Three implants in the edentulous maxilla to retain a removable prosthesis?
What would you think of placing three implants in the edentulous maxilla to retain a removable prosthesis, without palatal coverage, using Locator abutments? A recent study 1 looked at 23 patients who underwent this technique.
The results:
None of their 36 implants gave any indications of mobility or tenderness upon percussion. Suppuration was observed on one implant. Probing around the implants caused no (53%) or minor bleeding (47%). The incidence of adverse biological and technical events was near non-existent. The rates of replacement of male attachments varied, as did any changes of male attachment retention force…The marginal bone loss ranged between 0 and 5.3 mm.
What are your thoughts?
Read the Full Abstract Here
1. Clin Oral Implants Res. 2016 Oct;27 Maxillary 3-implant removable prostheses without palatal coverage on Locator abutments – a case series. .Mo A, et al.
9 Comments on Three implants in the edentulous maxilla to retain a removable prosthesis?
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DrT
11/1/2016
The number of patients, 23, and the period over which they were followed, namely 6 years is good enough for me to use this protocol. I would try to place the posterior fixtures as far distally as possible and the anterior fixture as close to the midline as is possible
Amir Mostofi
11/1/2016
The bone quantity and quality in the upper jaw is not great. You need to use at least four implants and preferably with a bar interconnected. Placing locator in such low bone quality at maxilla will put too much torque and pressure on individual implants and will increase the risk for failure. Locators works best in lower jaw where the bone is much more dense.
Dr Bill
11/1/2016
How you design the occlusion will be the test and what is on the lower arch. I always judge the movement of the implant prosthesis by how a denture is functioning without the implants there . If you can't stabilize the upper denture from horizontal movements and tipping in function you will need to solve this first The denture will tell you the movements and forces on the implants that will be hidden when attached but will show up with your failure down the road. You must have posterior vertical support in occlusion from bi's to molars just like you need with an upper denture.
I would not do any posterior cantilevers in occlusion,i.e occlude only over the implants or anterior to the distal ones No anterior occlusion in function. If you are doing removable I would do the corners of the occlusion with 4 not 3 implants. cuspid and molar. Metal frame to prevent the distortion of the acrylic from affecting the implants and extend onto the palate some with a horseshoe design O-rings or ERA might be better because there is no compressive freedom with the Locator but they will work provided you corner the occlusion JMHO from a denture guy
DrT
11/1/2016
So are you totally discounting the study referenced by the poster of this thread?
Dr Bill
11/1/2016
Yes I am discounting the article . You can do it. I wouldn't You do as many dentures as I have and you start to understand the occlusal dynamics of dentures in function ,add the maxillary bone issues ,your inability to follow the wear of the dentures produced by the unique chewing patterns and habits of each patient. Soon you have more function on the left than the right and then you have tension on the opposite side locator and compression on the right side If it works you will be changing out the resilient liners often. Where are you going to put the anterior implant, In the incisive canal or one side of the other Now you have created something that is not balanced at all Frankly, why would you do 3 instead of 4. It saves the patient money? Less surgery? NO and no. That's just a study to see if the envelop can be pushed. It doesn't make engineering or common sense to me to do this JMHO Dr Bill
DrT
11/1/2016
And where is YOUR evidence and research to support what you are saying?
Dr. Bill
11/1/2016
Just my opinion as I said. I suspect there is more support in the literature for 4 than 3 but you have to decide how you want to treat your patient. If its enough for you great. Not enough for me . You obviously have more experience than me to consider this as an option. But tell me where do you place the anterior and posterior implants in a design you are defending so vigorously? Does it matter if you create an isosceles triangle or just a triangle with respect to forces? What do you think the force vectors are on the anterior locator as the pt chews? Just curious Dr Bill
Montana
11/2/2016
The results should not be discounted, but interpreted rather carefully. Previous studies have shown a higher failure rate with single anchors in the maxilla. The reasons cited include: greater off-vertical implant placement angle due to ridge pitch in the maxilla compared to the mandible; this results in greater off-axial loading of the implant and accelerated wear of the resilient insert and the abutment. The second cause of failure is of course the relatively soft bone and typically minimal cortical layer. Next, the maxillary prosthesis is subjected to greater lateral forces than a mandibular as the occlusion and tooth arrangement is typically buccal to the lower.
There are limitations to the study: The study comments on absence of implant mobility or pain associated with them; this is really an inconsequential finding as implants are not mobile unless they are ready to fall out. Tenderness to percussion only seems to occur when the implant is in failure mode. Almost half the implants demonstrated bleeding on probing. is seldom a sequelae unless soft tissue is inflamed. The actual sample size is 12 patients with 2+ years. Bone loss is noted but there isn't a reference to calibration of measurement or baseline. In other words, the information is added to our continuing study of implant therapy but is too limited and somewhat unstructured to greatly influence one's treatment protocol.
With reference to the idea of placing three implants in the maxilla, placing one in each posterior as far back as possible may not be a good choice, as it forms a long triangle, the legs of which are greatly inside the loading area of the canine-second bicuspid chewing zone. This will create a buccal lever arm which can rock the prosthesis. Also, the bone is typically less reliable in the molar area.
I do not treat with solitary, maxillary anchors in edentulous patients, preferring to splint them with a rigid structure to prevent a bending moment and accumulation of strain at the implant site.
Montana
11/2/2016
Addendum to my post: Legs of the long triangle being "inside," I meant lingually to the occlusal position, creating the buccal lever arm.
