A two-session protocol was formerly selected for repairing three-dimensional bone defects by grafting with autogenous bone blocks. The technique that we present today demonstrates that three-dimensional vertical grafts of bone defects and implant placements can be carried out in a single session with exactly fitted bone ring grafts. The recipient site is prepared and the graft is harvested with trephine drills. The implant site is prepared in the graft before its removal from the donor site and the graft is fixed at the recipient site with absolute rigidity by the implant. The Ankylos implant is particularly suitable for this, because the special thread geometry gives it very good primary stability in the apical region, and therefore the graft can be securely fixed with the upper section of the progressive thread.

The rigid fixation and an accurate a fit as possible of the graft is essential to prevent bone loss in the graft during the healing phase.

Any remaining sinuses are filled with cancellous bone chips, bone replacement material or combinations (mixtures). The grafted area is also covered with a barrier membrane as additional protection against resorption processes. About four years ago the author developed a grafting technique that allows bone grafting and implant placement in one session, even with larger three-dimensional defects. In the meantime this technique has been refined and can be successfully applied for almost all indications.

It is important to note the following:
1. Sufficient residual bone is required for anchorage of an implant with primary stability.
2. As many vital cells as possible must be available at the recipient site in close contact with the cancellous bone of the graft.
3. The graft can be positioned rigidly so it is immobile.
4. The implant can also be correctly positioned for the prosthetic restoration.
5. The graft is contoured with slowly resorbable bone replacement material to counteract the volume loss.
6. The wound is closed securely and without tension.

Case study
A 31-year-old, completely healthy patient came to our practice wanting a solution for her persistent horizontally displaced and impacted top right first cuspid. (Figures 1 & 2)

The patient rejected an attempt at orthodontic treatment. We decided to extract the tooth surgically and replace it with an implant-borne crown. (Figures 3 & 4) The defect geometry (Figure 5) allowed a single-session procedure (grafting and implant placement) with the ring technique. After measurement of the defect with a trephine drill (Figure 6), the donor site on the chin was opened and prepared (Figure 7) with a trephine drill with a diameter 1 mm larger than the measurement. (Figure 8) The change of diameter was recommended because the size of the graft is defined by the internal diameter of the trephine drill. The external diameter of the trephine drill determines the size of the recipient site.

This keeps the gap between the graft and the site as small as possible. The implant site was prepared while the graft is still anchored in the bone, but only to the reduced depth allowed by the graft. (Figure 9) It is important to penetrate the cancellous bone of the donor region. The graft was prepared to the final depth with the trephine drill to accept the bone ring.

After preparation of the ring, the cancellous bone was detached from the lingual cortical bone. (Figure 10) This method means that as much cancellous bone as possible is included in the ring. The graft was then lifted slightly with the ring breaker. (Figure 11) A surgical kit specially for this technique (Figure 14) has been developed by the Zepf company in collaboration with the author. Additional bone fragments and cancellous bone chips could also be harvested. (Figure 16) The recipient site was prepared with a trephine drill 1 mm smaller in diameter than the trephine drill used for harvesting the bone. (Figures 19 & 20) The ring graft was then fitted (Figures 21 & 22) and fixed with the Ankylos implant after preparation of the implant site. (Figures 23-26) The remaining sinuses were filled with particulate bone 27 and covered and contoured with a thin layer of slowly resorbing bone replacement material. (Figures 28 & 29) The wound was then closed without tension (Figures 30 & 31) and a six-month healing phase followed. (Figures 32 & 34)

Conclusion
The major complication is dehiscence at the sutures, because this can cause complete loss of the graft (6 cases). This emphasizes the importance of closing the wound with absolutely no tension.

Paresthesia occurred at the donor site in a few patients, but disappeared at the latest after three months. The high success rate (only three implants lost) demonstrates that when the specified criteria are met this method can be recommended for single-session vertical augmentation of three-dimensional defects of varying indication.

In our practice I have by now treated more than 400 patients with this method in all indications. The advantage of this method is that the graft and recipient site are exactly fitted, which means that a very large proportion of vital bone cells are in contact with the graft. This is a very important prerequisite for almost complete revascularization of the graft.

The special thread geometry of the Ankylos implant with its very good primary stability means that 2-3 revolutions into the local bone are sufficient for this technique.

 
A trephine drill is used to remove the body ring and to prepare the host site - inner and outer diameters must match to ensure gap-free fit

With use of the ring technique, it is possible to carry out the vertical 3D augmentation for bony deficiencies and the implantation in a single session

 
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