Narrow Diameter Implants: Are There Absolute Contraindications?

Dr. A. asks:
What are the contra-indications to using narrow diameter or mini-implants? I see these being used more and more to replace teeth instead of conventional implants, and I’d like to know if there are there any true absolute contra-indications compared to conventional dental implants?

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36 thoughts on “Narrow Diameter Implants: Are There Absolute Contraindications?

  1. NARROW DIAMETER IMPLANT: ARE THERE
    ABSOLUTE CONTRAINDICATIONS?

    The word absolute in medicine is a term rarely used. There are limitations of treatment, which a doctor should take into consideration. The small diameter implant is usually an implant approximately 2mm in diameter. This makes the implant 16 times weaker to fracture than a 4mm diameter (strength is equal to the radius times the power of 4). Hence, higher forces (i.e. posterior regions, parafunction, crown height greater than 15mm, cantilevers, etc.) increase the risk of fatigue fractures.
    The small diameter implant is usually one piece. One piece implants extend into the mouth during healing and often are immediately restored. It is safer to allow an implant to integrate prior to loading it with the restoration. A higher risk of immediate restoration would be in softer bone. As a general rule, the maxilla has bone 50% weaker than the mandible. Hence, a higher risk is in the maxilla.
    As a result of greater risk of early failure and a greater risk of fracture of successful implants, the doctor should charge the patient more money for a small diameter implant than a regular diameter, to offset the increase risk of complications and the need to redo the treatment (which usually takes longer than the original treatment).
    There are several other limitations of treatment for the small diameter implant, including less surface area, inability to splint implant together when placed at an angle, less initial fixation, less range of prosthetic components, and a poor emergence contour of restorations to name a few.

  2. When the mini implants have a resilient attachment and the resiliency is preserved (meaning the attachment is processed properly) then the restoration is tissue and implant borne which is very good for the prognosis of the implants. Even a single implant (attachment) in the posterior to anchor a free-end partial denture is fine as long as you have the reciprocating function in the anterior (i.e. another resilient attachment).

    The anterior of the maxilla is another area of concern with these implants. And again the resiliency is important here but more so it is the ability to correct the path of insertion. If the path of insertion cannot be corrected and the attachments are divergent then we lose the true function of the attachments and this will impact the osseointegration of the implants.

    I think a rigid fixation on mini dental implants is one thing that really needs to be looked at because of the reduced surface area in the fixture body. When we decide to restore crown and bridge with these mini implants; we need to be more selective. I believe that in this situation it is best to stick to the anterior mandible and support this restoration as you would a monodont.

  3. i have been doing Minis for a while. It is my experience that I need to go on above what works in other people’s hands. If I do them on the upper, I consider them temporary or provisional implants. Due to the bone quality and surface area of the threads(even the Maxi), On the lower I use them for denture retention and they can be used for a lower anterior tooth( that is not in heavy occlussion). I alsays try to get the pts to upgrade to a conventional implant.

  4. I guess failure is a good teacher.I now feel maxillary minis with a denture loaded on ,ie D3 bone or worse ,to be absolutely contraindicated.These minis work ok in select d1 bone,ie. anterior mandible.I heard Dr. Misch speak at U.of Louisville this past Friday.His observation on mini implant is that they should be place judiciously,ie.narrow max. lateral area.

  5. Mini-implants into anterior mandible only with dense cortical bone. High degree of failure in other sites especially maxilla. I regard the mini implants as temporary implants for future replacement with proven conventional implant systems.

  6. Dr. Misch, I’m not sure where you got your strength formula, but if you use it to compare a 2.5mm implant which is more commonly used in the maxilla, the numbers show an increased strength factor of 6.55 for the 4mm implant. I would not disagree with you about the problems using this for a single tooth or even for a unilateral bridge, but I and many others have had great success on the maxilla with full arch interconnected fixed prosthesis. I’m not sure strength is a factor when we use 12 implants with a fixed prosthesis of any construction. I notice on your web site that you use 12 conventional implants on the maxilla. That is a great idea IF you have enough bone, IF the patient can afford 12 conventional implants, and IF the patient can afford bone augmentation/sinus lifts. Long term denture wearers will require all of the above. Age is also a factor. Do you want to be able to improve the quality of life for older patients who suffer with dentures? Are you willing to provide conventional implants at a lower cost for these patients? Or would you at least consider the possiblity that mini implants roundhouse bridgework might work and have a predictable prognosis? There are several other items brought up in your post such as angulation issues, immediate loading,emergence contours with mini implants, etc., but I will save those for another time.

