Presurgical Screening

Presurgical screening of patients in preparation for sinus grafting must include questions about factors that affect the successful formation of bone within the graft material chosen for the sinus augmentation procedure.

Exclusion criteria that should be considered include the following:

Preoperative Radiographic Screening

The preoperative radiographic examination begins with a panoramic radiograph. The clarity of the maxillary sinus, the presence of septa in the proposed surgical site, and an approximation of the thickness of the alveolar bone are visualized. Periapical radiographs do not usually contribute to the screening of the patient for sinus grafts. However, the panoramic radiograph has approximately 20% magnification error; also, detail is lacking on the facial-palatal thickness, morphologic structure of the alveolar bone and sinus floor, and status of the sinus membrane. Therefore, a reformatted computed tomography (CT) scan may be indicated for selected patients when more detail is desired (Figure 4-1, A-B).

• FIGURE 4-1 A, Computed tomography (CT) scan of the maxilla showing the reconstructed panoramic image and the axial cut. Before the bone graft is placed, a radiopaque stent with holes drilled into the planned implant site are used to determine the bone thickness at the proposed site.

• FIGURE 4-1 B, Reformatted cross section of the maxilla shown in Figure 4-1, A, showing the location of the cross section by number as it relates to the proposed implant location. The crosshatches at the bottom represent 1-mm increments, which allow thickness measurements of the bone. The proposed implant axial emergence is clearly evident in the stent.

CT scans are especially recommended for patients in whom the surgeon suspects multiple sinus septa or a pathologic condition in the sinus. The scans can document the thickness of the alveolar crest at the surgical sites and the thickness of the membrane. Before a CT scan is taken, all presurgical prosthetic planning should be complete, and a radiopaque stent indicating the positions of the planned restoration should be made. The scan is used to identify the specific locations of the planned implant sites and to provide the surgeon with an accurate understanding of the anatomy in the surgical location (see Figure 4-1).

Surgical Technique

The surgical procedure involves the removal or medial rotation of a window of cortical bone over the lateral aspect of the maxilla without perforation of the sinus membrane. Incisions should be made so as to allow adequate exposure of the surgical site and to avoid the placement of the incisions over the sinus window. After the lateral wall of the maxilla has been exposed, four linear ostectomies are performed to outline the window. The inferior horizontal ostectomy should be made as close to the floor of the sinus as possible to facilitate membrane dissection. The vertical ostectomies should be made close to the maxillary buttress and lateral nasal wall, again to facilitate membrane elevation. The superior horizontal cut should be made at the level of the planned augmentation height, which should allow placement of implants 15 mm long (DVD Figure 4-1, A). After the window has been created, the lateral bone still adherent to the sinus membrane can be either rotated medially (DVD Figure 4-1, B) or removed.

4-1, A-B

Surgery is performed in the operating room (OR) with the patient under general nasoendotracheal anesthesia or in an outpatient setting using local anesthesia and sedation as necessary. At surgery, an antibacterial rinse or povidone-iodine (Betadine) solution (or both) is used to reduce the bacterial count in the mouth. Steroids and antibiotics can be given intravenously before surgery. A local anesthetic, typically 2% lidocaine (Xylocaine) with 1:100,000 epinephrine and a longer-acting anesthetic, is administered to the maxillary vestibule and crestal tissues.

After a minimum of 5 minutes is allowed for the vasoconstrictor to take effect, a crestal incision is made. For the totally edentulous maxilla, two incisions are made, one on each side, sparing the anterior incisive canal region. Each incision is made on the crest, with anterior release starting in the lateral incisor region and extending vertically past the junction of the attached and unattached gingivae. Posteriorly, a vertical releasing incision is made in the second or third molar region and extending into the unattached gingiva. Incisions that cross the midline are avoided unless anterior onlay grafting is also planned.

For the patient with a partially edentulous maxilla with retained anterior teeth, the incision is crestal with the vertical release made anteriorly, avoiding the band of attached gingiva on the teeth, into the unattached gingiva. Posteriorly, the release is similar to that in the patient with a totally edentulous maxilla, but it may be directed over the tuberosity if tuberosity bone harvest is planned.

After the periosteum has been reflected superiorly, exposing the lateral wall of the maxilla, the planned ostectomy is visualized to start at the level of the maxillary sinus floor. The vertical osteotomies are parallel to both the lateral nasal wall and the anterior border of the maxillary tuberosity, where the maxilla curves posteriorly. The superior horizontal ostectomy is located where the vertical position of the augmentation is planned. A fiber-optic light source can be placed in the nose or against the palate to illuminate the sinus, allowing the surgeon to visualize the specific landmarks (e.g., floor of the sinus) and to perform an accurate ostectomy.

