CASE REPORT

Correction of bilateral impacted mandibularcanines with a lip bumper for anchoragereinforcement

Sachin Agarwal,a Sumit Yadav,b Neelesh V. Shah,c Ashima Valiathan,d Flavio Uribe,e and Ravindra Nandaf

Farmington, Conn, Navi Mumbai and Karnataka, India, and Cleveland, Ohio

aResidFarmibAssisCentecSenioD. Y.dProfeDentoKarnaOhio.eAssoCentefProfeCenteThe aproduReprinDivisiCT 06Subm0889-Copyrhttp:/

Multiple treatment options are available to patients with impacted manibular canines in addition to a retained de-ciduous canine. This article describes the treatment of a prepubertal girl, aged 10 years 6 months, with a skeletalClass I, dental Class II Division 1 malocclusion, retrognathic mandible, deep overbite, proclined maxillary inci-sors, midline diastema, and bilateral mandibular canine impaction. The orthodontic treatment plan included ex-traction of the deciduous canine and forced eruption of the impacted canines. A modified lip bumper appliancewas used both for forced eruption and to reinforce anchorage. Through the collaborative efforts of an orthodontistand an oral surgeon, an excellent esthetic and functional outcome was achieved. (Am J Orthod DentofacialOrthop 2013;143:393-403)

In the human dentition, maxillary and mandibularcanines are a necessity from both esthetic and func-tional perspectives. Maxillary canines are the most

commonly impacted teeth after the third molars.1 Mostimpacted canines remain asymptomatic; however,a number of potential implications have been suggested:labial or lingual malpositioning of the impacted tooth;migration of the neighboring teeth and loss of archlength; external root resorption of the impacted toothand the neighboring teeth; infection, particularly withpartial eruption resulting in pain and trismus; and re-ferred pain.2,3 Unerupted or partially erupted canines

ent, Division of Orthodontics, University of Connecticut Health Center,ngton, Conn.tant professor, Division of Orthodontics, University of Connecticut Healthr, Farmington, Conn.r lecturer, Department of Orthodontics and Dentofacial Orthopaedics, Dr.Patil Dental College and Hospital, Nerul, Navi Mumbai, India.ssor, Director of Post Graduate Studies, Department of Orthodontics andfacial Orthopaedics, Manipal College of Dental Sciences, Manipal,taka, India; adjunct professor, Case Western Reserve University, Cleveland,

ciate professor, Division of Orthodontics, University of Connecticut Healthr, Farmington, Conn.ssor and head, Division of Orthodontics, University of Connecticut Healthr, Farmington, Conn.uthors report no commercial, proprietary, or financial interest in thects or companies described in this article.t requests to: Ravindra Nanda, 263 Farmington Ave, L 7063 MC 1725,on of Orthodontics, University of Connecticut Health Center, Farmington,030; e-mail, nanda@uchc.edu.itted, revised and accepted, December 2011.5406/$36.00ight � 2013 by the American Association of Orthodontists./dx.doi.org/10.1016/j.ajodo.2011.12.030

can increase the risk of infection and cystic follicularlesions and can compromise the life span ofneighboring lateral incisors caused by root resorption.2,3

The incidence of mandibular canine impaction isabout 20 times less than impaction of the maxillary ca-nines.4 Treatment options for mandibular canine impac-tion are surgical extraction with premolar substitution,5

autotransplantation,6 and surgical exposure and erup-tion into the dental arch.7 Factors that influence the po-tential problems and complexity for the treatment ofimpacted canines are timing of the orthodontic treat-ment, type of surgical procedure to expose the impactedtooth, orthodontic mechanics, position of the impactedtooth in the arch,8 and eruption status of neighboringteeth. Maxillary canines erupt by the age of 11 to 13years; when the signs and symptoms of impacted ca-nines are evident, nearly all permanent teeth exceptthe second and third molars are present in the oral cavity.Unlike the maxillary canines, the mandibular canineserupt by the age of 9 to 10 years, and the permanent in-cisors and first molars are the only other permanentteeth erupted by this time, resulting in an increased de-mand for anchorage control for the management of im-pacted mandibular canines. This case report describesthe treatment of a patient with bilateral mandibular ca-nine impactions in the midsymphyseal region.

