Might skeletal anchorage be applied to ortho-dontic tooth movement and orthopedic jaw

movement?” With this question in 1983, Creek-more and Eklund were the first orthodontists tosuggest in print that a small metal screw couldwithstand a constant force of sufficient magni-tude and duration to reposition an entire anteriormaxillary dentition without becoming loose,painful, infected, or pathologic.1 Their caseopened an entirely new area for managing ortho-dontic anchorage, but may have been too pro-gressive and too invasive for its time.

Toward the end of the 1980s, a number ofclinicians focused on the use of standard dentalimplants as temporary anchorage for orthodontictooth movement and then as permanent abut-ments for tooth replacement.2-5 The major advan-tage of these implants is that they make it possi-ble to move multiple teeth without loss ofanchorage. They can be placed in areas wherenatural anchorage or conventional orthodonticappliances are impractical, including the edentu-lous spaces in the alveolus of either arch, thepalate, the zygomatic process, the retromolarregions, and the ramus. Disadvantages of dental

implants are the need for an invasive surgical pro-cedure, the limitations on placement sites im-posed by the implants’ 10mm length, the timerequired for osseointegration prior to force appli-cation, and cost. In addition, they are not recom-mended for female patients younger than 16 ormales younger than 18.

More recently, new onplants, miniplates,and palatal implants have been developed specif-ically for use in orthodontics.6-8 The miniplateshave been advocated as anchorage for molar in-trusion7,9-11; palatal implants have been used forspace closure, and most effectively for distaliza-tion of maxillary molars.5,7 Because these newdevices still have many of the same limitations asstandard dental implants, however, most ortho-dontists have now turned to miniscrews.12-17 Re-peating the experience of Creekmore, they havefound that small screws, like those used for rigidfixation in maxillofacial surgery, work well fororthodontic anchorage.14,15 The size of the screwshas been reduced even further in the last fewyears.16,17

The material generally used for miniscrewsis medical grade 4 or 5 titanium, although stain-

VOLUME XXXIX NUMBER 1 © 2005 JCO, Inc. 9

Clinical Applications of theMiniscrew Anchorage SystemALDO CARANO, DO, MSSTEFANO VELO, MDPAOLA LEONE, DO, MSGIUSEPPE SICILIANI, MD, DMD

Dr. Carano is an Adjunct Professor, Department of Orthodontics, University of Ferrara, Ferrara, Italy; an Adjunct Professor, Department of Orthodontics,St. Louis University; and in the private practice of orthodontics in Taranto and Bari, Italy; e-mail: a.carano@libero.it. Dr. Velo is an Adjunct Professor,Department of Orthodontics, University of Ferrara, and in the private practice of orthodontics in Padua, Italy. Dr. Leone is an Assistant Professor,Department of Orthodontics, University of Washington, Seattle, and in the private practice of orthodontics in Seattle. Dr. Siciliani is Chairman,Department of Orthodontics, University of Ferrara, and in the private practice of orthodontics in Rome.

Dr. Carano Dr. Velo Dr. Leone Dr. Siciliani

less steel has been proposed as an alternative.Recent histological studies in animals haveshown that the osseointegration of titanium mini-screws is less than half that of conventional den-tal implants.7,18,19 There was no significant differ-ence in the bone surrounding the miniscrew siteswhether the miniscrews were loaded or unloadedwith force.9,18,20 The presence of more compactbone in the mandible may account for some dif-ferences in miniscrew performance found be-tween the maxillary and mandibular arches.7,18-21

Incomplete osseointegration represents adistinct advantage in orthodontic applications,allowing for effective anchorage with easy inser-tion and removal. The miniscrew material and thespecific design of the self-tapping portion are stillimportant, however, in determining resistance tobreakage. Even though orthodontic forces are notnormally great enough to break the screws, therotational forces associated with placement andremoval can cause miniscrew failure, especiallyif the bone consistency is high or a partial inte-gration has occurred. Differences among variousminiscrew head designs have also been notedwith regard to soft-tissue healing.

