Dental Implants with an Internal Connection?

I feel compelled to answer your question since I invented the Internal connection in 1986 when I introduced the Screw-Vent, still on the market today. For years after that, I would hear how the external hex was the gold standard, or that an internal hex is just an external hex turned upside down. Following the issuing of the patent, which is due to expire this October, I licensed the patent to Straumann, 3i, Steri-Oss, Friadent, Calcitek and stopped about 5 other companies that were infringing in the early 1990's including Lifecore, Park Research, and Sapko's company. After sellling my implant business to Zimmer, they licensed BioHorizons and 3i. The RePlace Select introduced its internal connection design. My new ScrewPlant has a 2mm deep internal hex.... imagine how difficult it would be to restore an external hex with a 2mm projection and you will start to understand the advantages of an internal connection. The key advantages is improved tactile sense so that you can feel when the abutment is seated and do not need to take xrays to confirm seating. From a stability standpoint, not only can you double or triple the amount of anti-rotational engagement, the fixation screw is protected with internal connections from flexing under lateral loads because it is never exposed above the top of the implant. This flexing of the screw with the external hex is what caused micro-leakage and screw loosening. Finally, The interal connection allows narrower diameter implants. It is hard to beleive anyone is still using external hexes in this day in age.

One problem with an internal hex is the width of th titanium in a narrow implant. You do run the increased risk of fracture of the implant when you get too narrow. Also, due to the thinning of the titanium, many internal connection implants have a straight portion (some rough, some smooth) that will have a tendency to lose bone upon loading. Used appropriately, either one works very well.

One problem with an internal hex is the width of th titanium in a narrow implant. You do run the increased risk of fracture of the implant when you get too narrow. NIZNICK RESPONSE: The smallest diameter that should be considered is 3.7mmD. I started with a 3.5 and had to widen the neck to 3.7 for added strength. The new ScrewPlant has an external bevel instead of my original Screw-Vent with the internal bevel, now copied by BioHorizons, MIS and others. An external bevel with the abutment overlapping directs the forces inwards instead of outwards. Also, due to the thinning of the titanium, many internal connection implants have a straight portion (some rough, some smooth) that will have a tendency to lose bone upon loading. NIZNICK RESPONSE: Adding micro-threads like I have done on the ScrewPlant implant allows the threads to be brought up to 1mm from the top. Used appropriately, either one works very well. NIZNICK RESPONSE: The idea of implant design is to make it idiot proof if possible including rougher surfaces and self-tapping tapered designs to increase initial stability even in soft bone. The internal connection provides greater joint stability, so even if the design of the prosthesis falls short of ideal, or if the torque on the screw is short of 30Ncm, the screw will not work loose as easily. Used properly, a blade or subperiosteal implant also works... but that does not make them as predictable as osseointegrated implants. Why settle for a design with a proven track-record of lose screws and gapping margins?

Can you please present research papers comparing the amount of bacterial infiltration and/or the abutment micromovement in internal and external hexed connections implant systems? I believe that bone loss around the cervical portion of the implants is directly related with the above modalities

Dr. Niznick, A number of times you have claimed to have 'invented the internal connection in 1986'. Thomas Driskell had an internal connection for his implant in 1981. This was later known as the BICON implant. Perhaps he was your inspiration? Perhaps you ought to give credit where due?

Dr Niznick , Barry Edwards had a bit to do with internal hexes and angled abutments at that time and sends his regards. It has been good to read your input on this site.

Simnple. (Screw loosening and science aside) You can work with or without your eyes open and the check xray never shows you missed the connection no matter how far back your dental implant.

I had an internal connection with the Core-Vent in 1982 that accepted cemented abutments while Driscol had an internal connection that was a Morse Taper. Neither related to the patent I filed in 1990 that combined an internal wrench-engaging surface with threads in an internal shaft. Barry Edwards was also developing implants in England about the same time... I do not know if he ever filed any patents or whether he just incorporated my internal connection into his implant designs. In any case, he was a leader in his country.

Anything made idiot proof will always be proven to have a flaw by a smarter idiot. I don't think idiot proof as a design goal is necessarily the way to go. Any system can still be screwed up - either by placement or restorative errors. The importance lies in the clinician learning the system and using it appropriately. I believe Misch has demonstrated long term success with external hexes...as have others. There is also a lot of success with internal hex systems. Again, it all comes down to using the system appropriately.

There is no way to compare between internal and external connections by any means after all the research that was done on this issue for more than 15 years , the internal connection is superior by far regarding tolerance to lateral forces , abutment loosening , screw fracture , , subcrestal placement, esthetic results , ability for plattform switching and creating biological width and lot more features that make the internal connection (whether it is morse taper , internal hex or octagon )the best choice for implant connection design and especially if you count on a well documented and reputated system like Zimmer , Friadent that have a minimum of 2 mm length connection with excellent platform design and superior implant abutment connection fitness .

