Key Points
In this part, we will discuss
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Major and minor connectors
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Connectors for the upper jaw
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Connectors for the lower jaw
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Non-rigid connectors
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Connectors for acrylic dentures
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All the parts which comprise this series (which will be published in the BDJ) have been included (together with a number of unpublished parts) in the books A Clinical Guide to Removable Partial Dentures (ISBN 0-904588-599) and A Clinical Guide to Removable Partial Denture Design (ISBN 0-904588-637). Available from Macmillan on 01256 302699
Abstract
This article describes the types and functions of connectors for RPDs. It also considers the relative merits and limitations of these connectors.
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Designs of connector for the upper jaw
The choice of the shape and location of connectors is greater in the upper jaw because of the area available for coverage offered by the hard palate.
A decision on choice of connector type is based upon the requirements of:
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Function (eg connection of components, support, retention).
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Anatomical constraints.
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Hygiene.
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Rigidity.
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Patient acceptability.
Palatal Plate
Ring connector
Designs of connector for the lower jaw
The main anatomical constraint for connector design in the lower jaw is the relatively small distance between the lingual gingival margin and the functional depth of the floor of the mouth. In terms of functional requirements the mandibular connector does not contribute to support by distributing loads directly to the mucosa. It connects the RPD components and can provide indirect retention and guide surfaces.
With gingival recession there is even less room to manoeuvre and it may be difficult to design a connector that satisfies two of the main requirements: maintenance of oral hygiene and rigidity.
Five of the common connectors are illustrated diagrammatically and clinically.
Sublingual bar
Lingual bar
There are anatomical constraints in the lower jaw that may prevent the use of sublingual or lingual bars. Mention has already been made of lack of space between the gingival margin and the floor of the mouth. A prominent lingual fraenum may compound the problem and make it impossible to use either of these connectors. A mandibular torus may be of such a size that a sublingual or lingual bar, sitting on top of the bony protuberance, would be excessively prominent, creating major difficulties for the patient in tolerating the prosthesis.
Lingual plate
Non-rigid (stress breaking) connectors
Inevitably, the stress-broken design is a more complex construction and thus more costly. It may also pose greater demands on plaque control and be less well tolerated by the patient. The use of a rigid connector may make it easier to design a simple shape. For these reasons it is our preference to design distal extension saddle RPDs that incorporate the following:
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A rigid connector.
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Control of the load distribution to the various tissues by: – reducing the area of the artificial occlusal table, – maximising coverage of the edentulous area, – employing the altered cast technique, – using one of the more flexible clasp systems, – instituting a regular maintenance programme.
Acrylic dentures
Although this book is primarily concerned with the design and construction of dentures with cast metal frameworks, there are occasions when it is appropriate to provide dentures made entirely in acrylic resin.
The main advantages of acrylic dentures are their relatively low cost and the ease with which they can be modified. They are therefore most commonly indicated where the life of the denture is expected to be short or where alterations such as additions or relines will be needed. Both these reasons may make the expense of a metal denture difficult to justify.
Indications for such treatment include the following:
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1
When a denture is required during the phase of rapid bone resorption following tooth loss, for example an immediate denture replacing anterior teeth. In this case a reline followed by early replacement of the denture is to be expected.
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2
When the remaining teeth have a poor prognosis and their extraction and subsequent addition to the denture is anticipated. A transitional denture may be fitted under such circumstances so that the few remaining teeth can stabilize the prosthesis for a limited period while the patient develops the neuromuscular skills necessary to successfully control a replacement complete denture.
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3
When a diagnostic (or interim) denture is required before a definitive treatment plan can be formulated. Such an appliance may be required, for example, to determine whether the patient can tolerate an increase in occlusal vertical dimension required to allow effective restoration of the dentition.
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4
When a denture must be provided for a young patient where growth of the jaws and development of the dentition are still proceeding.
In addition, acrylic dentures may also provide a more permanent solution; for example, where only a few isolated teeth remain an acrylic connector may function just as effectively as one in metal.
When considering whether or not to provide an RPD in acrylic resin, the limitations of the material should be borne in mind. This material is weaker and less rigid than the metal alloys and therefore the denture is more likely to flex or fracture during function. To minimize these problems the acrylic connector has to be relatively bulky. This, in turn, can cause problems with tolerance and offers less scope for a design that allows the gingival margins to be left uncovered.
Another significant disadvantage of acrylic resin is that it is radiolucent so that location of the prosthesis can prove difficult if the denture is swallowed or inhaled.
Acrylic RPDs in the mandible often lack tooth-support making tissue damage highly probable. Such RPDs should therefore be avoided whenever possible.
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Davenport, J., Basker, R., Heath, J. et al. Connectors. Br Dent J 190, 184–191 (2001). https://doi.org/10.1038/sj.bdj.4800919
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DOI: https://doi.org/10.1038/sj.bdj.4800919