Not even close. Where have you been? When a tooth looses a bit of vertical bone support or is in traumatic occlusion or a combination of both there is an increase in mobility. These teeth can be successfully treated with occlusal and periodontal therapy and maintained in function for years. Once an implant has any degree of mobility it is ready for the scrap heap. It has progressed from ailing to failed status.

Thank you Robert for your contribution. As far as I know that the PDL acts as a shock absorbent in case of natural teeth, and any occlusal trauma causing widening in the ligament which leads to tooth mobility. In case of dental implant there is no PDL, but it is ankylosed with bone. Is there any mechanism by which dental implant can absorb the occlussal force ; ot it should be out of occlussion?

Ahmed -

The occlusal forces are transferred through the restoration and implant body into the bone. The restoration must be in occlusion or it is useless. The other teeth will overcompensate, drift and cause other issues.

Bob

Again thanks Bob, I discussed with some periodontologists the issues of occlussal forces on the implant. They agreed that the implant design might contribute to absorb the occlusal force and compensate for the absence of PDL!!!

Regarding the second point that the implant should be in occlusion is important as the mechanical forces promote bone remodelling around dental implant as bone remodelling in the long bones.

Hi Robert and Ahmed,

Regarding the initial question, an implant should not move. If it is moving, that means that it has lost osseous support, or had none in the first place - healed by fibrous encapsulation. Both are not good.

Regarding occlusion, the occlusal forces that are transmitted from the prosthetic on top of the implant, travel through the implant, and then are transmitted into the surrounding bone. A certain degree of occlusal force will maintain bone around the implant. But too much force, and bone will begin to breakdown around the implant.

Now, about an implant in occlusion. I presume you are talking about "in occlusion with the opposing dentition", since the prosthetic supported by the implant will always occlude with whatever the patient places in their mouth when they chew. To minimize the occlusal forces on an implant, since there is no PDL to compensate for excessive occlusal forces, the implant supported prosthetic should only be in occlusion with the opposing dentition, when the patient bites down hard on the prosthetic - in this scenario the PDL of the adjacent dentition has been maximally compressed/stretched. This way the implant is protected by the adjacent teeth, that have a PDL, from experiencing occlusal overload.

I hope that answers your question.

Tom

Dear Ahmad , Robert and Tom

If an implant loses its rigid fixation after a period of function (i.e becomes mobile) it cannot be restored to a functioning state once more. The only solution is to remove such an implant. Regarding the topic of PDL we had earlier the IMZ design which tried to solve this problem , however the intramobile cylinder suffered a great loss of mobility over time and needed frequent replacement . The manufacturing company stopped this product long time ago.

Regarding the empty mouth occlusion one can adjust the implants as you argued to have lighter contacts than the neighboring teeth but what about the case when we have full mouth rehabilitation with implant supported restoration? It is the matter of centralization of forces over the implant long axis which includes also the manner of contacts in lateral and protrusive excretions.

emad

Well, I understood from the above explanation that the destruction of the peri-implant supporting structure is irreversible in comparison to periodontitis and the adjacent teeth compensate in distrubuting the occlussal foces upon the implant prosthesis. But can someone explain the mechanism by which the adjacent teeth can do that?

natural teeth undergo excessive mobility as a result of PDL destruction, which may be accompanied by equal amount of bone loss or no bone loss at all if the process was limited to the ligament. In early stages the process is usually self-limiting and the tooth regains its stability once more by natural defensive mechanisms and maybe re attachment at the newer bone level. after several episodes the tooth reaches state of permanent mobility that usually have apico-occlusal direction.In this case it should be extracted.

In case of dental implants, the implant remains table until almost total bone loss around one or more surfaces is reached leading to mobility, similar to the terminal condition of a natural tooth.

Hello Ahmed and Emad,

It seems to me that there are a few different topics that are being discussed, leading to possible confusion of the processes.

Tooth mobility can result from loss of osseous support, for example, as a result from the destruction that occurs in periodontal disease (periodontitis). In this case the osseous destruction is generally irreversible, and the tooth is mobile since its foundation is gone.