  7. Dr Misch are you the same Dr Misch that wrote in the April Dental Economics p62

    Time to remove all teeth that have 7mm pockets and place an implant.

    “Periodontal treatment or Extraction and Implant Insertion”

    I disagree with that position now that LANAP is available.

    I also disagree with your remarks on Mini’s

    Here are some references

    Vigolo P et. Al IJOMI Survival Rate of Narrow Diameter Implants 2004; 19:703-709
    7 year retrospective 2.9mm diameter implants 95.3% survival rate (188/192)

    Mazor Z.et. Al Implant Dent 2004; 13:336-34 2.4mm diameter implants 96.9% survival rate (31/32) up to 5 years in function.

    Froum S. Simon H, Cho SC, Elian N, Rohre M, Tarnow D, IJOMI 2005; 20:54-60 Histologic Evaluation of Bone-Implant-Contact of Transitional Implants Loaded for Various Time Periods. Bone Implant Contact with TIs was similar to the conventional machined surfaced implants as documented in the literature.

    Cho SC, Froum S, Tai Ch, Elian N, Tarnow DP, PPA&D 19: 167-174, 2007 Immediate loading of Narrow –Diameter Implants in Severly Atrofic Mandibles. 94% survival

    Froum SJ, Cho SC, Taarnow D, IJPRD 2007; 27:449-455 100% Survival rate with Narrow Diameter Implants.

    Some advantages to Mini Implants they can be placed flaplessly, be used in thinner ridges, Less Pain, Less Bleeding, they can be used in medically compromised patients, Fewer Parts, and they are Less Expensive.

  8. Contra-indications for minis could be a ridge that would not allow for 1mm of bone in the Facial/Lingual dimension…but that would hold true for conventionals as well. I realize that we as dentists can expand the ridge….if the patient wants us to.

    Strength – Intra-Lock has a study that shows that their MILO mini implant is actually stronger than a larger 3.75mm conventional implant BECAUSE its a one piece design (no hollow core).

    Posterior Maxilla – multiple minis can be splinted together. Most dentists that place minis frequently place 2 minis for a molar and splint them together.

    Surface area – Lets do some math…Surface area = pi(3.14) x Diameter x Height…A conventional 4mm x 10mm would have a surface area of 126 sq mm. If we used 2 Intra Lock 2.5mm x 10 would give you a surface area of 157 sq mm. I bring this up not to say that minis are better than conventional implants but that if the argument of surface area is important lets look at it objectively.

    Cost – I see no reason to consider charging more for a mini implant than a conventional? Minis do work and we should just let the results speak for themselves. I think there are enought studies to show that minis do integrate and have survial rates equal to conventionals.

    Complications – I would ask everyone to consider that minis do not require anywhere near as much manipulation of bone, invasive surgical procedures and thus have less risk of complications. When failures occur there is much less of a defect to repair.

    Minis can offer a viable option to a set of patients that have not been able to follow through with implants (cost, time, money, surgery to name a few).

  9. concerning the laser assisted new attachment procedure coments… if you were around long ago. ENAP excisional new attachment procedure was created as a surgical ( blade ) replacement for curets removing the infected-inflammed lining of gingiva . the enap failed in many studies to show a difference. years later , curettage was shown to be so ineffective it also was deleted from the codes of procedures. if you think laser assisted ENAP is any better you should wait for studies. what is now out there is very weak…. to pay for the laser is likely the reason its still out there now.to claim the lining of any inflammatory or infected ( there is a difference between the two) lesion in soft tissue is the site of action is not the important issue.the lining changes from the etiology. the lining will reform again and again if you do not treat the etiology. mini implants also have a history, breakage, bone quality, wear on parts, torque values and naturally the biology all play a role. to think the problems are less, or let the liturature do the talking means you think less is more or the same. minis are mostly a compromise so expect the increase in long term problems due to limits on minis in all the aspects….mentioned.it is certaining not better, and mostly its for the practitioner to do something which is cases may not be possible.

  10. Why would the problems increase with minis? If no bone expansion is preformed? If no ridge splitting is done? If no bone graft is done? All of these procedures come with additional risk for the patient. All implants come with risks to our patients; where is it noted that minis have a greater risk?

    What study or case reports are you referencing when you state to ‘expect the increase in long term problems due to limits on minis in all the aspects’?

