Cylindrical Ringbone Allograft to Restore Atrophic Implant Sites: A Pilot Study
Atrophic or severely deficient edentulous single tooth dental implant sites require osseous augmentation before any dental implant surgery. This may be accomplished by several procedures, allowing for several months of healing in order to achieve osteogenesis. After the initial site preparation, an implant may be placed and then allowed to heal for 3–6 months before the prosthetics are placed. This entire procedure may take several months to a year to complete. With the technique described herein, these cases were treated with an allograft ring or cylinder of bone that allowed for immediate placement of an implant. The allograft augmentation and implant placement are done at the same appointment. This technique shortens treatment time and may be valuable in treatment of failed implant sites. Further study is needed to refine and improve this technique.
Figure 1. The site was severely atrophic from a longstanding root fracture. Figure 2. Periapical radiograph of the atrophic site. Figure 3. A full thickness flap was raised to demonstrate the bone loss. Figure 4. The concentric trephines are used to prepare the site and create a cylinder of allograft that fits into the site prepared with the smaller trephine. The larger trephine is used to cut a donor cylinder from the allograft block.
Figure 5. The smaller trephine prepares the site to accept the allograft. Figure 6. The allograft cylinder is taken from a block of allograft with the larger trephine. Figure 7. The allograft cylinder is seated into the prepared site. The drill sequence prepares the allograft and apical bone to accept an immediately placed 3.7 × 13 mm implant seated 1–2 mm below the rim of the allograft. The apical bone provides the stability. The site is then covered with a mixture of particulate allograft and calcium sulfate. A collagen barrier membrane covers the site before primary closure with silk suture. Figure 8. A periapical radiograph demonstrates the implant position. Figure 9. The site is drilled with the smaller trephine to accept the allograft cylinder.
Figure 10. The cylinder is wedged in the site and then drilled down into vital apical bone to accept an immediately placed implant. Figure 11. The site is covered with a 50/50 mix of particulate allograft and calcium sulfate. A collagen barrier membrane is placed, and the site is primarily closed with 3-0 black silk suture. Figure 12. After 4 months of uneventful healing, the implant can be seen in the site. There appears to be adequate facial tissue. Figure 13. The facial view of #4 site that was treated with the ringbone technique. Figure 14. The facial gingiva/bone complex at site #8 did not regenerate adequately for a good esthetic outcome. Figure 15. The facial gingiva/bone at site #9 did not regenerate adequately for a good esthetic result. Figure 16. There may be a physiologic limit for angiogenesis and subsequent osteogenesis in extracortical grafted sites. Extracortical grafts may not receive adequate angiogenesis for adequate osteogenesis.
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