Superior Border Augmentation
Superior border augmentation with a bone graft is occasionally jndicated when severe resorption of the mandible results in inadequate height and contour and potential risk of fracture or when the treatment plan calls
for placement of implants in areas of insufficient bone height or width. Neurosensory disturbances from inferior alveolar nerve dehiscence at the location of the mental foramen at the superior aspect of the mandible also can be corrected with this technique (Fig. 13-31). ‘ The use of autogenous corticocancellous blocks of iliac crest bone was described by Thoma and Holland in 195115 for superior border augmentation. However, as much as 70% resorption of iliac crest bone can occur with this technique.l” This large amount. of resorption may be the result of movement of the bone graft segments that were initially wired to the mandible allowtngslight
movement combined with the external rather than internal loads placed on the graft after healing. Currently these blocks of bone’ are frequently secured to the mandible’ with small rigid fixation screws, mini mjzing graft mobility. Tissue-guided regeneration with the use of. a membrane is often combined with the bony augmentation. In some cases implants can be
placed at the same time the bone graft augmentation is
FIG, 13-30 A, Appearance of maxillary alveolar ridge after removal of teeth. B, Intraseptal
removal of bone with rongeur. C, Clear acrylic surgical guide in place. Any areas -that interfere
with seating of template or cause blanching of tissue from excess bone or underlying soft tissue
should be removed (arrow).
FIG. ‘3-3″ Superior border grafting of atrophic mandible. Dia-
.grammatic representation of corticocancellous iliac crest blocks con-
. toured to adapt to configuration of mandible, then fixated with
miniplates and screws
Inferior Border Augmentation
Sanders and Cox 17 reported the first clinical use of an inferior border technique for augmentation of the atrophic mandible. This technique ts rarely, if ever, used. On occasion the augmentation of mandibular bulk with
inferior grafting is ac complished using iliac crest bone grafts, secured with rigid fixation (Fig. 13-:~2). In rare cases this technique is also combined with immediate placement of implants. Indications for use of this technique, in addition to atrophy-of the alveolar ridge area, included the prevention and management of fractures of the atrophic mandible. However, this technique does not address abnormalities of the denture-bearing areas, such as the increased interarch distance, superior border irregularities, or exposed position of the mental nerve, which result from mandibular atrophy.