  11. I do not care about two vs one implant on surface area. You are dealing with the weakest link. One part of the bone is not the same as another if you have placed enough implants. I just placed four lower minis. I did a full thickness flap and flattened the crest and sunk them in good bone. I still do not give the patient as good a prognosis as a conventional implant. I expect failure and if it doesn’t I am happy . Minis fail more than conventional implants no matter who you are and how good of a surgeon you think you are (even if you treat the pope…hey Carl).

  12. I see you charge $400 for minis and $1500.00 for conventionals..what’s up with that…should we all not be charging more for minis???

  13. Does exists tapered one piece narrow dental implants diameter 2,4 mm with the same strenght as classical implants dameter 3,5 mm. These implants are made from nanostructured titanium and name is Nanoimplant. It is possible use as final solo pillar implant. The nanostructured titanium is not alloy, but 99,9% titanium with increased mechanical properties. The biological properties are much more better than normal titanium.We use it with advantage more than 4 years.

  14. If one just looks at this issue from bone density (D-1 to D-4 and no other variables. Then any endosseous implant will work in D-1 bone. D-2 bone is less dense, thus the bone cell density less. So, less bone to implant surface, thus a smaller implant, then less surface to bone. When you get to D-3 and D-4, you are in far less dense bone. It’s basis engineering.

  15. Dear Dr.A,
    have crossed over the 500th and still counting. Started in 2000 and the implants are functionally impressive with pfm crowns perforating in use and the minis or reduced diameter implants either as single or bridges in D1 to D4 bones. Have yet to experience a fractured implant in use. Did fractured a few in the early years while inserting in D1 bone. Go ahead you will be surprised what the minis can do. Have stopped using the standard diameter implants.

  16. if you would review the stress and sheer strength of a mini , 1.8 mm , done at the U niversity of Alabama and the University of Georgia you will find that the 1.8 mm made of Ti6Al4V is more than three times stronger than commercially produced pure Titanium implants. Also we are,in the case of a removable proetheses,fabricating a soft tissus born prostheses and implant retained. With the convential implant this is not the case. The length of any implant is important,the longer the better,more surface area and stability. I have been placing implants for over 35 years, minis for over nine years. I have a failure rate of about 1.5%. I do make a compersentive evaluation of each patient. I require a cat scan in the dental mode. I tell the patient before treatement whether whether Ifeel they are a canadate for treaemene.The minis an the market today do have flaws,thus I have a mini which I have patened,US an International, which will be forth coming.

  17. If you review the stress and sheer strength of a mini, 1.8 mm implant done at the University of Alabama and the University of Georgia, you will find that the 1.8 mm made of Ti6Al4V is more than three times stronger than commercially produced pure Titanium implants. Also, we are in the case of a removable prostheses fabricating a soft tissue born prostheses and implant retained. With the conventional implant this is not the case. The length of any implant is important, i.e. the longer the better more surface area and stability. I have been placing implants for over 35 years, minis for over nine years. I have a failure rate of about 1.5%. I do make a comprehensive evaluation of each patient. I require a cat scan in the dental mode. I tell the patient before treatment whether I feel they are a candidate for treatment. The mini implants meet the definition of osseous integration which is “when the fixture is in eminent contact with the bone.” When you pass a 2.4 diameter implant through a 1.1 mm entry point, you have compressed the bone 1.3 mm. This I would call eminent contact. Also, over time since the surface treatment of the minis are the same as the conventional implants, they will undergo additional osseous integration. The mini implants on the market today do have flaws. Thus, I have a mini which I have patented, US and foreign, which will be forthcoming.

  18. Narrow diameter dental implants are being increasingly used not only to stabilize dentures but also for long term applications like crowns and bridges. I agree with Carl in that there is no such thing as an absolute contraindication in medicine. Even botox which will kill you if injected into your bloodstream is used ingeniously and judiciously to extend the youthful looks of people. The key word is “judiciously”. Know your medicine well and know what you want to do with it and then you can apply it safely and usefully.

    It is significant that one of the doyens of implant dentistry has recognized that narrow diameters have their uses especially in narrow ridges and in suitable bone. I started out with conventionals and with the advent of minis, incorporated them into my treatment planning and in many complex cases have successfully integrated them both into my treatment planning taking into consideration the patient’s expectations and budget,the materials available and their limitations and my own experience, knowledge and skill.

