Comparing Types of Dental Impression Materials
By David Hudnall, DMD
Making a good impression is essential for any endeavor that you choose to undertake in life. Making a good impression is also essential to the success of any indirect dental restoration. Always start with excellent dental impression materials that are suited for the application. Some materials are perfectly fine for certain procedures and not appropriate for others.
When deciding on which impression material to use, consider the cost/benefit ratio. Use a material with the accuracy appropriate for the procedure. Some important characteristics of dental impression materials include dimensional accuracy, dimensional stability after the impression has been taken, hydrophilic properties that allow the material to work well in the presence of moisture, tear strength, and ease of handling. You don’t want to spend more money than necessary on a material that provides a very accurate, stable impression when it is not needed.
The Best Types of Dental Impression Materials for Dentists
Alginate (Reversible Hydrocolloid)
Alginate is known for being inexpensive and easy to use. Alginate impressions set quickly and are easily removed from the mouth without tearing. But the material does have its drawbacks. It doesn’t produce the clear details characteristic of some other dental impression materials. There is a limited amount of working time to pour the model before the alginate impression becomes dry and loses its accuracy by changing dimensions. Alginate also doesn’t work well when more than one model must be poured from the same impression. Alginate is usually the dental impression material of choice for full-mouth opposing impressions, study models, orthodontic appliances, mouthguards, and even partial denture fabrication.
Also known as Rubber Base, polysulfide is known as a go-to two-part dental impression material. In use since the early 1960s, it is moderately hydrophilic, which allows for an accurate impression even in the presence of saliva or blood. Because it is not a rigid material, rubber base impressions are easier to remove from the mouth, and it lends itself to taking a full arch impression more easily than polyvinyl siloxane or polyether. It is also relatively inexpensive. One of the biggest drawbacks of polysulfide is that it does not adhere to itself, making it impossible to take a wash impression inside of an existing impression where voids are present. In addition, other materials must be relied upon for border molding and tray customization. Polysulfide is best suited for taking accurate impressions of fully edentulous arches or arches with a minimal number of teeth.
Polyvinyl Siloxane (PVS)
One of the major benefits of Polyvinyl Siloxane as a dental impression material is its ability to reproduce great detail, allowing very accurate models to be made. With the advent of light-, medium-, and heavy-body viscosities that bond together seamlessly, it is possible to create very accurate impressions with viscous material while supported by more rigid, less viscous material. Once set, it retains excellent dimensional stability, which allows the impressions to be packaged and shipped without the worry of accuracy for the final model. One of the biggest disadvantages is its susceptibility to chemical contamination from latex gloves and retraction cords, causing the material to be set incompletely, leading to inaccuracies. Polyvinyl Siloxane is ideal for obtaining the fine detail of crown preparations as well as fully edentulous arches. Because it tends to become locked into interproximal spaces, the material will tear, and it doesn’t work well for fully dentate arches. This is one reason polyvinyl siloxane is not recommended for partial denture impressions in most cases.
Consider 3D Impressions with CAD/CAM Technology
In the digital workflow, two very different methods are used to capture impressions. If an intraoral scanner is available, you can capture the impression digitally by scanning the area of interest. Whether it be a crown preparation for a single restoration or a mucostatic virtual denture impression of a fully edentulous arch, direct scanning technology can be used in place of the required physical impressions. If you don’t have in-office scanning equipment available, use a combination of heavy-, medium-, and light-bodied polyvinyl siloxane dental impression material to capture physical impressions in scannable trays that can be transported to the laboratory.
Accurate bite registrations are always an area of concern to most dentists. Digital bite recordings don’t provide the detail and accuracy needed for proper articulation. Since it is never a good idea to leave the bite up to chance, even in cases where you believe the digital models will be able to be hand-articulated, some form of physical bite registration is recommended.
When to record the bite registration in the digital workflow is another matter of discussion. For cases where the patient has a full complement of teeth or has enough teeth to provide natural occlusal stops, take the registration using a light-bodied PVS material, such as Blu Mousse, after the final impression has been taken. For complete denture cases processed by a digital workflow, it is advisable to allow the lab to make custom bite rims on the digitally-generated models. Using these bite rims, centric relation, vertical dimension of occlusion, lip support, and the midline can all be captured during the second denture fabrication appointment.
Digital Workflow Hasn’t Made Impression Materials Obsolete
Even though automation and a digital workflow have allowed laboratories to create more precisely-fitting restorations, the need for traditional impression and bite registration materials has not been eliminated. The use of procedure-appropriate materials continues to play a big part in the success of your final restoration. With the aid of advanced technology, Stomadent Dental Laboratory makes use of all of the options available to provide you with superior-fitting restorations that require little to no adjustment upon delivery, saving you time and money. Trust Stomadent to be your go-to dental lab. We have revolutionized digital workflow!
For additional information about CAD/CAM technology and digital workflow, contact Stomadent Dental Laboratory at 833-450-4102 or online today.