Dentists take impressions traditionally and digitally, and while both methods have pros and cons, I stand behind traditional impressions. They offer a cost-effective way to move forward with procedures and provide the accurate results every dentist needs.
The importance of impressions
Impressions are an especially critical component of clear aligner treatment. Align Technologies, the maker of Invisalign clear aligners, is very selective about the impressions used for cases; if one is slightly distorted or doesn't capture the entire tooth, the company will reject it. The extra time and expense associated with taking additional impressions can frustrate dentists and patients alike, so my team strives to ensure that the impressions we take are as accurate as possible the first time around.
The accuracy of impressions can also affect the final case results. If one doesn't fit perfectly at the beginning of a clear aligner case, the aligners could be off through the entire process; consequently, the teeth won't move the way you want them, which alters every step of the procedure from beginning to end. The importance of getting the best impression possible can't be overstated: It's a vital initial step and provides huge value when any kind of restorative work is being done.
The options with impressions
With traditional impressions, different materials offer varying benefits—faster setting time, improved flowability, ease of use, and so on. I recommend looking for the option that, when all is said and done, provides the greatest accuracy. In this case study I used my "go-to," Imprint 4 Penta Putty VPS Impression Material from 3M.
Imprint 4 Penta Putty has a fast setting time—2½ minutes—and is a stiffer substance with higher consistency, which I find easier to use and more comfortable for patients. When I've used more-viscous products in the past, they've spread out of the tray and spilled over into the patient's mouth; for full arch impressions, I want something that'll be easier for me to handle and more tolerable for the patient. I combine the putty with Imprint 4 Light VPS Impression Material, a wash from 3M that spreads minimally against the putty, but not out of the tray.
An automatic mixing unit helps eliminate air bubbles and user error when mixing the product and dispensing it onto the tray. Some putty materials required a two-step process that included me or my staff molding balls of putty into a workable substance, which not only was time-consuming but opened the door for contamination and inaccuracies in the mixing process. With the Pentamix 3 from 3M handling our mixing, we get a void-free and reliable material consistence each time.
The struggle with impressions
Many clear-aligner patients are undergoing treatment to straighten crowded and crooked teeth, which can make obtaining an accurate initial impression more challenging. In this case study, the patient's initial visit required several impression retakes because the crowding of his teeth was difficult to capture. Impressions taken during his refinement visit, documented below, were easier to capture because his teeth had straightened out over the time between visits.
Again, using the right impression material can make the process simpler. Selecting a product with the right levels of rigidity and flowability will help practitioners obtain an accurate impression more quickly and efficiently.
Case study and clinical considerations for success
This 40-year-old patient was undergoing clear aligner treatment to combat severe upper and lower tooth crowding. One tooth wasn't tracking correctly during treatment, which required new impressions at his refinement appointment to produce different aligners.
I selected a tray that would fit the patient's mouth (Fig. 1), then filled it with Imprint 4 Penta Putty (Fig. 2). Once the putty was evenly distributed in the tray, I used an index finger to make a trough where the maxillary teeth would be and created plenty of room in the trough for Imprint 4 Light VPS Impression Material (Fig. 3).
While preparing the impression, I dried the patient's teeth with both gauze and air to ensure a clean and accurate impression of the gingival sulci. I then placed the tray in the patient's mouth (Fig. 4) and obtained an impression of the upper arch after allowing for the material to set for the full 2½-minute intraoral set time (Fig. 5).
This same process was repeated for the patient's lower arch (Figs. 6 and 7). Once the material was set, it was carefully removed and examined, resulting in an error-free impression of the patient's lower arch (Fig. 8).
Lastly, I disinfected both impressions and mailed them to Invisalign, which scanned the impressions to ensure everything was captured correctly and then created a Clincheck, which is how I communicate with the company about tooth movements and aligner design. I assessed the Clincheck, approved the process and gave final sign-off on fabrication of the aligners.
In this case, I knew a traditional impression procedure would provide me with a consistent and accurate impression that would guide the rest of the procedure down the right path—to deliver my patient the most comfortable and aesthetically pleasing result.
With every case, the initial impression greatly influences the patient's final outcome. During patient assessment, I recommend taking a close look at your impression material choice, because a small pre-assessment can save you time in the long run. For this case, I relied upon trusted products to deliver an error-free result that would be accepted by the aligner manufacturer and provide the patient with a well-fitting aligner. The products did just that and the patient is on his way to achieving a beautiful smile he can be proud of.