supported by bone decreases, the lever effect increases. Root configuration should be considered when selecting abutment(s). Divergent roots of posteriors provide increased support compared to converging, fused or conical roots. Roots that curve apically provide increased support compared to those which have a fixed taper. The number of abutments required depends on both the position of the tooth to be replaced and the length of the span. Cantilever designs utilising one abutment is the design of choice for replacing a single tooth anteriorly and can also be used posteriorly. Occlusion of the pontic with the opposing tooth should be assessed. This may determine which type of design is most appropriate and therefore how many abutments are required. For resin bonded bridges the pontic should have light contact in intercuspal position (ICP) and no contact in lateral excursions. Biomechanical Considerations Torquing forces can occur when the pontic lies outside the interabutment axis line as the pontic acts as a lever arm. This is particularly applicable to long span bridges replacing multiple anteriors. Deflection varies directly with the cube of the length, and inversely with the cube of the occlusogingival thickness of the pontic. The longer the span, the more deflection occurs. The amount of deflection is 8 times greater when the length of the span increases to 2 pontics, and increases to 27 times greater with 3 pontics in comparison to a single pontic. It is likely that increased span length will result in the abutments being subjected to increased torquing forces. The thinner the pontic, the more deflection occurs. If the thickness of the pontic is reduced by 50% this causes an 8 times increase in deflection. Choosing pontics with increased occlusogingival dimension and using high yield strength alloys to construct the prosthesis will help reduce deflection. Indications for use Replacement of a single tooth or a small spanning space. Good oral health status and motivation of patient to maintain oral health. Periodontal status of remaining dentition at a stable and satisfactory level. Abutment teeth of good quality with minimal restorations and enough surface area and enamel present for adhesion. Splinting of periodontally compromised teeth to improve occlusal stability, comfort and decrease mobility. (Periodontally compromised teeth is also a contraindication). As a way of fixed retention after orthodontic treatment or extraction. Patient unsuitable for implants. This may be due to inadequate bone levels, expense or patient not wanting to receive