Bone Loss Around Upper Threads

Randy, a dentist, asks:

On several occasions patient have come to me with the beginning of bone loss around the upper threads of dental implants a couple of years after they were restored. For some reason most were single dental implant cases (although not all) and they usually had proper restorations.

I have tried building new bone over these dental implants after treating them with citric acid for 90 seconds using autogenous bone, xenografts and alloplastic materials alone or in combinations with each other with and without membranes. None of the cases I tried to treat were HA coated. Although in rare cases new bone has formed, in most instances there is nothing there upon re-entry several months later.

Am I the only one out there with this complication? Any suggestions that may help improve prognosis? Do we know the etiology of bone loss around dental implants that look fine as far as the position of the fixture and the restoration they support? Is there any point trying to save these fixtures? Thanks for any comments.

27 thoughts on “Bone Loss Around Upper Threads

  1. Randy:
    Usually when the restoration is ok and there is no other sign but bone loss the problem is probably oclussion at some level, normally the lack of a good disoclussion is the key factor.
    I am guessing most of those implants were probable machined titanium that have less capacity to handle lateral forces.
    It will be hard to get bone on top of that, some BMP might help but…..
    Saving the implant is a monumental task when they are in trouble…. It is up to you to decide if it is worth it, I usually tell patients that come to me like that that, there is no real future.
    Langer used to call this cases the ailling implants(precursor of failling).
    Good luck

  2. I am not a clinician but a rep for Astra. I respectfully disagree with Alejandro’s statements. The notation of bone loss around an implant does not translate to certain failure. I have seen xrays of Nobel implants that are 20 years old with 2-3mm of bone loss and the implants are stable, occlusion is not the problem. Monitor these sites with annual xrays and leave them alone unless perio or bone loss becomes more drastic.

  3. Most of the load is received by the upper portions of the root form implant. Late failure can begin in this fashion. As stated above overload and over stress the implant metallurgy. This may create microfracture flaws in the head and especially upper threads. This may provide a nidus for microbes and an inflamatory response and the complication of bone resorptive patterns. Etiology would be occlusal in nature and the microbers the secondary complication.

  4. The use of countersinking burs have created this bone loss during the first period of 2 to 3 years.
    the external hex has also a deleterious effect on it.
    the placement of the abutment has also a role to play on this biological zone where you have cortical bone so the type of implant threads you required for primary stability
    is not the same than that for the trabecular bone
    you can go thru the litterature and see the effect of forces on the cervical part of the implant
    bone required a rough surface
    to get attached to it not smooth surfaces
    distribution of these occlusal forces should be only on the long axis of the implant so check the bucco-lingual diameter of the crown
    a failing implant is an implant with infection or with movement not with the few mm
    of bone loss
    This should be dealt with improved oral hygiene and regular visits to dentist

  5. Do you think that the external hex is a factor or a co factor in bone loss around the top of the implant? Evey internal hex is an upside down external hex, although deeper and perhaps with less micro movement. If I had say a 13MM implant with 3-4 mm of marginal bone loss w/o any inflamation or signs of an exudate I would not be so fast to do any invassive treatment. If there were no symptoms then I would certainly inform and observe for any secondary complications. As far as oral hyg. is concerned as a factor or co factor I don’t feel that poor grooming habbits causes this type of issue any more than poor grooming habbits has anything to do with the wreck I saw at the side of the road I saw last weekend. A few threads of bone loss without any other symptoms could stay that way for many years as symptom free function. A concept used in endodontics as well and not new to the practice of Dentistry.
    It makes no sense to me to consider going in to scrub and graft.

  6. This sounds like clear case of bone remodeling due to the biologic width. Research has shown that the bone will remodel itself down 1.8-2.0mm from the micro-gap. (the space created at the implant abutment junction) The reason why you are seeing it down to the first few threads is that most companies will have you sink the implant down to the bone. After a few years the bone remodels itself and all of a sudden you start seeing the threads showing, which usually start are about 1.8-2.0mm from the top of the implant. A real world example, 3i for years had us all placing implants down to the crest. Now in recent months they have come out with the ‘breakthrough technology’ of platform switching, which is placing an undersized abutment on an implant to creat horozontal bone loss rather than verticle bone loss. Thus getting around the issue of biologic width. Another company that has addressed this issue is Straumann. They have incorporated an emergence profile into their implant design. Their protocol is to place the roughened surface to the bone level and let the polished collar (which is 1.8 mm) rest above the crest. Thus eliminating the issue of biologic width.

    My reccommendation would be to watch this case with periodic X-rays. Unless there is something else at work here, you should see that the bone will remain the same once it has remodeled 1.8-2.0mm below the abutment/implant junction.