DIAGNOSIS AND ETIOLOGY

A girl, aged 10 years 6 months, came with a chiefcomplaint of proclined maxillary anterior teeth and in-creased overjet. She was diagnosed with a skeletal Class

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Fig 1. Pretreatment facial and intraoral photographs.

394 Agarwal et al

I and dental Class II Division 1 malocclusion with a retro-gnathic mandible, deep overbite, proclined maxillary in-cisors, midline diastema, and bilateral mandibularcanine impaction.

Her medical history was not contributory. The pre-treatment facial photographs showed a brachyfacial,symmetric face and a convex soft-tissue profile causedby a retrognathic mandible. Upon smiling, 7 mm(90%) of occlusogingival length of the maxillary centralincisors was visible (Fig 1). The lower lip was everted, andthere was no functional problem. The pretreatment in-traoral photographs and dental casts showed that thepatient was in the mixed dentition. The first and seconddeciduous molars, permanent incisors, and first perma-nent molars were erupted in the oral cavity. She hadmaxillary and mandibular dental midlines coincidentwith her facial midline. The overbite was deep at 70%,with the mandibular incisors touching the palatal mu-cosa. Overjet was 8 mm. There were 8 mm of spacingin the maxillary arch and 1 mm of crowding in the man-dibular arch. The molar relationship was end-on (Class II)

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half a cusp width distoclusion of the molars on both thesides (Fig 2).

The pretreatment lateral cephalogram and orthopan-tomogram (Fig 3) showed that both mandibular canineswere impacted apically and labially to the mandibular in-cisors, in amirror-image-like pattern, with both canines inthe midsymphyseal region of the mandible. The long axesof the right and left impacted canines had angles of 35�

and 24�, respectively, with the midline on the panoramicradiograph. The crowns of both canines could be palpateddigitally in the labial mandibular sulcus. No signs of exter-nal apical root resorption were observed on the roots ofthe deciduous canines. The cephalometric analysis(Table) showed a skeletal Class I relationship (ANB angle,3�) with a flat mandibular plane angle (SN-GoGn angle,27�), a retrognathic mandible (SNB angle, 75�), proclinedmaxillary incisors (U1-NA, 12 mm and 59�), and uprightmandibular incisors (L1-NB, 4 mm and 27�).

The reported frequencies of mandibular canine im-paction range from 0.05% to 0.4%.4,9,10 No definitiveetiology has been reported as a causative agent for

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Fig 3. Pretreatment lateral cephalogram and orthopanto-mogram.

Fig 2. Pretreatment models.

Agarwal et al 395

mandibular canine impactions. However, genetics,obstructions to the eruption path, and abnormaldisplacement of the dental lamina in embryonic lifemight lead to impaction or ectopic eruption of themandibular canines.11

TREATMENT OBJECTIVES

The treatment objectives for this patient were as fol-lows: (1) get the bilaterally impacted mandibular canineinto the arch, (2) correct the deep overbite and the in-creased overjet, (3) close the spaces in the maxillaryarch, (4) correct the malalignment of the mandibular an-terior teeth, (5) achieve bilateral Class I canine and molarrelationships, and (6) improve the facial balance.

TREATMENT ALTERNATIVES

The possible solutions for correction of the impactedmandibular canines were the following.

1. Extraction of the bilaterally impacted mandibularcanines, while preserving the deciduous canines tofunction in place of the permanent canines. Al-though there was no obvious external apical root re-sorption of the mandibular deciduous canines, theseteeth would not be bonded during fixed appliancetreatment to prevent any resorption of their roots.After the fixed appliance phase, the vertical dimen-sions of these teeth would need to be restored. Forthe long-term preservation of these teeth, canine-guided occlusion would be avoided.12

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Table. Cephalometric analysis

Pretreatment Posttreatment PostretentionSNA 78� 80� 80�

SNB 75� 78� 78�

ANB 3� 2� 2�

Occ-FH 6� 4� 4�

SN-GoGn 27� 25� 25�

FMA 20� 18� 18�

U1-SN 130� 116� 117�

U1-NA 12 mm, 59� 7 mm, 35� 8 mm, 37�

L1-NB 4 mm, 27� 6 mm, 33� 6 mm, 34�

IMPA 101� 108� 109�

Y-axis 57� 55� 55�

G0-Sn-Pg0 153� 160� 160�

Ul-L1 100� 110� 109�

U1-A-Pg 14 mm 9 mm 10 mm

U1, Upper incisor; L1, lower incisor.

