Do you find yourself retaking many of your patient’s impressions? Whether you feel rushed to complete deadlines or find yourself needing to brush up on your skills, it’s good to review common pitfalls that occur when taking impressions and you can easily solve these faux pas.
One of the most challenging procedures in dentistry is obtaining an ideal impression for a fixed dental prosthesis. Making an accurate impression requires understanding the anatomy surrounding the finish line, the material being used both for impressions and gingival displacement, and the correct use of impression trays. Often a simple step such as not trying in the tray, underfilling, overfilling, or even failing to allow the material to sit for the required time prevents you from taking an accurate impression. However, if you struggle to identify the cause of the error in the original impression, the mistake may very well be made time and time again. Read below for some common errors that are made when taking final impressions and how solve these problems.
Most Common Impression Mistakes:
Drag Marks or Pulls in the Impression
If a drag mark is impairing the impression of any of the teeth or breaking up the gum line, it will not be sufficient to build a restoration. Pulls and drags appear as elongated distortions within the impression. Drag marks can be caused by several factors. One source of these types of errors is movement of the impression material in the mouth before the set is complete. If there is a drag mark behind the back molar, make sure the tray is completely off your patient’s teeth before pulling it out of their mouth. Additionally, it could also be a timing issue, so make sure you are leaving the tray on patient’s teeth for no less than 3 and a half minutes. Please remember to also keep the material stabilized within the mouth throughout its setting time.
Poor Margin Detail
The margin is one of the most critical aspects of a dental impression. Without an accurate marginal impression, problems such as overhanging or open margins, or an inadequately fitting restoration are more likely. Simply because the practitioner knows where the margin is, does not mean the technician or scanner will find it, if not exposed. A common cause of insufficient margin reproduction is inadequate tissue retraction. Using retraction cords with hemostatics is the best way to solve this problem. One technique is to use a double retraction cord. Another approach is to use syringable retraction pastes that are placed into the gingival sulcus after preparation. A diode laser can be helpful for widening the sulcus, improving visualization of the prepared margin while achieving hemostasis.
Inadequate Data Captured in the Impression
After removing an impression, dentists tend to only check the impression of the prepared tooth. However, if there is insufficient data in the remainder of the impression, the laboratory will not be able to accurately create your patient’s dental prosthesis. The try-in of the impression tray is an important step that must be maintained in protocol. This try-in allows the dentist to ensure that no tray borders are in contact with any tooth or tissue, and it prepares the patient for the upcoming procedure. Custom-made trays can be effective for this, especially when working with impressions that involve multiple teeth.
Air Pockets in the Impression
Air pockets in a patient’s dental impression form when moisture (blood, saliva, water) gets trapped in the impression material. These air pockets usually mean that there is not enough impression material in your tray to begin with. This problem can be solved by achieving hemostasis and keeping the tip of your material gun in the tray while loading the material.
Choosing the Correct Material
Selecting the right impression material is crucial for achieving an accurate and predictable impression for your patient. You must be familiar with the specific working time for the selected material and you must insert the impression within the working time. If the material is already beginning to set, it may not seat fully and will not capture the accurate data. It is also very important to remember that you should not use two different materials from two different manufacturers.
DDS Lab uses an impression rating system, and each impression is graded according to its quality. If you have questions about taking dental impressions, our experienced technical team can offer advice on how to achieve more predictable and higher-quality impressions.