This article illustrates the clinical applica-tions of a new titanium miniscrew designed fororthodontic anchorage.

Miniscrew Design

The conical screws used in the MiniscrewAnchorage System* (MAS), made of medicalgrade 5 titanium, are available in three sizes (Fig.1). Type A has a diameter of 1.3mm at the top ofthe neck and 1.1mm at the tip. Type B is 1.5mmin diameter at the neck and 1.3mm at the tip.Both types are 11mm long. Type C, which is9mm long, has a diameter of 1.5mm at the neckand 1.3mm at the tip.

The screw head consists of two fusedspheres (the upper 2.2mm in diameter, the lower2mm), with an internal hexagon for insertion ofthe placement screwdriver. A .6mm horizontalslot at the junction of the two spheres allows for

the attachment of elastics, chains, coil springs,ligature wires, or auxiliary hooks.

Mechanical Testing

Two methods were chosen to test thesescrews mechanically, representing two potentialmodes of failure during insertion and removal:torsional strength and bending strength. The testswere conducted in the Department of MechanicalEngineering at the University of Genoa, Italy, byseating the screws in a tapped brass block at athread depth of 6mm. For torsion-to-failure test-ing, a dial torque wrench with a recording devicewas turned in a clockwise direction, perpendicu-lar to the long axis of the screw. For bending-to-failure testing, a dial bending arm with a record-ing device was used to deform the screw along itslong axis in a clockwise direction. Six screwswere used for each test.

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Clinical Applications of the Miniscrew Anchorage System

Fig. 1 Miniscrew Anchorage System (MAS) screwsare available in three conical sizes. Screw headconsists of two fused spheres with internal hexa-gon for insertion of screwdriver. Slot can be usedfor attachment of elastics, coil springs, ligaturewires, or auxiliary hooks.

*Micerium, S.p.a., Via Marconi 83, 16030 Avegno, Italy; www.micerium.it.

The mean resistance to breakage in torsionwas 48.7Ncm for the 1.5mm-diameter miniscrewand 37.4Ncm for the 1.3mm-diameter miniscrew.The mean resistance to breakage in flexion was120.4N for the 1.5mm-diameter miniscrew and91.7N for the 1.3mm-diameter miniscrew.

These results suggest that the MAS screwscan resist a force much greater than that of anyorthodontic application. It is possible, however,to apply a torsional force of more than 40Ncmduring insertion or removal and thus to break thescrew. To limit this torsional force, the clinicianshould use a small screwdriver and hold it by thefingertips. If the self-tapping screw encountersextreme resistance during insertion, additionalpilot drilling may be required. At the time ofremoval, if the screw seems to be osseointegrat-ed, a minor surgical procedure may be needed toremove it completely.

Placement Sites

Miniscrews are used in place of traditional

appliances such as headgear and lingual arches incases where absolute anchorage is necessary.From a biomechanical standpoint, miniscrewsallow more bodily tooth movement during spaceclosure by placing the force vectors closer to thecenter of resistance of the teeth.

The sites most often utilized for MAS inser-tion in the maxilla include:• Interradicular spaces, both buccal and lingual• Extraction spaces• Inferior surface of the anterior nasal spine

In the mandible, the most common mini-screw placement sites are:• Interradicular spaces, both buccal and lingual• Lateral to the mentalis symphosis• Extraction spaces

In our experience, the most useful locationsare the interradicular spaces, either buccal or lin-gual, between the second premolars and first mo-lars in both arches, or the buccal space betweenthe upper lateral incisor and canine.

Surgical Procedure

A surgical guide can be made from a rec-tangular wire segment to help identify the mini-screw location on the intraoral x-ray (Fig. 2A).The self-tapping screw often requires no prepara-tion of the medullary bone. If the bone is toodense, however, a bur (.9mm for Type A, 1.1mmfor Type B) should be used to drill a pilot holethrough the gingival and cortical bone underlocal anesthesia. We recommend placing a stopon the bur to limit the depth of insertion to 2-3mm, but it is critical that the depth be 2mmshorter than the miniscrew. The axial inclinationof the bur must be the same as the desired incli-nation of the miniscrew.

