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CLINICIAN’S CORNER

Selective alveolar corticotomy to intrudeovererupted molarsDauro Douglas Oliveira,a Bruno Franco de Oliveira,b Helio Henrique de Araújo Brito,c

Margareth Maria Gomes de Souza,d and Paulo José Medeirose

Belo Horizonte and Rio do Janeiro, Brazil

Orthodontic intrusion of overerupted molars in adults is challenging for most clinicians. Efficient intrusion canbe achieved by combining selective alveolar corticotomies with a modified full-coverage maxillary splint toreduce surgical risks, treatment time, and costs for both orthodontists and patients. (Am J Orthod Dentofacial
Orthop 2008;133:902-8)
Orthodontic treatment of overerupted molarshas always been considered challenging formost orthodontists. Pure intrusion can only be

achieved when an adequate anchorage system supportslight and continuous forces that are directed through thetooth’s center of resistance.1,2 This approach is partic-ularly difficult when posterior teeth must be intruded inadults. The lack of compensation through growth3 andthe slower biologic response to orthodontic forces,when compared to younger patients,4,5 increase thecomplexity of this procedure. More adults now seekorthodontic care. Consequently, clinicians might seepatients who need molar intrusion more often.

The correction of supraerupted molars with conven-tional fixed appliances can lead to undesirable extrusionof the adjacent teeth that function as anchor units,lengthening the overall treatment time and compromis-ing the results.6 Various approaches have been pro-posed to intrude overerupted molars, including vertical-pull headgears,7 removable appliances with elastics,8

modified palatal arches,9 elastomeric chains,10 mag-nets,11 and skeletal anchorage systems.12,13 The needfor patient cooperation for long time periods and thedifficulties in applying well-controlled force systemshave been suggested as limitations of these earlymethods of molar intrusion.14 Although the use of

aProgram director, Orthondontic Graduate Program, Pontifical Catholic Uni-versity, Belo Horizonte, Brazil.bPrivate practice, Belo Horizonte, Brazil.cAdjunct professor, Pontifical Catholic University of Minas Gerais, BeloHorizonte, Brazil.dAdjunct professor, Federal University of Rio de Janeiro, Rio de Janeiro,Brazil.eAdjunct professor of oral surgery, Federal University of Rio de Janeiro, Rio deJaneiro, Brazil.Reprint requests to: Dauro D. Oliveira, Av Cristóvão Colombo, 550/404, BeloHorizonte, MG, Brazil, 30140-150; e-mail, [email protected], June 2006; revised and accepted, July 2006.0889-5406/$34.00Copyright © 2008 by the American Association of Orthodontists.
doi:10.1016/j.ajodo.2006.07.030
902

mini-titanium screws solved most anchorage problemswhen intrusion of posterior teeth is required, individualanatomical variations might impose limitations foradequate implant placement in some patients.15 Unsat-isfactory implant positioning can result in undesiredsequelae, such as root perforations,16 or lead to inap-propriate direction of intrusive forces, compromisingtreatment efficiency.

Tooth movement efficiency can be increased whenwell-planned force systems are applied to bony tissuesthat offer less resistance against the desired move-ment.1,17 Therefore, faster orthodontic movement takesplace, and treatment goals can be achieved in a shortertime, without compromising the results. Since treat-ment efficiency is always a concern in adult orthodon-tics, how can it be achieved when molar intrusion isneeded? Overall, orthodontic tooth movement is accel-erated when performed under increased bone turnoverconditions18 caused by either pharmacologic modula-tion19,20 or hormonal alterations.21,22 However, thesepossibilities have not yet reached routine application inthe daily orthodontic practice. The physiologic alter-ations observed when the bony tissues respond to atraumatic stimulus might help to elucidate an alterna-tive approach that could create a localized area ofincreased bone turnover and, consequently, decreasedresistance to tooth movement.