  7. There are several factors that will aid in bone loss around teeth and implants. However, the number one cause of bone loss about teeth is due to periodontal pathogens. The same is true for dental implants. Go back and look at the location of the implant abutment junction(IAJ).If the junction is subgingival, this microgap is a haven for the bacteria, and the is NO way to clean the area. The early implants placed the microgap above the gum line, this did not allow the toxins and bacteria to be in direct contact with with the soft tissue. It is the same principle as with a crack root of a tooth. The implant companies can say what they want, but the dental profession is implanting a pahtological problem in patients. The medical Docs are now looking at this area that may aid to systemic problems to their patients. Nobel and others do not want to own up to the problem. But, it real problen. Occlusion, biologic width, external hex, HA and other factors are not the main cause of this bone loss. It bacteria and the other factors just help the problen along. The PerioSeal Implant is the only implant that seals the microgap to protect the patient from the periodontal pathogens. If the dentist wants to continue to use the old design implants and cause problems, then place the gap above the gum line and create an esthetic problem.
    Don Callan

  8. Very questionable
    I am not sure how you are suseptable to peidontal pathogens when you dont have a periodontium present around a root form. If you don’t have the organ how do you get the disease? There is no periodontal ligament and no true gingival sulcus. You do have a peri implant sulcus . It is not the same as a tooth. It can get inflamed and infected but it is not peridontal in nature. The route of spread is just not the same. Besides, I have seen for years so many patients that don’t clean whether its teeth or root form implants, and they do not have disease. I have also seen people who do everything right and have loads of disease. I feel the model you present is too simple for such a confounding problem. What about the systemic level of the patient to modulate against these organisms?

  9. Randy,

    First of all, we need more information on the situation where you do see 2-3 mm of bone loss.

    What types of implants have you seen this with? What type of coating if not HA, any unique surface characteristics, where is the bone loss in relation to the implant platform? I agree with the comment that this may be the after effects of establishing biological width.

    What kind of symptoms are you seeing with patient with bone loss? Is there excessive mobility of the implants that require removal or surgical intervention??

    I agree with the Astra rep, I would rarely call 2-3 mm of bone loss “failure” of the implant.

    Before any clinicians jump to any conclusions with assumptions, since most of you have done that from Alejandro saying 2-3 mm of bone loss is doomed to fail, I totally disagree.

    To zeniou implicating external hexes, that is not scientifically based.

    To Don Callan who states this is a purely biological problem from bacterial toxins, that’s preposterous. Dentists have been placing subgingival margins on crowns and restorations, with a much larger microgap than those you find at the implant abutment junction, they are machined margins as opposed to transferred margins from an impression onto a stone cast. Your argument is flawed and has too much corporate influence for me to give any credence to.

    Biological width is a concept many of you should review before commenting. Concepts of crown lengthening ring any bells?

  10. To: SF OMS and SMS, go back and READ my responce. I DID NOT SAY it was all biological!!!There are many factors that that must be consideded. Try to have an open mind–PLEASE. You may want read some of the non- company articles.
    Don Callan

  11. Ditto on the above OMS comments, with one note.

    Subgingival margins do cause major problems on natural teeth: The more apical the margin the worse the hard/soft tissue response may be. Margins at, or apical to the osseous crest of teeth are a recipe for future problems. This is attributed to the 1) the need for connective tissue insertion into the root at, and coronal to the bone crest (Bio Width) and 2) potential for inflammation due to bacteria at the margins or breakdown products of the crown/alloy/etc.

    Implant microgaps at the bony crest may contribute bacteria but that’s about all. This is also not a natural niche for most oral bacteria (Titanium being very hard to metabolize). It is, however, hard for immune components to defend against if pathogens do set up shop. Given the consistency of the findings of early bone loss to the first thread we’ve got to view this as a predictable consequence of most implant systems. My opinion is that this is a natural remodeling process and probably not load related.

  12. I agree that 1-3mm of bone loss around the implant cervix is not a failure, given that the implant is immobile and the soft tissues are healthy. Simply that’s biology.We should also not compare the PDL with the peri-implant tissues.Take an example. Everybody of us noticed in x-rays that bone is kept up almost to dento-enamel junction in natural healthy teeth proximal to previous extraction sites.Usually, in implants the bone resorption morphology is the opposite.Is more than clear that if you leave an implant heal covered with soft tissues, you will not see any bone loss even after many years (sleeping implants). The problem starts after abutment connection and loading. It is not only one factor leading to this result. Bacteria infiltration at the implant-abutment connection, destination and size of loading forces, texture of the implant surface are some of them. Herman et al 2001, Todescan et al 2002, Piattelli et al 2003, Abrahamsson et al 1997, Lazzara 2006 are some papers that may help in this consideration. Apart from maintening proper hygiene,we may reduce this bone loss by placing the implants supra-crestally, using micro-roughened surface up to the implant cervix, using switched platformed implants and avoiding rotational and/or lateral over-loading forces.