Special attention is required during screwplacement to reduce the chance of injury to deli-cate anatomic structures such as vessels, nerves,and dental roots. A metallic marker, which can beattached to a vacuum-formed retainer or directlyto the brackets, can be used to show the positionof the miniscrew relative to the roots on the pre-and post-placement panoramic or periapical ra-diographs (Fig. 2B). To date, we have not seen

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Fig. 2 A. Surgical guide made from segment ofrectangular wire. B. Metallic marker helps avoidroot damage during miniscrew placement.

A

B

any trauma to anatomic structures during screwplacement. Vessels and nerves are easily avoidedby proper interpretation of the x-ray images. Theroots are more difficult to identify, but damagecan be eliminated by limiting any pilot drilling tothe cortical plate of the alveolar bone (2-3mm). Ifa self-tapping screw encounters a root duringinsertion, it will stop, and can then be redirectedby the clinician.

A manual screwdriver is used to insert theminiscrew, preferably between the free and at-tached gingiva. When properly placed, the screwhead will protrude through the soft tissue. Oncethe initial stability of the miniscrew has beenconfirmed, an orthodontic force of 50-250g canbe applied immediately. The head of the mini-screw has been designed to prevent compressionof the mucosa, but if this occurs after placementof a chain or nickel titanium coil spring, we sug-gest using Monkey Hooks** instead.

Post-operative antibiotics or analgesics are

usually not needed. To the best of our knowl-edge, no post-surgical complications have beenreported in the literature. Once the orthodonticanchorage is no longer required, the screw can beeasily removed with the manual screwdriver,usually without local anesthesia. The mucosagenerally heals within a few days, and new bonefills in the placement site.

Closure of Extraction Spaces

Loss of posterior anchorage during extrac-tion space closure can exacerbate the curve ofSpee and deepen the bite. Miniscrews providereliable skeletal anchorage for anterior retractionin either arch, whether a single tooth at a time oren masse.

Maxillary miniscrews are usually placedbetween the roots of the first and second premo-lars, where the large interradicular space typical-ly allows easy insertion without root interfer-ence. The screw heads can be situated at or abovethe mucogingival line, depending on the desired

Fig. 3 A. Case requiring both intrusion and distal space closure. B. Miniscrew positioned above mucogingivalline. C. Elastomeric chain attached to Monkey Hook instead of directly to miniscrew. D. After space closure.

**American Orthodontics, Inc., 1714 Cambridge Ave., Sheboygan,WI 53082.

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Clinical Applications of the Miniscrew Anchorage System

A

C

B

D

line of action. If both intrusive and distalizingforces are needed, the miniscrew should be posi-tioned above the mucogingival line (Fig. 3). Ifthe primary movement is to be a distalizing vec-tor, however, the miniscrew should be placed atthe mucogingival line (Fig. 4). The higher thescrew is placed in the maxilla, the more perpen-dicular to the bone it must be to avoid damage to

the maxillary sinus (Fig. 5). If the alveolarprocess is prominent, an auxiliary such as aMonkey Hook can be used to keep the chain orcoil spring away from the soft tissue, thus avoid-ing discomfort and gingival irritation (Figs. 3,4).

In the mandibular arch, miniscrews can beuseful in patients where maximum anchorage isneeded, such as bialveolar protrusion and Class

Fig. 5 A. Miniscrew placed high in maxilla must be more perpendicular to bone to avoid damaging maxillarysinus. B. If screw head is at mucogingival level, it should be inclined at 30-45° to interradicular bone.

Fig. 4 A. Patient requiring distal vector of space closure. B. Miniscrew placed at mucogingival line. C. Enmasse retraction of anterior teeth. D. Miniscrews in place after retraction, with no sign of inflammation.

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A B

C D

A B

III cases. We do not recommend placing mini-screws between the roots of the lower first andsecond premolars, however, because of the prox-imity of the mentalis foramen.