A round bur with irrigation is used to remove cortical bone and expose the gray, glistening sinus membrane (Figure 4-2, A). The lateral maxillary wall can be left intact and rotated inward as the new floor of the maxillary sinus, or it can be removed, depending on the clinician’s preference. A smooth, relatively new elevator is used to peel the sinus membrane from the floor of the maxillary sinus and lateral nasal wall (Figure 4-2, B). The membrane is elevated to the height of the desired augmentation. The edges of the sinus membrane are elevated initially, gradually increasing the distance of membrane elevation. Excessive elevation of one isolated portion of the membrane is avoided, because this would result in tension on the nonelevated membrane. The membrane must be sufficiently elevated to avoid excessive pressure when the sinus graft material is placed.

• FIGURE 4-2 A, Surgical photograph showing an incision at the crest of the ridge, followed by a full-thickness, mucoperiosteal reflection to expose the lateral wall of the maxilla. A round bur has been used to remove the cortical bone, exposing the underlying sinus membrane.

• FIGURE 4-2 B, Small Woodson elevator is used to elevate the thin sinus membrane from the inner aspect of the maxillary sinus.

Perforations of the sinus membrane may occur, depending on the experience of the operator, location of the horizontal ostectomy, presence of septa, and thickness of the sinus membrane (Figure 4-2, C). Small perforations are left untreated. If large perforations are present, the procedure is aborted and attempted at a minimum of 4 months later. Use of a patch, such as a collagen membrane or other resorbable membrane, is at the discretion of the operator, with the understanding that the addition of such materials may increase the chances of postoperative infection. If solid blocks of bone are to be used, an intact sinus membrane may be less important. After the membrane has been elevated, the bone harvest procedure is performed.

• FIGURE 4-2 C, Sinus membrane is raised, and the lateral wall of the maxilla is then rotated medially into the sinus. The membrane is elevated with a small perforation. Small perforations (such as the one shown) can be left alone with no treatment. If a large perforation is made, the procedure may be aborted, unless a solid block of bone is used rather than particulate bone. When the membrane is elevated and positioned in the superomedial aspect of the sinus, it often folds on itself; this folding closes over any perforations.

Jawbone Grafts

A small amount of marrow (1 to 2 ml) can be harvested from the maxillary tuberosity in the area of the third molars. An incision is made posterior to the hamular notch, with anterior or posterior release as needed. If the surgeon anticipates using the maxillary tuberosity as the graft harvest site, the crestal incision made to expose the maxilla is extended posteriorly to allow harvesting of the posterior maxillary bone. The periosteum is reflected to expose the posterior aspect of the maxilla. Rongeur forceps are used to harvest the bone, with care taken to avoid the sinus membrane and the large blood vessels located in the pterygoid fissure. Often, up to 2 ml of cancellous bone can be harvested from a maxillary tuberosity.

Another source of bone from the jaws is the symphysis. To gain access to the chin, the surgeon can make a sulcular or vestibular incision. The periosteum is elevated to place the osteotomy 10 mm inferior to the apex of any incisor teeth. The bone then can be collected with the use of a trephine, and the cortical plate can be removed and the marrow harvested. A collecting device can be used in the suction line when bone is drilled from the chin or ramus regions or bone scrapings are produced. The goal is to harvest viable endosteal osteoblasts, which can participate in the first phase of bone formation.

For the patient undergoing unilateral sinus graft surgery, the surgeon usually can harvest bone from the posterior maxilla, the mandibular third molar site, or the chin to obtain sufficient autogenous bone, mixed with an equal amount of DFDB, to augment one sinus (Figure 4-3, A-H). A scraping device can be used on the mandibular third molar sites to harvest cortical bone and a small amount of cancellous bone (Figure 4-4, A-H). The cortical portion of the mandible has very few viable osteoblasts. To gain additional bone, the surgeon also can use the chin as a harvest site. The chin cortex is removed with a round bur, and a sieve collection device is placed in the suction line. The round bur then is used within the confines of the cortical bone to harvest cancellous bone, which should contain viable osteoblasts.

• FIGURE 4-3 A, This 50-year-old man was referred for a left sinus graft to allow placement of three implants 15 mm long for an implant-borne restoration. This occlusal view shows a long span between the maxillary left canine and the maxillary left second molar. Both teeth are marginal abutments secondary to bone levels and root contours.