  13. Not to mention the addition
    of a hard guard in the event
    of parafunction..where possible in all implant cases
    to protect the investment of
    all.

  14. If you have the time you may want to read the following papers.
    Callan, DP. Superior Esthetics Without Micro-leakage of Bacteria and Bone Loss. Implant News & Views, May/June 2006, Vol. 8 No. 3 (6-11).
    Callan, DP, Cobb, CM and Williams KB.DNA Probe Identification of Bacteria Colonizing Internal Surfaces of the Implant-Abutment Interface: A Preliminary Study; J Periodontol, Jan. 2005.
    Callan, DP. Eliminating Microgaps: Implant System. Dental Implantology Update 2002. Vol.13 (11): 81-86. Callan, DP.
    Maintaining Cosmetics and Marginal Bone with a Dental Implant. Implant Dent 2000; 9:154-161.
    Callan DP, O’Mahony, A and Cobb, CM. Loss of Crestal Bone Around Dental Implants: A Retrospective Study. Implant Dent, 7:258-266, 1998. 51.
    Gross M, Abramovich A, Weiss E. Microleakage at the Abutment-Implant Interface of Osseointegrated Implants: A Comparative Study. Int J Oral Maxillofac Implants 1999; 14:94-100.55.
    Hermann J, Schoolfield J, Schenk R, Buser D, Cochran, D. Influence of the Size of the Microgap on Crestal Bone Changes Around Titanium Implants. A Histometric Evaluation of Unloaded Non-Submerged Implants in the Canine Mandible. J Periodontol 2001; 72:1372-1383.59.
    Jansen VK, Conrads G, Richter EJ. Microbial Leakage and Marginal Fit of the Implant-Abutment Interface. Int J Oral Maxillofac Implants 1997; 12:527-540.82.
    Mombelli A, Buser D, Lang NP:Colonization of osseointegrated titanium implants in edentulous patients: early results. Oral Microbial Immunol; 3:113-120, 1988.89.
    O’Mahony A, MacNeill SR, Cobb CM. Design features that may influence bacterial plaque retention: A retrospective analysis of failed implants. Quintessence Int 2000; 31:249-256.95.
    Quirynen M, Naert I, Van Steenberghe D, et al: A study of 589 consecutive implants supporting complete fixed prostheses, part I: periodontal aspects. J Prosthet Dent; 68:655-663, 1992.1.
    Abrahamson I, Berglundh T, Wennstrom J, et al. The peri-implant systems. A comparative study in the dog. Clin Oral Implants Res. 1996; 7:212-219.
    DPC

  15. Randy
    I notice that a number of correspodence identify the implant/abutment connection a the souce of pathogens causing your bone loss. I would suggest that this leakage is a result of leakage from your screw attachment. Have you ever unscrewed an abutment that has been in place for even a few months – you can smell the pathogens! A locking taper does not produce the same smell and in my experience implants with an abutment fixed with a locking taper does not suffer from bone loss in this area.
    My advise is the same – leave alone – there should be no more bone loss once it has receded past this junction. Throw away the screws
    Peter

  16. There could be mainly three reasons for marginal bone loss around the upper portion or threads of a dental implant:
    1.- If the implant was placed in sound and mature bone. invasion of the biological widht (Garguiullo,Cochrane)will cause a bone remodeling in order to keep at least 1.8mm. distance between bone and pathogens usually found in the gap of an implant-abutment interface.

    2.- If the fixture was placed at the same time of tooth extraction, an intense bone remodeling will hapen around the implant leaving some threads exposed, (Araujo,Lindhe,Botticelli), mostly the same happens when you place an implant in inmature bone.

    3.- Bacterial accumulation around the restoration which causes inflamation and disruption of the soft tissue seal between the implant and its surrounding mucosa with bacterial infiltration and subsecuent bone loss.

    So the first issue you have to asses is why did the bone loss happen.

    There is very few(Isdor), if there is at all ,scientificall evidence of bone loss around implants caused by overload under phisiologicall conditions.

    A common problem associated with such implants is the lack of inserted keratinized tissue sourrounding them. The former leads to a cronical inflamatory condition associated to these implants with even more bone loss due to bacterial infiltration between the soft tissues and the fixtures, this condition can become acute in any moment with simptoms like pain swelling and supuration.
    Under a clinicall point of view you should avoid any attempt of grafting the exposed threads because this is a very difficult procedure (you are grafting over an avascular innert surface and you only have one wall of remaing host bone)and ussualy you will end up with eve more bone loss.
    The only succesfull treatment you can apply is a free gingival graft and cleaning of the exposed threads. This way you can maintain health around the implant because you are restoring the soft tissue seal and therefore preventing bacterial leakage.
    If the only thing you can observe around an non simptomatic implant is some bone loss and there is enough inserted tissue surrounding it. the best thing you can do is not to do anything.

