It is important to remember that for each defect we encounter, there is an appropriate technique to treat it. We should have no doubts about the quality of regenerated bone, as it is the same as pristine bone. After the bone remodelling process, the grafted materials will, over time, become the patient’s bone.
The most important (and most difficult) step of bone augmentation is to maintain full soft tissue coverage. For traditional augmentation methods, this could be problematic because of the large amount of soft tissue mobilisation which is required to cover the augmented volume without tension. However, current interpositional approaches make it much easier to handle soft tissues. The speakers emphasised that for a safe application of the technique, 5mm of bone above the nerve is needed.
“The most important step of bone augmentation is to maintain full soft tissue coverage”
A short implant is now considered 6mm long; an extra-short implant measures 5–4mm. An 8mm implant is considered a standard-length implant (Figures 1-2).
When using narrow-diameter implants we have to make some prosthetic compromises, and the prosthesis design can be affected. There is a limited number of situations which can be solved with these types of implants in the posterior zone.
“An 8mm implant is now considered a standard-length implant.”
The speakers presented a case involving extreme atrophy in the posterior quadrant of the mandible. This could not be treated with anything other than regeneration. This raised the question: how much bone is needed to safely place short implants? And when should we decide to use regeneration? The speakers explained that at least 7mm (or better, 8mm) of bone should be present above the nerve, and the security margin should measure between 1–2mm. So the case presented did not have enough bone for interpositional grafting or for short implants. The suitable option would be vertical GBR and onlay bone grafting. It should be noted that the limits of these techniques could be estimated at about 4–6mm on average. Should more volume be needed, the approach would require the use of onlay bone blocks. Although in the final decision of what treatment method to undertake, the experience and skill of the surgeon should often be the deciding factor.
A second case was presented (Figures 3-4), involving a knife-edge posterior mandibular crest. A question was raised about the minimum width of bone required to place a narrow-diameter implant. The speakers agreed that 4mm should be the minimum. In the case of a 3mm-wide crest, lateral GBR was recommended with or without simultaneous placement of implants. Splitting was also discussed as an option when little corticalisation is present.
“The experience and skill of the surgeon should often be the deciding factor”
Another challenging situation which was discussed is that of deep bone defects between teeth in the anterior region. Again, it was clearly stated that short implants should be considered in the posterior zone and not in the aesthetic area (Figure 5).
“Short implants should be considered in the posterior zone and not in the aesthetic area”
Although these cases could be treated with short implants, the deep trough created would be difficult to maintain and the sloped spaces between implants and neighbouring teeth could be prone to forming deep pockets. So rebuilding the bone volume first and then creating a proper soft tissue margin to ensure long-term peri-implant health is recommended.