Revisiting implant controversies
When is it needed to remove an implant to solve an aesthetic problem
We still don’t know which technique for cleaning implants is best
Sometimes, inflammation can arise even in a correctly positioned implant, and we need to resolve this. The decision to explant is a difficult one to make, especially for the patient. The key factor is to properly decontaminate the implant surface; the problem, however, is that there is insufficient evidence on the best technique for doing this (Cha et al., 2019; Keim et al., 2019).
The speaker described a new electrolytic cleaning device which has promising initial results, but it is still in an experimental phase (Ratka et al., 2019) (fig 3).
When an implant is in the wrong place, there is often no way to manage it. Bone augmentation has its limits, and the implant is the ‘fix point’. If the implant has been placed too buccally, it is difficult to manage this since a new contour would have to be built in order to cover what is outside the anatomy (fig 4). We can opt to remove the implant, but this will lead to significant bone defects (fig 5).
Can we predictably correct post-explant defects? Complication rates reported in the literature range from around 12% in horizontal augmentations and up to 45% in vertical augmentations (Rocchietta et al., 2008; Jensen & Terheyden 2009). From this, we can conclude that augmentation techniques do not seem very predictable for a patient, especially considering the fact they have already suffered a problem with implants.
Biology set the rules, and we must follow them. The speaker described the four steps of intramembranous bone formation, which have been well established in the literature, from blood clot to provisional matrix, to woven bone to new mature bone (Cardaropoli et al., 2003). The key factors on which bone (instead of scar tissue) formation depend are: vascularity, inductive factors and mechanical factors.
The rules for increasing predictability in GBR
- Bone formation begins on the exposed defect surfaces and grows directionally towards the middle portion of the defect. Therefore, the more walls the defect has the more predictable regeneration will be (Schenk et al., 1994)
- The distance between walls is another important factor. The closer the walls are, the more predictable bone formation will be (Avila et al., 2010)
- Autogenous bone chips can act as centres for nucleating bone formation (Simion et al., 2015)
- Autogenous bone promotes higher levels of bone formation than other biomaterials (Schmitt et al., 2013)
- Predictability decreases when augmented volume is outside the bone contours; this is because of compressive forces that change the shape of the graft (Oppenheimer et al., 2008)
Correct 3D implant positioning is paramount. In cases involving poorly positioned implants, we often have to extract the implant.
Digitally planning your approach is one of the best ways to facilitate the procedure and prevent complications. Computer-guided bone harvesting can help us be sure that the bone volume needed is available in donor zones, like the ramus (De Stavola et al., 2015).
When reconstructing a defect, it is important not to go outside the bone contour. Khoury’s approach ensures good vascularity inside the graft due to the use of particulate autogenous chips and the fixing of two thin cortical bones to rebuild the lost bone profile.
After four months, implants can be placed using a computer-guided approach; GBR can be performed using membranes and biomaterials. Throughout the whole procedure, proper handling of soft tissues is very important to keep the reconstruction protected and covered while healing.