How to Take a Secondary Impression Using Silicone & Stock Trays
Achieving a precise secondary impression is essential for ensuring an accurate fit for dentures and other dental restorations. While custom trays are often preferred, stock trays provide a viable alternative when used correctly. By combining stock trays with silicone impression materials, dental professionals can obtain high-quality impressions suitable for laboratory processing.
The Importance of Secondary Impressions
A secondary impression captures the fine details of the oral tissues, ensuring a precise fit for the final prosthesis. Stock trays can be adapted to work effectively in this process, provided they are carefully selected and modified where necessary. Proper handling of silicone impression materials is crucial in achieving consistent and distortion-free impressions (Dentistry Today, 2024).
Step-by-Step Guide to Taking a Secondary Impression
1. Selecting the Right Stock Tray
Choosing the correct stock tray size is fundamental to achieving an accurate impression. The tray should extend sufficiently to cover all anatomical landmarks without excessive overextension. If a perfect fit is not available, minor adjustments, such as adding silicone putty, can help customise the fit (National Library of Medicine, 2024).
2. Creating a Stable Base with Silicone Putty
To enhance the accuracy of the impression, a preliminary layer of silicone putty is applied inside the stock tray. This step helps stabilise the tray and provides an initial adaptation to the patient’s oral structures. Once set, the putty serves as a foundation for the final impression.
3. Border Moulding for Optimal Detail
Border moulding is crucial in achieving a functional denture fit. This involves applying bite registration material to the periphery of the stock tray and having the patient perform functional movements, such as smiling and swallowing, to shape the material accurately. This step ensures that muscle movements and soft tissue contours are properly recorded (Dentistry IQ, 2024).
4. Applying Light Body Silicone for Final Impression
Once border moulding is completed, a light body silicone material is used to capture the fine details of the oral tissues. The silicone is carefully loaded into the stock tray, ensuring even distribution. The tray is then inserted into the patient’s mouth, and light pressure is applied to prevent distortion. The patient is instructed to remain still until the material sets.
5. Removing and Inspecting the Impression
After the silicone has fully set, the impression is gently removed and examined for accuracy. Key aspects to check include:
- Complete coverage of the required anatomical areas.
- The absence of air bubbles or voids.
- Proper capture of soft tissue details, such as the retromolar pad and vestibular depth.
If any issues are detected, adjustments can be made, and a new impression taken if necessary.
Common Challenges and Solutions
- Material Leakage: Stock trays often have perforations that can cause silicone to leak. Blocking these holes with fast-setting bite registration material prevents unnecessary overflow.
- Tray Fit Issues: If a stock tray is too large or small, additional silicone putty can be used to adjust the fit and improve stability.
- Ensuring Accuracy: Avoiding excessive pressure during the impression process helps prevent material distortion, leading to a more precise final result (International Journal of Oral Health Dentistry, 2024).
Why Stock Trays Are a Practical Choice
While custom trays provide the best adaptation, stock trays with silicone may not always be the most cost-effective option but remain a practical choice. By combining silicone putty, bite registration material, and light body silicone, clinicians can still achieve high-precision impressions that meet accuracy standards.
If you are a dentist looking to enhance your impression techniques or collaborate on denture fabrication, watch the full video to find out my thoughts and what I recommend! https://www.youtube.com/watch?v=_1c_H35RcHo
