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the acrylic temporary stent is also completed (7). An upper impression for a new denture is usually done just prior to the first surgery, as the teeth made for subperiosteal implants are always acrylic with zero degree inclined planes.

The subperiosteal implant framework should be no more

than half a mm in overall thickness. It contains usually four pro-11 truding posts, or if the framework is extremely flat because of the

bony topography, a horizontal bar (8) is sometimes included in-stead of the posts to give more support and stability to the sub-structure framework (9). Whether it be a bar or four posts, the two posterior posts always arise from a neck which extends from the mylohyoid strut (10), since this is the only area posteriorly where there exists attached gingiva. Anteriorly, the two posts protrude slightly to the lingual side of the residual crest (11). Both buccal peripheral struts contain perforations approximately two mm square (12), and continue anteriorly over and circumventing the mental foramina as a narrow single strut (13) to continue on as a fenestrated strut again in the symphyseal region (14) .

At the second surgical visit the tissues are incised, reflected and the implant is inserted (15). The tissues are sutured over the framework of the implant (16) and the temporary acrylic stent with its two posterior geometric acrylic planes of occlusion is seated over the protruding posts (17). The denture should be implant borne only, and impingements on the tissues should be relieved. The occlusion is carefully checked. One week later the sutures are removed. When the tissues have healed sufficiently, the metal superstructure is fitted over the protruding posts, the wax up of the new denture is fitted over the maxillary tissues and an inter-occlusal record of centric relationship is taken (18). The upper denture wax up is removed with the bite registration and

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