Restorative dentistry


Fig 2


Major retainer second premolar, minor retainer canine


Fig 3


Major retainer first molar, minor retainer first premolar


Fig 4


Three-unit movable bridge. Note the use of metal margins to reduce distortion


Continued »


to which the pontic is rigidly attached. Minor retainer: The retainer


to which the pontic is non- rigidly attached. In the clinical situation,


a single cantilever has one major retainer; a fixed/fixed bridge has two major retainers and the fixed/movable has one major retainer and one minor retainer.


The retentional demands of


a major retainer are greater in a fixed/fixed bridge than in a fixed/movable design. In the fixed/fixed bridge,


occlusal loading of the pontic causes the bridge to bend or flex, putting stress on the cement lutes. The non-rigid connector in the fixed/movable bridge breaks the stress on the cement lutes by dissipating the occlusal forces applied to the pontic. This lowers the


retentional demands on fixed movable retainers, and prepa- ration designs can be more conservative. In an analysis of 2,000 bridge


retainers, Roberts2 provided some recommendations for the design of major and minor retainers in fixed bridgework. These are summarised in tables 2 and 3 (see page 59).


Non-rigid connector The non-rigid connector in


fixed-movable bridgework may be referred to as having ‘male’ and ‘female’ components. This may be considered


using the example of a three- unit posterior fixed/movable bridge. The bridge comes in two


parts: usually the anterior abutment, or minor retainer, is a single crown with a rest seat or ‘female’ machined into its distal surface. The distal part of the bridge,


56 Scottish Dental magazine


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