Symmetrical Incisor Intrusion

Many patients present with moderate-to-severe deep bites requiring pure intrusion of theanterior teeth to level the occlusal plane. Unlessthe deep bite is so extreme that absolute anchor-age is needed, it may be inadvisable to placeminiscrews simultaneously in both arches inyoung patients. In these cases, miniscrews can beused to reinforce conventional orthodontic mech-anics. One of our most common treatment meth-ods involves the use of biteplanes bonded to thelingual surfaces of two or all four upperincisors.22

To provide anchorage during incisor intru-sion, miniscrews can be placed between theupper lateral incisors and canines (Fig. 6). Theinsertion should not be performed until after lev-eling and alignment, however, so that the maxi-mum amount of interradicular space will beavailable. To avoid tipping the upper incisorsbuccally during intrusion, the ends of the arch-wire should be cinched back.

Correction of a Canted Occlusal Plane

A canted occlusal plane is often consideredimpossible to level with traditional orthodontictreatment. Miniscrews, on the other hand, pro-vide skeletal anchorage for intrusion of theappropriate teeth on the canted side (Fig. 7). Thescrews can be inserted between the upper lateralincisors and canines, the upper canines and pre-molars, or the lower lateral incisors and canines.To avoid interference with the teeth to be intrud-ed, it is important to center the miniscrews be-tween their roots (Fig. 8).

Alignment of Dental Midlines

When an entire arch needs to be moved lat-erally to correct the posterior malocclusion, thedental midlines are usually aligned with inter-maxillary elastics, requiring considerable patientcompliance. Vertical forces may be contraindi-cated in some cases, or the intermaxillary elasticsmay decompensate the arches from a frontalprospective, causing the bite to open. In thesemore complex cases of midline deviation, mini-screws may be a useful alternative. A screw canbe placed either lingually or buccally so that thehead stands out at the crown margins (Fig. 9).

Fig. 6 A. Adolescent patient with deep bite. B. After leveling and alignment, miniscrews placed between upperlateral incisors and canines to reinforce anchorage during incisor intrusion. C. Bite opening with biteplanesbonded to lingual surfaces of upper incisors. D. After incisor intrusion.

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A B

C D

Thus, the line of force is directed more occlusal-ly, with an enhanced horizontal vector.

Extrusion of Impacted Canines

Various procedures have been suggested toprevent anchorage loss and avoid canting of theocclusal plane while an impacted canine is pulleddown into occlusion. Some authors have recom-mended inserting auxiliaries such as KilroySprings** on the main archwire.23 Others haveproposed using superelastic overlay archwires.24

Fig. 7 A. Patient with canted occlusal plane. B. Miniscrew centered between roots of upper lateral incisor andfirst premolar on canted side (ankylosed impacted canine was extracted). C. Intrusion of upper lateral incisorand first premolar. D. After leveling of occlusal plane.

Fig. 8 Miniscrew must be centered between rootsof teeth to be intruded to avoid interferencebetween teeth and screw.

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A

B

C

D

**American Orthodontics, Inc., 1714 Cambridge Ave., Sheboygan,WI 53082.

Fig. 9 A. Patient requiring lateral movement of entire maxillary arch to correct posterior malocclusion.B. Miniscrew placed in existing space between upper right canine and first premolar. C. Elastomeric chainattached between screw and archwire, directing force more occlusally and horizontally. D. After alignment ofdental midlines.

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Clinical Applications of the Miniscrew Anchorage System

A

C

D

B

In both systems, the teeth must be leveled andaligned before they can be combined into ananchorage unit.

Miniscrews can be used instead whenheavy forces are required to bring an impactedcanine into occlusion, without relying on the restof the teeth for anchorage (Fig. 10). Treatmenttime may be shortened—in fact, there is no need

to bond the entire arch during canine extrusion—and there are no undesirable side effects on theother teeth. Whether the canine is impacted pal-atally or lingually, the miniscrew can be placedto provide the most appropriate force vector; itcan even be removed and relocated as the canineis extruded. Auxiliaries can be used to make theminiscrew mechanics even more versatile.

