Larry, a dentist, asks us:
I am hearing more and more about using free-standing implants to retain
overdentures both in the maxilla and mandible. In the mandible, two
dental implants in the canine areas appears to be the most frequent design. In
the maxilla four dental implants in the canine and second premolar areas
appears to be the most frequent design. Bars seem to be on the way out.
My understanding is that bar retained overdentures are really RP4 designs in that they provide most of the support for the overdenture instead of the traditional denture bearing areas. In terms of maximizing chances of success, I think bars are a poor choice unless they have multiple dental implants for support and stability. I think the RP5 design using free- standing dental implants for retention and bearing areas for support provides the best overall treatment plan. What are you all doing? Are Bars in or Out? Thanks for any comments.
I don’t see how unsplinted implants in the maxilla improve the stability of the implants or the prosthesis. The force vectors during function provide too much lateral force on the implants and maxillary bone is not dense enough to handle it. I think bars are in. But then, maxillary overdentures are tough, with the lowest % survival rate of any of the implant supported prostheses.
Why fix it if it ain’t broken? I have been fabricating bar supported overdentures since 1974 with excellent success. Why change? Most overdenture failures that I have seen, including my own in those early years, were from poor diagnosis, poor implant placement, poor occlusal equilibration poor overdenture fabrication, or any combination of the above.
I think considering the higher skill, laboratory cost and time required for bar fabrication and the fact that bars provide partial or complete support for the entire prosthesis therefore requiring 4 or more implants, I go with two individual implants (ideally in cuspid position) for retention of a fully tissue supported denture.
The only situation I can justify the more involved and more expensive bar is when the residual alveolar ridge is somehow inadequate (in hight or width)to support the denture. This happens in case of extreme resorption or surgical removal of part of the jaw bone due to cysts/tumors.
Currently I use Locator abutments on two implants and the retention is usually more than what the typical older patient is comfortable with.
Locator abutments are usually my first choice these days.
Parsa T. Zadeh, DDS, FAGD, FICOI
BARS ARE OUT….at least in the anterior maxilla if they cross the midline. The dimensions for the bar and clips make the acrylic thick and impede speech. Also, anterior implants are for support and posterior ones for retention to resist tripping the denture on incising. Restorative dentists are too timid in recommending sinus grafting and only get the implants as far distal as the first premolar area. You have the four legs of your chair at the corners don’t you.
From the dental laboratory perspective we have seen a huge increase in Locator cases and a huge decrease in bars. That being said there are times when Locators do not properly retain and brace dentures, especially in the maxilla. We have had multiple Locator cases that the patient can’t easily remove, yet trips out during function. Especially when there is limited posterior occlusion. We have never had a bar case on the maxilla trip out of retention, especially milled bars. Beware of maxillary Locator cases with tremendous bone resporption and a Class 3 skeletal relationship to the mandible. Long term, bar cases in our experience require less maintenance, but at a higher upfront expense, which is well worth it in patient and Dr. satisfaction.
Free standing implants are ONLY free standing when the denture is out of the mouth. When the denture is seated, it acts as the bar to splint the implants. Bars unnecessarily complicate cases and if more than one bar is utilized with clips that are not parallel,they engage the retentive devices upon occlusal load. An undesirable situation in any of prosthetic design. This same situation occurs when more than two implants with stud attachments are used in an overdenture case. The center implant (in a three implant design overdenture) will engage the retentive device upon posterior occlusal force.
Having done all kinds of implant overdentures over a period of 25 years. It has been my experience that most bar cases break due to stress applied by mastication. However in cases that use 4 or more overdentures as o-rings, eras, stern, and locators. They work better due to the fact that they asorb the shocks applied by mastication.
I believe in splinting implants together whenever possible or economically feasable. Design of the bar is very important to prevent implant overload as in the rp4 designs especially when to few implants are placed or are improperly placed for a fixed case. On the same note I don’t design many RP4 prostheses. Why would you if you have adequate position and number of implants for a fixed case. Fixed cases are easier to take care of. I have the most implant failures with free standing implants.
I am a Prosthodontist practicing since 1986. I have done many Dentures and Overdentures, both teeth and implant assisted. In my opinion,the key to Implant Overdentures is in deciding whether they will be totally, or partially implant supported ( What I like to call an implant ‘assisted’ OD),and then designing them that way. The second most important key is ensuring proper fit and extensions for the soft tissues when doing an implant assisted OD. Frequently, my patients, or patients of my students at the University, come to me to evaluate a problem with an implant assisted OD. The vast majority of the time, the problem is associated with the OD attachments engaging when the tissue surface is not fully seated (clinically detectable by a ‘rocking’ of the OD around the attachments.) This leads to pt complaints about movement during eating, and rapid loss of retention for the attachments, and an unhappy pt. The solution is to evaluate the fit of the OD without the attachments and assure proper fit. Only then should the attachments be added, and doing this clinically is more predictable than in the lab.
Getting back to the original question about bars, based on my experience and that of some of the lecturers whom I respect, I feel bars are generally ‘out’ in the mandible. 2 cuspid area implants and 2 Locator attachments in a well fitting OD (covering and supported by the Retromolar Pad and most importantly the buccal shelf), will be a tremendous improvement compared to a CD. Pt education prior to implant OD tx is the third most important key. Pts must understand BEFORE tx that they must compare the implant assisted OD to a conventional CD and NOT a Fixed Bridge. Realistic pt expectations are actually extremely important for all Prosthodontic tx.