The Replace Select makes a 3.5mm, then is that at greater risk for head fracture. Does the literature support this. What gets reported?

COMMENT: The Replace Select makes a 3.5mm, then is that at greater risk for head fracture. Does the literature support this. What gets reported? NIZNICK ANSWER: This is the only implant that I am aware of which comes with a warning label advising not to exceed 45Ncm or Torque. The implant is too weak for several reasons. The tri-lobe extends out farther than a more rounded hex internal wrench-engaging feature and as such the wall thickness is only .009". This is about the thickness of two hairs. The second reason is that TiUnite can not be created on alloy so Nobel has to make the TiUnite version of the Replace out of pure titanium...their HA Replace implant is alloy for added strength.

Furthermore: Assuming the above JN sumation then what is the ability of this root form to duty cycle? Essentially hollow down the center, weaker as CP titanium, and narrow in macrogeometry as well. It is used in places like lateral incisors where the load is less. Less in a vertical mode, but if that root form is used in a progressive anterior guidance then it is in lateral load during chewing and perhaps night time parafunction. Are there published failures? Are clinicians reporting losses? How strong is strong enough?

The problem (fracture) usually occurs during insertion when torque is applied to the implant. To answer the question how strong is strong enough, if a company needs to warn a customer that the implant may break if you exceed a certain amount of torque, it is too week. The implant should be stronger than the bone and not the other way around.

The above comment holds up. A doc in RVC,NY you know from the Core Vent days has informed me of an incident when he wanted to reverse torque on insertion to line up the trigones and ruptured out the internal connection. That was the ONE he told me about. By the way he has a ton of experience. The cohesive hold in the bone on insertion was greater than the MR of the 4.3mm root form.

Just one furthermore on the above comment.. It could also have skipped out and gouged the trigone as well. But thin is thin. Again I just don't see reporting about this in the literature and therefore I assume it not to be a problem.

My dentist recommends I get either an Ankylos or a Bicon implant for missing teeth #3 and #4 on the upper right. I am curious what the dentists here have noticed with these two particular internal connection systems. Has one system shown to be more effective at eliminating the IAJ bacterial issue than the other? How about 10 or 15 years out? Which system [Bicon or Ankylos] functions better long term, and are there any pros or cons between the Ankylos and the Bicon? Thanks you for any thoughts you can pass along on what you have observed in the clinical setting regarding these 2 internal connection systems.

Dear Michael V, Both implant systems have carefully engineered internal connection, to reduce the microleakage. But there are more important things than that. Take primary stability for example- Ankylos has a much better (proven) primary stability than Bicon. The reason for that is that it is a screw implant, while Bicon with its concentric grooves originates from a cylinder implant system, called IMZ. In short- Ankylos is screwed in, Bicon is hammered in (nail-like). You choose for yourself. We`ve seen in the Bicon ads that morse connection is so strong that even big ships like tankers use it to hold their propellors in place. What they failed to mention is that besides morse cone (5-7 degrees), always a screwed nut is used. I hope that answers the question. It would be more than interesting for me to hear DR Niznick`s opinion on the topic also. Dr Yassen Dimitrov, Bulgaria

I believe the evolution towards internal hexes favors implants being used like teeth for either cemented cases or individual crowns. We see fewer screws loosening up with internal hexes. Anyone who has cemented a crown on an abutment and later had the screw loosten knows that this can be a nightmare. On the otherhand if you are doing screw retained bridges, external hexes give you much greater flexability in dealing with off parallel implant situations. I find it necissary to utelize both connections in my practice depending on the nature of the case.

anyone out there had any problems with late failures of endopore implants this after a year in lower right quadrant?

I AGREE WITH Dr.Niznick regarding the benefit of an internal hex or octogonal implant. First the abutement fits inside the implant, the quality internal implants have a 6 degree taper inside the hex. This causes a cold weld fit, even without the screw it is sometimes difficult to remove the abutement . This is a good thing since the screw will hold down the abutement as well as the tapered fit ( remember I am talking about the inside of the implant, the internal hex.) Another advantage is that the abutement fits deeper into the implant which allows for a more secure fit and allowing for anti rotation of the abutement. Remember an external hex is a proven good fixture but it does have potential for stripping the hex due to the limited height and constant micromovement from function. There is a valid point regarding smaller diameter internal implants and possible fracturing the coronal portion ( flowering) I find this with implant cases which are improperly loaded and recently with the nobel biocare 3.3mm diameter implants in Zone one bome. If you read carefully the directions specificially state to Tap the osteotomy prior to placement of the smaller diameter implants.I have been placing implants since 1992, I started with bullet implants, witnessed the evolution of the screw form, and now these new generation implants from nobel biocare( implants in a day) to Straumanns new SLA plus which is specially immersed in a solution which the company claims integration in 8 weeks.The best rule is use the implant you are most comfortable with and are having the best result. Sincerely Dr. Joe Como

