Although hard-tissue grafting protocols have typically recommended a 6-month healing period before placement of any dental implants at the graft site, it may be possible to secure an onlay graft to a wide but shallow alveolar ridge using implants that are then submerged and allowed to osseointegrate. This approach has the advantage of expediting treatment and making it less traumatic for the patient. A case is described in which a portion of an edentulous mandible was augmented with ramus bone secured with 2 dental implants.
When trauma, acute periodontal disease, or advanced atrophy of the alveolar ridge makes placement of implants impossible, grafting has become a well-established and reliable treatment option. Almost all bone-grafting approaches suggest that a 6-month healing period is necessary before implant placement at the grafted site. This allows for adequate integration of the grafted material. However, in one circumstance it may be possible to graft the ridge to obtain the necessary additional height and place implant(s) in a single-stage procedure, namely, when the patient has insufficient alveolar bone but the ridge is wide enough to accommodate an implant and allow for an acceptable biological width around it. When an onlay graft is placed on top of such a ridge, and implants are used to secure the graft material, the resulting treatment experience for patients can be faster, easier, less traumatic, and less expensive than a more traditional treatment approach. This article reports on a case in which an onlay graft from the ramus was performed in conjunction with placement of implants in a 1-stage surgical procedure.
The patient was a 58-year-old woman who had been edentulous in her right mandibular jaw for a number of years. She had been functioning with no prosthesis in that area.
Radiological examination (Figure 1) revealed the presence of approximately 5 mm of bone superior to the right inferior alveolar canal. However, palpation of the ridge indicated that the width was approximately 12 mm (Figure 2).
The treatment plan called for building up the height of the ridge in the molar region with a section of bone to be harvested from the ramus. At the same time, 3 (4.3 × 10 mm) implants (Replace Select, Nobel Biocare, Yorba Linda, Calif)were to be placed in the following positions: right mandibular first bicuspid, first molar, and second molar. Implants also were to be placed at a subsequent date at the left maxillary central, lateral, cuspid, first, and second bicuspid; the right maxillary lateral incisor and first molar; and the left mandibular first and second molar positions.
Sedation was administered along with local anesthesia, and a standard mucoperiosteal flap was created, exposing both the ramus and the ridge. Next, a tapered fissure bur was used to make a horizontal cut at the ramus, as well as mesial and distal vertical cuts. The cortical bone at the inferior border of the graft site was scored with a round bur, then a chisel was used to gently pry the section of bone free from the site. The harvested bone was roughly 8 × 12 mm (Figures 3 and 4).
Implant-positioning rings (V.I.P. Systems, Edmonton, Alberta) were used to determine precisely where the osteotomies should be created. The implant-positioning system consisted of 14 milled polished titanium rings that ranged in diameter from 5 to 11.5 mm.
In this case, a ring that matched the diameter of the left mandibular first bicuspid was selected and placed next to the right mandibular cuspid. A pilot drill was used to drill through the ring's central hole to mark the bone, then after removal of the ring, a tapered fissure bur was used to penetrate the cortical bone. The ring was repositioned, and drilling with spiral and pilot drills continued to roughly 10 mm below the top of the ridge. A parallel pin replaced the drill, securing the ring in position.
Although no implant was to be placed in the second bicuspid position, a second ring of the same diameter as the first bicuspid ring was secured on the site with a parallel pin. A third ring was then positioned in the first molar position, abutting the second ring. The parallelism of the pins was confirmed, and osteotomy preparation at the first molar site continued. Just like at the ramus and the first osteotomy site, all bone fragments were collected in a trap and set aside. Care was taken to proceed slowly, keeping the bottom of the osteotomy constantly in view to ensure that there would be no incursion on the inferior alveolar nerve.
