Proper placement of implants is critical in order to achieve the best possible aesthetic results. This is especially true in the maxillary anterior region. Extreme bone loss in an edentulous area presents a challenge to ideal implant placement. Several bone grafting techniques have evolved over the years to enable us to attain our goals. Each of these techniques has its advantages and disadvantages and therefore we must use our clinical judgment to decide which technique to pursue.
The techniques considered for ridge augmentation in this clinical case were:
- Autogenous block onlay bone grafting.
- Nonautogenous block onlay grafting.
- Segmental ridge splitting.
- Particular bone grafting.
Autogenous Block Onlay Bone Grafting
Autologous bone grafting used with dental implant was originally introduced by Brånemark et al in 1975.1 This technique involves harvesting bone from a recipient site such as the ramus of the mandible or mandibular symphysis and transplanting this block of bone to a recipient site. This technique can result in significant increases in width but less predictable to increase alveolar height. It involves surgery on a secondary site and it is thus more invasive and traumatic, which leads to higher morbidity of the donor site ie, impaired sensibility to teeth, gingiva, and skin. Another big disadvantage is the significantly high cost of this procedure compared to the others.
Nonautogenous Block Bone Grafting
The big advantage of this technique is that since the material is artificially produced, it eliminates the need for an additional surgical procedure to procure bone from a donor site. However in addition to having the same other drawbacks as the autogenous bone graft, this method is very technique sensitive. It must retain primary closure throughout the healing phase, otherwise it will fail. Failure of either block technique can result in a worse situation than the original.
Segmental Ridge Splinting
The segmental ridge split procedure creates a crypt surrounded by bone and periosteum into which implants and bone graft materials can be introduced with treasonable confidence that new bone can be constructed and that this new bone will provide a solid base for dental implants. Razor sharp bone chisels and a mallet are used to split the alveolar ridge. An implant is placed between the 2 cortical plates along with particulate bone graft material. This procedure is extremely technique sensitive and requires careful case selection. A ridge that is too narrow mesiodistally or buccolingually is almost impossible to split cleanly, and thus presents a high risk of resulting in a far worse situation than originally. It also does not address the loss of alveolar height.
Particular Bone Graft
Bone grafting using particulate material has also been done since the earliest days of osseointegrated implants. Materials have included freeze-dried allograft from tissue banks and nonallograft hydroxyapatite materials. Different particulate materials are supposedly used for osteoinductive and osteoconductive properties. The synthetic hydroxyapatite materials are mainly thought to maintain space and provide a scaffold in which natural bone can form. Different membranes are usually placed over the particulate graft material to both keep the material in place and exclude early migration of epithelial cells before osteoblasts have a chance to migrate and produce bone. Particulate grafting is the most widely used technique because it is less sensitive, less morbid, doesn’t require a donor site and is comparatively much more affordable to patients. It can be used for onlay grafting to increase width and height as well.
Yet even despite our best efforts, an implant may not end up in an ideal position. It is situations like these where expert prosthodontics can compensate and overcome a less than ideal implant position to attain a highly satisfactory result.
CASE REPORT
A 42-year-old female patient presented with a missing maxillary left central incisor with a severely atrophic localized edentulous ridge (Figures 1 and 2). Atrophy of the alveolar ridge had occurred in width as well as vertically.
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Figure 1. Initial preoperative view from labial from July 14, 2007. Tooth No. 9 missing. |
Figure 2. Initial preoperative view from occlusal from July 14, 2007. |
The treatment plan comprised first onlay bone grafting to increase height and width prior to placement of an implant and ultimately placement of a crown.
First Stage Surgery
Under local anesthesia, an incision was made from the distal line angle of No. 8 to the distal line angle of No. 10. Vertical incisions were extended at each line angle. A full thickness flap was elevated exposing a “knife edge ridge” of less than 1 mm thickness in the area of No. 9 and approximately 6 mm loss in vertical bone height at the center (Figure 3). Small perforations were made in the bone to create bleeding surfaces (Figure 4). A combination of large particle cortical PUROS bone graft material with Bio-Oss, a synthetic hydroxyapatite graft material was used (Figure 5). Graft material was placed on both labial and palatal sides of the ridge. The graft was then covered with BIO-GUIDE resorbable membrane and held in place with 2 titanium tacs (Figure 6).
