Restorative information - fixed Q&A
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Frequently Asked questions
Q. If you load immediately, don’t you produce a fibrous encapsulation at the implant periphery and hence clinical mobility in one-two years?
A. A fibrous tissue response down the line is possible with any conventional implant if it is subject to consistent lateral movement. Even micro-movement can be destructive to bone healing physiology during this phase. However, our MDI’s are placed directly through the crestal gum tissue into the underlying medullary bone with a very small starter opening; just enough to promote a self-tapping “take” and permit the auto-advancement thread design to then virtually draw the implant into the bone. This means that there is no conventional “healing period” since there is nothing that requires a period of repair. The direct contact of implant surface to bone is accomplished immediately with minimal surgical intervention. No bone is lost by drilling it away as would be the case in a typical implant osteotomy procedure, and the only bone loading force during slow turning insertion is mostly compressive, which bone is uniquely able to tolerate.
Most fundamentally, MDI’s implant surface doesn’t have to first grow into contact with the bone; it’s already there from day one, and it is mature support bone. How well the implant then performs under diverse loading conditions may have more to do with peripheral systemic issues like medical profile and heredity. The twenty-four year clinical experience with MDI’s has proven the integrity and legitimacy of this unique insertion protocol and made it possible to achieve immediate and sustainable loading without significant bone loss or mobility even in medically compromised patients over long-term applications.
Q. How do I restore the implant prosthetically? I can see that for a denture the implant has the O-Ball head. How about if I want to use the implant for a three unit bridge or for a single crown? Also, are they recommended for bridges or single crowns?
A. For fixed applications you can still use the same O-Ball head by blocking out the complete length of the abutment with an elastomeric shim before wax-up and casting to permit an easy “draw” of the pattern from the abutment analog and to avoid undercut or parallelism problems. Of course, you can also use the rectangular “prepable” head MDI abutment, as well as the O-Ball type.
Q. I’m using the MDI MAX implant for replacement of an upper lateral incisor. You frequently mention the use of a shim for casting to block out undercuts. Is the shim placed on the MDI intra-orally before the impression is taken for a crown, or should I send the shim to the lab and instruct them to place it on the master plaster cast before wax-up? Will the final crown have a positive seat if the shape of the implant was altered by use of the shim and therefore rotate when tried in instead of fitting with a definite seat? You also mention that the MDI can be shaped to allow for occlusal clearance or parallelism. Any problem doing this directly in the mouth using high speed with water or is generation of heat from high speed drilling a concern? Comments, please.
A. The usual sequence of procedure for fixed single or multiple restorations is to take an intra-oral impression in Polyvinylsiloxane or comparable material, place an IMTEC analog in the MDI location, then pour up the model. (An elastomeric shim would only be used intra-orally if you were doing a direct o-ring/cap pick-up.) A shim can also be placed over an O-Ball analog in a model to provide a spacer and undercut block-out for a wax-up. Make intra-oral adjustments with moderate speed and water spray.
Q. I know its possible to use well-integrated MDI’s for ongoing, long-term fixed ceramo-metal bridge restorations, as well as the typical shorter-term transitional prosthesis, but how do you provide a good fit and a smooth, polished finish to the ridge lap of the "ponabut" in the area of the mini-implant emergence through crestal soft tissue?
A. A step-by-step
protocol to accomplish this important procedure is as follows:
1. The finished, glazed ceramo-metal bridge, crown or splint is tried
to confirm proper occlusion, contacts and basic fit. Use of the Elastrometric
Shims should permit an easy “draw,” bypassing or clearing any angulation or
undercut variations.
2. The interiors of the ponabuts (and any ridge laps, if they need small additions to compensate for soft tissue remodeling changes) are etched with a micro-etcher to provide a reliable bonding surface.
3. Any high-quality, lite-curable composite resin paste, shade-compatible with the porcelain and with good flow characteristics, is then introduced into the interiors of the ponabuts to the level of the ridge laps.
4.
Restoration is then inserted over the abutments intra-orally and the patient
is instructed to bite slowly but firmly into a guided centric occlusion,
with extruded composite excess teased away from the cervical margins.
