Restorative dentistry


or major retainer, looks like a two-unit fixed cantilever bridge with a ‘male component’ on the mesial part that fits into the ‘female’ on the anterior abutment (Figs 4, 5, 6). Non-rigid connectors may be simple or custom made. Simple: A rest seat housed


within a filling. This is only possible when the rest is totally encompassed by amalgam or composite. Placing a rest in sound tooth tissue will predis- pose the patient to plaque accumulation and caries. Custom made: Precision


attachments are manufactured by companies such as Cendres & Métaux (www.cmsa.ch/ en), and can be purchased by the laboratory technician as preformed plastic patterns, which are placed in the wax pattern and burnt out prior to casting. (Fig 7) Several custom-made attach- ments have been described: • Ney attachment (Mini Rest)


• Triangular • T-shaped


Preparation According to Wise7, one of the basic principles of correct occlusal management is to ensure that occlusal forces are directed down the long axes of teeth. To achieve this in fixed movable bridge- work, it is important that components are housed intra- coronally. This means that additional tooth preparation is required. Hemmings and Harrington


reported in 20048 that, in order to reduce stress on the cement lute, the height, width and depth of the connector should be maximised to provide suffi- cient rigidity to the framework. Preparation techniques for


fixed/movable bridges have been described9. The usual sequence is:


Continued » TABLE 1


Advantages of fixed/movable bridgework


Preparations do not need to be parallel to each other, so divergent abutment teeth can be used


More conservative. Prepara- tions for minor retainers are less destructive than prepara- tions for major retainers Parts can be cemented sepa- rately, so cementation is easy May permit future modifica- tion


Allows movement of sections during function


Load on the weakest retainers and abutments may be reduced


Prevents posterior teeth tilting, as is sometimes the case with a cantilever bridge Allows for flexure of the mandible


Disadvantages of fixed/movable bridgework More space is required within the preparation to accommodate the movable compo- nent


Wear of the


movable joint may result in abut- ments becoming cantilevered


More complicated to construct in the laboratory than fixed/fixed


Higher lab costs Metal may show occlusally


Length of span is limited


Not suitable for anterior bridges


Scottish Dental magazine 57


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