As impression materials have improved over the years, edentulous impression techniques have been forced to evolve with them to take advantage of newer materials. The invention of PVS impression material gave practitioners hope of easier and quicker edentulous impressions.
As we all know, PVS impression material by trait is hydrophobic. In fixed prosthodontic impressions, we are more able to control this limitation by packing cord, drying the prep, etc. When impressing a full edentulous arch, this fluid control becomes more difficult especially in the mandibular arch. Because of this, you will find that most edentulous impression techniques that utilize PVS use Aquasil by Dentsply. Aquasil is generally thought to be the least hydrophobic PVS material. A dentist out of Tulsa, OK has taken this niche and run with it. His name is Dr. Joseph Massad. He lectures world wide on the topic of removable prosthodontics and almost exclusively on using PVS to impress edentulous arches. In most circles, this is called the Massad Technique.
There are a lot of intricacies and details that make this technique difficult to explain in a short forum like this, but I will gloss over the big pictures. If anyone is interested in learning more about this, there are plenty of publications and courses available.
The Massad technique utilizes pre-fabricated trays that come in several different sizes for each arch. For most patients, a very good fit can be found with one of these stock trays. Once a tray is selected, PVS putty is used to make tissue stops in several areas. After the tissue stops are put in, the tray should be able to be repeatedly sat in the patient's mouth in the same position. Once the stops are set, either PVS putty or heavy body PVS is syringed on the borders of the tray. The tray is than reseated in the patient's mouth and border molding exercises are completed.
Border molding with PVS is not much different than impression compound except for the fact that PVS sets on it's own schedule, whatever that might be. Where as impression compound can be cooled with ice water as soon as borders are molded. This makes this technique a bit more technique sensitive.
After the stops and border molding has been completed, the entire tray is "washed" with either medium or light body PVS or a combination.
This is then reseated into the patient's mouth and left so set.
The final product should look something like this. I feel that PVS is a great impression material and the Massad Technique is an excellent way to get a nice edentulous impression. However, this method is very technique sensitive. When not done correctly, thie technique yields an impression with borders that are short and thick from too many washes of lighter bodied materials. I think appropriate training is needed to use this technique with consistent success. This technique is quite a bit more expensive than rubber base and impression compound because Aquasil impression material is quite costly and this technique uses an abundance of material.