The first edentulous impression technique that we will discuss is the one that most of us were probably taught while in dental school. A rubber base impression in a custom tray border molded with impression compound remains the tried and true method for obtaining edentulous impressions.
I feel that the key to the success of this impression technique is the custom impression tray. This gives the practitioner much more control of material thickness of both the impression compound and the impression material. I feel that almost any edentulous impression technique could be made better with a custom tray. There are many materials on the market that can be used to fabricate a custom tray. Light cured materials like Triad are available but are a bit more expensive. Chemical cure materials are also available that are quite inexpensive. Fabrication of a custom tray takes a small amount of time, but I feel that time is more than made up for during the impression process. Advantages to this method is that the border molding process can be done incrementally and at the clinician's own pace with impression compound. Impression compound can be added to in deficient areas if needed, unlike PVS putty. Compound has the advantage of being sensitive to setting with cold water so that as soon as the clinician has the compound where it is needed, the tray with compound can be submerged in a cold water bath for instant setting. PVS putty takes time to set which could cause distortions.
Rubber base has one basic advantage over PVS and that is cost. It does have some disadvantages including difficult mixing, bad taste, and a long set up time (up to 8 minutes.) As far as accuracy goes, rubber base equals that of other materials like addition silicone, poly ether, or PVS.