, 3M LAVA True Definition, 3Shape Trios and Cadent iTero, found similar accuracy, and showed that “digital intra-oral scanner impressions can be used for fabricating accurate short-span screw retained implant supported fixed dental prosthesis with a misfit range of 12.40 to 90.20 m.”
Dental implant restorative is a growth area for dentistry minimally impacted by dental insurance. Intraoral scanners have become increasingly useful for implant diagnosis as planning becomes more digitized. In Lee et al’s report from 2015, 36 patients had a single missing molar replaced with an implant. “Of the 36 patients, 6 required contact adjustments, 7 required occlusal adjustments, and 3 required a gingivectomy around the implant to completely seat the restoration. Chair time for adjustments did not exceed 15 minutes.” Clearly, IOS and accompanying implant related technology [in the lab setting] provide better accuracy than building cases on stone models, plaster mountings, and resin-based adjuncts.
Tracking and Managing Occlusion
Another, but rather unexplored advantage of intraoral scanning technology is tracking and managing patient occlusion. In 2014, Meireles et al, looked into occlusal wear tracking: “Eight extracted teeth were etched with acid for different times to produce wear and scanned with an intra-oral optical scanner. Computer vision algorithms were used for alignment and comparison among models…Results demonstrated that it is possible to directly detect sub millimeter differences in teeth surfaces with an automated method with results similar to those obtained by direct visual inspection.”
One thing to keep in mind is, chair time is expensive. If IOS can cut chair time and the cost of traditional impression materials, the investment might be worthwhile. However, there is a balance to consider because not all situations easily lend themselves to the current state of the art. Some clinicians have acquired lasers to help control the challenges gingival tissue presents.
As with all things, when considering an intra oral scanner, we need to avoid biases, do our homework, and keep an open mind.