Immediate Platform Switched Implant with Provisional and 2 year follow up with final restoration

your treatment looks fine. I would not expect any trouble. I would have extracted and made a three unit bridge since the adjacent teeth are already crowned

This is a great result, with the gingival margin higher than on the original tooth, which is rare!. Of course we do not see a cross-section radiograph showing the thickness of the labial plate before or after the procedure. In short, it may not be easy to reproduce this result in every case using this protocol. The current trend is to allow a 2+mm gap between the labial bone plate and the implant, and to fill that with a slow-resorbing bone graft. This seems to be the best way to maintain and preserve the labial wall. To achieve this, a smaller diameter implant set to the palatal can be used. This requires a greater emergence profile to achieve the desired tooth form, which can best be achieved with a custom Zirconia sleeve set on a Ti-Base. With a surgically guided protocol you can have the implant placement optimal, and the abutment with a provisional crown pre-prepared, ready for placement at the time of surgery. This provides the optimal environment for healing and maintenance of the Peri-Implant gingival complex providing the abutment is left in place throughout the healing period. It can be hard to achieve the desired emergence with a platform switched implant unless it is set very deep. Platform switching is an interesting concept but is by no means essential for a good result.

Dr. Carter, Excellent results with this case. Since I am new to implantology and use Nobel for implants, the newer Nobel implants have a 0.70mm PMC (they call it Precision milled, I like to think of as Polished metal collar to keep it straight in my head), what are your thoughts on placing those PMC, implants in Anterior maxilla or mandible? Also, do you recommend placing PMCs at 1 mm sub-osseous? Thanks in advance. Again, great case and thanks for all your other contribution which makes us all better dentists.

Having restored implants since the mid 80's I have seen a huge shift in implant designs. The two biggest changes have been platform switching and the conical connection. Neither are new concepts. The original straumann implant had a true morse taper (conical connection) and 3i (as referenced above) accidently recognized changing the platform. Astra developed an implant 25 + years ago that married the two concepts (also by accident). It is now well documented that these two key innovations, along with threads and roughened surfaces to the collar, help stabilize crestal bone. I don't usually prescribe an implant with any polished collar. We know bone won't stick to polished titanium, it needs a thread or roughened surface (micro or macro retention) for bone apposition. Therefore, I like an implant that has the following: roughened surface to the top of the implant, conical connection, and platform switch. As Dr. Carter has mentioned, if you use a flat surface connection (3i, nobel replace select etc) they may have an internal hex or trilobe for indexing the abutment but the connection is still flat which allows for micromovement and bacteria percolation at the microgap which leads to bone loss. And, to platform switch these implants the abutment needs to be narrower. This then forces the restorative platform to be smaller and introduces more force to the retaining screw if the restoration has any lateral force (mastication, parafunction etc). So I always use a platform switched, conical connection implant. These implants require a precise fit of the cone of the abutment to the internal walls of the implant for optimum strength. Therefore, in my opinion, do not use after market products with a conical connection. Just because an abutment in "compatible" doesn't mean it's the same as OEM (original equipment manufacturers) parts. The implant direct abutment is "compatible " with the nobel conical connection but the cone part is shorter and the hex is longer. Therefore the abutment does not fully engage the internal conical walls of the implant body like nobel designed it to do thereby creating greater forces on the walls of the implant and to the retaining screw. These newer systems were designed as implant/abutment complexes, not as a separate implant and separate abutment. They are meant to work together to strengthen the abutment/implant connection interface. Also, make sure you document in your records which abutment company was used by your lab. Different manufacturers use different screw designs. The abutment screws from implant direct are different from Atlantis which are different from the OEM screw. So if a screw breaks you need to know the abutment manufacturer and get the screw from them. There, is modern implant dentistry confusing enough! So, my recommendation is to stick with a tried and true implant company, use platform switching, conical connections and OEM parts. The cost of failure is too high to save a couple bucks here and there.

The situation in regards implant design is confused and often misleading. The one real development over the last fifteen years has been the use of a rough surface on the implant which develops a faster and stronger link to the adjacent bone. However, if this rough surface becomes exposed then it attracts plaque and this can hasten the development of Peri-Implantitis which, once established, can be difficult to eradicate. For this reason, it’s important to ensure the rough surface of the implant goes down below the bone line when placed, the so-called “Bone Level” concept. This can be difficult to ensure when the bone surface is curved, as it usually is. This curvature to the bone line is what “Depth Stops” hit and prevent the channel preparation drills going deeper. Unfortunately most implant companies did not change their surgical kits to allow deeper placement to ensure the rough surface was under the bone level when they introduced bone level implants. Then it is a matter of what emerges out of the bone. It can be a machined collar attached to the implant, though this will be cylindrical in form. Alternatively, it should be a more bio-compatible surface, the best being Zirconia, the worst being gold, because this soon attracts biofilm and plaque. With modern digital technology it’s simple to develop custom form Zirconia emergence sleeves which can be bonded to attached to Ti-Base components. This can produce an ideal emergence profile, with an aesthetic material, where there is no need to place a sub-gingival margin for the final crown. Conical vs. flat platform connection is not that critical except that conical components inherently build greater vertical discrepancies into the restoration. Conical implants are by no means “sealed” and do leak in function. Platform switching is not that critical either, perhaps 0.2 to 0.3mm of benefit in the short term, but they often make for a region which is more difficult to keep clean, which can be a problem in the long term.