396 Agarwal et al

2. Extraction of the deciduous canines and auto-transplantation of the mandibular permanent ca-nines was considered as a possible solution. Onlya few reports describing autotransplantation of animpacted mandibular canine have been reported inthe literature.6 To the best of our knowledge, no lon-gitudinal study has evaluated the transplantation ofmandibular canines. In the present case, the rootformation of the mandibular canines was two thirdscomplete, making them ideal to be transplanted, butthe procedure would require extensive removal ofbone from the thin midsymphyseal region of themandible, which could have jeopardized the adja-cent teeth.

TREATMENT PLAN

Orthodontic correction of mandibular impacted ca-nines necessitates a stable source of anchorage. Theonly teeth available to provide anchorage were the man-dibular first permanent molars. To reinforce the anchor-age, an assembly was fabricated in which both firstpermanent molars were connected by using a 0.040-inround stainless steel lingual arch (Fig 4). On the buccalside of the molar bands, stainless steel tubes with an in-ternal diameter of 0.030 in were soldered. The length ofthe tube was adjusted so that the mesial end was at themidbuccal point of first deciduous molar. The stainlesssteel tubes were curved according to their respectivearch-form segments. A lip bumper was fabricated from0.021 3 0.027-in stainless steel ovoid archwire by add-ing self-cured acrylic resin in the incisor region. At thedistal legs of the lip bumper, a few bends were madethat would friction lock it once the distal legs weredrawn through the stainless steel tubes. Small steel

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hooks were soldered onto the wire of the bumper justdistal to the acrylic part for engaging the elastics. Thesehooks limited the distance that the leg of the lip bumpercould go into the stainless steel tube, thus keeping theacrylic pad 4 mm away from the mandibular incisorsand transferring the distal force from the lip to themolars.

A distalizing and extrusive force was applied bythe elastomeric chain on the canines from the steelhooks soldered on the lip bumper. This force was ex-pected to produce controlled tipping of the caninesaround the center of rotation at the root tip apex(Fig 5). A reactionary force acting on the molar thusmight result in mesial tipping of the molar. Sincethe acrylic pad of the lip bumper was at the middleof the crown of the mandibular incisors, a distal forcewas expected to be experienced by the molars, whichwould counteract the mesial reactionary force(Fig 5).13,14

TREATMENT PROGRESS

The maxillary incisors, mandibular incisors, and max-illary molars were bonded with a 0.022-in MBT pread-justed appliance (3M Unitek, Monrovia, Calif). In themaxillary arch, a 0.016-in nickel-titanium archwire wasplaced for leveling. The molar band assembly incorpo-rating the lingual holding arch, and the soldered stain-less steel tube were cemented on the mandibularmolars. Surgical exposure of the impacted canines wasdone using a closed-eruption technique by raisinga full-thickness mucoperiosteal flap and bonding a but-ton with an attached gold chain on the crown of theimpacted mandibular canines.

After 2 weeks of soft-tissue healing, the lip bumperwas fitted by inserting the distal legs into the buccalstainless steel tube until the soldered stainless steelhooks came into contact with the mesial end of thetube. A force of 75 g was applied to the canines by at-taching an elastomeric chain from the distal end of thegold chain to the soldered stainless steel hooks. A pan-oramic radiograph taken 1 month after the initial ap-plication of the force (Fig 6) showed initialuprighting of the impacted mandibular canines. Theelastomeric chain was changed every 4 to 5 weeks. Af-ter 15 months of treatment, the left canine was visiblein the oral cavity (Fig 7). The lip bumper was removed,the mandibular left canine and the first permanent pre-molars were bonded, and a 0.016-in nickel-titaniumarchwire was inserted for alignment of the teeth. Anextrusive force on the mandibular right canine wascontinued from the mandibular right first premolarfor the next 6 months, until it had erupted enough

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Fig 4. Appliance design.

Fig 5. Biomechanics: F, Force applied by elastic power chain on canines; Fr, reactionary force felt bymolars from F; CROT, center of rotation; FB, force produced by the lip bumper.

Agarwal et al 397

in the oral cavity to be bonded (Fig 8). The assembly(lingual arch and stainless steel tubing) on the molarswas removed, and brackets were bonded to correct

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the mesiodistal and buccolingual positions of the ca-nines. Progressive panoramic radiographs showed con-tinuous eruption of the mandibular right canine and

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Fig 6. Radiographs showing initial uprighting of the impacted canines.

