The question of bone versus soft tissue only

1) I know we have come a long way in bone regeneration but I was always taught that regenerating bone outside of the alveolar housing is very difficult and challenging. Over the last 20+ years I have experienced these challenges myself in my clinical practice. Why is it then that now with the POPA procedures we can add non-autogenous bone graft material (oftentimes without the addition of any biologics or membranes as in the original Wilckodontics technique) and have this  bone graft material turn into vital bone that can support moving teeth significantly outside of the alveolar housing? Do we actually have any evidence besides post-op CT scans (which may only be showing the non-resorbed bone graft material) that these facially and lingually applied bone grafts are turning into actual vital bone, i.e. that we are truly regenerating bone…..Or are they just turning into a thick encapsulated collagen matrix, a “glorified thick soft tissue”?

Firstly, I would highly recommend Brugnani's text for an excellent overview on this emerging and wonderful technology.  Quite frankly, I think that orthodontists not incorporating POPA into their daily schedule are not practicing at the level of care required today.  See Fig. 1 below.

Tom Wilcko elegantly demonstrates, histologically new bone, similar to GBR type bone at sites where bone was not previously present.   My experience is that we can adequately grow GBR type bone where root surface exposure has not occurred.  I have not been successful in demonstrating on follow up CBCT definitive bone on previously exposed root surfaces.  Therefore, the presence of an intact periodontium, albeit without alveolar bone,  for example a fenestration or dehiscence with intact untouched connective tissue attachment lends itself to this situation.

I have at least six re-entry cases demonstrating this phenomenon histologically. See one of my re-entry histological cases, Fig. 2, below.

2) For 3-4 decades clinicians have routinely done pre-orthodontic gingival augmentation AND root coverage procedures in Ortho and non-Ortho cases without adding any bone. But we have not experienced any significant recurrence of recession post gingival grafting (by whichever means). Clinicians have presented their long-term 20+ year results of stable soft tissue grafting results. Are they cherry picking and choosing what they show? Is post-operative recession indeed being experienced by all these patients and are we just sweeping these failures under the rug or are we not following these patients long enough to see these recurrences?

Difficult answer.  Some of our worst recession cases are post orthodontic.  Renkema, in a terrific Meta Analysis, demonstrates the risk of post orthodontic crowding 4x-8x greater in the treated crowded dentition than in the not treated dentition.  And of course, that makes sense that most orthodontic treatment for crowding is arch expansion, especially in the mandibular arch where we cannot gain space, as we do in the maxillary arch through SARPE's or other procedures.

However the cases that  these clinicians show are post recession.  The recession and particularly the relapse (up to 75% between 10-20 years is avoidable if hard and soft tissue grafting is completed before initiating orthodontic de-crowding treatment.

3.) Danny Buser very honestly points out that with his buccal bone grafting technique he is not expecting all his bone graft to turn into solid vital bone and that is the reason he calls it “Buccal Contour Augmentation” rather than “Buccal Bone Augmentation”. It is now apparently universally accepted that we need a 2mm thickness of bone circumferentially around an implant for a long-term stable result (BTW: Can someone please point me to the research where this 2mm number came from…I am sure it exists but I just don’t have it).

The bone grafting material that Buser uses for contour augmentation is the same as the material that many of us use currently for POPA, which includes a very slow resorbing Bio-oss.  So if you look at the GBT or contour augmentation histology in which Bio-oss is used by Buser, you will see remants of unresorbed Bio-oss granules.  The same appearance as the histology I have posted.

The essence of my questions was not really to question the benefits of the corticotomies but rather whether we need the bone augmentation or whether soft tissue augmentation alone is sufficient (or do we need both as you have advised)?

Bone grafting materials are Bio-Oss  + DFDBA 2:1. I typically use a thin Alloderm covering the graft, both as a barrier and also to  thicken soft tissue.  This is a hypothesis - no evidence to support the concept. I do not use biologics.

Again, the reason for bone is both for soft tissue support and to limit further recession, but also to enhance orthodontic stability in the long-term.  This has been well documented and demonstrated by Ferguson and Wilcko with up to 10 year follow up. See Fig 3 below.

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Fig.1

Fig. 2

Fig. 3