Fig. 10 A. Patient with palatally impacted maxillary right canine. B. Miniscrew placed as anchorage for appro-priate force vector without involving other teeth. C. After uprighting and partial extrusion using only mini-screw, case completed with maxillary fixed appliance. D. Final results, showing root parallelism.

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A

B

C

D

Molar Intrusion

Opinions have differed regarding the effica-cy of orthodontic intrusion of posterior teeth.Although miniscrews can be a reliable source ofanchorage, it is difficult to place them preciselyin the narrow space between the roots of the firstand second molars without interfering with theroots.25 In some cases, more than one screwmight even be needed to withstand a relativelyhigh intrusion force. Therefore, we suggest lim-

iting the use of miniscrews to situations wheresimple intrusion of one or two molars is neededand where placement will be unproblematic(Figs. 11,12). In open-bite cases requiring bilat-eral intrusion of the posterior segments, mini-screws are not an ideal solution.26

Molar Distalization

Fixed and removable maxillary molar dis-talization devices for the correction of Class II

Fig. 11 A. Patient requiring intrusion of maxillary right posterior segment for leveling of occlusal plane. B. Mini-screw inserted in interradicular space between upper right first and second molars, with elastomeric chainused for intrusion. C. After seven months of intrusion, treatment completed with mandibular implants.

Fig. 12 A. Patient requiring intrusion of upper right second molar. B. Miniscrew inserted in edentulous spaceof upper first molar. C. After leveling of anterior teeth, upper arch was prepared with .017" × .022" stainlesssteel archwire, and elastomeric chain was used for intrusion. Case was completed in five months.

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A

B

C

A B C

malocclusions without the need for special pa-tient compliance have become increasingly pop-ular over the past decade. These appliances rangefrom fixed devices that are activated by theorthodontist27-30 to open-coil springs,31-34 butmost utilize some form of palatal coverage toprovide anchorage and prevent incisor flaring.Nevertheless, studies of molar distalization have

shown a considerable amount of anterior anchor-age loss.35

The ideal site for skeletal anchorage wouldbe the palate, but this requires a surgical proce-dure to place the implant and another to removeit. In our experience, screws less than 2mm indiameter are unstable when used for palatalanchorage and routinely fail.

Fig. 13 A. Patient with asymmetrical Class II malocclusion. B. Distal Jet appliance placed and activated.C. Miniscrew positioned mesial to activation locks, blocking mesial movement of appliance. D. After distalmolar movement, further compression of coil spring moves lock away from miniscrew; anchorage loss is pre-vented by bonding light-cured composite between screw head and lock. E. Maxillary left canine moved dis-tally by elastic attached to Distal Jet, then built up with composite for esthetic purposes. F. After completionof molar distalization, Distal Jet converted to passive retainer, and lingual brackets bonded to posterior teeth.G. Five months later, Distal Jet retainer removed, and Class II correction completed.

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A

C

E

G

D

F

B

Fig. 14 A. During molar distalization, compression of Distal Jet’s coil spring moves activation lock distally,away from miniscrew (blue). B. Loss of anchorage can be prevented by bonding light-cured composite (yel-low) between screw head and lock.

Fig. 15 A. Patient with asymmetrical Class II maloc-clusion treated with Distal Jet, with miniscrews placedmesial to activation locks to block mesial movement.B. After molar distalization and removal of Distal Jet,miniscrew repositioned just mesial to distalized molarto stabilize it while the remaining teeth are moved dis-tally.

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A B

A

B

The MAS + Distal Jet** may be a solution.After the Distal Jet appliance has been placedand activated, palatal miniscrews are insertedbetween the roots of the first and second premo-lars, mesial to the activation locks attached to theanterior rests (Fig. 13A-C). The miniscrewsblock mesial movement of the appliance duringdistalization, thus preventing loss of anterioranchorage. Further compression of the DistalJet’s coil springs will move the locks distally,away from the miniscrews (Fig. 14); during thisphase, anchorage loss can be prevented by bond-ing light-cured composite between the screwheads and the locks (Fig. 13D). After molar dis-talization, the Distal Jet is converted to a passiveretainer, and brackets are bonded to the teeth forcompletion of the Class II correction (Fig. 13E-G). Another option is to remove the miniscrewafter molar distalization and replace it just mesialto the distalized molar, where it will stabilize themolar while the remaining teeth are moved pos-teriorly (Fig. 15).

