Dr. M asks:
I am presently evaluating the design for both upper and lower bar-retained overdentures. The upper will have eight dental implants and the lower will have six dental implants. The position of the dental implants will follow recommended positions as outlined by Misch. My question centers around rather to design a screw-retained or cement-retained bar with attachments.
I am aware that the cement-retained bar will require abutments height of a minimum of five millimeters of height for retention. This simpler design and potential for upfront ease of placement and construction are appealing. Any thoughts as to the comparison of the long-term in comparison to the screw- retained bar vs. the cemented bar? What other factors are important in choosing between one of these techniques? As of present, the type of attachments will probably be a combination of Hader and Locators. Thanks.
There is no question that making a cement-retained bar is easier and less costly. I have done both, and I would never do a cement-retained bar again. I have had two of them loosen on just one abutment and had to tap the bar off. On one of them, I slightly bent the bar and had to remake it. I have also had screw-retained bars break and had them repaired with laser welding. If they had been cemented, it would have been so much more difficult. Screw-retained is the way to go.
If you’re prepared to place abutments on these eight implants why don’t you just make it a fixed case?The only reason that would preclude the fixed case would be significant hard and soft tissue deficiencies that you could compensate for with the overdenture.If I could place 8 implants in the right location on the upper arch I would prefer a fixed case(so would the patient).That said ,if you must do the overdenture I prefer the screw retained bar for ease of servicing down the line if the need arises.Good Luck
Dear Dr. Menal:
You are defeating the purpose of an overdenture! Please tell me that you are doing an overdenture because you have extensive deficits in soft and hard tissues. An over denture is usually a cost containment measure. Threre is no need for so many implants, and better yet, in a costly bar construction. If you are doing it for cost reasons, place two implants in the mandible and four in the maxilla and restore with locators or other attachments. If you are placing eight implants in the maxilla and six in the mandible, consider making a fixed case. As a prosthodontist, I have seen too many patients present with expensive implants and crappy dentures on top. Help your patients spend their money wisely. A properly fitting and selected prosthesis is much more important than the number of implants placed. Any patient will be much happier knowing that they have spent their resources wisely. Most patients will be dissapointed to have spent so much money for 14 implants and still have a denture–that is not what defines successful treatment.
If indeed you do need to replace hard and soft tissues for this patient the finest overdentures that we have seen are being done as Camstructures by 3i. These are available as primary bars, hader bars or as hybrids. The primary bars are by far the most stable and will give the patient the stability of a fixed case. If done with a premium denture tooth such as Vita Physiodens or similar you can get some pretty remarkable esthetics. The palate can be kept exposed so the drawbacks are really quite minimal. When doing a restoration that replaces significant soft tissue this type of restoration is truly the most predictable. We have done many of these quite successfully.
Zev has very valid point.Unless you are replacing deficient hard and soft tissues with excessive interarch distance, Can you explain necessity to do over dentures with so many implants?
I am sure you must have some valid reasons for so many implants,may be due to very poor quality of bone,size of implants,or parafunctional habits or else?
A far as your question is concrned,I would go for screw retained, iregardless of other factors, just to avoid recementing bar frequently.
Thanks for the quick reply and yes to the several questions about tissue/bone loss -This patient is a Type I Division D for both arches. Extensive osseous grafting has been done to allow implant placement.
The screw retained bar will have a large microgap and will allow the periodontal pathogens into the area and may cause future problems. I feel it best to use cement unless the abutment junction is kept supragingival.
Dr.Callan
Microgap should not be a problem if one stage implants are used with indexed abutments and bar is soldier to gold sleeves.
In the contrary if two stage system is used for cement retained bar, microgap problem will not go away as bar will be cemented over prosthetic abutments, and so abutment/implant microgap will still remain.
So it is not what retainig system is used, but what implant types are used will determine the final outcome regarding presence or abscence of microgap.
Forget the bar and magnetics to fabricate overdenture. Those are cost and time consuming to maintain. Telescopic prosthesis, especially electroforming system would make you and patient happy. That is easy to fabricate and trouble free to maintain
I am a resident at LLU-Implant Dentistry and we regularly do screw retained because it is easy to retrieve, easier to repair and the most frequent complication will be maybe changing a screw you should consider thinking the prosthetic material wheter resind teeth vs. ceramics and the material of the framework(ex. gold, titanium, zirconia) and the compatibility with the opposing dentition.
In regard to Dr M’s case of placing 8 maxillary implants in good positions, I would like to suggest the following type of prosthesis.
Available from the attachment maufacturers are plastic bars that are used to make Dolder bars,using plastic blanks that are castable and fit over tapered abutments, or UCLA type direct to the implant, wax up a bar that is castable and has parallel walls. If the implants are not perfectly parallel, the bar can be cast in sections.This is the primary bar.
The cast bar is screwed into place in the mouth, and then it is picked up in an alginate or other impression ( sections can be luted together temporarily ), and a new model is poured.
A wax up is made over the primary bar, relieved wherever necessary, and Lew Attachments are placed in posterior areas that allow adequate access by the patient to open and close these precision bolt locks. The wax up should also have beads or grids to allow the denture acrylic and teeth to bond very well.
What will be produced will be a very easy to maintain primary bar that can be flossed, brushed, waterpicked,by the patient; and an overdenture that can be very reduced in size and yet very strong because it is sitting on a metal secondary substructure — so that it holds the denture teeth, fills the missing natural anatomic defects, and when the Lew Attachment bolts are closed, it feels and functions the same way a fully implant supported fixed bridge would. It is less costly for the dentist and the patient, and the esthetics are excellent.
I wwould be happy to share with the readers my color photos of previous cases.
Gerald Rudick dds Montreal
Dear Dr Rudick, I am interested in the prosthetic construction you proposed, could you please send me a link to the pictures? Thank you in advance!
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Best regards:Dr Yassen Dimitrov
Dr. Rudick,
Could you also please share those photos with me? Thanks.
JFuruyama@aol.com
Dr. Rudick,
Could you send me a link to those pictures, too?
Thank you in advance; e-mail:
greg@drzabek.com .
Could you send me a link to those pictures, too?
Thank you in advance; e-mail:
dramitnarang@hotmail.com