The loss of dental implants continues to increase with the continued rise in popularity of dental implants, but our understanding of why implants are lost has not evolved. There are as many proposed explanations for early implant loss as there are professionals without consensus. With regard to late implant loss, the diagnosis is invariably peri-implantitis, without considering possible causes other than bacterial ones. This lack of a clear etiology of implant loss at any point in time has prevented our profession from changing what can be done differently to predictably reduce the incidence of implant loss.
Determining which therapies have the best treatment outcomes and which variables contribute to the most failures is also a very important concern in medicine. As a result, large healthcare organizations conduct in-depth data collection and analysis to determine what leads to the best patient outcomes and to determine which variables can be controlled to prevent failure. When a healthcare facility collects data to determine what works and what contributes to treatment failure for a given disease, all possible factors are evaluated. All comorbidities, all medications, all patient specifics right down to the age, training and experience of the surgeons are impartially evaluated to know what works and what doesn't. Fortunately for dentistry, this methodology has already been applied to dental implantology in two large health institutions, with the following results:
The following study was conducted at the Mayo Clinic:
Early implant failure associated with patient factors, surgical procedures, and systemic diseasesprosthesis J. 2019 Jul;28(6):623-633. doi: 10.1111/jopr.12978. Epub 2018 October 22
Results:Of the 8540 implants identified during the study period, 362 (4.2%) failed within the first year after placement with a mean (SD) of 129 (96) days after placement. Univariate analysis showed no impact on failure in the first year for most candidate predictors. Preplacement surgical procedures associated with increased early implant failure were bone augmentation alone (HR, 1.45; 95% CI, 1.02-2.05; p=0.04), socket preservation (HR, 2.67; 95% CI, 1.33-5.38; p=0.006) and xenogeneic material (HR, 2.12; 95% CI, 1.11-4.04; p=0.02). After adjusting for age, sex, and implant duration, no or multiple medical conditions or single or multiple medications increased a patient's risk of implant failure in the first year after placement.
After a comprehensive evaluation of all factors, it was determined that the only cause of early implant failure was cadaveric bone graft fitting. Socket transplantation was not the causative factor, as sockets enlarged with autograft did not increase early implant failure.
In another study conducted by a large Chinese health institution using the same methodology, the results are as follows:
Risk factors for early implant failure: a retrospective study of 6113 implants
Clin Implant Dent Rel Res. Jun 2021;23(3):280-2 doi: 10.1111/cid.12992. Epub 2021 March
Results:A total of 6113 implants in 3785 patients were included. The early implant failure rate was 1.6% at the patient level and 1.2% at the implant level. Early implant failure was significantly associated with implants placed in the posterior maxilla with specific surface modifications and in previously enlarged sites (p<0.05). Risk factors for maxillary implants included surface modifications and bone augmentation procedures (p<0.01), while risk factors for mandibular implants included gender and bone augmentation procedures (p<0.05). For implants placed in previously augmented sites, implants placed in the anterior mandible had a higher risk of early failure (p<0.05).
Again, after extensive evaluation of early implant loss in a large patient population, the contributing factor to early implant loss was socket transplantation with bone grafts from cadavers. Both studies found that it was not the socket graft at the time of extraction that caused implant loss, but that this was only found when the graft material was cadaveric bone graft. When a study reports its findings, it is not confirming a scientific fact. However, when two studies conducted by different researchers at different institutions give the same results, the scientific fact is confirmed.
Now that it has been scientifically confirmed that cadaveric bone grafts are the only predictable factor leading to early implant loss, let's examine the mechanism and how it affects late implant loss. We considered two studies documenting the development of marginal bone loss.
Relationship between osteoporosis and marginal bone loss in osseointegrated implants: a 2-year retrospective study
J Periodontology. 2016 January;87(1):14-20. doi: 10.1902/jop.2015.150229. Epub 2015 3. September.
This study, as the title suggests, was conducted to determine whether osteoporosis causes marginal bone loss. There's no doubt they didn't set out to investigate whether bone augmentation with bone grafts from cadavers caused marginal bone loss, but that's what they found. The only statistically significant factor associated with marginal bone loss was socket transplantation with cadaveric bone graft. Another study was more specific and prospectively examined the use of cadaveric allograft bone grafts:
Crestal bone resorption in augmented bone using mineralized freeze-dried bone allograft or pure bone during submerged implant healing: a prospective human study
Clin Oral Implants Res. 2016 fev;27(2):e25-30. doi: 10.1111/clr.12512. Epub 10.11.2014.
In this study, the authors extracted teeth and transplanted an allograft into the test group and compared this group with ungrafted sites. The implants were recessed with a cover screw and evaluated at the time of placement of the healing abutment. The study found that only sites transplanted with allografts cause marginal bone loss and this has nothing to do with what is known as physiological bone remodeling.
