Methods for Traditional Dental Impressions: The Foundation of Restorations

Traditional Dental Impressions

After a dental case has been diagnosed and proper preparations have been made, the patient is now ready for the impression-taking phase. Poor dental impressions make up for the majority of issues found in flawed dental restorations. It is possible for even the most experienced clinician to encounter clinical challenges when taking dental impressions.

To fabricate a dental cast, dental impression materials are used to copy teeth and surrounding oral structures (see above image). It is vital to the success of a case that the dental impression provides an exact replica of the patient’s oral structures in order to ensure a precise fitting restoration.

A dental model made from a dental impression allows for the visualization and study of teeth from angles that are difficult to see in the patient’s mouth, which allows for a better diagnosis and treatment plan. It is important to ensure that the impression material has accurately recorded the details of the tissue so that the final restoration or prosthesis fits properly.

Below are some ways to improve traditional impression-taking techniques.

Techniques to improve traditional dental impressions

1. Make sure that your impression trays are rigid, sturdy, and well-fitted.
2. Depending on the impression technique and indication, choose wash materials with appropriate viscosities. 
3.  Make sure the retraction is adequate.
4. The area should be clean and dry, so stop any bleeding and thoroughly dry. 
5. Apply a tray adhesive to ensure the impression material will adhere to the tray. 
6. Make sure the impression material is uniformly mixed. It is important to fill the tray with enough impression material.
7. Wear gloves that won’t interfere with the impression material’s setting.
8. To avoid air entrapment during intra-oral syringing of wash material, keep the tip immersed in the material at all times.
9.  Load the tray parallel to the long axes of the prepared teeth and insert it slowly into the mouth. To avoid contact between teeth and tray bottom, apply controlled pressure while seating the tray. Be careful not to exert pressure or move the tray in a way that could cause distortions. 
10. Before removing the impression, follow the manufacturer’s instructions. 
11. Check the impression to make sure the margins were captured. Look carefully for any issues with the impression, such as voids or tears. 
12.  Disinfect impression properly before sending to Burbank Dental Lab.

While these tips are fairly straight forewords taking an accurate dental impression can be a challenge even for the most experienced dental offices. However, without an accurate dental impression, the entire case can be compromised as this is the only representation the dental lab has of the patient.

Below we will explore some of the common issues found with traditional dental impressions.

Common issues found with traditional dental impressions

1. Distortions are a common issue found with dental impressions. These are difficult to catch and often are not found until a new impression is taken as a comparison. Distortions can be the result of impression trays that are too flexible, material detaching from the tray, going beyond the stated working time of the material, etc. 
2. Voids, especially those found on the margins, can cause restorations that are short and/or open. These can occur for a variety of reasons, including defective material, bubbles in the syringe, and blood/saliva in the area. (Figure 2, shown below in purple)
3. Tearing of the impression can also cause short or open margins. These can occur because of poor retraction techniques, the impression tray is removed before adequate time is achieved, or the impression material is not adequately mixed, etc. 
4. Unable to read the margins. This is one of the most common issues that dental labs experience with traditional impression methods. This can lead to a restoration that does not fit. Again this can be caused by blood and saliva, poor retraction, and poor impression material. (Figure 3 shown below in yellow)
5. There is show-through of the impression tray. This can cause occlusal issues in the final restoration. It is often caused by using too little impression and/or too much pressure applied when taking the impression. 

There are several issues that can occur that can affect the accuracy of dental restoration. Some of the most common reasons a dental impression will experience a poor replication of the patient’s mouth are listed below.

The most common reasons a dental impression will experience a poor replication of the patient’s mouth

• Material is not properly mixed.
• The setting of the impression material is inhibited due to interaction with other materials used in the case. This can include the use of latex gloves. (Figure 4, shown below)
• Removing the tray before the indicated time set by the impression material manufacturer.
• Impression material is stored improperly.
• The impression material has expired.
• Poor retraction methods
• Saliva and blood have contaminated the site.
• Exceeded the manufactures recommended working time.
• Air bubbles in the syringe
• The impression tray is too flexible.
• The impression tray is placed too quickly or repositioned after being placed.
• Not enough impression material is used.
• Too much pressure is placed on the tray while taking the impression.
• The teeth come in contact with the tray.
• The tray is not supported long enough during the initial setting of the impression material.
• Not enough wash material was used.

The impression phase of a dental procedure sets the foundation for accurately designing and creating a dental restoration. This is the only reference that the lab has to the patient’s mouth.

Accuracy is the key to ensuring the final restoration will have excellent margins, contacts with adjacent teeth, and proper occlusal contacts. The more precise the impression, the fewer adjustments will be needed chairside.

Call or chat with us today to find out more about the digital dentistry processes and traditional dental workflows.