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Questions About Miniscrews

Regarding your [url_new=http://www.jco-online.com/home.asp?page=article&Year=2005&Month=1&ArticleNum=7&SessionID=target="_blank"]Editor's Corner, "Answeringthe Questions About Miniscrews"[/url_new], in the January2005 issue of JCO: Your initial reluctance toendorse such procedures was, I believe, well warranted.I don't feel orthodontists in the UnitedStates or any other country should feel they have"fallen behind" for not enthusiastically endorsingminiscrews as a source of intraoral anchorage.

The comprehensive article in that same issue,[url_new=http://www.jco-online.com/home.asp?page=article&Year=2005&Month=1&ArticleNum=9&SessionID=target="_blank"]"Clinical Applications of the MiniscrewAnchorage System"[/url_new], by Dr. Carano and colleagues,documents successful applications ofskeletal anchorage to achieve various orthodontictooth movements. The problems and limitationsof miniscrews are also clearly pointed out in thisexcellent article, which I would recommend to allyour readers. However, the literature and recordsof finished cases in private offices and postgraduateorthodontic programs around the worlddemonstrate similar orthodontic correctionstreated equally as well without skeletal anchorage.The question, then, is why use invasive proceduresif the results are no better and treatmenttimes no shorter than with non-invasive techniques?It seems the debate on miniscrews shouldnot be about who places them, but rather whoneeds them and why. It is not enough to do anorthodontic procedure just because you can. Itmust be justified by the end result being advantageousto the patient and the orthodontist.

The interest in skeletal anchorage raises, Ibelieve, a much bigger issue--that of force valuesin orthodontics. For the past 50 years, spurredby Begg's 1956 article, "Differential force inorthodontic treatment",1 the trend has been to uselower, lighter forces. As force levels drop, anchoragerequirements also drop. So low, in fact, thatit has been shown that it is not necessary to useheadgears or palatal bars or to include secondmolars to enhance anchorage in even the mostsevere malocclusions.2

The use of miniscrews could, I believe, leadto the use of unnecessary, even deleterious, heavyforces. This is evident from the authors' statement,"Miniscrews can be used instead whenheavy forces are required to bring an impactedcanine into occlusion." Heavy forces shouldnever be applied to impacted teeth. This causesthem to resist movement and become, in effect,"anchor teeth". I have seen the records of a patientwith a wire wrapped around the neck of animpacted canine (such a procedure is no longernecessary and definitely not recommended),where such great force was applied that the adjacentteeth were intruded from reciprocal forces.The subsequent use of light force (approximately1oz) permitted reversal of the intrusion and rapideruption of the canine.

The suggested use of skeletal anchorage formolar intrusion seems the most appropriate, consideringthe advantageous vertical force vectorsand the lack of reciprocal extrusive forces onother teeth. However, the authors do point out thedifficulty in proper placement of miniscrews insuch cases and recommend only unilateral application.As alternative, non-invasive means of posteriortooth intrusion, I would first consider usingelastics with an Essix appliance3 or employingfixed or removable magnets.4

Actually, many of the problems purportedto be "solved" or addressed by miniscrews in thisarticle are actually manmade, caused by Angle'sedgewise slot itself. These include:

  • Deepening of the anterior bite when closingposterior spaces.
  • Difficulty intruding anterior teeth and correctingdental midlines.
  • Need for heavy forces to overcome sliding andactive friction and to correct Class II and IIIinterarch discrepancies.
  • These obstacles to desired tooth movements,which are directly related to the Angleslot, were recognized long ago by one of his beststudents: "each and every tooth is now an anchorageauxiliary".5 If one is going to use a slotdesigned in 1925, one is going to have to be preparedto fight 80-year-old battles that may requireenhanced anchorage. There have beentremendous strides in the past 50 years--both inarchwire metallurgy and slot geometry. Whyignore them? It is now possible to utilize preadjusted, edgewise-type brackets in conjunctionwith light intraoral traction forces of 2-3oz toachieve rapid anterior bite opening, Class II or IIIcorrections, and space closure when required.6

    In view of the above, not to mention the effectinvasive surgical procedures could have onreferrals, increases in liability and associated insurancepremiums, and overall patient anxiety, Idon't feel any orthodontist should consider skeletalanchorage as "a mainline clinical technique."