• FIGURE 4-3 B, Crestal incision is made with anterior and posterior vertical release. After the lateral wall of the maxilla has been exposed, the ostectomy is performed; the sinus membrane is elevated with no perforations.

• FIGURE 4-3 C, New temporary bridge is made, which is duplicated and used as the surgical guide. Holes are drilled as prescribed by the prosthodontist. The surgical guide is placed on the tooth preparations. The drilling sequence is completed with the membrane safely elevated superiorly.

• FIGURE 4-3 D, Bone graft is harvested from the chin. After a local anesthetic has been infiltrated, a vestibular incision is made, followed by sharp and blunt dissection to expose the symphysis. A sagittal saw is used to perform corticotomies, and the cortical plate is removed. The cancellous bone under the cortex of the symphysis is removed with the aid of a curette and an osteotome. After the bone graft has been harvested, the mentalis musculature is anatomically reapproximated, and the mucosa is closed with polyglactin 4-0 sutures using an atraumatic needle.

• FIGURE 4-3 E, Bone graft is combined with demineralized, freeze-dried bone (DFDB) in a 1:1 ratio to yield approximately 8 ml of graft. The graft is placed into the medial aspect of the sinus, followed by the implants and additional graft material. Additional material then is placed to augment the thin alveolar ridge.

• FIGURE 4-3 F, After 6 months, the implants are exposed through a crestal incision. The implants are covered with bone.

• FIGURE 4-3 G, Occlusal view showing the implants just before placement of the final restoration.

• FIGURE 4-3 H, Final restoration in place.

(Prosthetics by Dr. Gerald Chiche.)

• FIGURE 4-4 A, This patient wants a fixed prosthesis; he no longer wants to wear his maxillary removable partial denture. The width of the alveolus is adequate.

• FIGURE 4-4 B, Incision is made slightly palatal to the crest, with anterior and posterior vertical releasing incisions proximal and distal to the sinus graft window. The ostectomy is performed, and the lateral bone is removed. The intact sinus membrane is observed.

• FIGURE 4-4 C, Membrane is carefully elevated and reflected medially into the sinus.

• FIGURE 4-4 D, To harvest intraoral bone, the surgeon makes a retromolar incision to expose the external oblique ridge. A bone collecting scraping device is used to collect shavings of cortical bone from the external oblique ridge. Approximately 2 ml of cortical shavings, with a small amount of cancellous bone, is harvested from the ramus.

• FIGURE 4-4 E, To increase the amount of available bone, the surgeon exposes the symphysis and uses a round bur at approximately 1000 rpm with a sieve in the suction line to collect cortical and cancellous bone.

• FIGURE 4-4 F, Bone harvested from the symphysis through the suction line sieve on the left and the shavings from the external oblique ridge on the right are combined.

• FIGURE 4-4 G, Equal volume of DFDB is combined with the final volume of autogenous bone to produce approximately 8 ml of bone graft material.

• FIGURE 4-4 H, Bone graft composite is packed into the sinus site. After approximately 6 months, the implants are placed; after an additional 6 months, the final restoration is completed.

When bone from the jaws is used, the volume of the graft usually must be augmented with either an allograft or a xenograft, depending on the clinician’s preference. Future use of alloplasts in various forms or recombinant proteins may affect the need for harvesting cancellous marrow.

Tibia Bone Grafts

The advantages of harvesting bone from the tibia are decreased postoperative morbidity and the ease with which the procedure can be performed under intravenous sedation in the surgical office. Disadvantages of tibia graft harvesting are the potential risks of leg fracture and possible prolonged edema in overweight patients.

In either the surgical office or the OR, the leg and foot must be prepared with meticulous sterile scrub, paint, and sterile wraps to ensure a sterile field. Often the sinus membrane elevation is accomplished first; the surgeons then rescrub, regown, and prepare the tibia for graft harvest. If attention to sterile detail is thorough, infection at the graft harvest site is rare.

The harvesting of tibial bone involves identifying Gerdy’s tubercle, after which a sharp dissection to the periosteum overlying the tibial cortex is performed (Figure 4-5, A-I). Two techniques can be used to harvest tibial cancellous bone: (1) a periosteal osteocortical flap can be elevated, based on intact periosteum along the superior aspect of the cortical window, or (2) a small cortical window can be created, which is covered with periosteum after the bone has been harvested.