    However, with the greatest of respect, having read the classic Contemporary Implant Dentistry, I wish to highlight some misconceptions and give my opinion.

    As pointed out earlier, many narrow diameters or minis used for fixed applications are 2.4mm to 2.9mm in diameter and are made of solid titanium alloy grade 5. They are certainly stronger than say a 4mm diameter fixture that has a hole in the middle to receive an abutment. Say the abutment is 2mm in diameter. That leaves the surrounding rim with a thickness of only 1mm! That is weaker definitely than a solid 2.5mm diameter mini. Furthermore, many of the conventional fixtures are made of titanium grade 3 or 4 which is 99.9% pure titanium and is softer and therefore weaker than the alloy.

    One piece minis heal very well if they are placed in with a torque of at least 35 to 50ncm.Reason being that the healing challenge is much less than conventionals and also the transmucosal wound is very small, so that chances of infection in a normal patient is minimal.

    As for the misconception that the surface area is insufficient, Paresh Patel has given an eloquent correction to that. Minis are usually placed longer than conventionals and in multiples. So as Patel has pointed out, two 2.5 by 10mm minis give a total surface area of 157sq mm. This has a greater surface area than a conventional of 4 by 10mm which gives only 125sq mm. 2.5 by 13mm gives 100sq mm. 2.5 by 16mm gives 125sq mm. All these are commonly used such that the argument of insufficient surface area for osseointegration holds no water.

    The initial or primary stability of minis, I find often surpasses that of conventionals. In fact, I surmise that because of the minimal trauma and small entrance, the surrounding bone and soft tissue has overwhelming healing advantage when compared to conventionals that invokes a much greater healing challenge to the surrounding tissues. The overwhelming healing advantage in the context of minis may mean that the classical necrotic margin phase of osseointegration may be bypassed and osseointegration in the case of minis may be taking place almost immediately. Anyone wants to do a PhD on this?

    Narrow diameter users must concede however that the charges of inadequate prosthodontic solutions to solve the problems of non-parallellism, insufficient prosthetic components, and poor emergence profile may have some credence. These problems I believe are being sorted out. As it is, narrow diameters or minis are here to stay and will be increasingly integrated into treatment plans to cater to all sorts of situations that it can solve much better than conventionals. I look forward to minis making great strides to make the benefits of implant dentistry affordable to everyone who needs them, and not just to the well-off only. I forsee that they will play an increasingly greater part in the development of implant dentistry and am preparing a book…”Minimized Dental Implants” and hope to outline and deliver elegant prosthodontic solutions to minis that will address the current shortcomings as pointed out.

  19. Dr Chow – Amen to all your comments. There is absolutely no reason not to use mini implants. I have been cementing full arch mini implant hybrid bridges as a denture alternative for the past two years. My opinion is that a CEMENTED bridge on mini implants is an affordable alternative for patients unwilling or unable to pay for the all on four bridges, or the conventional implant porcelain/metal solutions. Cementation to minis eliminates the micromovement responsible for most implant failure in a full arch situation. By using quality denture teeth and a quality denture acrylic with high flexural strength, I can quickly construct a highly aesthetic denture alternative which can be loaded immediately. Patients go home happy, and so do I!

  20. 1. Bone density related: dont waste your time with D4 bone, in D3 you are taking big chances.
    2. Clenchers: You better know the biomechanic concepts of Dr Misch contemporary implant dentistry and know how to apply it clinically plus parafunctional forces management with splints, biofeedback and medication. OR DONT DO IT!, in fact DONT DO IT!
    3. Psychogenic factors: I have had to remove perfectly functioning healthy mini implants in a patient that couldnt stand seen screws in his mouth, just to have him call me 6 months later to put them back.

    Alvaro Ordonez

  21. One day I am going to hold a picnic and invite all my happy denture wearing clients who have minis (over 600 of them now)and invite some of you “experts” along to break the news to them that the treatment doesn’t work.

  22. Can anyone comment on Alvelac socket preservation , a bioscafold material that is self resorbable and preserves the buccal lingual width of the fresh socket.

  23. Thanks for the kind words guys. While I am yet feeling elated and therefore a little brash, let me push the debate a little further.

    We all know that the transmucosal passage of the dental implant when compared to the transmucosal passage of an actual, real, original living tooth is actually a pathetic imitation of the real thing. The real thing has a nice epithelial attachment with a nice drain around the tooth constantly flushed with antibacterial substances and prohealth nutrients for the gingivae. Not only that the gingival cuff has circular fibres, connective tissue to tooth fibres, bone to tooth fibres , connective tissue to bone fibres etc. that gives each tooth a nice firm resilient yet elastic cuff around the it. Go review your periodontology texts and see for yourself.