The MAS + Distal Jet should not be used inthe mixed dentition, because the palatal screwmay interfere with developing permanent teeth.

Molar Mesialization

Molars are often moved mesially in ortho-dontic treatment to close extraction spaces oredentulous spaces. Molar mesialization is not asimple movement and can lead to problems suchas loss of anterior anchorage and molar tipping.Furthermore, if there is a knife-edge alveolarridge in the space to be closed, alveolar bonemay be lost.

A miniscrew placed mesial to the space, ata height that will produce a force vector approx-imating the center of resistance of the molar, canbe a valuable source of anchorage. If the screw isinserted after the initial leveling and alignmenthave been completed, a full-size archwire can beused to prevent mesial crown tipping of themolar during space closure. Because mesialmovement is usually slow, especially in themandibular arch, no more than 2-3mm of molarmesialization should be attempted (Fig. 16).

Fig. 16 A. Patient requiring closure of upper and lower residual spaces.B. Miniscrew placed distally to mandibular canine for application ofmesial force against lower molars. C. Class III elastics used for molarmesialization.

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A

B

C

**American Orthodontics, Inc., 1714 Cambridge Ave., Sheboygan,WI 53082.

Intermaxillary Anchorage

Miniscrews are a convenient source ofanchorage in both extraction and nonextractiontherapy when intermaxillary forces are appliedwith Class II elastics or anterior repositioningappliances. Many undesirable side effects can beproduced by such mechanics, including biteopening and excessive proclination and protru-sion of the lower incisors. One possible solution

is to place a miniscrew between the roots of thelower first and second molars or the second pre-molar and first molar. The location between thesecond premolar and first molar (as close as pos-sible to the first molar) is generally preferable,because the screw must be inserted perpendicu-lar to the alveolar process, which can be difficultin more posterior regions where access is limit-ed. In addition, the interradicular space betweenthe second premolar and first molar is wider than

Fig. 17 A. Class III patient with intermaxillary elastics attached from upper second molars to miniscrew insert-ed between lower canines and first premolars. B. After protraction of maxillary arch.

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A B

Fig. 18 A. Patient needing upper third molar, which was severely compromised periodontally and in Brodiebite, to be brought into occlusion and uprighted for prosthetic reasons. B. Sectional rectangular wire used toupright third molar, with fixed biteplane bonded for immediate bite opening. C. Palatal miniscrew used forskeletal anchorage to allow application of inward and upward force vector, limiting molar extrusion and cor-recting Brodie bite. D. Third molar alignment after less than five months of treatment.

A

B C

D

the space between the first and second molars.Placement of the miniscrew mesial to the firstmolar may also prevent mesial movement of theentire lower arch, although care must be taken toavoid contact with the molar roots.

In Class III treatment, when the maxillaryarch needs to be advanced, miniscrews can beplaced between the roots of the lower caninesand first premolars for elastic attachment (Fig.17). If the mandibular arch needs to be reposi-tioned distally, the miniscrews can be placedbetween the roots of the upper first and secondmolars or second premolars and first molars.

Upper Third Molar Alignment

Miniscrews can also be useful in cases withmultiple missing teeth where conventional ortho-dontic mechanics are difficult to apply. Forexample, an upper third molar can be uprightedwith a fixed sectional wire, utilizing a palatalminiscrew for skeletal anchorage to limit un-wanted extrusion of the molar (Fig. 18).

