Should I use transmucosal abutment (multi-base) or directly screw my hybrid to implants?

I tend to always use an intermediary abutment for exactly the reasons you've stated. I like working supragingivally to verify framework fit and to decrease discomfort. The smaller retaining screws certainly have a lower fracture strength but still plenty strong to retain a hybrid (we've been doing it for 50 years!). Also, in case of over stress, I'd rather have a broken retaining screw than over stress the implant or try to retrieve a fractured abutment fragment inside an implant. Pay no attention to your well meaning colleague!:)

I realize your question for the group is restorative in nature. However, after reviewing your case photo, I can't help but notice that several of the implants are positioned in alveolar mucosa without adequate bands of attached gingiva. Regardless of the abutment selected, peri-implant health cannot be easily maintained in this environment. I would strongly encourage you to seek the services of a periodontist who can assist your patient in securing attached gingiva circumferentially around each fixture. This will certainly assist the patient in preventing peri-implantitis.

I absolutely agree with MW. Any time you have a hybrid with sub-g connection you should use a transmucosal abutment to raise the restorative platform. With so many abutment options today, you really don't waste vertical space unlike the early days when collar sizes were limited. Cone shaped abutments also make seating easier than working on a flat top. My last word, direct to the implant means you cannot engage the axial walls of the implant interface, so you have to bypass. This places greater strain on the screws, so they may be larger but they are working a lot harder.

The function of the multiunit abutment is to create "draw" between all the implants to allow seating of the bar framework - think of "draw" and "path of insertion" in terms of crown and bridge. So unless all your implants are parallel to each other in 3-dimensions, it would be impossible to passively seat your framework on them. In short use the multi-unit abutment; do not over torque the small framework retention screws, and every time you take the framework off, use new retention screws. Furthermore, as another commenter mentions, having adequate amounts of keratinized tissue around those implants will help the patient maintained them, and decrease your chances of biological complications.

Unless you believe the distal extension of the bar will result in a much more stable prosthesis why complicate things. Forget the abutments and bar which will restrict inter arch space, unnecessarily increase the cost, will probably require more maintenance and is difficult to fit passively. Not to mention making oral hygiene more difficult for the patient. Just place a good stud attachment directly on each fixture. I am not aware of any studies that claim that this is inferior or less functional than the bar. Parallelism of the fixtures should not be a concern. The down side of this suggestion is that the dentist will make less money and will be denied the pleasure (ha, ha) of periodically changing the riders. Plastic riders are easy to change but don't last very long. Metal riders can be difficult to change. Much easier to change the inserts in say a Locator, or equivalent, attachment. FYI: I am retired after 45 yrs of general practice, have restored 250 implant supported prostheses and do not represent any manufacturer.

As Ernest mentioned, a Locator attachment is an option if the case is to be completed with a removable appliance. However, the "Locators" eventually wear out, and need replacement ... more frequently if there is less parallelism between the implants. Furthermore, you will have more off-axis loading of the implants, and less force distribution, because your implants are not splinted. And last but not least, if you are looking at using the Locator option, make sure you have keratinized tissue around your implants, as that tissue is going to get a lot of abuse with the denture "clipping" in and out. If the patient desires a fixed prosthetic, the multiunit is your only option. Yes, the multiunit and bar take up restorative space - but you have to account for that in your very initial treatment planning of the case!

I respect the last comment replying to my suggested treatment. However I would like to make the following reply based on my 45 yrs of patient care: 1. Locators like all attachments wear out and need to be replaced. However, they do have a good life span even when the roots or implants are not parallel. If they do need changing it will take less than a minute per attachment and can be done by an dental assistant. 2. Off axis loading of individual fixtures cannot be avoided. Every single tooth implant sustains off axis loading when under function (anterior and posterior) and this has not been a problem. 3. Hygiene around and under bars appears to be more difficult to maintain and if the patient can access the soft tissue, attached or unattached, with only a toothbrush the soft tissue health should not be a problem. It may be necessary to resort to periodontics if the tissue requires regardless of the restorative option chosen. 4. It concerns me that, in these blogs, so little attention is given to the financial status of the patient. We all aspire to do the absolute best treatment for our patients but compromise sometimes allows the patient receive treatment that otherwise they could not afford.