When responding to a traumatic stimulus, the bonytissues initially have a biologic stage called regionalacceleratory phenomenon characterized by a transientincrease in bone turnover and a decrease in trabecularbone density.23 After fractures or surgical osteotomies,the regional acceleratory phenomenon significantlystimulates healing and tissue reorganization by a tem-porary burst of localized tissue remodeling.24 Alveolarcorticotomies are surgical interventions limited to cor-tical bone that were suggested as an alternative to
facilitate the treatment of complex occlusal problems
mailto:[email protected]

American Journal of Orthodontics and Dentofacial OrthopedicsVolume 133, Number 6

Oliveira et al 903

combined with orthodontic therapy.25 Although nostudies have directly investigated whether corticoto-mies result in alveolar bone regional acceleratory phe-nomena or how they influence tooth movement, clinicalreports have shown that orthodontic movement waspotentiated when started shortly after selective alveolarcorticotomies.26,27

The initial reports on combining orthodontic ther-apy and alveolar corticotomies suggested that treatmentwas facilitated because the bone blocks limited by thesurgical cuts could be moved individually by using thecrowns of the teeth as handles to which orthodonticforces were applied.25-28 Wilcko et al29 questionedthese statements, implying that the healing stimulusgenerated by the corticotomy leads to increased boneturnover and a less dense trabecular bone. The authorssuggested that decreased trabecular bone density andnot movement of independent bone blocks would betterexplain the effects of alveolar corticotomies on orth-odontic therapy. Despite these opposing points of view,all clinical reports showed increased treatment effi-ciency. This article describes the combination of selec-tive alveolar corticotomies and a modified full-cover-age maxillary splint to efficiently intrude overeruptedmolars in adult patients.

Surgical procedure

The surgeries were performed with the patientsunder local anesthesia. Full-thickness flaps were raisedon both buccal and lingual surfaces to expose thealveolus surrounding the overerupted maxillary firstmolars. Cortical bone was removed by using a #701surgical bur under continuous and abundant irrigationwith cold sterile saline solution. Vertical cuts weremade on both mesial and distal interproximal areasstarting 2 to 3 mm above the alveolar crest andextending 2 to 3 mm past the estimated root apices. Ahorizontal corticotomy was performed connecting theinterdental cuts. Several small round perforationsequivalent to the bur diameter were also made insidethe areas circumscribed by those cuts (Fig 1) to increasethe healing stimulus. All surgical cuts were made in thecortical plate, barely penetrating the trabecular bone.After careful irrigation, the gingival flaps were reposi-tioned and sutured appropriately. Antibiotics and anti-inflammatories were prescribed from 24 hours before to3 days postsurgery.

Intrusion appliance design

Maxillary and mandibular alginate impressionswere taken, and the working models obtained withstone were mounted in a hinge axis articulator. A
full-coverage flat-plane maxillary splint was fabricated
with acrylic. Ball clasps were added between the firstpremolars and the canines to increase appliance reten-tion, and small J-hooks were placed on both buccal andlingual surfaces of the first molars. The acrylic coveringthe maxillary first molars’ occlusal surfaces was re-moved to allow intrusion force delivery. Closed Sen-talloy coils (GAC International, Islandia, NY) were tiedto the J-hooks with steel ligatures (Fig 2) to allowconstant 100-g intrusive forces apically through thecenter of resistance of the molars.

PATIENT 1

A 36-year-old woman was referred to the Depart-ment of Orthodontics of the Pontifical Catholic Univer-sity of Minas Gerais in Brazil for an evaluation aboutthe chances of intruding overerupted maxillary rightand left first molars. The patient reported losing allmandibular first and second permanent molars in earlyadolescence. These teeth had never been replaced,resulting in overeruption of both maxillary first molars(Fig 3, A).

Three treatment options to level her maxillaryocclusal plane were presented: (1) restorative levelingwith full crowns and possible need for root canaltreatment, as well as periodontal surgery to obtainappropriate cemento-enamel junction dimensions; (2)subapical osteotomies for immediate bone-block intru-sion; and (3) selective alveolar corticotomies followedby orthodontic treatment to intrude the maxillary firstmolars. The patient was informed of the risks, advan-tages, and disadvantages of all therapeutic approaches.She decided to undergo orthodontic treatment aftercorticotomies and signed a consent form assuming allresponsibilities for her decision.

Seven days after surgery, orthodontic forces wereapplied with the modified maxillary splint previouslydescribed. The patient reported mild postcorticotomydiscomfort, describing it as similar to the soreness she

Fig 1. Selective alveolar corticotomy.

felt after previous tooth extractions. She followed the

ith sup

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904 Oliveira et al

recommendations for full-time appliance wear, exceptduring meals and oral-hygiene procedures. Two and ahalf months after the force application, the maxillaryfirst molars were fully intruded (Fig 3, B). At this point,fixed appliances were placed to continue treatment,and, 3 months later, progress records were obtained forreevaluation (Fig 3, C). Cephalometric superimpositionbefore treatment and 6 months into treatment showed

Fig 2. Modified maxillary splint w

Fig 3. Patient 1. Intraoral photographs: A,application; C, 6 months postcorticotomy.

complete and pure intrusion of the overerupted molars

(Fig 4, A), without commonly seen side effects, such asclockwise rotation of the mandible and anterior biteopening. Comparison of the periapical radiographsshowed improvement in the crown-to-root ratios, noadjacent tooth extrusion, and no root resorption (Fig 4, B).

