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.

Accuracy

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.”

Implant Applications

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.”

The ROI

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.

Ceramir Crown & Bridge (Doxa) is a new, unique category of permanent cement that might be the best suited cement available for zirconia. Additionally, it has been shown to chemically form hydroxy apatite on the surface of tooth structure, integrating the cement to the tooth, photo below, hence the description, “bioactive.”

What is Ceramir C&B?

Ceramir C&B is a hybrid composition of Calcium Aluminate and glass ionomer, that when combined with its liquid, undergoes an acid-base reaction similar to hydraulic cements.

The incorporation of the Calcium Aluminate gives it several unique properties that separate it from conventional GIC’s. After 3-4 hours of setting time, Ceramir C&B changes its pH from a very mild acid to a base of pH of ~ 8.5. Mild, lasting alkalinity allows continuous formation of apatite when adjacent to phosphate containing solutions of dentin. Additionally, the alkalinity of its dense matrix fixes the glass ionomer structure to help prevent the ionomer glass from continuously leaking over time. Below, we see hardened hydroxy apatite in the surface of the cement.

Alkalinity also helps with pulpal compatibility. Histological data shows that even at a minimum distance from the pulp, there is virtually no irritation resulting in inflammation.

Ceramir C&B relies on the mode of hydration by its key component, Calcium Aluminate, and the ionic bond of the GIC to bond to the tooth. That means, etching enamel or dentin and using a bonding agent isn’t needed. Moreover, its hydrophilic nature makes the material insensitive to oral fluids, while its alkalinity helps prevent bacterial growth and sensitivity.

According to Johanna Engstrand, et al, Ceramir C&B’s properties are unique. “Zinc phosphates are too acidic and do not contribute with Ca ions. Resin-based materials are not alkaline, and do not show extended ion leakage. Glass ionomers have an ion leakage but are acidic and cannot induce HA formation on its surface.”

Published by the American Ceramic Society, 2010

Author, Hermansonn, et al

“Ceramir C&B has a 2 minute working time, and a setting time of 4-5 minutes. Its film thickness is 15 microns. Its compressive strength at 24 hours is 160 MPa, similar to many resin-based cements, such as Rely x Unicem (157 MPa) but far greater than Rely x Luting’s (96 MPa). However, after one month, the bioactive nature of Ceramir C&B boosts its compressive strength to 200 MPa.”

Unlike RMGIs that expand as much as 4% and then contract, and resin cements that shrink as much as 4% then expand. Ceramir net change is essentially zero: “Expansion of Ceramir C&B is at most, 0.4%, and is due to the free growth of hydrated crystals associated with the formation of apatite. However, bulk expansion, measured as expansion pressure was recorded to be zero.”

Bacteria Resistant and virtually no Microleakage

Ceramir C&B is the only cement with the necessary components to form HA. Zinc phosphates are too acidic and have no free Ca ions. Resins aren’t alkaline and don’t provide ion leakage to the extent required to form HA. RMGI ion leakage is acidic and therefore, can’t initiate HA formation on dentin.

One advantage of Ceramir alkalinity is its antibacterial properties. Secondary caries caused by a wide variety of bacteria is a major concern for all. Jiang, in 2011, conducted a resazurin test on Rely x™ Unicem, Ketac™ Cem Aplicap™ (RMGI), Harvard zinc phosphate, and Ceramir® C&B cements for their antibacterial (S. mutans) properties. After different time periods, up to 10 days, Ceramir C&B with its calcium aluminate showed the strongest antibacterial properties, while the RMGI showed none. The other cements have only slight antibacterial properties. The strong showing of Ceramir is due to its initial pH 5.4 ending at pH 8.5.

Another important attribute of Ceramir C&B cement is a lack of microleakage. Because the process of forming HA creates a nearly insoluble barrier intimately integrated with dentin, Ceramir cement was reported in 2015 by Jefferies, et al, to have only minimal microleakage, and far less than the tested GI and RMGI: “There was no evidence of marginal gap occlusion for the three conventional control cements, whereas both bioactive, surface apatite-forming cements demonstrated occlusion of the artificial marginal gaps.”

The photos, left, described by Jefferies:

“Artificial margin gaps at 8 months of incubation in phosphate buffered saline: upper left photomicrograph is Fuji I (glass ionomer material), ∼110 μm gap; upper right is Rely X Luting Cement (resin-modified glass ionomer), ∼80–100 μm gap; lower left ProRoot MTA (calcium silicate/Portland cement-like hydraulic cement), ∼100 μm gap; and lower right Ceramir Crown & Bridge (calcium aluminate/glass ionomer cement), ∼300 μm gap. Cement material is positioned above the gap space, whereas dentin segment is below the artificial gap.”