• FIGURE 4-5 A, Tibia can be used as the bone graft harvest site. The leg is prepared and draped. The anatomic landmarks, including the head of the fibula, the patellar tendon, and Gerdy’s tubercle, have been drawn on the leg. The incision line drawn across Gerdy’s tubercle is shown.

• FIGURE 4-5 B, Tibia has a wide plateau region with a bump (Gerdy’s tubercle), which is the entry site into the cancellous portion of the tibia. The bone is harvested across the wide portion of the tibia and inferiorly; in this way, thinning of the superior, weight-bearing portion of the tibia is avoided.

• FIGURE 4-5 C, After administration of a local anesthetic to anesthetize the periosteum of the tibia, a skin incision is made. Hemostasis is meticulously maintained with electrocautery. Sharp dissection is used to reach the periosteum of the tibia overlying Gerdy’s tubercle.

• FIGURE 4-5 D, If a periosteal osteocortical flap is to be raised, incisions are made through the periosteum to expose the bone along two vertical sites and one horizontal location. A fissure bur can be used to create a trough through the cortex. The cortex is elevated from the tibia with the periosteum intact on the flap of bone. This elevation allows replacement of the cortex, maintaining its vascularized attachment to the periosteum.

• FIGURE 4-5 E, In a second approach, the periosteum is raised from the bone. A bur is used to remove a piece of cortical bone 8 mm in diameter over Gerdy’s tubercle.

• FIGURE 4-5 F, Bone curette is used to collect cancellous bone from within the tibia.

• FIGURE 4-5 G, Up to 22 ml of cancellous bone can be harvested from one tibia, which is sufficient to graft bilateral sinuses.

• FIGURE 4-5 H, Lateral aspect of the maxilla is shown after the lateral aspect of the maxillary wall has been removed, exposing the intact sinus membrane.

• FIGURE 4-5 I, Membrane has been elevated, and the tibia bone has been placed.

Iliac Crest Grafts

In addition to the tibia, the iliac crest can serve as the source of large amounts (more than 20 ml) of cancellous marrow. The technique for harvesting iliac crest cancellous marrow involves elevation of the iliac cortical crest and curettage of the marrow. The cortical plates are replaced and sutured back into position.

Multiple approaches can be used to reach and harvest bone from the iliac crest. For sinus grafting, the anterior approach usually is performed, because it does not require turning the patient after the sinus elevation has been completed. In addition, a satisfactory amount of bone usually can be harvested from the anterior approach. To limit blood loss and minimize gait disturbances, the technique most often used involves a relatively avascular approach, with great care taken to avoid the sensory nerves that traverse the iliac crest region. After a sterile preparation and draping of the anterior iliac crest, a local anesthetic is administered. Blunt dissection with hemostatic control using electrocautery is used to approach the anterior iliac crest. The approach should be performed from the lateral anterior aspect to prevent reflection of the insertion of the tensor fasciae latae muscle, which will minimize long-term gait disturbances. The muscles are separated rather than incised, with the dissection medial to the gluteus medius muscle and lateral to the iliacus muscle. In the area of the iliac tubercle, fibers from the external oblique and other muscles may need to be elevated when large pieces of bone are harvested, but these fibers should be left intact if possible. The sensory nerves usually pass over the anterior and posterior spines and are encountered in fewer than 2% of patients. Usually they can be retracted, and sensory loss thus is a rare complication from iliac crest bone harvest.⁴⁸

For the harvesting of cancellous bone only, the iliac crest is approached, and the periosteum is not reflected. Incisions through the periosteum are made only where the osteotomes are used to create a linear bony incision with two anterior and posterior bony releases. These cortical cuts can be made with a saw or sharp osteotomes. The cortical plates of the crest then are outfractured, maintaining the soft tissue attachments to the periosteum. The cancellous bone is collected with bone curettes; suturing of the periosteum reapproximates the crestal bone cuts, and the wound is closed in layers.

For the harvesting of blocks of corticocancellous bone, either the lateral or the medial cortical plates of the iliac bone are stripped of periosteum (Figures 4-6, A-E, and 4-7, A-M). A saw with copious irrigation or sharp osteotomes are used to outline and remove a piece of bone. Additional cancellous bone can then be collected, after which the wound is closed in layers.

• FIGURE 4-6 A, Panoramic radiograph showing a patient with less than 2 mm of maxillary bone between the oral cavity and sinuses. The treatment plan calls for harvesting blocks of bone from the iliac crest and simultaneous placement of eight implants.