Introduction

Distal extension removable partial dentures (RPD's) derive their support from the abutment teeth and the mucosal tissues overlaying the residual alveolar process.  There are differing philosophies in the scientific literature regarding how much support should be provided by the abutment teeth and how much support should be provided by the soft tissues.^1,2,3,4  However, there is consensus that:  (1) occlusal stress should be shared by both in such a manner that neither the abutment teeth nor the residual ridge is abused; (2) accurate fit of the denture base is an important factor in minimizing stress on the abutment teeth⁵; (3) stability of the prosthesis is the most important requirement for proper function and patient comfort.³  Generally speaking, there are two commonly used methodsfor making impressions for the fabrication of distal extension base RPD's.  Some dentists prefer to use a stock impression tray and irreversible hydrocolloid.  Others prefer to use a border-molded custom tray and polysulfide rubber or one of the silicone impression materials. The likelihood is that no matter which method is used there will be some distortion of the soft tissue in the edentulous area(s).  The distortion that occurs is a result of the difficulty in being able to precisely position a loaded impression tray in many patient's mouths without the tray making contact with the soft tissue in the edentulous areas.  The two most commonly used methods for overcoming this problem are the altered cast procedure or relining the RPD prior to insertion. The advantage of the altered cast procedure is that an accurate relationship between the denture base and the metal framework is established prior to tooth arrangement which should result in less occlusal adjustment at the time of insertion.  The objectives of the altered cast technique are to obtain the maximum possible support from the distal extension base of the RPD and to accurately relate the soft tissue surface of the denture base to the metal framework.  A method for carrying out a framework try-in, making the altered cast impression, and obtaining maxillo-mandibular jaw relation records in a single appointment will be described below. ^9,10 (Fig.1)