The Maxilla, however, is a different story. Compared to the mandible, bone quality and quantity are generally less, and forces and force vectors are generally more. Also, contours and bulk of the prosthesis are more critical in the anterior and tooth position is more critical. This leads to a situation where there is very frequently a space problem in the anterior, especially if a bar is used. Splinting of the implants will improve the ability of Maxillary Implants to overcome the unfavorable force factors. However, this usually causes the space problem. One option is to make 2 bars to minimize hardware in the anterior. However, this leads to a loss of cross arch splinting that is on a curve, which is much more mechanically favorable than straight line splinting.
Due to the above unfavorable factors, my choice is to rarely do implant assisted ODs in the Maxilla. A fixed hybrid prosthesis (and only if unavoidable, a fully implant supported double bar OD) can usually be done when sufficient implants have been placed. When insufficient implants have been placed, then an implant assisted OD will usually have one or more of the problems previously mentioned. I also have a problem recommending the expense and surgery of implants when the pt still ends up with a Removable prosthesis. A well made conventional Maxillary CD can satisfy the vast # of pts and if the ridge is too poor for that, then it is likely too poor for implants and an OD (without grafting or zygomatic implants.) To directly answer the original question regarding the Maxilla, I believe bars are still ‘in’ for the Maxilla in selected cases, as are free standing implants and attachments. Case selection is key, followed by proper design and execution.
I hope my verbosity was matched by usefulness of the content.
I like to believe that I am open minded and I look forward to reading the opinions of others.
Dr. Ron Haas offered a summary so to the point. However, these points are not well understood by many restorative doctors who I have to work with. I will have another source to quote if Dr. Hass wouldn’t mind in my future discussions with restorative doctors.
From a lab/biomechanical point of view, I recently presented the topic of the closure of the Inter-Implant Space (maxillary or mandibular) with an Implant Borne Bridge (IBB) and found considerable interest among Dentists attending the ICOI/Montreal meeting.
My objectives were to create an efficient, cost effective implant supported prosthesis for the often encountered patient scenario of not enough bone, but a desire for a fixed implant supported prosthesis.
The IBB answers that need with a completely rigid, attachment-free, highly hygienic, patient removable solution that combines
prosthetic simplicity with great esthetics and function. It is a “feathered flange prosthesis” assuring very high patient comfort as it replaces the lost hard and soft tissue volumes only. It creates a very cost effective environment in which well established prosthetic pathways lead to the correct restoration of the maxillary and/or mandibular arch with correctly positioned anterior teeth (o. oris/lip support, esthetics ßàfunction interplay) and correctly positioned posterior teeth (buccinator support) incorporated into an occlusal plane that is in tune with the patient’s biomechanical / rehabilitative needs.
Based on work started in the late 1940s defined by Dr. A. Gaerny, Switzerland, as the “Closure of the Interdental Space”, I evolved the current IBB design into an extremely simple implant restoration that
- competes effectively with Spark erosion technique approaches, (albeit that we still do quite a few spark erosion cases on a daily basis),
- utilizes free-standing abutments (no inter-implant bars needed, great hygiene),
- utilizes a secondary connector made from Vitallium 2000 resulting in great cost savings,
- utilizes advanced inner/outer telescopic design principles,
- utilizes “hydraulic attachment effects” for prosthesis retention (no moveable attachment parts to be replaced),
- offers full repair/add-on ability without having to replace the restoration (in case of prosthesis / case extension over time, or implant loss at any time),
- costs significantly less as modern materials and advanced design features are fully applied.
As far as long term follow ups go, there are ample long term references by Huober G.; Gaerny A.; Zarb GA, MacKay HF. Sekine H; Kishi M, Yasaki H, Nakayama I, Uetake M, Mori T.; Voitik AJ.
Glad you felt the comments were helpful. By all means feel free to use this information for any Dr or lab tech. I would also be happy to answer any further questions from Drs in this discussion group on any Prosthodontic topic.
I’ve read all the above and have a question for someone willing to answer all or part. Since Oct ’05 I’ve had two grafts (maxillalry) with the sinus lift. Lots of complications. 8 implants put in June ’06 3 on left, 3 on the right and 2 smaller in the middle. I was planning to have the fixed prosthesis with porcelain etc. Then 2 weeks ago one implant on the right had to be removed. Interesting point is that with all the sophisticated medical equipment there was no visible problem other than bone loss between 2 implants on the right side. Turns out that behind the “sick” implant all the bone was gone all the way to the sinus even tho it appeared to be stable. The surgeon removed the implant, cleaned the area out and now with the remaining 7 I’m being encouraged to consider a removable overdenture with a “spark erosion” bar. Can someone explain what their experience is? An elderly patient has the fixed superstructure as I had planned but she’s having lots of problems keeping it clean as well the crowns keep coming off. Are 7 implants okay?
Thanks for whatever info you give me.
what about 2 implants in the premolar and canine area of each side( total 4 implants), and a telescopic over denture for restoration? what is the disadvantages of this treatment plan??!!!!thanks