Angled implants under locator attachments for maxillary denture retention?
I have a middle-aged female patient who owns a restaurant and wants dental implants to retain her maxillary denture so that she can not have the palatal acrylic and then she could taste her food better. The prosthodontist sent an acrylic guide with request to “put 4 the implants in the marked spots for locator retention”.
I had recommended a fixed appliance, either bar or all on 4-6 but she cannot afford that. I can place four 11.5 – 13 mm tapered implants, a la all on four technique, (3.7 diameter in the anterior and 4.2 in the posterior). However, they would have to be 30 degrees from vertical in order to put the implant tables where the prosthodontist wants them. There is no vertical bone to be had.
Additionally if I move them palatally to place them more vertically, then they will essentially require more denture acrylic which would “crowd” into the palate she so much wants to feel. Actually they will be about 3-4 mm palatal to that in the anterior as it is. I will also remove about 2 mm of soft tissue reduction and about 3 mm of bone reduction to create adequate space for the locators + 4-5 mm thickness of acrylic over the locators as the denture is now about 3-6 mm in thickness.
Angled GPS abutments (similar to Locators) are now available from Implant Direct as are angled ERA attachments that are up to 30 degree from vertical. Does anyone have much experience with such a set up (angled attachments to parallel the line of draw) on angulated implants? My concern is that since the implants are not splinted, there will be more lateral force on them. Has anyone found longer term (I know the attachments haven’t been out very long term, but what ever experience you have, I’d like to know) problems with locators on angled attachments in the maxilla?
24 Comments on Angled implants under locator attachments for maxillary denture retention?
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CRS
12/13/2014
I would not compromise your initial plan due to patient finances That said work closely with the prostodontist if he feels locators will work with a thirty degree draw then let him deal with this issue. If a bar will work then let the patient commit to this at the get go. Be careful not to paint yourself into a corner with compromising for patient finances, gave a back up plan with the bar. The patient will want it done right and you want to avoid chasing complications for free. The all on four is a strict protocol to be predictable.I Don't have a film to truly advise you.
Geoffrey Bauman
12/13/2014
Thanks for the feedback. I advised the patient and prosthodontist up front that I'd rather to a bar or other fixed appliance. He advised me he was doing locators. The implants are standard size and 13 mm long so I'm thinking it should be fine since I see mini-implants designed for just such off-angle use. I just haven't used them off angle for locators before. I appreciate your comments.and wholeheartedly agree.
Geoff
Albert St Germain
12/16/2014
The advantage of a bar on the upper is one of cross-arch splinting, which the locators don't provide. In our area the surgeon we work with will not consider an open palate locator prosthesis, and all the lecturers in our sponsored implant mini-residency program have emphatically advised against such an arrangement, although I've heard some anecdotal comments about their use, which have not been substantiated
Food for thought: If the implants fail, then is the prosthodontist, who seems quite dogmatic, willing to accept that responsibility?
Don't do something you're not comfortable with, especially if you feel it may compromise your treatment.
Mark Montana
12/16/2014
I'm not a fan of maxillary stud over-dentures, particularly with off axial loading. I much prefer to splint the implants so they work as a team. An alternative to consider is the Conus abutment from Atlantis. Because the abutments are milled to be parallel with intimate contact to the telescopic (Syncone) sleeves, all four implants will again work as a team.
However, as you are not designing the restorative component, your choice is to discuss alternatives (sounds like you've done this), agree to place the implants but advise all parties that your commitment ends at integration, or step aside. We all get talked into things, but how often does it work out and at what cost in worries.
mwjohnson dds, ms
12/16/2014
I agree with the last two commenters. As a prosthodontist, I would never recommend free standing implants in the maxilla especially if the palate (primary denture bearing area) is removed. Then all the force goes to the implants. You need cross arch stability and stabilization. You also need to spread the attachments out. Even in the best of situations of tilting the posterior implants the locators will only be at the 1-2nd premolar. When the patient functions on the molars, the denture will fulcrum around the posterior locators and the anterior locators will disengage and the denture will move/come loose. With a bar retained overdenture, the hader/bredent or whatever clip can be cantilivered beyond the last implant to add A-P spread to the clip arrangement for better stability and retention. My philosophy is if they want the palate removed it's 4-6 implants and a bar or fixed bridge. Don't compromise! Otherwise, tell the patient to save their money and make a conventional denture. KISS principle works every time.