5. Restoration is removed from the patient’s mouth leaving uncured composite resin inside the surface-etched “ponabuts”. Any excess is trimmed away, with any voids touched up with additional composite resin paste. Restoration may be reseated and adjusted until inspection reveals an acceptable result, with easy draw and smooth compensation for any abutment angulation variations.
6. Composite resin is then lite-cured until surface is hardened. Internals may be fine tuned with slow speed bullet shaped diamonds (with copious water spray) to provide an easy fit intra-orally.
7. When all occlusal, contact and internal adjustments are finalized, the ridge laps of the ponabuts are brushed with a micro-fill composite resin glaze and lite-cured until completely surface hardened. A time saver that insures a complete bonding cure at this final stage is to employ a Dentsply Triad (or comparable brand) bench-type lite curing unit.
8. Restoration may now be temporarily cemented with ease of removal. If the fit is quite snug, and ease of removal is questionable with so-called “temporary” cements, then a reasonable alternative is a mix of antibiotic ointment (such as Neosporin) with a denture adhesive (such as Fix-O-Dent) for a good transitional seal. Final cementation may be accomplished with zinc Oxyphosphate or materials of your choice. On a personal note, I prefer the classic zinc cement because of the ease of removal of the hard-set excess from all margins.
Q. I have recently started treating cases using the MDI and am very excited about the prospects. I have chosen to use one in a case in which I will be placing a few root form implants where appropriate, but want to use an MDI for a site (with minimal buccolingual width) and restore with a “pontabut.” My question is: how exactly do I make the prosthesis? I have IMTEC’s FAQ on your system and think I can picture the prosthesis; however, I’m not sure about any special considerations for preparation and impressions, as well as instructions for laboratory work. Thanks for your input.
A. I would not get too upset about the pontabut design. Just design a normal pontic with normal ridge lap, normal proximal contours and contacts to maximize esthetics, phonetics and occlusion. Then, simply think of the tissue-contacting surface of the pontic having a small receptacle in it (i.e., a hole) to receive the MDI abutment head (remember, it’s only 1.8mm in width) wherever it emerges through the ridge soft tissue (hopefully, through keratinized attached gingiva) and enters the underbelly of the ponabut. In other words, the final product is both pontic and abutment and therefore called a pontabut combining both features in one entity, and totally unlike any other implant system. Composite resin or resin cement then fills in any marginal voids around the entry area of the MDI abutment head into the Pontabut during final cementation.
Q. Dr. Sendax, I am an oral and maxillofacial surgeon practicing in Westchester County. I have yet to use the mini implant system. A patient recently presented to my practice for placement of a dental implant into site number 7 which is congenially missing. Having gone through considerable orthodontic treatment, there is only approximately 4mm of inter-radicular bone in this site. The orthodontist does not believe they can create any additional space. Obviously, this is insufficient for a conventional 3.25mm mini implant. I am hopeful that your MDI implant may work as a long-term restoration. My concern obviously is aesthetics in this anterior area. I am requesting your advice how a natural emergence profile can be obtained with this implant system.
A. In response to your e-mail, the Sendax MDI system works extremely well in areas of limited spacing often encountered in congenitally missing sites, since it is a l.8mm width implant, approved by the FDA for both transitional and long-term applications. As to emergence profile and related esthetic considerations, there should be no concern since the prosthetic tooth/crown replacement is essentially a pontic with a ridge lap access opening for the small l.8mm abutment head (either square or O-Ball). We call it a ponabut since it incorporates features of both a pontic and an abutment and therefore permits ideal esthetic design. It’s a little hard to visualize this concept at first until you are more familiar with the MDI system, but your restoring colleague should have no trouble with it once a modest learning curve is mastered.
Q. I attended your mini-residency in NYC recently. I have placed 8 mini-implants so far with no concerns or problems. A question: When you are working with a processed acrylic crown and bridge temporary and you want to attach some MDI’s to it, do you put a shim over the implant and add Jet acrylic to the abutment area and then cement the temporary over the implant? I have several with Coe-soft temporarily but I want to convert the Coe-soft to something more retentive. Also, if you’re working with a fixed porcelain to metal bridge and wish to add a mini-implant, what do you use in the hollowed out pontic area to attach it to the implant? Composite? Jet? Do you use the shim to avoid undercuts?
