Implant Placement - Dentures Q&A
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Frequently Asked questions
Q. I have a patient that I would like to place your MDI’s in her anterior mandible. She only has 8mm of bone height. I was going to place the 10mm MDI’s and possibly have 1mm through the inferior cortex. Comment please.
A. There is nothing intrinsically problematic about this strategy. The primary difficulty I see is trying to self-tap an MDI through the last few mm’s and inferior cortex of the extra-dense symphyseal bone leaving you with the likelihood of either stripping the bone or burnishing it. Also, if you do manage to penetrate through with great effort, you run the risk of bone abscess. Better to stop when you hit too dense a layer of anterior bone and allow a few MDI threads to remain uncovered by bone and/or gingiva if necessary. Remember, don’t over-instrument the bone.
Q. I have a patient with a very heavy bite who has a history of fracturing his upper dentures. He’s asked me about the MDI. Also, what do you suggest as protocol when an MDI fails? Do you replace it with a longer one? Do you go adjacent?
A. For heavy bite and TMJ parafunction cases, I recommend to start with a soft liner in the O-Ring caps that have been incorporated into the denture. Remove the O-Rings from the caps, and then use a non-runny soft liner (either powder/liquid mix or automix) in each mini-cap and the entire soft tissue bearing surface. Insert the prosthesis in the patient’s mouth over the O-Ball abutment heads in centric and vertical occlusal and allow to set. This will leave the patient with a reasonably stable overdenture where the heavy occlusion will be born mostly by the soft liner and will protect the MDI bone support from functional and parafunctional over-loading. Eventually, you can convert some or all of the O-Ring caps to regular O-Ring retainers as needed by the patient and if the MDI’s are stable and comfortable.
As to implants that are loose or exfoliated, I recommend replacement without charge within a reasonable time frame after insertion, especially if I feel that poor bone resource is the likely cause for failure. Each clinician must be responsible for formulating a policy as to replacement charges based on his/her learning curve status. It applies to length, location and number of such replacements or repositionings. It’s basically your call, since you know from your X-rays and working the region far better than someone else how to proceed with reasonable confidence.
Incidentally, doctors sometimes ask me if they should refund the cost for a failed MDI if the patient is unhappy. Once again an individual call, but I would advise approaching refunds cautiously since there is a suggestion or hint of error on your part. Better to focus on replacement without charge on the basis that you are still in the exploratory stage of determining where the best quality of bone for MDI support is located.
Q. What is your favorite sequence for placing MDI implants? For instance, do you work from one side to the other or do you place the two center implants first or the two outside implants first?
A. Each case is different, as you well know. Keep in mind that you need to stay well mesial to the vulnerable mental foramen and associated nerve “loops” and distal to (superior to) any extremely dense symphyseal bone in the midline. We recommend you present the procedure to your patient as an exploratory process to test the bone quality and quantity rather than as a “tentative implant placement.” This is a professional and truthful approach, and importantly, less stressful for you and your patient.
Q. On a full lower denture, I placed four MDI implants, three 13mm’s and one 10mm. I placed them too close together to use one of the posts allowing only three metal housings. I felt I was placing the implants into the body of the mandible through the little attached gingival I had. When I was finished and was placing the housings, they were all lingually inclined, impinging on the lingual tissues. The one that could not be used because it was too close to the other implants was also so lingually inclined that it couldn’t have had a housing on it anyway. After one week the patient lost the 10mm post. (It was positioned farthest to the left and supported one of the retention caps). Clinically I feel I had left too much cold cure acrylic around the implants and/or she bit on her denture too hard during set that was causing pretty severe tissue irritation and probably loosened the implant. Currently, there are three solid implants, two with metal housings (both positioned on the right side) and one with no housing. The retention of the denture is quite good but the right side is solid and the left lifts a little during eating, making it uncomfortable to the patient. I would like to place one or two more implants on the left side to balance the retention. I would like someone to look at the case and show me the optimum position and other suggestions. The patient is fine with doing the other implants. I have a ceph lateral film, a pano and a lower study model. Please advise me how I could get someone to discuss this with.
A. Your best bet when you want to progressively load your MDI’s at the outset is to use only a soft liner rebase over the implants and the entire tissue-bearing surface of the denture. This would have eliminated any starting complications from your first case by giving you time to evaluate the viability of the MDI’s before committing yourself and the patient to the more efficient O-Rings in their encapsulations. In fact, I use this sequencing myself in most of my own cases. And be most careful to use the Elastomeric shims on the square 4mm base portion of the abutment to avoid the excess acrylic locking on during O-Ring cap pick-ups. Also, I recommend you enroll in a mini-residency or MDI seminar at which time you might bring along your diagnostic materials for evaluation.