Fig 7. Mandibular left canine erupted into the oral cavity.

Fig 8. Both mandibular canines erupted into the oral cavity.

398 Agarwal et al

simultaneous uprighting of the roots mesiodistally (Fig9). It took about 9 months to adjust the occlusion andget the molars and canines into a Class I relationship.The total treatment time was 30 months.

TREATMENT RESULTS

At the end of the treatment, a well-aligned dentitionwith Class I molar and canine relationships was achieved.The patient had a consonant smile arch, the teeth hadgood interdigitation, and normal overjet and overbitewere achieved. The maxillary midline was coincidentwith the facial midline, and the mandibular midlinewas shifted to the right by 1 mm (Figs 10 and 11). Theposttreatment panoramic radiograph showed no appar-ent root resorption and well-aligned root angulation of

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the teeth (Fig 12). The cephalometric analysis showeda decrease in ANB from 3� to 2� (Table). The proclinationof the maxillary incisors was decreased (from 59� to 35�),whereas the mandibular incisors became more proclined(from 27� to 33�).

The posttreatment intraoral photographs showednormal clinical crown length of both mandibular ca-nines. The gingival tissue looked healthy, with no gin-gival recession or periodontal pockets with anadequate zone of attached gingiva. There were somewhite spot lesions and some interdental papillaryovergrowth in the mandibular labial region. Canine-to-canine lingual bonded retainers were placed inboth arches. After 2 years in retention, the occlusionwas well maintained, with minimal apparent gingival

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Fig 10. Posttreatment facial and intraoral photographs.

Fig 9. Panoramic radiographs show continued root correction of the mandibular right canine.

Agarwal et al 399

recession observed in the mandibular canines (Figs 13and 14). Overall and regional superimpositionsshowed favorable growth of the mandible and im-provement of overjet (Fig 15).

American Journal of Orthodontics and Dentofacial Orthoped

DISCUSSION

Nodine11 reported that the frequency of impaction ofthe mandibular left canine is greater than the mandibu-lar right canine, and there is a sexual prediposition, with

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Fig 11. Posttreatment models.

Fig 12. Posttreatment lateral cephalogram and ortho-pantomogram.

400 Agarwal et al

impaction occuring more commonly in females. Joshi15

stated that absence of the developing mandibular canineunder the deciduous canine delays the resorption pro-cess and results in an overretained deciduous canine.In our patient, there was no sign of physiologic root re-sorption of the deciduous canines, since the mandibularcanines were ectopically impacted.

The mandibular canines in the pretreatment pano-ramic radiograph should be designated as ectopicallyimpacted mandibular canines rather than transmigratedcanines, because none had crossed the mandibular mid-line.15 Howard16 stated that canines that lie between 25�

and 30� in the midsagittal plane are ectopically im-pacted, but they do not migrate across the mandibularmidline. An overlap of the canines appears to exist ifthe angles are 30� and 50�; when this angle exceeds50�, it results in transmigration of the canines. However,in our patient, the mandibular right and left canines hadinclinations of 35� and 24�, respectively, so there wasa chance of more migration of the right canine thanthe left. Greenberg and Orlian17 published radiographicevidence documenting ectopic movement of a caninefrom a position apical to the mandibular incisors tothe opposite side of the arch in 30 months. Stafne18

pointed out that the greatest movement of canines takesplace before complete development of their roots, andthe teeth always travel in the direction of the crown. Tak-ing the above factors into account, we started the

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Fig 13. Postretention facial and intraoral photographs.

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orthodontic correction of the mandibular canines assoon as possible. We speculated that delayed treatmentmight have allowed the right canine to erupt in the mid-line labial to the mandibular incisors, making later treat-ment mechanics more complex.