Tuss
12/17/2014
If you feel a fixed bar solution is the best option then regardless of finances thats the best treatment to pursue (maybe stage it over a longer time frame to allow patient to pay) The angled locator solution is available on Straumann and a few other systems and off-axis loading in this case is not a major negative as the collar hiegth is under 3mm so no huge cantilevers. I think the finite element studies show stress concentration at the head of the implant as per normal. The maion key is hygiene around the locators and not wearing denture at night. If she has any bruxing tendancies then think twice
Geoffrey Bauman
12/17/2014
Thanks to all for your comments.
Geoff
S.SenGupta
12/17/2014
What is often misunderstood about bar vs Stud attachments is ...
When you have a connected bar you are effectively loading the implants at all times in function. Thus an implant"supported" prosthesis.Much like a fixed bridge...and indeed you have and need cross arch stabilization.
When stud attachments are used then the implants are not loaded during function....or only minimally .The implant's primary function is retention...Thus an "implant retained" prosthesis.The most pressure exerted on the implants are when the patient removes the over denture.A full hard bitewill not transfer force down the long access of the implant...it will instead be dread across the intaglio surface of the denture asks normal for any non implant denture.
If the stud attachments are creating fulcrums and rocking... then the retro fitting of the denture has been done inaccurately.
Stud attachments are an excellent cost effective option.I have had many cases inservice for now coming to the 2nd decade....you do however need to change the rubber rings or plastic components from time to time.
Geoffrey Bauman
12/17/2014
Thank you Dr. SenGupta for your comments. I understand the retention vs. support phenomenon though I am a Periodontist and have not loaded a denture over stud attachments, I ponder the clinical effect of retention vs. support in considering the case. In this case the GPS angled locators will be on 4 standard size implants of 11-13 mm in length in 2nd bi and canine positions and I am also placing one with a healing abutment in the #9 position to help with biting foods in the anterior and indirect retention. When you do your reline along with pick up of the attachments in the denture, how firmly to you have the patient bite? My sense is to have the patient close somewhat firmly so that in non-function and early function the tissue will absorb more of the weight of the denture. I've even thought that in this particular set-up if something very minimal in thickness could be placed between the anteriors (in the correct position) and have the patient bite on that at the time of reline/attachment pickup, then the arch posterior to the terminal implant would tend to carry more force in function and have less tendency to fulcrum on any of the locators. Just a thought, but not sure how one would implement it "just enough" and in the correct position without opening the posterior too much
What is your experience with that? Do you have the patient bite somewhat firmly? I won't be doing this, but it's good info to pass on to dentists that I work with.
Thanks again,
Geoff
mwjohnson dds, ms
12/18/2014
unfortunately, when you place four free standing implants in the maxilla and remove the denture bearing foundation (the palate) the "overdenture" becomes implant supported. The soft tissue support is negligible so don't even consider that the soft tissue will bear any of the forces; they will all go to the implants. With tissue thickness on the ridge crest of 3-5mm, the tissue will easily displace under function and not offer anything in terms of denture support. The locators offer minimal movement apically under function so when the tissues compress the implants will get all the force. Don't fool yourself into thinking that four spaced out implants in the maxilla are the same as two implants in the anterior mandible. Two implants retain the mandibular denture but add minimally to its support. It's all soft tissue supported and the primary denture bearing foundation (the buccas shelves) are still intact. When designing full arch implant restorations we need to take into account the resiliency of the attachments, the A-P spread of the attachments, the resliency of the mucosa, the denture bearing ( or lack of) foundation and forces (opposing a denture, natural teeth or another implant reconstruction). Fully edentulous treatment is expensive and difficult, especially the maxilla. Make sure what you are planning will work mechanically before you place the implants. Otherwise its an expensive mistake for you and the patient.