    The dental implant has only a pseudo epithelial attachment and a few if any specialised soft tissue fibres and at best is actually an iatrogenic and pathetic imitation of the original! The Archilles heel of dental implants is this transmucosal passage. Peri-implantitis is a problem we all have to tackle like periodontitis. And with dental implant placement growing in the double digits around the world, it is going to be an increasing problem.

    The best solution is probably a tooth germ implant which may be a generation away. We may be stuck with dental implants for some time yet.
    One way to tackle it and hopefully to decrease the incidence of peri-implantitis may be to decrease the diameter of the implants as it emerges through the mucosa. One shortcoming of conventionals is its large diameter especially done in the name of an aesthetic emergent profile. Narrow diameters may be one of the answers to decreasing and managing the incidence of peri-implantitis.

    Nuff said.

  24. No contraindications ! Lack of bone quality can be matched with a increased number of implants.
    In contrary:
    Multistep procedures are an act of artistic implantologic dentistry trying to simulate what is not true and is definitively wrong in case of patients over 70 jears. Therapy time should be in a relation to expected benefit (of the patient). Multimorbidity of patients also limits the number of surgical acts for corrective measures.
    They are usefull and indispensable for well situated people having time and no other concern (Hollywood Stars and those who would like to be..)

    The biggest disadvantge of 2 piece implants is that you have to adapt individual bone to match prefabricated length at a given diameter availbility.
    Or you have to graft !

    Being a blasphemic I use to cut off disturbing length in order to match the bone during implantation. This can be done only with single piece implants !
    In case of resorptive thread exposure I just cut off the exposed thread wing allowing soft tissue to cover it in a safe way and preventing further bone loss.
    Resective treatment is the most secure way in periodontology as in implantology. And it is not that easy to predict non-intended resorption.

    Applying valid principles of thinking on 2-piece- implants on natural tooth would be equal to indicate the necessity of extraction of all tooth showing 30% bone loss. Would you dare ? Exaktely therefore I think the best way is the shortest viable.

    The possibilities to preserve implants showing a loss of 30% bone “attatchment” are critically dicussed and generally doubted referring long term out-come on this blog.

  25. While Minis are proven useful and functional by dental practitioners all over the world, comments based on WRITTEN THEORIES suggesting the IDEAL treatment should be respected – i agree.

    ALTHOUGH that, repeated clinical trials had been DONE to prove it works, even with marvelous results. IN FACT, tens of hundreds dental doctors out there, especially those in low living quality country, poses successful results.

    Blatant denial to use Minis based on theories alone should be rejected with proof. This is the nature of Science. End of Story.

  26. Complete contraindications for Mini Dental Implants are patients who have had recent IV bisphosphonate therapy. Relative contraindications are numerous. There is no option for a 2 stage procedure here since it is a one piece implant. Initial stability of 30 NCm is key. If that can be achieved with a mini dental implant you have a very high probability of success. I don’t discriminate areas of the mouth or my estimation of bone density type even with CT data. I have been surprised numerous times. For example, Dr. Misch has indicated that at least 10% of patients have good type D2 bone in the Posterior Maxilla and at least 25% in the Anterior Maxilla. Also, in the same study he presents that at least 28% of patients have D3 or SOFTER bone in the Anterior Mandible. Although the risk is greater to find soft bone in the maxilla, our service to our community should involve offering these options. Here is my philosophy: I charge basically the same fee for conventional or mini implants. I plan to make the treatment fast and easy for my patients by using the MDI. If the MDI is not stable to 30 NCm, then I place a conventional 2 piece implant. Simple as that. It takes about 5 minutes more and I’ll use the mini as a lab analog or for patient education after i sterilize it. I have placed thousands of MDI’s for every application you can imagine. They will work well if you follow my recommendations above. Good luck!

    Ben

  27. Many of my complex cases are treatment planned with both narrow diameter and regular diameter dental implants. My experience in cases when I use only narrow diameter is that I complete my cases much faster than when it involves regular diameters. As such, it behoves serious practitioners to keep both types in mind when treatment planning because I forsee that we are beginning to shift towards a more balanced and sensible approach rather than a prejudiced and narrow approach.

    Cheers!

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