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Dentistry is truly a great profession for those of us who love gadgets, technological advances and dreaming of the possibilities of future developments.
A little over two years ago, my good friend and lab man brought to my attention the technology of digital impressions. We looked at Sirona’s CEREC, Schein's D4D and the iTero by Cadent. We eventually decided to purchase the iTero system. This article will discuss the cost comparison of conventional impressions to that of digital impressions using the Cadent iTero system, which I have been using since January 2007.
Learning Curve
If you’ve used an intraoral camera, the learning curve for using the iTero scanner is practically non-existent (Figs. 1a and 1b). After one or two patients, you've got it. Otherwise by the end of the second day of training, you are ready to solo. The only change thereafter is your speed. Your first couple will take 10-15 minutes, the next few may take you 8-10 minutes. And the time just continues to fall from there. Within a few weeks, you should be able to scan an upper and lower quadrant in less than 5 minutes. And incidentally, all opposing arches are taken by my staff at the beginning of the appointment while I do exams.
Time. Accuracy. Efficiency. If I had to put the benefits of using the iTero digital impressioning system in a nutshell, that would be it. And here’s the deep dive....
Figure 1a: If you’ve used an intraoral camera, the
learning curve is practically non-existent. |
Figure 1b: During active scanning, the area
being scanned appears on the monitor. |
Savings
I have studied this a lot, and if you're looking for big savings in disposable goods, you won't find it. The real saving comes in time. We have cut our crown prep appointments from 90 minutes to 70, and the cementation appointment has decreased from 40 minutes to 10. Crowns are routinely cemented in 10 minutes. (Incidentally, we have kept this a 40-minute appointment and we use the extra time for emergencies and to catch up if we're running behind.) I have outlined a typical scenario: see Digital Impression Workflow.
Accuracy means a better fit
My remake percentage was 2-3%--already low according to my lab. But since taking my impressions digitally with iTero, it has dropped to 0.36%. We have had a couple of remakes due to poor shade choice or other esthetic problems, but not for poor fit.
When conventional impressions are taken and models are poured, there is expansion and contraction of the materials. Because iTero models are milled from a block of polyurethane, these distortions (discrepancies) are eliminated. The dies are milled to fit into a solid model, giving a more accurate representation of our patient and eliminating sectioned and pinned models used with stone.
I have also noticed greater marginal integrity -- the die margins remain intact during the waxing process (Fig. 2) because the urethane is much harder than the stone and does not scrape away. This also eliminates breakage from accidental dropping of models.
With conventional impression systems, moisture control and air bubbles in the final models are a factor. When scanning, 5-10 seconds of isolation is all that is needed. Bubbles or distortions are eliminated with milled models.
Figure 2: The die margins on the iTero milled
models remain intact for accurate waxing. |
Productivity
With digital impressions, room turnover is much quicker because staff do not have to clean up impression guns and the associated mess or the lab work required with conventional impressions (such as lab slips, opposing models, bite registrations, and packaging for delivery to the lab.
ROI
I have established a production goal in my practice of $500.00/hour ($8.33/min). Last year, I produced 550 units of crown and bridge (Fig. 3). If iTero only saved me five minutes per crown, that is 2,750 minutes in a year. And 2750 x $8.33= $22,907.50—so iTero has paid for itself in one year. And this doesn't take into account the good “press” I receive from patients because they see us as a progressive, state-of-the-art practice. That 2,750 minutes is 45.8 hours that can be used to do more dentistry or to take off as another vacation. The choice is yours.
Figure 3: Digital impressioning is suitable
for multiple-unit, multi-restoration cases. |
Toss the goop?
Have I eliminated impression material for standard indirect restorative cases? Yes. Today I used iTero for a crown on a third molar. I don't normally do 3rd molar crowns, but this patient did not want to lose any of her teeth. She has a very difficult tongue to work around and just average opening. I can use the scanner to push the tongue out of the way and I only have to maintain this position for 10-15 seconds max.
Any contraindications? I cannot use iTero for crowns that fit existing partials or for implants at the fixture level. If you normally take impressions of the implant abutment, you can scan it. Again, I still take conventional impressions of impression posts because I prefer fixture level impressions. iTero has said they feel we will be able to do fixture level scans within the year. I'm keeping my fingers crossed.
Digital Impression Workflow
Let’s compare the standard procedure followed for both conventional impressions and digital impressions.
For conventional impressions, anesthetic is given and then the assistant takes alginate impressions of both arches for the opposing model and construction of the temporary. She then pours the opposing model.
With iTero, an electronic lab prescription is filled out that includes patients name, doctors name and the lab to be used, due date, preparation margin design, type of restoration to be completed and restoration shade. For veneer or esthetic restorations a stump shade must also be given, and taken completed before scanning can be done; this ensures that the lab receives all the necessary information to avoid delays. This also solves the problem of forgetting to get a shade or what usually happens--absence of a stump shade--which requires removal of the temporary and more importantly a return visit by the patient. Now the alginate for the temporary is taken and the opposing arch is scanned.
The difference between the 2 systems at this point is the lab time for the assistant to pour the opposing impression.
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Preps are completed as well as tissue management. Tissue retraction is a must with either system. With iTero, if you can’t see the margin, you can’t scan it, just as with conventional impression systems. I’m often asked if I can scan subgingival margins. Yes, if the gingiva is beveled outward and you can see the margin from the occlusal view. My lab confirmed that although we can fill the sulcus of the prep that is sub gingival with impression material, there are often voids due to the presence of blood or tissue that was not held off the prepped margin. This often results in the need for multiple impressions. Using a laser, retraction cord or other means to retract the tissue ensures good scans or impressions and resulting working model.
With conventional impressions approximately 7 minutes are required start to finish for each impression. Scanning takes 3-4 minutes and can be verified as you proceed. With iTero the inter-occlusal clearance can be seen through a color-coded system, allowing adjustments to be made while the patient is still anesthetized. This eliminates calls from the lab asking for more clearance or for reduction copings to be used at the seat appointment. The bite registration is acquired by relating the buccal surfaces of the upper and lower models in the last two scans, eliminating the need for a wax bite or other registration material.
Alternative: Insufficient clearance is detected immediately through a color-coded bite registration allowing corrections to be made and new scans to be taken while the patient is still present and anesthetized. This eliminates calls from the lab asking for more clearance and new impressions.
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