The term "physiological bone remodeling" is used to indicate that marginal bone loss after implant placement is normal. These studies make it clear that marginal bone loss is not normal, as it only occurs when bone grafts from cadavers are used. Rather than using the term "physiological bone remodeling" it is a more appropriate termbone graft failure.
We have confirmation that cadaveric bone grafts and Bio-Oss in particular are the only factors responsible for early implant failure. But what about late implant loss? There are no published studies that have evaluated the long-term success rates of implants placed in allografts or sockets transplanted with Bio-Oss. The most common bone grafting procedure in dentistry is preservation of the mandibular chamber with bone grafts from cadavers. This procedure is performed thousands of times every day without scientific backing to justify the procedure. We claim that the studies were conducted but not published because the results were unacceptable to the authors. Another possible reason for the lack of publications is that articles do not pass peer review because they do not like the results. We know this is happening because we blocked peer-reviewed publications because the articles did not support the use of cadaveric bone grafts. However, we can find publications that provide us with information on the long-term success rates of implants placed in sockets transplanted with allografts.
Successive reimplantation of dental implants at sites of previous failure
J Oral and maxillofacial surgery. 2020 Mar;78(3):375-385. doi: 10.1016/j.joms.2019.10.001. Epub October 13, 2019.
This study evaluated the success rates of dental implants after up to 3 implant placements in the same site. The results were that implantation success rates were significantly worse for reimplanted implants. This study was similar to the large study done at the Mayo Clinic. The author identified all patients with implant failure. The authors collected much of the data collected in the Mayo Clinic study, including whether sites received a bone graft. The author has provided statistics on all variables listed in his material and methods, except whether the site was grafted. In our opinion, this is not an accident. For a professor at an American dental clinic, allografts are the paradigm and cannot be questioned. In the discussion, the author talks about site-specific reasons for failure and states that bone quality is considered one of the reasons for implant failure. The author then states that all replantations were transplanted with allograft. In this article, the author notes that each subsequent replantation yielded lower success rates and each of the replantations received an allograft, and the author even omits the possibility that the graft material caused the poor bone quality and the implants failed. You can't be that blind.
Comparison of three different types of implant-supported fixed prostheses: a long-term retrospective study of clinical outcomes and cost-effectivenessClin Oral Implants Res. 2019 abr;30(4):295-305. doi: 10.1111/clr.13415. Epub 2019 29. März.
In this study, the authors examined different types of restorations to determine whether the type of restoration had an impact on implant failure rates. They compared implant failure rates for replacement of 3 adjacent teeth with single crowns (not splinted), an implant-supported bridge, and splinting of 3 implants. They also collected information on other variables to see if they could have an impact on implant failure. The other variables examined were smoking, diabetes. History of periodontitis, maxillary, mandibular, cemented, screw-retained bone augmentations, guided surgeries and implant failure for each type of restorative tooth replacement. The evaluated factors are listed below with their level of significance.
Splinted implants performed the worst but also had twice as much bone augmentation as the implant-supported bridge. Regarding the number of bone augmentations among the three types of restorations, the significance level was 0.003 p, but the authors ignore their own data and never mention the fact that the splinted group with more failures had twice as many bone augmentations. It is not possible from this article to determine whether the reason for implant failure is related to the type of restoration or augmentation of allograft implant sites. The authors did not even mention the possibility that the allograft caused implant failure. This is the kind of misinformation that results when a profession adopts a paradigm that cannot be challenged.
We now know the cause of early implant failure and marginal bone loss. So let's look at the mechanism to better understand how cadaveric bone grafts cause marginal bone loss and implant loss. Again, we turn to the medical literature. Bone grafts from cadavers produce sclerotic bone, which is mineralized scar tissue. Osteoarthritis also produces sclerotic bone and how it is broken down has been elucidated.
In this image of a joint, an injury occurs that causes inflammation that leads to the formation of sclerotic bone, as indicated by the white arrows. With continued application, the sclerotic bone fractures until the sclerotic bone collapses (Image D).
In this electronic scan image of the joint above, the sclerotic bone is developing fractures that are clinically undetectable.
As fractures build up over time, the bone begins to break down and this is evident radiographically as bone loss. When fractures occur in normal bone, the bone repairs the fracture and bone collapse does not occur. We will now discuss how the sclerotic bone produced by cadaveric bone grafts results in marginal bone loss.
The second molar was extracted 6 months earlier and grafted with a mineralized freeze-dried bone allograft. The edge of the sclerotic bone is noted.
Day of implant placement with concealed cover screw.
