Problems with Retention of Denture on Upper using 4 Astra Locator Abutments: Advice?

Last Updated: Aug 27, 2012

I placed 4 Astra implants in the upper jaw and the patient wore his conventional upper denture while healing. I then exposed the implants and took an overlying impression with the copings and sent it to the lab for the rebase and also for processing of the 4 locator caps. Since then he cannot wear the denture. It seats initially but then on eating he finds it rocks and he can displace it with his tongue! It is well extended and supported on soft tissue with a deep post dam. The occlusal contacts are even right and left as he has an opposing lower partial denture and balanced contacts all the way around. Vertical dimension and freeway space are acceptable. Without the lower denture in place he only has anterior tooth contact so he knows not to eat without it. I used the red connectors for the non parallel implants as there was some divergence and I cannot seem to improve the situation??? Is there anything else I can do or check? I stripped the entire denture down again, and retook the impression using a wash of Impregum in occlusion and was very happy with it…. but again same problems! I know I can increase the retention by switching to the 4lbs green connectors but I want to first diagnose the problem. This is the first time I have used this system. Any thoughts?

15 Comments on Problems with Retention of Denture on Upper using 4 Astra Locator Abutments: Advice?

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Charles Schlesinger, DDS,

08/28/2012

The first thing I would check is if the housings were passive in the hollowed out denture. You may be pivoting on one of the housings/abutments. Are you picking up the housings yourself, or did you have you lab process them? I never have my lab process them- just the smallest amount of discrepancy will cause rocking or non-seating. I would remove all the housings, reline until stabile. Wihout housings, your denture should not rock. Then hollow out denture and put housings on the abutments, but do not pick them up. If no rocking, then pick up with acrylic. If it rocks, you are pivoing on a housing and need to relieve the denture more to accommodate it.

mjohnson dds, ms

08/28/2012

Dr. S is correct, I pick up the locators intraorally. Also, if implants diverge, it may be better to go with a bar/snap attachment so you can parallel the retentive elements. Unfortunately, this would require remaking the prosthesis. If all your implants are anterior, then function on the posteriors will cause the attachments to pop loose. Another reason to go with a bar and clips so you can extend the bar more distally and space the clips out as far as possible.

larry cohen

08/28/2012

always pick-up yourself intraorally without pressure from occlusion. should be fine and be sure to use the little white spacers for relaxed pick-up

John Fazio DMD FAGD FICOI

08/28/2012

I assume you are using the extended range male housings from your description. If so, try stripping your denture then taking a wash impression for your reline with new male housings placed on the abutments at impression. After your reline, it takes just a small adjustment to remove any acrylic still holding up the denture seat. This way you can get the best possible tissue support for your denture. Implant-retained tissue supported dentures (RP-5) in the maxilla can be tricky with 4 implants. Better to treatment plan long term for an implant-retained (RP-4)prosthesis in the maxilla.

Dr J.

08/28/2012

I agree with those that say the locators are best to be done chair-side intraorally instead of the lab. The shrinkage and distortion from the impression to stone model etc creates the problem. Next time have the lab leave the area of the locators hollow so you can do it chair-side.

Nina King

08/28/2012

Hello again: Thank you for your help. I have processed the denture housings in the lab ( thought it was best but I guess not!!!) The patient feels the rocking is only on one of the anteriors. The implants are in the canine and second premolar areas so quite well spaced out. Can I simply hollow this one out and remove and reline a single housing or do I need to remove them all?

Dr Ben

08/28/2012

Well Depends on the impression material and lab. I have done several at my lab rarely had any problem. Implant make is not a problem either. As Dr. Johnson said implant angles can be an issue and the only way to sort it is with a bar. also if denture is not rocking on model then there can be a problem with your cast. also I hope your denture has buccal flange.

Dr. Knowles

08/28/2012

I have had similar propblems. Now I always pick up locators in office. I would do all four, not just the one that you think is the problem. I started using Muco Hard (Parkell) to pick these up and have been pleased with the results.

Dr G J Berne

08/28/2012

I also totally agree that picking up the attachments in the mouth is the best way to go. Also it is a good idea to have the patient bite heavily whilst the attachments are being picked up. This way if there is any compression of the denture during chewing the locators won't cause any rocking which has been experienced by the person asking the question.

Dr. Alex Zavyalov

08/28/2012

Locator is supposed to be adjusted in the mouth by pressing the mucosa with denture (fingers or occlusion). Itâ€™s difficult to install it properly on the plaster rigid model.

nailesh gandhi

08/29/2012

i always prefer chairside work.

nailesh gandhi

08/29/2012

i always prefer chairside work. All opinions expressed are very true.

dr bob

08/29/2012

First the denture needs to be well made with the teeth set over the ridges and the case built in proper verticle and centric relation. The denture should seat and not flip out when compressive force is applied to the teeth even with no implants aiding in retention. Implants can not make an ill fitting denture into a good fitting denture. The denture must be supported by the tissues when it is loaded. The implants should resist displacement forces. Those forces that would result from gravity, stickey foods, etc. that cause movement that lifts the denture off of the ridges allowing the separation of the denture from contact with the underlaying mucosa are what the implants must resist. With an overdenture the implants should not load so much with compressive forces as to prevent the denture to settle onto the mucosa. If the implants prevent the tissues from taking up the load the denture will rock on the implants and come loose.

CRS

09/24/2012

I have a question what positions were the implants placed? Do you have a panorex? I space mine at the canine and first molar regions, eventually the palatal acrylic can be removed with good retention. Are the locators too close together? Any feedback?

TOBooth

11/19/2012

All the locator abutments should be engaging at the same height into the denture , that may be your problem.

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