Equipoise is balance of force design. It protects, preserves and strengthens abutment teeth while directing all masticatory forces down the long axis of the abutment tooth. Equipoise was designed by Roach in 1930. Roach concepts on Equipoise were later modified by European and North American dentists giving us similar clasps concepts with other names. It is designed for use on the palatal / lingual surface of the abutment.
The design creates forces along the long axis of the abutment tooth with passive retention. All clasping in this Removable Partial Denture System is designed intra-arch. In Equipoise Class II Lever design, an element of support, and contention and retention for the distal buccal surface of the abutment must be placed. The Class II lever design has the rest(fulcrum) opposite of the retentive tip of the clasp (resistance arm) and the denture base (the effort arm).
Principles of Equipoise Removable Partial Denture
1. Minimum strain to the abutment.
2. Greater retention.
3. Improved esthetics.
Criteria fulfilled by Equipoise Design of Removable Partial Denture
5. Built in Permanence
E-clasps are designed on the mesial or distal aspect of the teeth facing the edentulous area. It is a lingual back-action clasp that is fully reciprocated, vertically and horizontally. The clasp always moves in the same direction as the denture base while directing all forces down the long axis of the retaining abutment tooth. Equipoise clasp are placed on canine and premolars, in clinical cases of Kennedy Class I and II.
E-clasp Tooth Preparation
The occlusal rest is prepared with a cylindrical diamond stone. On bicuspids the rests should be spoon-shaped and encompass 1/3 the mesiodistal width of the tooth and at least 2/3 of the buccolingual width. Rests on incisors are prepared over the cingulum or on the incisal edge of the tooth. The cingulum rest should be at least 1 millimeter deep and one-half the width of the tooth mesiodistally away from the edentulous area. The incisal rest should be at least 1.5 mm deep and 1.5 mm wide.
An interproximal access of at least 1 mm is necessary to give the minor connector enough strength to support a well contoured rest. This preparation is made by removing 1/2 mm of enamel from the abutment and 1/2 mm enamel from the adjacent tooth. A 1 mm tapered diamond stone is recommended. Rubber wheel or polish cut surfaces.
Picture of Equipoise Removable Partial Denture
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- This page was created on July 21 2012.
 Goodman J: Equipoise – The Proven Partial Denture System, Equipoise Dental Prosthetics, Inc. 1989
 Micheelsen JL, Astudillo LE: Design of the Partial Removable Denture, Amolca 2008
Jesus Lecitona+, DMD, MScD-Prosthodontics