  17. The VA study of the early 1990′s, inserted almost 3000 implants and all of them were submered. They measured the bone height relative to the top of the implant and the labial plate thickness at time of placement and at uncovering. Bone loss was directly related to how thick the labial plate was, with 2+mm of bone loss occuring in those implants with less than 1mm of labial plate thickness. I guess this throughs a monkey wrench into the theory that bone loss is related to pathogents, lack of keratinzed tissue, occlusal loading, need for platform switching etc.

  18. A factor that is often overlooked is BIo-mechanics,the sress breaking ability of the implant system.It is a vital facet in the maintainance of crestal bone and of course placing the abutment supra crestally.Micro gap talk is just to sell certain systems we live in a comercial world where you can adapt results to give the answers you need

  19. To Jerry Niznick:
    Why does this throw a monkey wrench into the theories of loading, microgaps and bacteria?
    The stress-breaking ability of the implants at the marginal crest wil determine the amount of bone-loss at this sight: because initially a crater-from is seen the results you are mentioning are clearly explained. A crater in less than 1mm thickness wil give vertical bone loss!

    To Peter Says:
    Micro-organisms in the micro-gap do play a role. Referring to the old literature by Jan Lindhe, it is clear that the combination of pathogens and (over)loading gives more bone-loss.
    So let’s stop with saying it’s only this or that reason that will cause the bon-loss. It is multifactorial.

    In conclusion: I agree with most comments that if the bone-loss is now stable the implants are not lost. The results are clearly physiological due to the mechanisms explained before by others (bone-maturation, micro-gap, loading and implantdesign, biologic width).

  20. There are at least eight theories as to why crestal bone loss occurs and possibly all of them have some contributing factor but the reality is that we do not clearly know the specific etiology or set of factors responsible for crestal bone loss. We have all seen significant numbers of cases which successfuly defy each and all of the dogma explanations discussed above for crestal bone loss. Until we truly understand the system(s) behind the etiology of the crestal bone loss phenomenon, the profession will be vulnerable to being exploited by manufacturers design claims of superiority.

  21. In order to determine the etiology of (crestal) bone resorption around the collar threads of an implant, one must keep in mind that many causes and effects could be intermingled. Sometimes, it is very difficult to find only one specific cause. The following situations may explain the clinical entity to some extent, although the physiopathology of bone resorption around the neck of an implant is multifactorial, and of course, much more complicated than this. The theoretical causes are:
    Smoking.
    High C/I Ratio.
    Low Bone Quality or Lesser Bone Density (D3 & D4).
    Dynamic Load versus Static Load (Loose abutments or ill fitting restorations).
    Hormonal Disorders.
    Fixtures with close proximity to Cantilevers.
    Occlusal Trauma (Overload or Biomechanical Stress).
    Establishment or an excessive Biologic Width (normal up to 2 mm epithelium &1.5mm connective tissue).
    Plaque Accumulation and Bacterial Invasion.
    Level of Micro-gap between Abutment and Fixture.
    Autoimmune Response and Cytokine Release (Controversial).
    Crushing of Marginal Bone and Microfractures due to Installation Stress of Self -Tapping Implants.
    Not enough space between two implants or/ an implant and natural tooth.
    IMPLANT DESIGN: (Crestal Module not Divergent and/or Polished Collar/or scalloped neck or surface topography/macroscopic and microscopic features).
    Trauma from Surgery (e.g. Periosteal Reflection).
    As it was mentioned before, it is almost impossible to explain a certain clinical case by only one of these situations and usually two or three of them are involved in the etiology.

  22. My experience is once rapid saucerization develops around an implant it is usually progressive and almost impossible to recover. More often than not the implant is doomed and the decision is whether to explant early or later. Early removal will usually salvage more bone than playing the waiting game. If the implant surface is HA or roughened the odds are worse than with smoothed machined. Of course today most placed implants are roughened so the problems become intensified.
    This brings me to comment to the Astra Rep who remarked that he or she has seen 3 to 4 mm. bone loss that is stable arount 20 year old Branemark implants. I have been around long enough to know that in the early days surgeons did not stock a lot of implants and often 13 mm. implants were imbedded to 10mm. or less because they did not have a shorter implant handy. This left several mm. of implant exposed above crestal bone which while it may later look like bone loss occurred and then became stable, the reality was that there was no bone loss at all only an implant not placed level with the crest. Having smooth machined surfaces these undersubmerged implants for the most part thrived fairly well although the restorations were grossly ugly.

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