    Author's Reply

    First of all, I am very pleased that this opendiscussion of skeletal anchorage has beenstarted between orthodontists in the UnitedStates and those in the rest of the world, as Ibelieve it will be highly beneficial. I would liketo begin my response to Dr. Kesling with the initialissue in the debate--that is, who shouldinsert the miniscrew. We are strongly convincedthat for the best patient management and mostefficient clinical application, it should be theorthodontist. With apologies to the researchercited in the Editor's Corner by Dr. Keim, theWild West he has seen exists only in JohnWayne's movies. In Europe, and I believe even inAsia, there are well-defined regulations thatallow the orthodontist more clinical freedom, sothat we can use our expertise in matters that maybe outside the realm of traditional orthodontics.This has been the basis of our study, promotion,and testing of skeletal anchorage with miniscrewsin clinical orthodontics.

    Furthermore, I want to make clear thatbefore presenting our Miniscrew Anchorage System(MAS) to the world, the late Dr. AldoCarano and I, together with the entire team at theUniversity of Ferrara Department of Orthodontics(directed by Prof. Giuseppe Siciliani),thoroughly investigated this complex issue withoriginal research into subjects such as the safedrilling zones in the bone.7 We also tested varioustypes of screws, creating three prototypesbefore achieving the final screw that is nowavailable. We have applied and improved the surgicalprocedure for some time, making sure thatthe clinical results in all their biological and biomechanicalaspects, together with the patient'sreactions, were carefully monitored.8 In otherwords, the MAS is a device that has been thoroughlytested over the last five years by differentclinicians, following precise guidelines and indications.

    That the "vexata quaestio" of whetherorthodontic treatment should be done with so-calledheavy or light forces is still debated doesnot reduce, in my opinion, the validity of skeletalanchorage obtained with miniscrews. Dr.Kesling's preference for using light forces that,according to his experience, would eliminate theneed for miniscrews should not obscure the factthat the Begg technique is not commonly used inthe rest of the world. In fact, we have receivedstrong feedback from many clinicians regardingthe effectiveness of miniscrews as skeletalanchorage.

    On one point I agree with Dr. Kesling: thatmany orthodontic problems could be managedwithout miniscrews. In our experience, however,because it is a simple and minimally invasivetechnique (it takes no longer than five minutes toplace a screw), without complications or the needfor drug therapy either before or after insertion(only two screws out of a sample of 543 havecaused local inflammation), and very comfortablefor the patient, we strongly recommend thismethod to solve traditional orthodontic problemsin a short time, without the need for patient cooperation and with less stress for the clinician. I donot use any system "just because I can", but becauseI have found it a more effective and efficientalternative to solving my old problems.

    All of our readers should be aware that theyare looking at only the most obvious aspect ofminiscrews--skeletal anchorage--but that this isnot the only reason for using them. For example,there is a biomechanical advantage in that miniscrewscan be placed almost anywhere intraorally.By moving them closer to the center of resistanceof the teeth, we can get a more bodily, andtherefore more physiological, tooth movement.This not only saves time and eliminates the needfor intraoral auxiliaries, but is much more comfortablefor the patient than traditional orthodonticappliances.

    It is possible that some biomechanicalproblems are "manmade", as Dr. Kesling haspointed out; on the other hand, I see situationsthat would be impossible or very difficult toresolve without using miniscrews. He suggestsmolar intrusion with Essix appliances or magnets,but I would question the need for patientcompliance with the Essix and elastics, and thecomfort and cost of magnets. Are these systemsany more effective than skeletal anchorage? Weare the first to admit (and I thank Dr. Kesling forpointing it out) that at the moment, intrusion ofan entire arch is not possible with miniscrews,but single-tooth intrusion is highly effective andpredictable, with light forces (a maximum of 1-2oz). The use of miniscrews does not necessarilyimply using "heavy forces".