Q. I would like to expand the use of the MDI system in immediate extraction cases. IMTEC technical people have emphasized the importance of having superior cortical bone for success in the symphysis area. I’d like to know what your recommended protocol is in handling immediate cases. I have thus far told my patients that we need to wait about six months after the extraction before we place the MDI. I would appreciate a quick response since I have several immediate cases coming up and want to provide timely service to my patients.
A. I’m afraid there is no “protocol” for handling immediate extraction cases. You are on your own with this issue, since it is the residual bony architecture that is most important after extractions, not how long you need to wait before MDI insertions are contemplated. If the bone is there to receive a 1.8mm or 2.4mm starter (and with no infection and only minimal inflammatory soft tissue) it is possible to insert MDI’s from the first day on. You must also be the one to evaluate your patient’s insertion site and decide if the area is stable enough to proceed with good access and visibility.
Q. Would you have any reservations about using the MDI’s for the maxillary edentulous patient exhibiting severe hyperplastic ridges (soft, spongy and movable tissue)? I have a patient who currently wears a full upper denture with several unsuccessful reline attempts. She claims the spongy tissue was removed surgically several years ago, leaving her with a flat upper ridge.
I am considering four MDI’s in the maxilla, similar to recommendations for full lower denture MDI’s. The tissue is approximately three millimeters in thickness and very movable. Can I place the MDI’s into this soft tissue (and of course into bone) without worrying that 3mm of the implant screw might be in soft tissue not bone, because of the 3mm thickness of tissue? Is there a higher risk of failure or peri-implantitis?
A. IMTEC always advocates that, where possible, MDI’s (as well as conventional implants) should emerge through keratinized, attached ridge gingiva, rather than through unattached mucosa. It is well accepted that tough, keratinized tissue is much more resistant to bacterial invasion and peri-cementitis as well as peri-implantitis, than loose mucosa, and it is a reasonable concept that this applies to MDI’s as well. The great advantage of the MDI insertion protocol is the fact that this ultra-thin mini-implant has such a small footprint that it can readily be accommodated in even a small patch of keratinized ridge tissue, making it much more likely that the MDI can be accommodated in very sparsely keratinized atrophic ridges as compared with the relatively bulky traditional implants that often end up in unattached mucosa. This does not mean that implants placed through non-keratinized tissue are doomed to failure, but the prognosis is always better for emergence through attached gingiva. Since we also advocate placing our insertions directly through soft tissue and into the underlying medullary bone with a minimal “starter” opening without incisions, flaps or sutures, in most cases we can assume a more stable soft tissue profile surrounding the MDI’s without worrying about significant remodeling, die-back or loss of our original keratinized crestal tissue.
Q. How important is the strict following of the recommended insertion and reconstructive protocol? Also, please comment on fracture rates.
A. The protocol is critical. Long-term experience has demonstrated a consistent record of safety and effectiveness of the original concept that these devices, when placed utilizing a strict insertion and reconstructive protocol, have the ability to function both for transitional and long-term applications. As for fractures, they’re totally minimized when the titanium alloy (Ti6A14Va) is utilized instead of CP titanium. Records of clinical trials have proven that the optimal resistance for final seating of an MDI Implant is 35 NCm. Any value beyond 45 NCm could result in a fracture of the implant. Lateral forces placed on the implant during insertion can also cause fracture. Both can be controlled by the careful clinician.
Q. Please discuss placement issues as far as parallelism of the mini-implant is concerned.
A. Parallelism questions primarily depend on how many implants are involved. A greater number of implants requires more parallelism since it gets more difficult to insert and remove the prosthesis if multiple angulation problems are present. The best rule is to try to insert the MDIs as nearly parallel as possible, and if angulations are too excessive, the best approach is to use a soft liner rather than O-Ring retention in such areas, especially with multiple MDIs (more than two). Simply tease out the O-Ring with an explorer or comparable tool from its retaining cap and fill it with self-cure soft liner over the O-Ball head intra-orally. When set, a modest degree of retention will still be present but without excessive binding, even with less than ideal angulation. Another approach is to slightly strip the internal fit of an O-Ring with a tapered bullet-shaped diamond instrument at moderate speed and light water spray. This relief should reduce the tendency for the O-Ring to bind on the O-Ball head when inserting or removing a full or partial prosthesis when off-parallel MDI implants are present.