Once the first-molar osteotomy (roughly 4.3 mm in diameter and 5 mm deep) was completed, a tapered fissure bur was used to drill through the dense cortical bone and into the medullary bone at a number of points around the site (Figure 5). This was done to enhance the blood supply at the graft site, stimulating bone growth between the recipient bone and the graft.1–3
The section of donor bone was placed on the prepared ridge at the first-molar site to assess how closely it would adapt to the site. A fissure bur was used to eliminate any high spots and void space, taking care to reduce the overall bone thickness as little as possible. This adjustment process also served to decorticate the donor bone. After the adaptation was deemed to be acceptable, a 4.3-mm-diameter hole was created in the donor bone (Figure 6) and threaded (Figure 7). An implant was screwed into the donor bone (Figure 8), then into the osteotomy (Figure 9). An implant was also placed at the first bicuspid osteotomy at this time.
Another ring was placed on top of the onlay graft, adjacent to the first-molar implant, and a third osteotomy was created, drilling through the donor bone and the ridge below it (Figure 10). This third osteotomy was then threaded, and the third implant placed (Figure 11). Healing screws were connected to all 3 implants (Figure 12).
The bone particles collected during osteotomy creation (Figure 13) were mixed with a xenograft (BioOss, Osteohealth Co, Shirley, NY) and platelet-rich plasma. This mixture was plastered around the graft site and smoothed to the ridge contours (Figure 14). In cases where larger voids exist, irradiated cadaver bone can also be used as part of the mortar.4
Collagen material (Bioguide, Osteohealth) was draped over the graft site (Figure 15), and mattress sutures were used to stabilize it to the soft tissue (Figure 16). An alternative approach would be to delay attaching the healing screws until all the grafting had been completed. The surgeon would then punch holes in a collagen membrane (Neomem, Citagenix Inc, Laval, Quebec), place the membrane over the implants, and attach the healing screws, thus fixing the collagen in place. A radiograph taken immediately postoperatively (Figure 17) revealed the apex of the 2 posterior implants to be positioned just above the inferior alveolar nerve.
The 6-week postoperative evaluation found normal healing with no parasthesia or infection (Figure 18). Approximately 3 months after the initial surgery, topical anesthesia was applied to the implant sites with a ligament syringe, and the thin pieces of mucosa that covered the implants were removed (Figure 19).
Impressions were made, abutments were fabricated, and approximately 2 weeks later the final fixed prosthesis was cemented in place (Figures 20 and 21). Further remodeling of the grafted bone was evident in the radiograph taken at this point (Figure 22). Figure 23, a radiograph taken 6 years after implant placement, shows continuing remodeling.
The grafting technique used in the case described herein is only indicated when the mandibular or maxillary ridge has a width of at least 8 to 10 mm (enough to accommodate a 4.3-mm implant and allow for approximately 2 mm of ridge around it). Additionally, this technique is not indicated for patients who are smokers,5,6 have alcoholism, or are in poor systemic health.7
The technique described in this article could be used when working with bone harvested from a number of potential sites.8 However, the proximity of the ramus and the ease of access to it makes the ramus the optimal choice. In the experience of the author, morbidity associated with ramus grafts is significantly lower than that for symphyseal grafts. Whatever the source of the donor bone, achieving a close approximation of the graft material to the recipient bone is essential.
Although the patient in this case had approximately 5 mm of bone superior to the inferior alveolar nerve, the author has found the technique to be useful for patients with as little as 3 mm of bone. In such extreme cases, use of a 10-mm implant with a 2-mm polished collar is indicated.
In the author's experience, use of the implants to fix the donor bone to the ridge results in a more secure connection than that achieved when using traditional bone screws. The author has used this technique more than a dozen times, and in every instance patient satisfaction has been high and excellent results have been achieved.
Use of a 1-step implant technique when grafting a wide but shallow ridge relieves the patient of the need to undergo 2 major surgical procedures and compresses the time required for implant therapy. Furthermore, the shallowness of the osteotomies created in this approach provides the surgeon with excellent visibility and ensures that no penetration of the mandibular canal will occur, eliminating the risk of inflicting nerve damage.
David M. Vassos, DDS, is in private practice. Address correspondence to Dr Vassos at 213 Le Marchand Mansion, 11523 One Hundredth Avenue, Edmonton, Alberta, Canada T5K0J8 (firstname.lastname@example.org).