    With an impacted canine, it is always possiblethat exposure of the tooth will reveal ankylosisor close proximity to other teeth within thebone. In this case, whether the forces used arelight or heavy, all applied forces will unload onthe anchorage teeth. The main point is one oftiming; the orthodontist should wait for eruptionof the canine before continuing with treatment,because the remainder of the arch will be used asanchorage no matter what force is applied. Onthe other hand, if we insert a miniscrew as anchorage,there are no adverse side effects, and wecan continue treatment on the remaining dentition.The case that we showed in our JCO articleis an example of this concept. We saved 10months of fixed appliance treatment with thispatient because we used only two miniscrews tobring the impacted canine into the arch.

    As Dr. Kesling implies, there are otherquestions yet to be resolved, including anchoragein edentulous areas, vertical control of the occlusalplane, and anchorage for intraoral devicessuch as the Distal Jet or Pendulum and for orthopedicdevices such as the Delaire mask. At present,we are investigating all of these areas.

    We strongly believe, based on scientificevidence borne out by clinical application, thatskeletal anchorage with miniscrews not only offersthe orthodontist an improvement in the effectivenessof clinical systems, but also providesa number of alternative solutions. In this initialphase of great enthusiasm, as in any new endeavor,there will undoubtedly be excesses. For thatreason, it is essential that we set up standards andguidelines for rational miniscrew applications.The contributions of American orthodontists,thanks to their considerable clinical experienceand their cultural and scientific traditions, will beof fundamental importance.


    Additional Reply

    Since I was probably one of the first involvedin the use of mini-implants (since 1995), Ihave the pleasure of answering Dr. Kesling's letter.He is right in stating that orthodontists in theUnited States do not need to feel they have fallenbehind. Actually, Creekmore was the first topublish on skeletal anchorage.9 Still, it has to beadmitted that the recent burst of papers on skeletalanchorage does not come from the U.S.

    Dr. Kesling and I agree that skeletal anchorageis here neither to replace other types of anchoragenor to treat non-compliant patients. On theother hand, skeletal anchorage definitely widensthe spectrum of orthodontics. As an early example,when Roberts and colleagues inserted aretromolar implant, it became possible to bringmolars forward without adverse effects on theanterior unit.10

    Unfortunately, as Dr. Keim points out in theEditor's Corner, the situation today is much likethe Wild West.11 Many implant systems are poppingup, and few indeed with a scientific basis.Many authors are so eager to show their particularsystems that they refrain from waiting for thecases to be finished. I believe miniscrews arehere to stay, but I think that, as with many otherappliances, there will be an initial wave in whichthey may be used indiscriminately before theyfind their proper place. In some universities, atleast, the use of the mini-implant is now on solidscientific ground.

    Dr. Kesling draws attention to the trend ofreducing force levels and mentions that "the useof miniscrews could lead to unnecessary, evendeleterious forces". The force levels, I believe,are independent of the use of skeletal anchorage,and the statement by Dr. Carano and colleaguesthat heavy forces should be used to bring acanine into the arch must be considered theauthors' own approach. Unfortunately, as Dr.Kesling also states, many of the problems wefight are manmade.

    He is correct that many of the cases presentedcould have been corrected without skeletalanchorage. There may, however, be situationsin which adverse effects can most efficiently becontrolled by skeletal anchorage. Examples ofsuch cases are shown in my [url_new=http://www.jco-online.com/home.asp?page=article&Year=2005&Month=9&ArticleNum=539&SessionID=target="_blank"]article in this issue[/url_new].

    I am happy that JCO has taken up the questionof mini-implants in its Editor's Corner. Skeletalanchorage will be a supplement to help withproblems that cannot be solved by any preadjustedtechniques. In addition to being a great supportto adult orthodontics, as we have seen inrecent issues of the journal, it has become asteadily growing part of our clinical practice.



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