mwjohnson dds, ms
12/18/2014
Also, as an aside to Dr. Baumans thought of placing another implant at #9 to decrease rotation, if you're asking the patient to spend more money on a fifth implant, have the patient use that money and the cost of the four locators and put it towards a bar/clip. It will probably be a wash financially. Also, in planning implant positions, evenly space the four implants around the arch from 2nd bi to 2nd bi (so anterior implants wind up a little farther anterior than the cuspids). this gives a good A-P spread to the implants. Have your prosthodontist use hader clips anteriorly and cantilever off the distal of the bar the 2.2mm bredent ball attachments. You will be amazed at the retention and stability of the prosthesis. No rock, total implant support and the attachments are tripoded far apart for maximum resistance to function. I wish you and your patient all the best!
MWJ
mpedds
12/18/2014
The palatal bone is basal or non resorbing bone. Upon biting, as the soft tissue compresses the bearing force will be upon the palate. In a denture without the palate all the force is borne by the soft tissues and then the alveolar bone which is subject to resorption. So sooner or later the implants will become load bearing. If the implants are to be for retention only you must have palatal coverage.
Geoffrey Bauman
12/20/2014
I thank you all for your comments. The patient was referred to a prosthodontist to manage the prosthetic aspects of the case with a recommendation of fixed replacement. THe prosthodontist said the patient can't afford fixed replacement and requested 4 implants to support locators. I am not asking the patient for more money for the 5th implant That was going to be a "gift" to help prevent rocking (as indirect retention). I informed the prosthodontist that my understanding in the past was the a palateless denture more or less required a bar or other fixed restoration and this is the plan I received. For those who say it is doomed to failure, can you point me to some studies?
When I was in perio training, in 1980s, single stage implant placement was considered risky, immediate implants were too risky also and carried a high degree of failure, immediate loading was absolutely taboo as that was given as one reason that so many implants failed in the 1970s and before, mini-implants were also only temporary and only hustlers would use them to support a denture permanently. All of these things have since been disproven. That is why I wanted some feedback on the forum here. I understand where the nay sayers are coming from. That's been my understanding since the 1990s. What I was looking for was experience of someone who has "experienced" stud attachments under a maxillary denture or could point me to some studies, particularly recent studies. The patient is awaiting scheduling and I'll hold for any further comments.
Thanks again,
Geoff (I didn't know that my full name would be put on the forum, but there you are it's out there now. It wasn't given on earlier posts).
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12/21/2014
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Dr S SenGupta
12/23/2014
Hi Geoff
For the implant width and length described I really do not see a problem here.
You have used standard implants...there is a lot of surface area area there.
Also you have good length.
The implant length is a factor with these retention cases which is why the long mini implants work as over dentures as length is a greater factor to width for over denture retention cases VS over Denture Implant supported cases.
I have to dis-agree with our colleague mwj regarding no soft tissue support.
As I said in my previous post... if the retrofitting is done properly the implants in housings (o-ball variety) can only be for retention.
In other words the denture intaglio surface still compresses soft tissue in function...and does NOT load the implants vertically along the long axis.This is the whole point of the concept.Look at the cross section through a housing in all the catalogs....there is a "space" very deliberately above the head of the oball.when it is connected via the internal rubber ring...the o-ball should not be hitting the roof function...or barley contacting.
I dont understand why mwj does not think there is tissue support in the maxilla?After all horse shoe shaped upper is the same as a lower over denture on 2 ball attachments?Granted regarding the buccal shelves on lower but you will still have some palatal support from the palate even if it is a partial palate..
I would suggest a chrome horse shoe internal frame for the upper...more comfortable and less bulk...you have loads of retention!
Dr S SenGupta
12/23/2014
Goeff
To answer your question regarding technique...