This type of prosthesis implies regular (a two-month checkup) for screw tightening. If you are sure that the patient can visit your office for it, go ahead.

Poor advice, from Ernest I would advise using the intermediary attachments for retrievability and if there is a future problem with fractured screws. That's how these implant systems are engineered. It is prudent to avoid future problems, just look at all these posts on this blog, broken screws, abutments due to what I feel is cutting corners based on whatever patient wishes, finances etc. it always amazes me how a dentist tries to get around implant principles based on their experience in whatever, then the subsequent treating doctor and more importantly the patient is left holding the bag. I like the perio comment, perhaps a CT graft in future using the relieved prosthesis to stabilize the graft, or if these are new implants give the tissue a big if time to adapt. Stick with the initial parameters first vs creatively being a hero trying to circumvent. Great comments, thanks for reading.

I think these fixed hybrid restorations are a periodontal disaster waiting to happen. Pt oral hygiene is difficult if not impossible as is maintenance by a hygienist. If your patient has a susceptibility to periodontal disease you will be in big trouble in the future.

After reviewing the original question and the comments I would like to add the following for discussion: 1. I would like to see a panoramic radiograph to: a) see the relationship of the crest of bone to the gingival crest, b) see where the 5th implant is hiding or is that a typo that 5 implants are supposed to be present. 2. There was mention of taking off the bar. Why is it necessary to take off the bar? 3. Placing the proper stud attachments directly on the implants is no more traumatic to the patient than placing the abutments which would not be necessary. 4. Maintenance by the dentist and the patient will be much easier and checking at the normal hygiene appointment should be all that is needed. Having to tighten a loose attachment is very rare. 5. Economics aside I to have yet to see a study that shows that a removable prothesis retained by a bar is better accepted by the patient or lasts longer than a removable prothesis retained by individual implants. I did plenty of bars in my practice but now believe the bar just complicates treatment and is unnecessary in most situations.

Without a radiograph but based on the clinical pic these implants currently have an intermediary abutment on them. I prefer to not use intermediary abutments and go to implant level because more parts mean more chance of breakage and more interfaces means more potential microgaps for bacteria to hide

In regards to Ernests comments. If cost is an issue, then two implants and locators work fine. Once four implants have been placed, the patient has a significant investment into the restoration (double the surgical costs). Cost savings should have been discussed up front. I am assuming (probably not always correctly!) that the patient wants the best since they have more than two implants. To have a successful prosthesis it should be implant borne. With the current implant arrangement, only a bar, with 15-20mm cantilevers posteriorly to spread the clips apart or a fixed hybrid will meet this criteria. Four locators is not the ideal restorative option after the patient has spent a lot of money on implant placement. The locators create a prosthesis that is implant retained but soft tissue supported and by being soft tissue supported the prosthesis will rock as the residual ridges continue to resorb and the attachments will wear more quickly. Under function the denture will fulcrum around the distalmost locators causing the anterior locators to release. Also, denture sore spots occur since this prosthesis is soft tissue supported. Give the patient increased function and comfort by making a prosthesis that is totally implant supported. It doesn't matter if its fixed, or removable but bar supported. In regards to hygiene, yes hybrids are more difficult to clean but infinitely more comfortable and functional. In my thirty years of restoring implants I have not seen greater failure rates in hybrids vs. bars. We are talking about the anterior mandible, the most dependable bone for implants.

I agree with most of what Dr. Johnson says except for the down side of stud retained removables which is exaggerated. Had we been in on the planning of this case we probably would not be having this discussion. The ideal treatment if four implants are to be placed, in my opinion, would have been All On Four. The low end treatment could have been four minis. However, as four implants have already been placed and there is so much we don't know, future discussion probably will not help the dentist doing the case. I would like to hear what his experience has been five years from completion.