Mandibular Overdenture: How to Increase Stability?

The simplest and possibly most effective treatment is to place 2-4 mini-implants in the anterior region. I would start with only two in the cuspid region, as some patients have problems removing the prosthetic wirh four. I use the MDI 3M ESPE brand, but there are many good manufacturers on the market.

Remember this is a implant stabalized situation not a fixed situation and thus this movement is I think is helpful in reducing forces on the implants especially if they are minis Peter

Some movement is to be expected with a two on the floor case.

Place more 4 implants and do a protocol.Explain very well patient what he is paying for and do not create any kind of expectation to him unless, you are going to have problems.As a surgeon I am giving up this kind of treatment...

Two mandibar implants = no denture adhesive. That's the only promise we can make with two. The denture still moves because it is still a tissue born prosthesis.

Two implants in the premolar region will give you an "implant retained mandibular overdenture that is basically a complete denture, tissue supported. Your overdenture will only be as stable as it was before the implants, as they are only meant to provide retention. The fact that it holds on to the implants makes it more stable, but the stability should come from it being well fitted to the ridge, extending and covering all the places it has to extend to and cover. Make sure that your overdenture fits well by relining it and verifying the fit. that should reduce the amount of movement. You could add more implants, but if it does not fit well, you still would have problems.

Thanks for that very clear explanation of retention vs stability, Dr. Boudet.

A conventional midline implant will increase retention and eliminate the fulcrum.

The implant position may prove adequate. Proceed as planned and evaluate patient response to two implants before modifying the treatment plan. After implant placement, my patients wear the final prosthetic unattached for three months during integration. At that point, I typically take a pick up impression and have my lab add the attachments in conjunction with a hard reline. If a hard reline is not needed, I use MucoHard to pick up the attachments chairside. It has been my observation that the patients most satisfied with two implant overdentures are those that had a full lower denture previously. Patients converted directly to a two implant retained system in conjunction with full mouth extraction will sometimes return seeking additional stability.

Dr. Boudet was correct in explaining you have a tissue supported and implant retained prothesis. Make sure there is NO contact in function of the implant retentive portion with either the metal housing or the denture base material itself. This will eliminate the rotational problem you were afraid would occur. Your stability will come from the occlusal scheme selected (linear non-interceptive is the best in my opinion), border outline (myostatic extension will eliminate muscle lifting the prosthesis) and the correct vertical and centric positioning. Needless to say you must have a well fitting denture base to tissue relationship.

You did not tell us your patients expectations for the final restoration. If teeth that have little or no movement are expected a fixed or bar retained over denture on four to six implants is needed. If your patient is expecting a denture that will stay in place when functioning but otherwise work like a full tissue supported denture then you are golden with the two implants. ( locator or "O" ring attachments are easy and work well for this) What is the opposing dentition? Natural teeth functioning against a lower implant case must be done with care as not to over load the implants. A plane of occlusion must in any case be established so as to avoid destructive forces being transferred upon the implants. A tissue borne case results in less force on the implants as the tissue resists most of the forces. ( only if it fits well )

dr.bob is right about antagonist teeth. Any prosthetic treatment plan has to consider it. During food biting prosthesis definitely will work as a lever.

De acuerdo con Rotgerus 4 miniimplantes de 1.8 o de 2.4 de IMTEC ,O de OCOBIOMEDICAL

The only movement that is supposed to happen is compression of soft tissue in the distal segments. The denture is supposed to be tissue supported and implant retained. If you have movement around the fulcrum you are creating an implant supported case on a small bone to metal surface area...... This is caused by the poor location of the implants or by inadequate prosthetic construction of the denture that should be tissue supported. Implant location is dependant on the shape of the mandible,especially if you have treatment planned 2 implants. (notwithstanding occlusion classification) If you have a "U" shaped mandible the 2 implants should be at or anterior to the "corners of curvature" If you have a "V" shape keep them anterior in canine positions. Generally, premolar and distal is poor positioning for only 2 implants and creates the problems described. The case in question, based on info provided can only be rescued by a third implant placed in the anterior mandible. Note the denture must be as well extended ...and its "fit" when it is connected to implants should be exactly the same as when if the implants were not there. Secondly you cannot retain this denture with a bar on 3 implants...unless you are entirely sure that you want the forces of a fixed partial denture.