than to use a bladevent that is inserted directly over and lingual to the mental foramen.

The main reasons for using a pre-mental foramen bladevent are the presence of a cuspid limiting space in front of the foramen; defects in more anterior sites that contraindicate their use as implant sites; and the desire to shorten the gap between anterior and posterior abutments.

A pre-foramen bladevent is not advisable for most posterior abutments unless the bridge includes stable anterior teeth and can be carried around the arch to include the opposite cuspid. The pontics should extend no further posteriorly from the bladevent abutment than the first molar.

Caution: The groove made over the foramen area must be far enough on the lingual side of the ridge to prevent injury to the neurovascular bundle exiting the mental area as well as to avoid injury to the inferior alveolar nerve distal to the mental foramen.

Anterior Support Only

When the only possible implant sites are anterior either a full lower subperiosteal implant can most readily be successfully used or the latest five piece rami-symphyseal implant system. This involves inserting an anterior blade as well as one blade into each ramus which immediately becomes attached with each other and to the anterior blade by virtue of hollow tubes and extension arms, thus making all elements form into a one-piece horseshoe. However, both of these systems will be illustrated in great detail later on in this text (1) , (2) .

To give added support to a denture in such situations, sometimes a bladevent is inserted in each cuspid area (3). The posts should be extremely short and joined together with a Dolder or Andrews type bar (4) for the support of the denture. The denture anteriorly should not fit tightly over the horizontal bar (5) as taking off and on as well as the eventual resorption in both posterior quadrants underneath the free end saddles could dislodge the implants. Either a gentle fit of acrylic over the bar would be desirable or Gerber, Ceka, or Lew attachments serve as excellent supports, (6), (7), (8). Also, the copings themselves that cover the implant posts can

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