Dr. Sendax, I’m very impressed with the system, having placed conventional implants for 12 years.
A. You are on the right track with the critical use of the Elastomeric Shims in all the applications you referred to. In addition, to get good bonding of jet acrylic or composite to acrylic, metal or porcelain you should invest in a micro-etcher. The aluminum oxide etch powder will provide a much enhanced bonding potential for your cases. You’ll have to try out several techniques until you arrive at the preferred method.
Q. I read Dr. Ron Bulard’s article on use of the Sendax MDI in the July 2001 edition of Dentistry Today, and it raises a question. I am heavily involved with the CEREC system, that as you know, has the ability to make single crowns chair side. Is there any reason why I can’t use the MDI system to replace teeth in one visit, i.e., preparing a pre-molar CEREC crown over a mini implant? Since my practice is mainly fixed restorative, this is primarily the area that interests me. The literature I’ve received from IMTEC describes the full denture application. If so, this seems like it will be able to push the envelope of restorative dentistry much further. Also, from the insertion protocol, it seems like no special surgical skills are necessary which would make this system accessible to a wide range of general dentists.
A. Your basic concepts are right on target as to the intrinsic fixed crown & bridge prosthodontic potential for the MDI system. We made a strategic decision at the outset to introduce the concept to the profession as a removable solution to the unstable and unusable lower (and in many cases the upper as well) denture problem that plagues so much of the world population. Once the learning curve and essentially simple technique is mastered, it is a logical progression to incorporate fixed prosthodontics as well, which is what I am personally doing in my clinic. Also, the CEREC concept should certainly be applicable to the MDI system.
Q. Dr. Sendax, I attended
a mini-residency at your Manhattan office in October and have my first
MDI case this month. Please clarify a few things for me about sequencing:
My patient has teeth #20 and #21 and nothing more posterior. She presented
with a failed cantilever bridge – #20 splinted to #21 with a very small
pontic hanging off #20. The vertical space is extremely limited in the
area of the cantilever. So far I have redone the post and core on #20,
and performed a root canal on #21. I am planning to do the following at
the next appointment and in the following sequence: Post and core #20;
final prep #20 and #21; insert two MDI’s in the space of #19; and
cement a temporary (20, 21, 19). Question one: Do I have to do the soft
reline for the pontabut with a cold cure soft acrylic or can I cement the
temporary with temporary bond? Question two: Do I need to wait longer than
two weeks to take the final impression? Is it advisable to take a final
impression at this insertion appointment?
Also, what is the code used for the MDI? Is it the same code regardless what is put over it? In other words, is there a different code for a Sendax MDI used in a denture attachment than for say under a bridge? Further, what are the codes used for the crown and pontic placed over the mini? Also, do you use a different charge for a crown over one of the MDI’s than for a crown over a natural root? Thanks in advance for the information. I’m very excited about these MDI’s and hope they will work.
A. My suggestion is to use temporary bond for the tooth preps of #20 & 21, but reserve a soft liner for the O-Ball MDI abutments which you want to be sure of, as to stability and integration, before loading with a temporary cement, just as a precaution when initially utilizing these MDI’s as bridge abutments so as not to inadvertently pull out an incompletely integrated implant when removing the temporary. As to waiting time before taking impressions, I don’t see any reason to delay unless you are unsure of stability and full bony integration. If they sound really rock solid when tapped I would proceed with impressions. The MDI concept is that the MDI’s should be ready to function from day one.
On the matter of codes, there is no special code for MDI’s. Use the regular code for endosseous implants, but remember that implants are rarely covered by dental insurance. Codes for full coverage and pontics involving MDI’s would be the same as for any routine crowns and pontics. But, once again, if insurance companies are made aware of the presence of implants under crowns or pontics as supports, they may try to exclude coverage. Check your patient’s insurance benefits booklet for details. Obviously you must decide whether or not the extra benefits you expend on implant-supported bridge prosthodontics warrant additional fees.