Long Term Ridge Preservation

Every day in the clinic we see dramatic post extraction ridge resorption. We accept this as normal because it happens for most patients. Dentistry has developed methods to preserve the alveolar ridge and we have studies that show minimal ridge resorption at 6 months when a site is grafted. In sites that are not grafted, studies have shown that between 37 and 50 percent of sites need to be grafted for implant placement.

However, because many patients delay implant placement, questions remain about the long term benefits of grafting. In the long term (2 or more years), does grafting prevent alveolar ridge resorption or do all ridges resorb irrespective if the site was grafted or not? Does the type of bone graft have different long term effects on whether the alveolar ridge will resorb or not? Is there a difference in long term ridge resorption between bone grafts that are resorbable and bone grafts that are non-resorbable?

We all have patients who delay implant placement, so let’s look at a few cases and then we can discuss this further.

Tooth #3 presented with an abscess associated with a fractured distal buccal root. The tooth was sectioned with each root removed atraumatically. The site was grafted with Socket Graft Injectable and covered with the synthetic membrane. Socket Graft Injectable is fully resorbed in approximately two months.

The patient finally returned 14 years after the extraction. The radiograph in 2023 exhibited minimal crestal resorption.

Upon reflection of a full thickness flap, a broad ridge presented with minimal loss of ridge width.

A 5.4 X mm implant was placed subcrestal to provide for an ideal hygienic emergence profile.

Day of implant placement.

10 weeks after implant placement, the bone has grown over the collar of the implant and along the healing abutment.

In another case, the patient returned for an implant 9 years after extraction and grafting with Socket Graft Injectable.

Flap reflection exposed a broad crest with minimal loss of ridge width or height.

A healthy middle-aged woman had a mandibular first molar extracted and grafted with mineralized freeze-dried bone allograft 2 years prior. (A) Both the buccal and lingual ridges have resorbed and the grafting procedure failed to preserve the ridge. (B) The black arrows show the extent of the residual bone graft particles. The white arrows identify bone particles that have migrated out of the crest and into the gingiva. (C) This photograph shows areas on the gingiva where bone particles are exiting the gingiva into the oral cavity. The rapid exfoliation of the bone graft particles resulted in failure of the graft to preserve the mandibular ridge.

This case was a young woman with a history of extraction of #6 and grafting with mineralized freeze-dried bone allograft 7 years prior. (A) Loose bone particles are noted in the gingiva (white arrow). The radiograph shows a concentration of bone particles at the crest (yellow arrow). The bone graft particles extend into the extraction site approximately 6mm (black arrows). (B) The alveolar crest is covered with bone particles imbedded in connective tissue as noted on the radiograph. (C) A photomicrograph of a core sample shows cadaver bone graft particles in the loose connective tissue of the gingiva. ‘C’ identifies cadaver bone and ‘S’ identifies sclerotic bone. The core sample was filled largely with fat cells with no osteoclasts present and no resorption of the bone graft particles or the sclerotic bone. There are no basic multicellular units active in remodeling the graft site. The bone is sclerotic. In this case, the bone volume was preserved and implant placement was possible.

This patient presented with a failed bridge, and the bicuspid was extracted and grafted with Socket Graft Injectable. It was obvious that there was abnormal bone in the edentulous site, and the patient reported that when the teeth were removed a bone graft was placed. Her treating doctor reported the area was grafted with mineralized freeze dried bone allograft 18 years prior.

While the dimensions of the alveolar ridge appear to be maintained, the crest was filled with allograft particles in granulation tissue. The ridge volume was preserved, and implant placement was possible.

These cases show that both resorbable science-based bone grafts and cadaver bone grafts can maintain the alveolar ridge long term. Ridge maintenance with resorbable Socket Graft is dependent upon producing healthy vital bone that maintains its volume over time. Ridge maintenance with cadaver bone grafts is dependent on the rate of exfoliation of the graft material, and exfoliation of the graft material is determined by the intensity of the host immune response. A significant systemic immune response to the allograft causes immediate failure of the graft and failure of the graft procedure. In the allograft case presented after two years, the lower immune response required this amount of time for the ridge to collapse to the point of being unable to place a dental implant. However, in the 7-year and 18-year cadaver cases, low level of immune response resulted in glacial exfoliation of the allograft material and ridge preservation was successful. Recent studies have found chronic systemic sensitization as a result of freeze dried bone allografts can compromise the success of organ transplants. We will be reporting on this in a future email communication.

The long-term Socket Graft Injectable cases indicate that if normal healthy bone is formed in the extraction socket, then ridge resorption is minimalized indefinitely. This would indicate that ridge resorption is not a normal result of tooth extraction. There must be other factors that determine the fate of the post extraction alveolar ridge. In other words, the routine resorption of the alveolar post extraction is caused by the procedure, not by the loss of the tooth. One of the differences between the Socket Graft Injectable cases is the atraumatic extraction. If a tooth is grasped by a pair of forceps and forcefully removed, the bone is irreversibly damaged and no matter what graft material is used, the alveolar ridge will show resorption. This, in combination with failing to treat the extraction socket wound, produces even greater alveolar ridge resorption.

Causing harm to the patient for the sake of expediency or lack of knowledge or skill is not accepted in medicine and should not be accepted in dentistry. Even today, dental students are trained to remove teeth standing up because they are able to apply greater force for tooth extraction. The resorption you see in your patients is iatrogenic and not a normal physiologic reaction. For those practitioners interested in improving the care you are providing to your extraction patients, SteinerBio is here to help. We can direct you to the proper techniques and we also are available to walk you through the procedure as you treat your own patients.

For a greater understanding of bone resorption and regeneration please view this free CE course:


American Society for Bone and Mineral Research (ASBMR)

Tissue Engineering and Regenerative Medicine International Society (TERMIS)

American Academy of Implant Dentistry (AAID)