then the lower alginate impression is taken, making sure to mould enough of the impression cream beneath the bar to include an accurate account of the underlying soft tissues. When the impression hardens, it is removed making sure it picks up the metal super-structure. If this was done correctly, the inside of the impression should only show the four clasps, and not the bar which should be completely buried (19) .

The final models are poured and articulated. Several thicknesses of tin foil are moulded over the mandibular model, so the base of the denture will not be tissue bearing (20).

Both waxed up dentures are fitted in the mouth and final adjustments of esthetics, vertical dimension and centric relation-ship are made.

The dentures are processed and fitted. All minor adjustments are made (21) .

In those situations, where, due to a dehiscency or near dehiscency of the mental nerve bundles, the buccal peripheral strut must be brought very close to the lingual strut, or become continuous with it, in order to strengthen this weakened area, a continuous Dolder or Andrews type bar is processed directly with the implant framework, rather than the usual four posts (2 2 ).

20

22

A technique previously described by the author in preparing the bone for a subperiosteal implant when either or both of the inferior nerves are dehiscent and the mental foramina have been totally destroyed because of vertical resorption will be briefly discussed (1) . Lifting up the inferior nerve bundle gently with a

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