At the healing abutment indication, marginal bone loss developed at the ridge with floating bone particles in the gingiva. Let's use the orthopedic literature to explain what caused the marginal bone loss. Sclerotic bone is fragile, and instead of adapting to stress like normal bone, sclerotic bone develops microfractures. These microfractures develop along the entire length of the implant, but at the crest where movement of the fractured bone is possible, the bone fractures and migrates to the gingiva, resulting in marginal bone loss. Bone-to-implant integration does not occur in sclerotic bone produced by bone grafts from cadavers because sclerotic bone is scar tissue that lacks the ability to remodel. The implant is held in place by friction like a wooden screw. As the sclerotic bone cannot repair the microfractures formed during implant placement with continuous loading, these fractures accumulate over time and the bone collapses, as we have seen in the orthopedic literature. This process is demonstrated in the following case of late implant loss:
The premolar was extracted and grafted with mineralized lyophilized bone allograft. After healing, the implant was placed and worked for several years. Examination of the bone loss on the mesial side of this image reveals bone fragments in the granulation tissue.
Bone chips floating in granulation tissue. In peri-implantitis and periodontitis, bone resorption occurs before infection and bone is never found in the granulation tissue. Therefore, bone loss in this case is not caused by peri-implantitis. The diagnosis in this case is not peri-implantitis, but bone graft failure. We are not aware of any studies that have evaluated the long-term success rates of implants placed in sockets augmented with Bio-Oss or allograft, therefore we have not established a scientific basis for implant placement in sockets grafted with these materials. We know that cadaveric bone graft materials cause marginal bone loss. We know that cadaveric bone grafts are the variable that causes early implant failure. Although no one has ever published data on the long-term success rates of implants placed in sockets transplanted with Bio-Oss or allografts, we do know that a high percentage of implant failures occur in sites transplanted with bone grafts from cadavers. Clinical observations suggest that more implants placed in sockets transplanted with bone grafts from cadavers are lost than as a result of peri-implantitis. Cadaveric bone graft studies rarely have no graft as a control. When cadaveric bone grafts are compared to nograft, the results are that cadaveric bone grafts produce less mineralization than nograft, so they actually inhibit bone formation. But it gets worse. A recent study conducted at Harvard and a university in Israel compared MFDBA and a collagen membrane to a collagen bone graft product to assess the effectiveness of the two materials in ridge augmentation surgery. Everything has been done to ensure a good result. They excluded patients who had any reason to have suboptimal results. Ridge augmentations were mainly done in areas bordered by teeth that are very easy to augment. The study was very well done. At 9 months, as expected, the collagen graft failed completely and produced no increase in ridge width. Those who follow our posts know that collagen should never be placed in or on a bone graft. What's interesting about the study, however, is that the MFDBA, which was covered with a collagen membrane, also completely failed. In the MFDBA membrane group, there was an increase of 0.38 mm to 2 mm below the crest; at 5 mm below the crest there was a gain of 0.27 mm; 8mm below the crest there was a loss of -0.34mm of bone width. The authors spent the entire article trying to cover complete cadaveric bone graft failure. Normally, a study that breaks the established paradigm would never be published, but in this case, the authors had no choice but to publish the results because the study was published on ClinicalTrials.gov before the start of the study. Many academic journals and institutions require that a clinical trial be published on Clinicaltrials.gov, as this obliges authors to publish their results without modification to address their bias. In this case, university authors were forced to publish results that contradict what they are teaching you to deal with your patients. The company that paid for the collagen grafting study would certainly never want that study to be published either. Bone grafts from cadavers are never resorbed and produce sclerotic bone that does not integrate with the implant surface. Only normal bone has a high implantation success rate, and only fully resorbable synthetic bone grafts that produce normal bone that can integrate with the implant have the potential for long-term success. Bone grafts from cadavers are researched and taught in all dental clinics across the United States. Almost all speakers promote its use in various clinical applications. Cadaveric bone graft material is the paradigm in the United States, so its effectiveness cannot be questioned. If you perform ridge augmentation with cadaveric bone graft and it fails, the problem lies with the surgeon or the patient, because the paradigm teaches that it cannot be the material that fails. In dentistry, the cadaveric bone graft paradigm teaches that it is the best possible bone graft, and as a result, there is a lack of research into bone and bone graft biology, reflecting the damage that such a paradigm can do to a profession. It is instructive to read what Max Planck said about scientific paradigms: "A new scientific truth triumphs not by convincing its opponents and letting them see the light, but because its opponents eventually die and a new generation grows up who trust it."
American Society for Bone and Mineral Research (ASBMR) Tissue Engineering and Regenerative Medicine International Society (TERMIS)