We never get a second chance to make a first impression. And in the dentist’s office, nobody wants to take a second impression! A perfectly fitted, customized dental restoration begins chair-side. Without an excellent impression, it’s impossible for a lab to fabricate a high-quality, aesthetically-pleasing restoration … or we can make it, but a dentist will spend precious time having to adjust it, possibly eventually having to start all over. That just leads to frustration on everyone’s part. No need for all that. Let’s focus today on five of the most common dental impression errors — and how to avoid them:
Poor tray selection
One of the most common errors is choosing the wrong size tray for an impression. When it comes time to make the impression, check the tray in the mouth to see if it’s the correct size. Be sure the tray you choose is large enough to capture all the needed information without distortion and to cover all the teeth without contacting the soft tissues. The tray must be long enough to capture the entire arch and wide enough to allow adequate tray seating. Once the impression is complete, no part of the tray should show through the impression material.
Poor margin detail
Details are important, and since margins are the most important part of an impression, it’s critical to strive for the best result possible — on the first try. After all, without knowing where a restoration should end, figuring it out becomes a guessing game for the lab. Typical margin errors can be avoided by using a double retraction cord and hemostatic agents to reduce the accumulation of fluid near the gums.
Improper material mixing
Once impression material is mixed, it should be consistent in color and texture with no streaks. When working with cartridge materials, bleed the cartridge before attaching the tip. This allows the catalyst and base to flow uniformly, which helps avoid possible mixing issues. Also, be sure to use tray material and wash from the same manufacturer. They are designed to work together, and even slight variations from one company to another could produce inconsistent results.
Trapped fluids — blood, water or saliva — can cause impression bubbles. This can compromise the luting agent, eventually leading to an improper fit.
Drags, pulls and tears
Sometimes problems like drags, pulls and tears arise when working with viscous materials. Drag marks can occur for several reasons, including when impression material moves in the mouth before being set. Be sure to pull the impression tray completely from a patient’s teeth before pulling it out of the mouth; this can help prevent drags. Drags can also be caused by timing; trays should stay on a patient’s teeth for at least 3.5 minutes. Be sure the impression material is stable during the setting time. Pulls may happen when the material starts to set before the tray is inserted in the patient’s mouth or when the tray is removed before the material has fully set. Tears can also occur if the material has not fully set before removing the tray from a patient’s mouth.
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No one wants to repeat an impression. But if it’s not executed perfectly, it could lead to errors that drastically impact the finished product. One tiny imperfection could lead to a patient’s restoration fitting imperfectly. Then the entire process has to start over. Take time to become acquainted with the most common dental impression errors so that at the end of the day, everyone — the dentist, the lab and the patient — has something to smile about.