Tooth mobility can also result from occlusal trauma. Excessive occlusal forces (e.g. a premature occlusal contact) will result in the PDL adapting to remove the tooth from these forces, and enlarge the PDL space. The tooth becomes more mobile. In the absence of inflammation (e.g. gingival/periodontal inflammation) no destruction of the PDL occurs! The PDL remodels to accommodate the excessive force . If the excessive force is removed (e.g. premature contact is removed), the PDL will reform back to its original size. In the presence of gingival/periodontal inflammation, it is proposed that accelerated breakdown of the periodontal apparatus will occur in a corono-apical fashion. Emad, I am not familiar with the apico-coronal description of permanent mobility that you mentioned. Also, I do not understand the reasoning for extracting a tooth in such a state. Please explain.

Ahmed, in regards to peri-implantitis and implant mobility, implant mobility is due to loss of osseous support. The loss can be as a result of excessive occlusal forces, that are transmitted from the implant to the supporting bone. The compressive force on the bone results in bone resorption, and loss of integration. However, the term peri-implantitis is typically reserved for the inflammatory disease involving implants, not occlusal trauma on implants. Nevertheless, the end point is the same. If as a result of the inflammatory process in peri-implant disease, a significant amount of implant supporting bone is lost, the implant will become mobile, just like Emad mentioned earlier.

Last of all, Emad regarding full mouth rehabilitation with implants. Yes, the entire force is distributed onto the implants, hence the risk of overload increases significantly! You are absolutely right about centralizing the forces of occlusion over the implant long axis as one method of dealing with this issue. Another is splinting the implant restorations, thereby distributing occlusal forces over all involved implants, helps minimize the chance of occlusal overload.

Hope that helps,

Tom

Dear Tom

thank you very much for your rematks.

what I ment by apico-cronal mobility is when a tooth can be pressed into its socket in an apical direction and then returns to its occlusal position once more. in such cases the mobility is permenant as there is total apical destruction of bone compined with crestal loss either partial from one surface or more and the tooth is doomed to be extracted. usually no clinical measures can help in such case. the trem apico-cronal direction was used by me in the discussion as description nothing more

again thank you for the nice discussion

Hello Emad,

Thank you for the clarification. I completely agree with your statement. Such a tooth would be considered to have Class 3 mobility (according to the Miller mobility scale - Miller, 1950). Excellent discussion indeed.

Tom

Dear Tom

thank you ery much for your reply.

keep in touch

Thank you indeed for your explanation.

I agreed with Tom that there are many topics have been discussed which led to confusion. The role of PDL in distributing the occlussal forces on natural teeth and the effect of these forces on dental implants are clear from biomechanics point of view.

The tooth mobility in case of periodontitis increases with time due to gradual bone loss, therefore the tooth mobility can be classified into grade I , II ...etc. Dental implant is ankylosed to surrounding bone, hence the question is (does the implant mobility follow similar pathway to that of tooth mobility in case of periodontitis? or any mobility indicates implant failure).

Hello Ahmed,

Any amount of implant mobility indicates failure, since osseointegration is an all or none concept when it comes to implants. As Emad mentioned earlier, an implant with even a small amount of remaining osseointegration will not be mobile. However, once that is lost, the implant becomes mobile. Where as in a tooth, mobility can occur when there has been no loss of periodontal support (as in the case of occlusal trauma), or with loss of periodontal support (as in periodontal disease). Therefore, tooth mobility and implant mobility, even though called "mobility" in both circumstances, represent different states of health of the tooth or the implant.

Dear Tom and Ahmad

I think one of the reasons for such conflict is the use of periotest device to measure implant "mobility" by some colleagues earlier than 2005. the criticism of this method as seen in the literature proved that the periotest value Pt V remains constant in a failing implant until total bone loss and actual clinical mobility is seen. no one now argues that we can measure implant mobility quantitatively during the clinical performance. it is all or none

Many thanks

emad

Dear Ahmad

I recieved arequest from you asking for a copy of my publication: indirect sinus floor elevation for osseoitegrated dental implants, published in JOI . pls send me your private mail adress to send you a PDF file. I'm not allowed to upload the file to a third party web site.

my mail is

[email protected]