Q. Should a clinician ever bend an MDI?
A. Bending an implant for parallelism is never recommended since there is always a danger of abutment weakening and fracture. On the other hand, undesirable bending during insertion is not encountered with the strength of titanium alloy MDIs.
Q. I recently placed four MDIs in a patient on her mandibular using no incision. She had a knife-edge ridge with a ridge of tissue on top. After placement, the tissue grew over the implant heads and the denture won’t seat. I placed the implants until they were snug. Should I have removed the excess tissue, or perhaps not have seated the implants so deeply?
A. As much as I like to retain any attached, keratinized ridge tissue around MDIs, you may have to do some gingivoplasty to expose the implant abutment heads. You might try putting a soft liner in the prosthesis first to see if the tissue might remodel sufficiently on its own without surgery to expose the heads. Most important of all is to be sure you have well integrated MDIs, so I wouldn’t be concerned about seating the implants too deeply.
Q. I’m an oral surgeon and have a patient who I think is a good MDI candidate. She’s 71 years old and was recently diagnosed with Parkinson’s Disease. Her mandibular denture is unstable due to severe alveolar resorption, and the patient is having more difficulty with it now that she’s developed significant tongue thrusting motions. I think I could place four 13mm MDI implants, but wonder if her tongue movements would doom them. Any experience with that, or any thoughts? Also, how critical is angulation for these implants with O-Ball attachments?
A. The patient sounds like a perfect MDI candidate. As for the prognosis question there should be no special concern about tongue thrusting and immediate stability even in a Parkinsonian patient if the MDIs have been placed according to the proper insertion protocol. Using only a minimal starter opening through the crestal soft tissue and underlying cortical bone and then for about a third of the length of the threaded portion of the MDI into medullary bone should provide sufficient entry for the MDI to be totally self-tapping. Using the finger wrench, winged thumb wrench and finally the ratchet wrench for a few turns should secure a rock solid MDI, braced immediately by compressed bone without any conventional healing period needed. The low-profile abutment head also minimizes lateral iatrogenic loading pressures and moderate angulation variations provide few insertion or removal problems with the gentle but retentive MDI O-Rings.
Q. I have now placed thirty-seven MDIs. I have had a total of five become mobile, two in the past two weeks in the same patient . I realize every case is different but what would be the main reasons for that to happen? I believe in one case where both came loose, it was a lower full denture; I don’t think I had the patient’s existing denture seated all the way down to the ridge when I attached the O-Rings. I also think the metal housings were in contact with the inside of his denture, so all of the occlusal forces were on the implants, with no tissue bearing areas. One of the other three that came loose was a 13mm MDI that I was not able to screw all the way down. Some threads were exposed, which I try not to have happen even if I have to change the length or type of implant. So maybe it was too heavy.
Also, with lower overdentures, do you usually place more than two mini’s? Do you always try to use their existing denture so long as the base is thick enough to accommodate the O- Rings? I find myself using the micro metal housings more than the regular housings that come with the implants. My best results have been with a new denture over four mini’s. Comments please.
A. Thanks for the update, even with some negative reports
(re: loosening and exfoliations). Best advice I can give you about using a
patient’s existing denture is that these cases must be relined with a
hard or soft liner for stability preferably before picking up O-Ring encapsulations.
In fact, it may be best to simply remove the existing hard acrylic overlying
the MDIs, provide sufficient relief (clearance) and then reline the entire
denture including the MDIs with soft liner to avoid over stressing them from
lateral traumatic contacts, especially if you have some reservations about
the integration of the MDIs at this stage. Defer O-Ring loading pickups until
your confidence level is adequate.
As to length of the MDIs, we always recommend not over screwing into dense
Type 1 bone, and to either use a shorter implant or try to deepen your
starter drilling by pecking away a little more of the apical bone to get
a better take. Also you can use only two MDIs if the bony integration is
solid and secure, but clearly three or four gives you a better margin for
error or exfoliation. In short bite, limited interarch space situations
the micro O-Rings are indeed a better bet and that’s why we offer
them as an option.
Q. Can the O-Ball be used for a removable partial? Fixed?
A. Absolutely. It's suited for both types of applications. Just be sure to always use the elastomeric shims as spacers and to prevent inadvertent lock-on during fabrications.
Q. Is the alveolar nerve the only reason the MDI are placed in the anterior portion of the mandible or can they be placed in the posterior if a clinician is careful about nerve location?