Dr. Johnson and Dr. Hunt, Thank you so much for your detailed descriptions. I only use Nobel and I have placed both Nobel Active, (1 mm subosseous) as recommended. I know about Straumann making tissue level implants which were supposed to be left at gingival level with the understanding that the polished collars will provide hemi-desmosomes to connect to the polished surface. But with some of the newer PMCs, I am not sure if I should aim for sub or at Osseous crest? The issues being, I figure burying the implant provides better osseo-integration due to no forces on the fixture, but if I place PMC sub-osseous, there is no integration at the bone with PMC. So I guess placing the PMC right above osseous crest should be what we aim for. Thanks again, reading your replies helped me formulate the thought about possible ideal location for PMCs.

https://www.semanticscholar.org/paper/The-effect-of-inter-implant-distance-on-the-height-Tarnow-Cho/4f511f498643ddd8014b9a51c9168ee2d975dbd1 Keep this in mind and a lot of problems are solved!!

In response to the request for more information in the Vertical discrepancies of Conical vs. Flat platform implants the following articles should get you started: Semper W, Kraft S, Mehrhof J, Nelson K. (2010a) Impact of abutment rotation and angulation on marginal fit: theoretical considerations. Int J Oral Maxillofac Implants 25(4): 752-8 Semper W, Heberer S, Mehrhof J, Schink T, Nelson K. (2010b) Effects of repeated manual disassembly and reassembly on the positional stability of various implant-abutment complexes: an experimental study. Int J Oral Maxillofac Implants 25(1): 86-94 Semper-Hogg W, Kraft S, Stiller S, Mehrhof J, Nelson K. (2012) Analytical and experimental position stability of the abutment in different dental implant systems with a conical implant-abutment connection. Clin Oral Investig 17(3): 1017-23 Wiebke Semper Hogg, DDS, Kris Zulauf, DMD, Jürgen Mehrhof, MDT, Katja Nelson, DDS, PhD The Influence of Torque Tightening on the Position Stability of the Abutment in Conical Implant-Abutment Connections. Int J Prosthodont 2015;28:538–541. doi: 10.11607/ijp.3853 In response to the request for more information in the the stability and leakage potential for comical implant systems, the following articles should also help get you get started: J Synchrotron Radiat. 2015 Nov;22(6):1492-7. doi: 10.1107/S1600577515015763. Epub 2015 Oct 9. In situ microradioscopy and microtomography of fatigue-loaded dental two-piece implants. Wiest W, Zabler S, Rack A, Fella C, Balles A, Nelson K, Schmelzeisen R, Hanke R. An In Vitro Pilot Study of Abutment Stability During Loading in New and Fatigue-Loaded Conical Dental Implants Using Synchrotron-Based Radiography Tatjana Rack, MS, Simon Zabler, PhD, Alexander Rack, PhD, Heinrich Riesemeier, PhD, Katja Nelson, PhD, DDS I hope this helps.

I agree- all true conical fit implants will have a vertical displacement- approximately 18-20 microns as they are torqued to place. they are a 360 degree wedge, so as they are tightened they produce loading on the internal walls of the implant through friction- this is how the Morse taper engineering concept works in joints. Another interesting note is that the radiographs presented are not standardized- they almost never are. Both vertical and parallax errors along with magnification produce false crestal bone positions of upto 1.2 mm !- see Malloy's article in IJMOI. Sadly we all do a really poor job of making good enough radiographs that allow bone assessment. The question of polished titanium under the bone is relative to the amount of polish- let us never forget that the original implants were machined smooth to some degree which some today consider "polished". Bone is never up to the top of an implant either- if it were we'd all see it every time we removed a healing abutment- we don't, we recognize a biological compartment allows soft tissue to attach to the implant itself- if you are in disagreement- try blowing air around an implant that was placed at bone level- see if the bone is visible again ! This may not be so if an abutment is placed at time of surgery and some form of "seal" develops between the implant and abutment converting it into a one piece implant. Absolutely always ONLY use original components- remember we are now mechanical engineers when we restore implants- things such as component fit, materials and how the screw is tightened all follow strict laws. Remember the parts are protected by patents generally, so to allow for a non-original component to be sold it must differ in design. Even screws are not the same- threads and materials differ- see Jaarda's work decades ago that described the issues. (And if you would only put original parts on the car you drive- why wouldn't you use the same degree of care with your patients.) So if you use Nobel only use Nobel, Straumann only Straumann, Astra you have a choice Astra- or Atlantis, etc..

The data in the articles I gave the references to above show that the flat platform systems generally have about 10microns discrepancy whereas the conical systems vary from as little as 15 microns to as much as 144 microns, quite a wide range. Don't get me started on the amount of rotational discrepancies on implants which can vary greatly and which of course can change each time the abutment is placed into the implant!