We could have treated this patient with 2 3 4 me-chanics along with a lingual holding arch, but reaction-ary forces would have resulted in excessive proclinationof the incisors and mesial tipping of the molars.Becker19 used a modified Johnson archwire appliancefor the simultaneous forced eruption and alignmentof an impacted maxillary central incisor. A similar as-sembly was used for this patient; however, the anchor-age requirements were much greater, since bothcanines were involved, and the impacted teeth werefar from their final positions in the arch. To minimizethe reactionary force on the molars, a lip bumper as-sembly was added, which was held by friction in thebuccal tubes soldered to the molar band. The lip

American Journal of Orthodontics and Dentofacial Orthoped

bumper was positioned in the middle of the mandibu-lar incisor crowns, so that it produced a distalizing andextrusive force on the molar. The distal force was ex-pected to be in equilibrium with the reactionary force,thus preventing mesial tipping of the mandibular mo-lars. The correct mesiodistal inclination of the mandib-ular molars can be appreciated on the posttreatmentpanoramic radiograph (Fig 12).

To minimize the need for second-order correction inthe later stages of treatment, force was applied on themandibular canines to achieve controlled tipping aroundthe root apices. The force vector, which would have re-sulted in the desired tooth movement in this patient,must point distally, buccally, and occlusally. Such a forcevector was created by attaching the elastomeric chainfrom the hooks soldered on the distal legs of the lip bum-per in the region of the first deciduous molars, thus pro-ducing controlled tipping around the root apices of thecanines (Figs 5-8).

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Fig 14. Postretention lateral cephalogram and orthopan-tomogram.

402 Agarwal et al

Miniscrews are becoming more popular when addi-tional anchorage is required. However, the patient wasin the early mixed dentition, when the possibility ofdamaging the developing follicles and roots of thepermanant teeth was high.20

Most studies about root resorption adjacent to im-pacted teeth have been done for impacted maxillary ca-nines.21 Apart from the proximity of the impacted canineto the roots of the incisors, other factors that could in-crease the chances and severity of apical root resorptionof the mandibular incisors in this patient were extendedtreatment time, mandibular incisor intrusion, and thefact that mandibular canines must pass the roots ofthe incisors on their way to their normal positions inthe arch. During active eruption of the mandibular ca-nines, the mandibular incisors were not ligated witharchwires and were free to move if the crown of the up-righting canines hit the roots of mandibular incisors,thus reducing the chances of further damaging the rootsof the incisors.

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The posttreatment appearance of the gingiva, torque,alignment, and position of the impacted tooth in thearch are important factors for determining the successof the treatment.22 Gingival health is usually affectedby the type of surgical procedure to uncover the im-pacted canine (open vs closed), eruption of the tooththrough attached or movable mucosa, and the patient'soral hygiene. Vermette et al22 found that labially im-pacted anterior teeth uncovered with an apically posi-tioned flap have unesthetic results and more gingivalrecession than those uncovered with the closed-eruption technique. Moreover, Becker et al23 found nodifferences in the widths of the attached gingiva or thecrown lengths, and no clinically significant differencesin sulcus depth and bone support of impacted maxillaryincisors treated with a closed-eruption surgical tech-nique compared with adjacent normal incisors. Our pa-tient was treated with the closed-eruption surgicalexposure technique, and the canine was brought intothe arch through the attached gingiva; this resulted inan adequate zone of attached keratinized gingiva,good bone support, and no excessive periodontal prob-ing depths. The gingival health was maintained even 2years after treatment (Fig 13).

Although, at the initiation of treatment, two thirds ofthe root formation of the canines were complete, makingthem ideal teeth to be transplanted, extensive surgery,anticipated bone loss, complications such as loss of thetransplant, the need for an implant or other prostheticsolution, and uncertainty about the longevity of this so-lution made autotransplantation an alternative only ifforced eruption and alignment of the canines had failed.

Because of the long treatment time, some white spotlesions were expected at the end of the treatment. Thepatient was advised to continue using fluoridated tooth-paste and mouthwash after treatment, and the size andseverity of the lesions were reduced during the 2 yearsafter treatment (Fig 13). The treatment results werewell maintained, and there has been no clinically detect-able gingival recession with respect to the mandibularcanines 2 years after treatment, and the long-term sta-bility is expected to be good.

CONCLUSIONS

Alignment of ectopically impacted mandibular ca-nines is a challenging, but achievable, option. A meticu-lous biomechanical plan is essential for successfulresolution of such a severe malocclusion. Early interven-tion might be advisable in patients with impacted man-dibular canines as a cautious measure, preventingpossibly greater complexity of the orthodontic treatmentfrom altered paths of eruption.

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Fig 15. Overall superimposition and regional superimposition (black, pretreatment; red, posttreatment;green, postretention).

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