A. Both anterior and posterior applications are appropriate with a level of care.
Q. Can the MDI be placed in the posterior area of the maxilla? How careful should one be of the sinus cavity?
A. The only concern about the sinus is that if you penetrate into the sinus cavity there is no supportive bone present, therefore a waste of implant surface. Its best to place MDI’s just anterior or posterior to the sinus walls (maybe “biting” into these walls or the sinus floor all of which are good supportive cortical bone for MDI’s).
Q. As far as office equipment is concerned to place the MDI, is a panoramic x-ray sufficient?
A. Both Pans as well as periapicals (and even occasionally bite-wings) have their place diagnostically and for post-ops to best levels.
Q. How many degrees can you be off on parallelism? Should you start over or compensate another way?
A. Moderate off-angle placements will all work when you consider that abutment heads can be prepped or that O-Ball heads have the rubber O-Rings which are quite forgiving unless extreme angulations are involved (soft linings can be used in such extreme unparalleled situations). Rubber O-Rings can be relieved internally with a tapered bullet -shaped diamond under water spray for an easier retention and release.
Q. I have now placed 29 MDI implants and know how easy the procedure is. My only problem has been with the patient that has less than 1mm width at the top of the mandibular ridge. It’s obvious that l.8mm implants will not penetrate a1mm ridge. Therefore, a] do you open these patients up and remove bone to a suitable width level? b] If so, can you still put the denture in place knowing that there will be considerable swelling? c] Or, do you do the leveling first as a separate procedure and let it heal before placing the implants?
A. The issue of what to do about very thin crestal bone is to essentially ignore it as long as it widens inferiorly, as do most ridge anatomies, even very atrophic ones. Just initiate the process by lightly tapping a very thin starter drill in this delicate bone until the ridge widens sufficiently to encompass the l.8mm width with a millimeter or two to spare labially (bucally), and lingually. I like to use a very thin tapered diamond drill for this purpose in a friction grip. A conventional high speed air turbine horse power, ratcheted back process will in most cases almost automatically reduce and flatten crestal anatomy just enough and make it unnecessary to do this initially as a separate surgical procedure which might result in excessive crestal bone loss and remodeling. Also, if one spot proves inadequate just move down the line to the next adjacent location until you find a better candidate.
Also, as to post-op morbidity, edema can be minimized by drilling only through attached, kereatinized crestal gingiva, and the only discomfort usually reported by MDI patients is in the area of the needle sticks for local infiltrations. From a prosthodontic standpoint, there is no reason why the implants can’t be put into immediate function with O-Ring attachments. You can hedge this if you are concerned about post-op complications by simply using a soft liner temporarily in the O-Ball receptacles and softly reline the entire prosthesis simultaneously for maximum initial comfort and negligible chair time.
Q. Dr. Sendax, I had the pleasure of taking your one-day clinical seminar in your office in February. I learned a lot and am now much more comfortable in placing mini-implants.
I have a clinical question and I invite your comments. I am treating a ninety-year old female who has muscular dystrophy. Her anterior teeth have extensive cervical decay. Treatment options generally result in extraction with a removable partial denture or four root canal therapies followed by crown lengthening and porcelain/metal crowns. Because of the moderate bone loss, the second option is not only very expensive to patients but also with only a fair prognosis.
I remember seeing in a dental journal some time ago an innovative idea of placing mini-implants through the mandibular incisors and several millimeters into the alveolar bone. A crown is then placed on each coronal portion of each implant. Your thoughts, please.
A. What you are referring to are endodontic stabilizers, meaning that you must do root canal therapy before you can do this kind of procedure, and even then it is very technique-sensitive with a guarded prognosis. Your best bet is to try and save teeth in a ninety-year old patient, and supplement any lost teeth with MDI’s as necessary. Much less traumatic for the patient.
Q. Dr. Sendax, I’ve purchased insertion tools and implants and am now surveying candidate patients. One problem that I frequently encounter in association with the severely resorbed mandibular symphysis when placing conventional implants relates to the difficulty in establishing a zone of immobile gingival through which the intended implant(s) will emerge. With respect to the Sendax MDI O-Ball implant, for use in lower overdenture cases we find sometimes that the minimal width zone masticatory mucosa that might exist crestal to an edentulous ridge is displaced lingually to the desired exit point of the implant. Thus, absent a surgical effort, the implant placed non-surgically will be placed through mucosa. Have you found this to impact either prognosis or comfort?