PATIENT 2

A 39-year-old man sought prosthodontic care to

erelastic nickel-titanium springs.

atment; B, 2.5 months after intrusive force
pretre
restore his edentulous regions and improve mastication.

luatio


Oliveira et al 905

He prematurely lost all mandibular molars due tocarious lesions. Consequently, the maxillary first andsecond permanent molars on both the right and leftsides overerupted. Intrusion of these molars was re-quired for prosthetic reestablishment of appropriatefunction. The patient did not want either extracting andsubstituting the overerupted molars by implants orsubapical surgery for immediate molar repositioning.He decided to undergo selective alveolar corticotomiesand orthodontic intrusion.

The extension of the surgical cuts was the onlydifference in relation to the surgical technique de-scribed above. Surgical cuts surrounded both molars onthe labial surface and the proximity to the palatineartery limited the vertical cuts lingually. One weekpostsurgery, orthodontic forces were applied with themodified full-coverage maxillary splint. The maxillarythird molars contributed to appliance stability. After 4months of full-time wear, occlusal plane leveling wasobserved (Fig 5).

DISCUSSION

Posterior teeth that are supraerupted due to early

Fig 4. Patient 1. A, Pretreatment and 6-mosuperimpositions; B, periapical radiograph eva

loss of their antagonists are commonly seen in adults

without access to dentistry during childhood and ado-lescence. Conventional treatment options to correctovererupted molars include crown reduction followedby full-coverage restorations30,31 or posterior segmen-tal osteotomy to impact the elongated segments.32

Although still used, both clinical approaches havedisadvantages. While the first method usually removessound tooth structures frequently requiring endodontictreatment and periodontal surgery, the second has therisks associated with general anesthesia and highercosts. Thus, orthodontic intrusion of overerupted mo-lars would increase the quality of the multidisciplinarytreatment needed to restore appropriate function inthese patients.

Orthodontic treatment efficiency is especially im-portant when treating adults. These patients have spe-cific demands and usually want to achieve their treat-ment goals as soon as possible to reduce the negativeeffects of orthodontic appliances in their social andprofessional lives. An ideal scenario for efficient toothmovement combines well-planned force delivery sys-tems1 and decreased alveolar trabecular bone densitywhere the resistance against the desired movement is

rogress overall and maxillary cephalometricn, pretreatment and postintrusion.

nth p

reduced.17 The optimum force system for molar intru-


906 Oliveira et al

sion is obtained when low and continuous forces areapplied apically through the tooth’s center of resistancefrom both the buccal and lingual sides.33 Adequateanchorage units are also required to eliminate or min-imize undesired side-effects from the reactive forces.2

The previously reported orthodontic approaches formolar intrusion fulfill only some of these requirements.

The modified full-coverage maxillary splint wepropose might overcome some limitations of the earlymethods described for orthodontic intrusion ofovererupted molars. Vertical-pull headgears deliverintrusion forces only from the molar buccal surface,and a tipping moment is created.34 The application ofintrusive forces with elastics8 or elastomeric chains10

requires frequent reactivations due to early force deg-radation35,36; this can be impractical for both patientand orthodontist. We suggest superelastic nickel-tita-nium springs, which permit constant force applicationover a wide range of activation without requiringfrequent checkups.37 The modifications in maxillarysplint design allow the intrusive forces from both thebuccal and lingual surfaces, eliminating the tippingmoment noticed with high-pull headgears.

Although skeletal anchorage systems solved theneed for patient cooperation, anatomical variations canlimit ideal micro-titanium screw placement in somepatients who require molar intrusion.15 When mini-implants are not placed correctly, the resultant line ofintrusion force passes away from the molar’s center ofresistance, generating uncontrolled rotational moments

Fig 5. Patient 2. A, Surgical procedure; B, intrumodel after 4 months of intrusion.

and decreasing intrusion efficiency. The intrusion ap-

pliance shown in this article might be a viable alterna-tive when ideal implant positioning is risky or impos-sible. During appliance construction, the hooks thatserve as points of force application are positioned tocreate a line of force directed apically through thecenter of resistance of the molars. In addition, the use ofthe entire occlusion as the anchorage unit for molarintrusion has been successfully reported.8,33 However,the dependence on patient cooperation is a disadvan-tage of the suggested approach. To overcome thislimitation, selective corticotomies were performed toincrease alveolar bone response, reducing treatmenttime and consequently diminishing the demand foroverall appliance wear.

