A cobalt/chromium casting with a hinge and lock arrangement to utilize the naturally occurring lingual undercuts in the lingual sulcus of a partially dentate individual for the retention of a prosthesis.
In the posterior mandible, deep lingual undercuts often present a design problem in a partial denture situation where the use of these areas is somewhat restricted by the bilateral application. Changing the path of insertion may allow utilization of one of these areas. However a two-part design or swinglock principle is needed to make use of both regions.
This allows full extension of the denture into the functional lingual sulcus and thereby gives both increased support and retention to the prosthesis as well as maximizing the lateral bracing provided.
• The placement of such a prosthesis can be a problem depending on where the hinge and lock come in the arch form. The degree to which the gate can open is somewhat limited as the tongue can interfere with this opening.
• Poor plaque control is also commonly found in this region and therefore may be exacerbated by the placement of such a design.