Discussion

Miniscrews are already widely used inEurope and Asia, but there is still some skepti-cism in the United States, where many orthodon-tists consider them too invasive to be part of theirdaily practice routines. One concern is whetherplacement of a miniscrew should be performedby the orthodontist or the oral surgeon. MostAmerican orthodontists refer out any procedurethat is not strictly orthodontic, such as oral hy-giene or extraction of permanent teeth, even if itis part of the orthodontic treatment plan. In ouropinion, however, placement of a miniscrew isnot simply a surgical procedure, but requires spe-cific planning based on orthodontic considera-tions such as force vectors and the types of anch-orage and tooth movement required. Sometimesthe screw needs to be relocated to a better posi-tion during treatment, which may become com-plicated if the patient has to be referred to a spe-cialist.

Histological studies have confirmed thattitanium screws are biocompatible and are easily

removed because of their incomplete osseointe-gration.10,25 What is still unknown is whether dif-ferences in size, shape (conical or cylindrical),head design, pilot drilling, and physical proper-ties can influence the likelihood of successfultreatment or minimize potential complicationssuch as breakage at the neck during the applica-tion of orthodontic forces. One potential problemis the trend toward reduced diameters of self-tap-ping screws. We believe this could lead to a dan-gerous reduction in their mechanical resistance,and therefore consider testing to breakage in tor-sion and flexion to be a fundamental step beforethe clinical application of any new miniscrews.In our preliminary testing of the MAS screws, wefound they were able to resist forces muchgreater than any applied in orthodontic treat-ment, but that caution was required during inser-tion and removal to avoid applying torsionalforces that might break the screws.

Conclusion

Although more research is needed intomany aspects of miniscrew application, the casespresented in this article and elsewhere in the lit-erature clearly demonstrate the versatility andtechnical advantages of skeletal anchorage. Inour opinion, orthodontic treatment using a skele-tal anchorage system is not only more effective,but offers a variety of treatment alternatives inchallenging cases where traditional mechanicscannot be used. Advantages of miniscrews overother forms of anchorage include:• Optimal use of traction forces, regardless ofthe number or positions of the teeth• Applicability at any stage of development, in-cluding interceptive therapy• Shorter treatment time, with no need to preparedental anchorage• Independence of patient cooperation• Patient comfort• Low cost

Of course, there are potential complicationscommon to all implant procedures, including:• Damage to anatomic structures such as nerves,vessels, and roots• Loss of a screw during placement or loading

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• Breakage of a screw within the bone duringinsertion or removal• Inflammation around implant sites

With the MAS, we have experienced noneof these problems except for the loss of threescrews during force loading. Breakage may bemore likely with screws of smaller diameter.Furthermore, the MAS offers several advantagescompared to more invasive osseointegrated sys-tems:• Increased selection of insertion sites• Ease of insertion and removal• Ability to withstand immediate loading• Applicability in growing patients• Low cost

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3. Celenza, F. and Hochman, M.N.: Absolute anchorage in ortho-dontics: Direct and indirect implant-assisted modalities, J.Clin. Orthod. 34:397-402, 2000.

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6. Block, M.S. and Hoffman, D.R.: A new device for absoluteanchorage for orthodontics, Am. J. Orthod. 107:251-258, 1995.

7. Umemori, M.; Sugawara, J.; Mitani, H.; Nagasaka, H.; andKawamura, H.: Skeletal anchorage system for open-bite cor-rection, Am. J. Orthod. 115:166-174, 1999.

8. Mura, P.; Maino, B.; and Paoletto, E.: Midplant: L’ancoraggioassoluto in ortodonzia, Ortod. Tecnica 3:7-11, 2000.

9. Daimaruya, T.; Nagasaka, H.; Umemori, M.; Sugawara, J.;Mitani, H.: The influences of molar intrusion on the inferioralveolar neurovascular bundle and root using the skeletalanchorage system in dogs, Angle Orthod. 71:60-70, 2001.

10. Sugawara, J.; Baik, U.B.; Umemori, M.; Takahashi, I.; Naga-saka, H.; Kawamura, H.; and Mitani, H.: Treatment and post-treatment dentoalveolar changes following intrusion of mandi-bular molars with application of a skeletal anchorage system(SAS) for open bite correction, Int. J. Adult Orthod. Orthog.Surg. 17:243-253, 2002.

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24 JCO/JANUARY 2005

Clinical Applications of the Miniscrew Anchorage System