The 7 Golden Rules for a Perfect Impression
Do you want to learn how to perfect your dental impressions?
This blog post will explore the process in creating perfect dental impressions using top quality Solventum (3M) products.
Taking impressions is often a complex process and it is essential that is stage is carried out properly to get the best impression and therefore the best fitting final restoration.
To help with this, Solventum (3M) have put together 7 golden rules that should help you achieve perfection with your indirect restorations.
1. Choose the appropriate impression material and suitable tray
Probably the most obvious and important rule is the first one. Always choose an appropriate tray/wash impression material viscosities and material class according to the impression technique and indication to be carried out.
Use properly fitting, rigid, and sturdy impression trays. In the impression taking procedure, several different materials and techniques are available. Elastomers are the best materials to comply with the requirements needed for indirect restorations.
Polyether, for example, produces highly accurate results in a single step using one or two different viscosity materials (monophase or one-step). Polyether is probably the most forgiving when moisture control is difficult as polyethers are inherently hydrophilic from the beginning. Polyether is the perfect material for high-quality impressions, especially for implants, dentures, complex multi-unit cases and cases where moisture control is a challenge.
3M Impregum Penta Polyether Impression Material is still the only true polyether impression manufactured in the world and is considered “the gold standard” for the most challenging of cases.
Vinyl polysiloxane (VPS or A-Silicone) is the most widely used material for one- or two-step techniques, again using two different viscosities.
In many clinical situations, digital impression taking is now a predictable method that facilitates a direct transfer of the intraoral situation into the virtual world of CAD/CAM procedures.
3M Imprint 4 VPS impression material has been on the market for over a decade and has won several industry awards and accolades thanks to its intrinsic hydrophilicity. Imprint 4 reproduces fine details even in moist environments, so you can work quickly and confidently.
2. Ensure adequate retraction
Quite simply, if the lab can’t see the margin on the impression it is going to be a difficult job to make the indirect restoration fit properly. Always ensure adequate retraction and, if necessary, stop any bleeding to achieve a clean and dry situation. If retraction agents are used, rinse and dry thoroughly. In modern day dentistry, retraction can be achieved by using a retraction paste, a retraction cord or sometimes two retraction cords if situation dictates this. Using too small a cord or leaving a cord in place for too short a time, can lead to poor access to the sulcus.
While some techniques are promoted as eliminating the need for retraction, it seems that if the tissue is laying up against the margin, the impression material, even with a putty material “forcing” wash into the sulcus, may not capture the margin on a reproducible basis. Retraction takes time to develop and can take anything from 2 to 15 minutes depending on the material or technique adopted.
3M Astringent Retraction Paste is a simple and effective means of gingival retraction.
As the capsule has one of the finest tips on the market, the astringent retraction paste can easily be inserted right where it belongs – deep directly into the sulcus. With the ability to be delivered from nearly all traditional composite guns make this paste a versatile and easy to use option for retraction.
3. Thoroughly apply the tray adhesive
Ensuring proper attachment or adherence of the impression to the side walls of the tray is essential. Debonding or detachment of the impression from the edge of the tray can lead to distortion of the preparation or the jaw. Let’s not forget that we need to ensure that the tray adhesive is compatible with impression material being used. Do remember to ensure that the tray is adequately covered with the tray adhesive and that the adhesive is dry before the tray is loaded with material. Not using tray adhesive can lead to failures with the final impression.
One of the only trays available on the market that doesn’t require an adhesive are the 3M Impression Trays. These impression trays offer time saving benefits thanks to its self-retentive fleece strip which means there is no need to apply an adhesive. They are easy to customise making them ideal for implant impressions, as well as offering additional patient comfort due to their ergonomic design.
4. Ensure a homogeneous mix
It’s always difficult to control the quantities and homogeneity of the mix with handmix impression materials so many clinicians have moved to automix materials. Several automix systems are available in the market, but one of the most popular is the 3M Pentamix system.
The 3M Pentamix 3 Automatic Mixing Machine ensures a uniform mix of the impression material filling the tray sufficiently with the impression material.
With all Penta materials and Garant cartridges from Solventum (3M), proper automatic mixing is guaranteed which significantly reduces the risk of having to retake impressions. In addition, the Pentamix 3 mixing machine is currently the fastest dispenser available on the market.
It’s always recommended to bleed before applying the mixing tip to ensure even dispensing. Always use the correct mixing tip as recommended and ensure mixing instructions are followed.
5. Keep the tip immersed
No matter which impression material is used, always ensure to keep the tip immersed. This avoids entrapping air in the impression which can lead to errors during casting.
3M intraoral syringes are innovative single use, hygienic, and help reduce the amount of material waste by up to 67%.
The most popular benefit of 3M intraoral syringes is that they can be prepared and prefilled up to 12 hours in advance.
6. Check preparation margins
After removing the tray, always check preparation margins and make sure that margins are captured entirely and properly.
The following appearances may lead to inaccurate results: voids, tears, material distortions, flow defects, detachment from tray, delamination between heavy and light body, shine-through of tray.
7. Disinfect impressions properly
Among the several methods used for disinfecting impression materials, the chemical method was most frequently used over the other methods including microwave irradiation, steam autoclave, UV light radiation, ozone, and electrolysed oxidising water disinfection.
Autoclave, microwave, and chemical disinfection methods can produce minor dimensional changes compared to other methods. Both autoclave and microwave increase material temperatures, and this may cause distortions. Do ensure that the impression material’s manufacturer allows these methods.
Immersion of impression materials in different disinfectants was reported to be more effective than spraying their surfaces. This is due to longer exposure time of the impression materials to the disinfectant by immersion than by spraying their surfaces. Nevertheless, spray disinfection is the most popular method of disinfection, especially for hydrophilic impression materials such as hydrocolloids. It’s very important to rinse with water to remove any disinfectant solution on material’s surface.
The effect of chemical disinfection on the impression materials varies with the method and duration of disinfection, type, and concentration of the disinfectant, and the type of impression material. Generally, most common effective disinfection solutions used are 1% NaClO and 2% glutaraldehyde. 10 minutes is the maximum time recommended for no dimensional changes.
Both VPS and polyether impressions need to be stored in a cool, dry, and dark place, and they should be shipped to the dental laboratory wrapped in dry paper towel and placed in an open bag if still moist. The dry paper will draw any moisture from the surface, leading to an optimal condition for transportation. Do not store impressions in sealed plastic bags while still moist. Variations in temperature should also be avoided.
View the full range of Solventum (3M) products here.