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Figure 3. Preoperative view from labial of bone (alveolar ridge) with flap reflected (July 14, 2007). |
Figure 4. Tenting screw in place during first bone grafting procedure (July 14, 2007). |
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Figure 5. Bone graft material (BIO-OSS + Puros cortical) in place during first bone grafting procedure (July 14, 2007). |
Figure 6. BIOGUIDE membrane in place covering bone graft material. Membrane held in place with titanium tacks. First bone graft procedure (July 14, 2007). |
The flaps were closed with 4-0 vicryl sutures (Figures 7 and 8). The patient was placed on a 7-day regimen of amoxicillin along with a chlorhexidine (Peridex) rinse. Healing was uneventful (Figure 9) and the graft site was allowed to heal for 6 months before the area was flapped open again. Modest bone augmentation (approximately 2 mm gain in thickness; one mm gain in height) had taken place, however, it was still deemed insufficient in both quantity and quality to place an implant.
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Figure 7. Area sutured—occlusal view (July 14, 2007). |
Figure 8. Area sutured—labial view (July 14, 2007). |
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Figure 9. Preoperative view—occlusal (January 12, 2008). |
Additional bone grafting was done using the same materials and techniques as the first procedure (Figures 10 to 12). Again healing was uneventful and the site was allowed to heal for another 5 months (Figure 13). The site was again flapped open revealing an additional 1- to 2-mm gain in thickness but less than a 1-mm gain in height. Bone quality was judged to be poor-fair.
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Figure 10. Grafting material placed. |
Figure 11. Membrane placed. |
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Figure 12. Sutured with BIOGUIDE membrane (January 12, 2008). |
A surgical stent was used to place the implant in the correct mesial-distal position, however, in deference to the quality bone; it was decided to place the implant slightly within labial to the surgical stent position. This was done in order to place the implant completely within the labial palatal borders of the ridge rather than risk perforating or completely obliterating the palatal wall in trying for ideal location from a prosthetic point of view. Additional bone grafting was placed around the implant using a nonresorbable TEFGEN membrane (Figures 14 to 17).
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Figure 13. Preoperative view prior to implant placement (June 14, 2008). |
Figure 14. Implant in place—occlusal view (June 14, 2008). |
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Figure 15. Implant in place—labial view (June 14, 2008). |
Figure 16. Bone graft (BIO-OSS + Puros cortical) in place (June 14, 2008). |
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Figure 17. Sutured implant in place (TEFGEN membrane, black silk sutures) (June 14, 2008). |
Figure 18. Implant uncovered with cover screw in place (December 20, 2008). |
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Figure 19. Final prosthetic smile (December 20, 2008). |
Healing was uneventful and the implant was uncovered 6 months later. The membrane was removed and a healing abutment was placed (Figure 18). The patient was referred back to the restorative dentist a few weeks later and the case was restored (Figure 19).
CLOSING COMMENTS
Extensive bone grafting was done in an effort to augment a severely atrophic edentulous single tooth area for the purpose of placing an implant. Despite these efforts, the final placement of the implant resulted in a location more labial and apical than ideally desired.
Reference
1. Brånemark PI, Lindström J, Hallén O, et al. Reconstruction of the defective mandible. Scand J Plast Reconstr Surg. 1975;9:116-128.
Suggested Readings
Listrom RD, Symington JM. Osseointegrated dental implants in conjunction with bone grafts. Int J Oral Maxillofac Surg. 1988;17:116-118.
Misch CM, Misch CE. The repair of localized severe ridge defects for implant placement using mandibular bone grafts. Implant Dent. 1995;4:261-267.
Misch CM. Comparison of intraoral donor sites for onlay grafting prior to implant placement. Int J Oral Maxillofac Implants. 1997;12:767-776.
Schwartz-Arad D, Levin L. Intraoral autogenous block onlay bone grafting for extensive reconstruction of atrophic maxillary alveolar ridges. J Periodontol. 2005;76:636-641.
Dr. Rosenstein is a periodontist in private practice in New York City and Suffern, NY. He did his undergraduate and postgraduate dental training at University of Medicine and Dentistry New Jersey Dental School, Newark, NJ, and a general practice residency at Lenox Hill Hospital, New York City. He can be reached at (845) 357-5002 or rosenstein@aol.com.
Disclosure: Dr. Rosenstein reports no disclosures
