The three key elements of the Equipoise system are:
Retention Stability Esthetics
Preserves abutment teeth
During mastication, the clasp tip, moving in the same direction as the denture base releases from the undercut on the abutment tooth. Therefore, the biting force transmitted to the abutment tooth is vertical, down the long axis of thetooth via the occusal rest. Damaging horizontal forces on the tooth are minimized. And, because the clasps disengage, less metal fatigue and fewer adjustments are the results.
Superior retention and stability
As the denture base begins to move off the tissue, the clasp tip moves in the same direction as the denture base. The clasp tip thus engages the undercut and the partial is retained and stabilized. No flopping around or down. No wiggle.
The golden rules
This case exhibits the three most basic rules of Equipoise design:
1. Occusal rests are placed on abutment tooth away from edentulous area
2. Clasp tip moves into the same edentulous area
3. Small stabilizing rests are placed next to anterior edentulous spaces
First tooth preparation
The interproximal access area is normally prepared with a tapered diamond stone or #557 carbide. Approximately ½ mm of enamel should be removed from both the abutment and the adjacent tooth. All interproximal guide planes must be parallel to one another for an easy path of insertion.
Rest Directs Forces
Dimensions of the posterior rests are here noted. Choose between either cingulum rests offer better esthetics, an incisal rest can be most effective in distributing biting forces on
the long axis.
The Equipoise Unit
Includes occusal rest, lingual clasp, and interproximal guide plane. During insertion and removal of the partial, the plane reciprocates the frictional force applied to the tooth via the clasp tip. This ice tong effect is necessary to prevent horizontal torque on the abutment.
Decay? Especially in the interproximal
Most case studies show a burnished proximal tooth surface where the guide plane slides into place. This sealed tooth structure appears hi-shined and nearly impervious to dental caries. Other surfaces of the abutment tooth, the prepared rest and undercut, will require the same level of hygiene as a conventional partial.
Sensitivity?
Except for crowned abutment teeth, all Equipoise tooth preparation should be placed within enamel and without the aid of a local anesthetic. In very few cases, young partial denture patients (under 20) have experienced discomfort and sensitivity of prepared teeth. Discretion is advised in designing Equipoise for these patients.
Technique Tips
Interproximal preparations must be parallel to allow a direct, easy path of insertion. Open contact areas must be preserved between appointments or "drift" causes fitting difficulties. Uses a resin "plug" or other material to preserve the space.
Due to superior retention, patients may have problems removing the partial due to Equipoise design. A notch cut in the flange areas will help them to unseat the prosthesis.