How strong is strong enough? I had an incident 4 years ago of fracturing two 3.5mm Replace implants while torquing them in hard bone. At that time I did not know about the 45N warning . The implant head split at junction of the tri-lobe with the external surface. Luckily I was able to change the position of the implants without changing the prosthetic plan (from 23, 26 to 24, 25). I quit using Replace narrow platform implants (3.5mm) ever since. I had excellent results with Replace RP and WP implants (100% success at 5 years).

Dear Michael V, I have to agree with Yassen from Bulgaria. I have used Bicon implants. You can never achieve initial stability, which by the way may not be that important. I think Dr. Yassen answer was very good. I am also interested in hearing Dr. Niznick response.

A.A: All the instances of the 3.5 Replace Select implant tri lobe splitting at time of surgery has been caused by over torquing the implant by either: not utilizing the manual torque wrench properly. Or by not using the dense bone drill instead of the regular tapered drill. If we take a small sample of fractures that occurred at placement, I would guess the vast majority of cases were mandibular, and the dense bone drill and or the tap was under utilized or not used at all. Nobel makes an implant retrieval instrument which is designed for removing an implant that has become irretrievable by normal methods. It is not a trephine instead it cold welds itself into the inside of the implant. You simply turn it in reverse and the implant backs out.

Internal hex is by far and away superior to external hex for many reasons. Restorative, stability, micromovement, bacterial infiltration, platform switching to promote biological width, etc.... But in my dealings with connections...I have to go out on a limb and go with conical connection above all of them. In doing research over implants with hex connections vs. conical connection....the instances of failure due to bacterial infiltration and micromovements in hex connections is greater percentage wise than those of conical connections. Friction based conical connections provide better osseo integration, promote better papilla stimulation, less micromovement, and almost no chance of bacterial infection between the abutment and the implant.

Dear Jerry I enjoyed reading your comments and agree with most of them as you and I were there at the time. I have always admired your honesty and ability to state exactly what you believe. Just to put the records right you provided the internal hex in your original corevent design for the purpose of placing the implant with a hex key. I used your corevent system successfully for many years during the 1980's and once I found myself lecturing to you at the University of Sydney on you implant system if you remember. I suggested to you in early 1986 that we should collaborate as I had an idea for an improved abutment for the corevent implant. You thanked me but declined the offer and I remarked that I would have to design my own implant body to accommodate the new design I had in mind. You wished me luck and since we have always respected each others desire to be autonomous. In October 1986 I patented a solid grit blasted and acid etched cylindrical implant design that included an internal hex for the purpose of locking a machined angled cemented or screw retained hex lock post into the internal hex in the implant body. Some months later early in 1987 you patented the screw vent implant with and a similar hex-lock post system. You attempted in the 1990's to enforce an injunction on my company to prevent the manufacture of our hex-lock abutments and implants. The injunction was unsuccessful as my patent anteceded yours by several months. We have been producing a solid cylindrical grit blasted, acid etched implant with a hex lock abutment uninterupted since October 1986 and have a wealth of prospective research, retrospective clinical data and evidence based practice to support the efficiency of the design. So I guess this makes you the father of the internal hex as you correctly claim to be and me the father of the internal hex lock abutment.

The way patents work in the US, you can publically disclose your invention and still have 1 year to file for the patent. I publically disclosed the internal hex connection and mating internal hex lock abutment January 20, 1986 at a USC Symposium with 600 dentists present. Many people remember that meeting and remind me of it today, because Albrektsson was present and when the moderator asked if there were any questions, he walked up on the stage to make a statement critical of my reference to Branemark's published research. The January date (may have been a few days before or after the 20th) became a hotly contested date because every company that I sued for infringement raised the disclosure date - it was almost a year to the day from filing the US patent. In fact, I was selling the Screw-Vent with its mating abutments by May of 1986, long before the October patent date of your invention.

I also worked on the concept for over a year before the filing date in October 1986 in the UK. In the UK you can not make the device public until you have patented it. I was unaware of your device before I filed my patent. The law in the UK would have prevented the registration of my device if yours was registered prior to the date of my pending patent. As you say the difference in the law between the two countries explains the situation.

The only advantage of the external connection its the act as a fussible element between the implant and the bone. If lateral forces end up with screw loosening or screw fracture in same cases, this its a warning sign that we have to check our rehabilitation (oclusion, parafuncion), this warning sign its not present in internal connection because the absence of this fusible, the lateral forces goes directly to the bone. (sorry my bad english)