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Winter 2022 Newsletter
Autogenous bone grafting
Our patient is a 65-year-old male with unremarkable past medical history and a history of failed implants in left posterior mandible. He presented a clinical challenge due to his vertical and horizontal bone defect. Preoperative CBCT taken by patient’s general dentist (Figure 1), which showed 6 mm of vertical bone height available superior to the inferior alveolar nerve (IAN) canal. He had an edentulous space spanning from tooth #34 to #37 missing teeth #35 and 36. We discussed different treatment options including short implants, fixed prosthesis in form of a bridge spanning from 33 to 37, removable partial denture and bone grafting in preparation for implant supported crowns. Patient expressed interest in the last option. Risks, benefits and alternate treatments were discussed, and patient decided to undergo bone grafting under general anesthesia. Final approved treatment plan:
Autogenous bone grafting from left ramus to reconstruct the alveolar ridge.
Two implants at sites #35 and 36.
Implant supported crowns at sites #35 and 36 once appropriate healing occurred.
Figure 1: Pre-operative CBCT showing inadequate bone height above the IAN canal for implant placement.
In terms of bone grafting, since we needed to reconstruct both vertical and horizontal dimensions of the alveolar ridge, we determined that the best suitable option would be autogenous block graft mixed with allograft.
The procedure will be reviewed in detail later in the course of the newsletter. Following appropriate healing of the bone graft, new CBCT was taken, which showed appropriate healing and available bone in the alveolar ridge for support of two implants at sites 35 and 36. Implants were then placed under local anesthesia. 4 months after the placement of implants, permanent crowns were placed, and patient was allowed to resume full function in left mandible.
Surgical technique: Autogenous ramus block graft can be performed under local or general anesthesia. CBCT imaging is of paramount importance in treatment planning to identify the quality and quantity of available bone and the exact location of the IAN canal with respect to the ridge. After administration of local anesthetic with vasoconstrictor in the area of edentulous ridge and left ramus, a standard horizontal incision (about 3 cm in length) is made in the buccal aspect of mandibular vestibule extending from the premolar region to the ascending mandibular ramus. Dissection is then made down to the periosteum and a sub-periosteal envelope flap is reflected exposing the entirety of the lateral aspect of left mandible extending from the premolar region to the ascending ramus.
Figure 2: Intra-operative view of grafted ramus at the recipient site affixed with two screws and allograft particles around the grafted site.
A surgical handpiece, a piezoelectric surgical device or a hall drill can be then used to perform osteotomy on the superior, inferior, mesial and distal aspects of the outline of the block graft. Osteotomy is performed to the depth of medullary bone keeping in mind the location of the IAN in this region to avoid neurosensory deficits post operatively. Once all osteotomies are performed, a chisel and mallet can be used to fracture the block graft from the rest of the mandible.
The block graft is then tailored to the appropriate size and shape of the recipient site. 1.5 mm or 2 mm fixation screws are then used to fixate the block graft in place to the recipient site. Sharp edges of the bone are trimmed with a round burr and allograft mixed with autogenous bone chips (harvested from the donor site) are then packed around the block graft (Figure 2).
Figure 3: Immediate post-operative x-ray showing increased height of the grafted site and the fixation screws in place.
A collagen membrane is then secured over the grafted site. The periosteum is then scored in the buccal and lingual flaps to allow for a tension free closure. Tac screws or para-periosteal sutures are then used to secure the bone graft/membrane in place and resorbable or non-resorbable sutures are then used to reapproximate the flaps in a tension free closure.
Patient is then placed on post operative antibiotics and analgesics and are usually seen 2-3 weeks post operatively. Patient is advised to avoid chewing on the surgical site and to apply ice packs to the donor site to avoid excessive swelling or hematoma formation. The patient had an unremarkable recovery and was followed up with in 9 months for placement of two dental implants at sites #35 and 36. Figure 3 illustrates the post-operative x-ray following the bone grafting procedure. Figure 4 shows the post-operative x-ray following the placement of dental implants. The implants were allowed to osseointegrate for an additional 4 months prior to restoration with implant supported crowns by the referring dentist.
Figure 4: Immediate post-operative x-ray showing appropriate implant position at sites #35 and 36.
Discussion
Autogenous bone grafting is the gold standard for reconstruction of mandibular alveolar defects in preparation for dental implant placement. Our patient lacked appropriate bone height and width for placement of two implants in left posterior mandible. Options for reconstruction included Guided Bone Regeneration (GBR), Autogenous bone grafting using mandibular ramus, symphysis or anterior iliac crest or use of osteoinductive agents like bone morphogenic proteins. We chose to proceed with autogenous bone grafting due to the size of the defect and the rigidity of the bone needed for stability of mandibular implants. In author’s experience, regenerated bone following GBR is usually soft and bone resorption is usually expected to be more around dental implants following the first few years of occlusal function. Using the appropriate surgical treatment and technique, we were able to achieve an outstanding result for this complex case.
Ashkan Mobini DDS FRCD(c)
Please direct any questions to the author via the following email address: info@tofs.ca
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