EDI - European Association of Dental Implantologists

66 EDI
Case Studies
The bone crest was curetted to remove all soft tissue.
While the CT scans provide an excellent image of
the defect, direct visualization is the only way to accurately
assess its horizontal and vertical dimensions
the amount of bone to be harvested from the donor
site. A limited incision in the parietal region revealed
the donor site. No hair needed to be shaved off.
The periosteum was incised and reflected and
bone grafts were outlined using a cutting bur with a
tip diameter of 1.5 mm parallel and about 5 cm away
from distant from the midline. Three rectangular
bone grafts 4 x 1 mm in size were designed at the
donor site. The head of the round bur was shifted
down to the diploe layer. The oozing of blood from
the excision site revealed penetration to the appropriate
anatomical level of the skull. The final step was
to use a curved osteotome to free the intended bone
grafts from the donor site, to avoid sourcing any
material from the inner table of the skull. Bleeding
from the diploe layer was controlled with bone wax
and the scalp wound was closed using double layer
vertical-mattress resorbable sutures.
The harvested bone was placed in a sterile physiologic
solution or in moist gauze to maintain as much
the vitality of the block as possible. The recipient bed
was prepared by perforating with a small, straight
fissure bur. This created bleeding channels in the
recipient bed, assisting the formation of neovasculature
from the palatal periosteum. Once the recipient
bed had been prepared, rotary instruments were
used to shape the blocks of donor bone to fit the
recipient bed as closely as possible. One block was
adapted and attached on the buccal aspect of the
alveolar ridge as a veneer graft, while a second block
was adapted to serve as an onlay graft and attached
to the first calvarial block. To secure the block grafts
in place, two titanium alloy screws per block, at least
1.5 mm in diameter, were used (Fig. 4).
The bone blocks were secured using the lag-screw
technique. With this technique, the hole that is
drilled through the graft is wider than the screw
thread. The bur used to drill the host bone should be
smaller than the diameter of the screw. When the
head of the screw is tightened against the block, the
graft is compressed onto the host bone surface. The
graft must remain immobile during healing.
Sharp edges of the bone blocks were rounded off
with large diamond burs. Gaps around the block
grafts were filled with bone chips harvested from the
donor site. Several authors have reported that resorption
can be reduced by covering the bone graft with
a barrier membrane. However, we believe that barrier
membranes are not necessary with calvarial block
bone grafts, which already show minimal resorption.
Once the graft is secured, closure of the soft-tissue
Fig. 4 Panoramic x-ray taken one month after the bone reconstruction: the retention
screws are in place.
Fig. 5 Histologic preparation of the external cortical layer
of the calvarial graft at implant placement. The picture
shows the typical compact osteonic structures of the calvarium,
with signs of active remodelling and new vascular
ingrowth. The vital bone containing osteocytes in the
inner core of the osteons surrounded lamellar non-vital
bone, suggesting that non-vital bone was recolonized by
blood vessels and osteogenic cells via the Haversian canals (original magnification
x 200; specimens stained with haematoxylin and eosin).
flap requires primary closure without tension. An
incision through the periosteum at the base of the
flap usually allows for tissue coverage. Vertical mattress
sutures (Vicryl 3-0) are used to resist any pull on
the wound edges.
The main complication associated with onlay bone
grafts is wound dehiscence with graft exposure. Postoperative
antibiotic and analgesic therapy was routinely
practiced for seven days. Patients were also
given chlorhexidine digluconate (0.2 %) for ten days,
and the sutures were removed after ten to twelve
days. No major complications or evident seromas
were detected at the donor site. After four months of
healing, the fixation screws were removed under
local anaesthesia, grafts were re-contoured, and the
flap was repositioned to restore an adequate amount
of attached gingiva for a better aesthetic result. During
this procedure, a bone biopsy was removed with
a trephine bur and processed for histological testing
to study the vitality, revascularization and remodelling
processes of the grafts (Fig. 5). The gingiva was
conditioned by modification of the artificial teeth of
the provisional restoration using composite resin.
After three months of soft-tissue healing, an acrylic
radiographic stent was prepared on the base of a
diagnostic wax-up of the missing teeth according to
the Nobel Guide computer-based planning protocol.
To facilitate the double CT scanning technique and