A. Attached keratinized gingiva is always desirable for both short and long-term applications. That said, there are also exceptions to the rule, but there is always the risk of after-insertion mucogingival complications, including tender, vulnerable peri-implant soft tissues (especially where muscle attachment “pull” is evident labially or lingually). Best approach, if topography is too hard to read, is to bite the bullet and do a limited incision to visualize the location of the most useable underlying bone for pilot entry and be less concerned about immobile gingival since it probably is virtually non-existent in the case you describe. And fortunately, the minimal l.8mm footprint of the MDI is much less vulnerable to peri-implantitis problems than larger, bulkier conventional implants.
Q. I have a few question: 1. How many months would you wait to place an MDI into an extraction site following the extraction? 2. Would the waiting period be altered at all if you placed a freeze-dried bone graft into the socket immediately following the extraction? 3. What was your diamond of choice (size & shape) that you used in your high-speed handpiece to create the pilot hole for the MDI?
A. MDI’s do not require a specific socket healing time before placement if you can find a solid septum of bone in or around the socket periphery that will accept a l.8mm width MDI or if the socket depth is so minimal that apical to the socket there is a substantial height of uninvolved virgin bone to receive the pilot drill opening; However, waiting for initial socket healing is also a reasonable approach. Of course, placement of bone graft matrix material (with or without a barrier) in the actual socket hole is an acceptable ancillary procedure to level out the defect following MDI insertion, but should not really affect immediate MDI placement at the time of extraction. Any coarse-grained, long, thin, tapered diamond should work well to make the initial pilot starter opening.
Q. Are there any indications for immediate placement of the MDI after extractions in the mandible? If not, how long do you suggest waiting post-extraction before placement?
A. The basic rule for MDI placement after extractions is never to place them directly in any area of inflammation or infection. If you can find an adjacent region without inflammatory issues, then you can feel comfortable about placement of the MDI’s at any time, but the longer you wait for such inflammation to subside, the better the prognosis.
Q. Dr. Sendax, I’ve been using the MDI’s the last few months with very few failures as of yet. I recently ran into a case of a patient with knife-edge ridges and I was unable to get a good start with a 1.1mm drill because it kept bouncing off the ridges and being deflected either lingually or facially. I thought about doing a crestal incision and flattening the ridges to get a start with the drill but I hate to sacrifice bone. Any suggestions?
A. The best approach to narrow ridges is to use a high-speed conventional turbine for better control with a friction grip, thin, tapered diamond drill. If you use medium speed via the foot controller with water spray, you can tap the crest until you feel solid cortical bone just below what I would have to assume is minimally thick crestal soft tissue. If the chosen site is poor, move on to another adjacent spot with attached gingiva and continue the straight up and down tapping through the cortex into medullary bone a few millimeters in depth with constant water spray. If you continue to feel medullary bone contact, proceed for a few more millimeters of up and down gentle drilling and stop. If your angulation is reasonable, then try your implant into this “starter” opening and see if you have a good self-tapping ”take.” If it’s okay, then continue to auto-advance the implant with the finger driver and thumb wrench, then followed by the ratchet wrench, as required by bone density, to full depth.
Q. Dr. Sendax, I had the first mini I inserted come out today. I must have over-instrumented the bone. It sounded solid and lasted about one month. Is this the learning curve you mention? Anyway, I was disappointed. A question: How long after an extraction to wait till the bone is healed to insert a mini in the general area?
A. Sorry to hear about your first exfoliated mini, but as you pointed
out that is indeed part of the learning curve. The question is also best
answered by acknowledging that while over-instrumentation may have certainly
played a part, other considerations also might have been negative factors:
poor quality and/or quantity of bone? You make no mention of location,
height or length. Healed site or recent extraction site? Immediate or progressive
loading? Soft liner, O-Ring retainers, cemented (provisionally or finally)?
What kind of occlusal management, number and type of other abutment supports
and muscle dynamics/habits/fixed vs. removable, etc? As you can see, not
such an easy analysis. Don’t despair; just keep all the variables
in mind.
As to healing time before MDI placement following extraction, there is
no best answer since this is another tough judgment call, with a long list
of variables: for example, residual bone circumferentially around the post-extraction
socket periphery, and height of residual bone apically before you reach
vulnerable sites. Theoretically if there is no infection and minimal soft
tissue inflammation, you can try to insert an MDI immediately. However,
the longer you wait post-op, probably the easier it is to analyze these
factors and have the best prognosis.