You cannot have the patient bite hard when retro fitting.
If you do ...the acrylic sets when the denture is compressing the soft tissue.
So you get one of 2 problems....either the soft tissue is very thick and pushes the denture off in recoil...thus retention is lost.
Or ...the denture ...even when passive.. compresses the tissue at all times.
You don't want either problem.
When retro fitting you are looking to have the patient occlude correctly.No clenching certainly nothing placed between teeth...this will create big problems!
Forget the implants as bridge abutments and their relationship to each other, and think like you are working on removable dentures....we never ask anybody to bite hard for anything with full dentures...its all about adapting to the soft tissues over the hard tissue base.
In the same way when you do a chair side hard lining ..you don't want patient to bite hard...otherwise your lining takes the shape of the compressed tissue...thats not what you want. Bring teeth together deliberately with light force and into correct occlusion.
Then i manipulate the lips and cheeks around the denture to get correct extensions...(.often there is a lot of acrylic to replace in a retro fit especially with angles.) Over many years of using Mini and Hybrids and Standard implants this technique has really proved to be extremely accessible to a vast array of patients with all types of budgets...Good luck
John Ackley
12/23/2014
A few ideas on this case. The Atlantis Conus option is very elegant, provides a nice open palate and rigid fixation while retaining retrievability for proper hygiene. We have done several of these and the feedback has been very positive. Another thought would be Spheroblock abutments from Rhein 83, these do an excellent job of angle correction with a very reliable retentive option, nylons are easy to change and offer varying levels of force much like locators. A possible surgical option would be to use a bi axial fixture to correct the angulation at the superior portion of the fixture. These are available from Southern Implants ( Keystone/Lifecore ) Best of luck with the case.
Tom Wierzbicki
12/23/2014
What is the opposing dentition like? This will have a huge impact on the long-term treatment outcome. If the patient has a complete lower denture, you can probably get away with angled implants supporting a locator retained complete upper denture, not ideal, but doable. If it is natural dentition, the system may fail due to the stronger off-axis forces that it will be subjected to. As mentioned earlier, the success of angled implants relies on splinting, and specifically cross-arch splinting.
Best of luck with the treatment,
Tom
Raul Mena
12/23/2014
i understand the many reasons that must of you do not want free standing Locators in the Maxilla.
I have done many bar to support overdentures in the maxilla, but there are other means to support Maxillary Overdentures.
For a long time I have changed to 3 different other options:
Quantum's free standing O-Rings
Quantum's free standing ResQ abutments
Quantum's Eco-Fix abutments
For full disclosure I am the President of Quantum Dental Implants.
Raul Mena
Mark Montana
12/23/2014
GPS and Locator abutments do not have the relief or resiliency of O-rings and therefore soon become permanently active in maxillary over-dentures following even slight resorption of the supporting tissues, particularly if the palate is removed. As I wrote previously, I'm not a fan.
mwjohnson dds, ms
12/23/2014
I agree with Dr. Montana, there isn't much vertical play in a locator attachment. By the time the soft tissues compress even slightly you'll be riding on the locators. Ball abutments have significantly more vertical play than locators and, actually, can be a better overdenture attachment than the locators due to this fact.
Dr Bob
12/24/2014
Mark, I agree and will use free standing "O" rings as less force is applied to the implant in function. The ERA and Locator type attachments have much less vertical and lateral resiliency than the o-ring with not that much more retention, and are much more likely to result in an implant supported denture. I have when needed used o-rings with the one piece ball small diameter implants in the maxillary (not immediately loaded) and even that can work well, but will not use a small diameter locator implant as free standing in the maxilla as it is more likely to over load and fail.
Geoff
12/24/2014
Many thanks for all the comments. Looking forward to more if others have experience in this area, particularly longer term. I appreciate the points made about the greater forgiveness of O-rings in function. Thanks for those comments.
Thanks again,
Geoff
Raul Mena
11/2/2015
Can you be more specific ?