The successful clinical application of corticotomy-facilitated orthodontics has been shown to reducetreatment time in adults26,27 as an intermediate therapybetween orthognathic surgery and conventional orth-odontics to correct moderate skeletal malocclusions,38

and before the application of orthodontic forces onovererupted molars.6,39 Mostafa et al6 described suc-cessful molar intrusion combining corticotomy andfixed edgewise appliances. Although they did notmention the amount of force applied, rapid movementof the tooth-bone segment without anchorage loss wasreported. Hwang and Lee39 demonstrated the correctionof supraerupted molars after performing localized cor-ticotomies and applying orthodontic forces with full-time wear of magnetic appliances and night use of avertical-pull chincup. Despite earlier reports that ap-

ppliance; C, pretreatment model; D, progress
sion a
proximately a force of 90 g per tooth is required for


Oliveira et al 907

molar intrusion,40 a force of more than 90 g was exertedwith repelling magnets because the authors believedthat heavier forces were necessary to move the boneblock with the tooth. The theory of bone-block move-ment has been used to explain orthodontic movementafter alveolar corticotomies since the introduction ofthis therapeutic approach.25-28 However, the postsur-gery increase in regional bone turnover was suggestedas a more adequate explanation for this phenomenon.41

While the influence of corticotomy on alveolar bonephysiology and tooth movement has not been directlyinvestigated, indirect evidence might support the in-creased bone turnover theory. Animal studies showedthat orthodontic tooth movement is faster under in-creased alveolar bone turnover conditions.18-22 In ad-dition, the initial bony-tissue response to a traumaticinjury is an increase in bone turnover.23,24 Based on thisevidence, we decided to use orthodontic forces in therange needed for tooth intrusion, applying 100 g pertooth to be intruded.

The results reported here showed 4 mm of intrusionon the maxillary right and left molars within 2.5 monthsin 1 patient and 3 to 4 mm in 4 months on both themaxillary right first and second molars on the secondpatient. These findings are similar to those reported byHwang and Lee.39 Other orthodontic treatment ap-proaches obtained molar intrusion without previousselective corticotomies. However, the average activetreatment time required for complete intrusion waslonger. Yao et al13 used skeletal anchorage to obtain anaverage of 3 to 4 mm of intrusion in 7.6 months.Sherwood et al42 obtained 4 mm of intrusion in 6.5months using mini-titanium plates, and Enacar et al9

registered approximately 4 mm of intrusion in 8.5months using a modified transpalatal arch. The resultsin our patients reported here indicate that the healingstimulus caused by the corticotomies might reduce theoverall treatment time required to intrude overeruptedmolars. However, animal studies and further researchwith larger clinical samples are needed to better under-stand how corticotomies affect alveolar bone metabo-lism and orthodontic tooth movement.

This treatment approach combines a simple andlow-cost modified maxillary splint designed to deliverideal intrusive forces. The use of Sentalloy coils allowsconstant force exertion over longer periods of time, andthe transparent appliance might not compromise esthet-ics. Incorporating localized corticotomies shortly be-fore orthodontic treatment appears to decrease bony-tissue resistance against the intrusion forces, increasingtreatment efficiency and reducing the demand for over-
all appliance wear and patient cooperation.
This therapeutic approach might be a viable optionwhen skeletal anchorage has risks to the patient orrestricts the application of adequate intrusion forcedirection. It should also be considered if the patientdesires a shorter treatment time.

CONCLUSIONS

Successful intrusion of overerupted molars is a signif-icant clinical challenge to orthodontists. Although pros-thetic leveling of the occlusal planes might restore soundteeth, subapical interventions for immediate repositioninghave surgical risks and higher costs. Therefore, an inter-mediate alternative to increase treatment efficiency andminimize patient discomfort would be welcome. Ourpatients demonstrated that combining selective alveolarcorticotomies with a full-coverage splint modified toincorporate superelastic nickel-titanium coils can be aviable alternative to efficiently intrude overerupted max-illary molars and reduce surgical risks, treatment time, andcosts for both orthodontists and patients.

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