identical unerupted maxillary incisors in monozygotic twins · ances placed on the maxillary...

CASE REPORT

Identical unerupted maxillary incisors inmonozygotic twins

Hasan Babacan,a Fırat €Ozt€urk,b and Hidayet Burak Polatc

Sivas, Malatya, and Kayseri, Turkey

Mesiodens is the most common type of supernumerary tooth found in the premaxilla. It might be discov-ered by the orthodontist by chance on a radiograph or as the cause of an unerupted maxillary centralincisor. The genetic transmission of supernumerary and impacted teeth is poorly understood. The occur-rence of identical unerupted maxillary central incisors and mesiodentes in monozygotic twins suggeststhat genetic factors might influence the etiology of this problem. In this case report, we discuss the treat-ment of unerupted maxillary permanent incisors caused by mesiodentes in monozygotic twins. (Am JOrthod Dentofacial Orthop 2010;138:498-509)

Delayed of eruption of a permanent maxillaryincisor (due to a supernumerary tooth) is aproblem encountered occasionally by an

orthodontist. These supernumerary teeth, located inthe premaxillary region, are known as mesiodentes.The prevalence of mesiodentes has been estimated at0.15% to1.9% in the population.1,2 Although there isno significant sex distribution in deciduoussupernumerary teeth,3 males are affected about twiceas frequently as females in the permanent dentition.1-4

Mesiodentes have been reported to cause delay orfailure of eruption of the permanent incisors in 28% to52% of reported cases.5,6

Brodie7 first reported delayed eruption of centralincisors in 1936 using radiographic records of a 10-year-old boy with a mesiodens. He noted mesiodentesin 3 other members of his family. Since then, several pa-tients with a mesiodens have been reported, and varioustheories such as hyperactivity of the dental lamina,2

a phylogenetic relic of extinct ancestors who had 3 cen-tral incisors,8 and a dichotomy of tooth buds, one ofwhich is the mesiodens,1 have been proposed as the eti-ology of mesiodentes. Although genetic origin isthought to contribute to the development of a mesiodens,the familial pattern of occurrence and mesiodens intwins strongly supports genetics. Autosomal dominant

aAssociate professor, Department of Orthodontics, Faculty of Dentistry, Cum-

huriyet University, Sivas, Turkey.bAsistant professor, Department of Orthodontics, Faculty of Dentistry, Inonu

University, Malatya, Turkey.cPrivate practice, Kayseri, Turkey.

The authors report no commercial, proprietary, or financial interest in the

products or companies described in this article.

Reprint requests to: Hasan Babacan, Cumhuriyet Universitesi Disx Hekimligi

Fak€ultesi, Ortodonti AD. 58140 Sivas, T€urkiye; e-mail, babacanhasan@

yahoo.com.

Submitted, July 2008; revised and accepted, August 2008.

0889-5406/$36.00

Copyright � 2010 by the American Association of Orthodontists.

doi:10.1016/j.ajodo.2008.08.043

498

inheritance with incomplete penetration has been theproposed genetic theory.1,6

Many twins have bilateral occurrence, and unilateralmesiodentes can be mirror images.9 The aim of this re-port was to illustrate the orthodontic treatment of unilat-eral mesiodens in monozygotic twins with identicalmalocclusions.

DIAGNOSIS AND ETIOLOGY

The patients, AY and UY, are monozygotic twinbrothers. They were referred to our clinic when theywere 10.5 years old for orthodontic treatment of im-pacted maxillary left central incisors. Their medical his-tories showed no systemic diseases, and the dentalhistories showed no facial trauma or other developmen-tal anomalies. Each had a balanced facial profile (Fig 1).Clinical analysis showed that both children were in themixed dentition, and their left central incisors were miss-ing. Space loss and midline shift of the right central in-cisor had occurred, and the left lateral incisors haddrifted mesially in both children (Figs 2 and 3).

Radiographic examinations showed that a mesiodenswas preventing the eruption of the maxillary left centralincisor in both twins (Fig 4). Maxillary anterior occlu-sal and periapical radiographs showed that the mesio-dentes were palatal to the impacted central incisors(Figs 5 and 6). Cephalometric analyses showed a ClassI skeletal relationship, with a normal growth pattern(Fig 7, Table). They had similar clinical, radiographic,and cephalometric characteristics with a similar clinicalappearance, so their treatment objectives and alterna-tives were the same, as was the treatment progress.

TREATMENT OBJECTIVES

Based on diagnostic records, the treatment objec-tives were to (1) remove the mesiodens before surgical

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Fig 1. Pretreatment facial photographs of AY and UY.

American Journal of Orthodontics and Dentofacial Orthopedics Babacan, €Ozt€urk, and Polat 499Volume 138, Number 4

exposure of impacted central incisors, (2) erupt the im-pacted central incisors orthodontically, (3) develop idealoverjet and overbite, and (4) correct the midlines androot angulations.

TREATMENT ALTERNATIVES

Treatment options included (1) wait for spontaneouseruption of the impacted central incisor after surgicalextraction of the mesiodens, (2) remove the mesiodens

Fig 2. Pretreatment intraoral photographs of AY and UY.

500 Babacan, €Ozt€urk, and Polat American Journal of Orthodontics and Dentofacial Orthopedics

October 2010

with surgical exposure of the unerupted tooth, and (3)remove the mesiodens with orthodontic traction of theunerupted tooth.

After careful consideration of all parameters, re-moval of the mesiodens with orthodontic treatmentwas the chosen plan.

TREATMENT PROGRESS

The twins were treated in a relatively analogousfashion, with 0.018 3 0.022-in Roth system fixed appli-ances placed on the maxillary permanent teeth anddeciduous molars. After the maxillary teeth were

leveled, the boys were admitted to the oral and maxillo-facial surgery department for their surgeries. Thelabially impacted maxillary central incisors weresurgically exposed with an envelope flap. Under localanesthesia, the supernumerary teeth were removedwith an elevator after bone removal (Fig 8). A buttonwith a gold chain was bonded to the impacted central in-cisors. The surgical flap and closure were carefully per-formed to prevent poor periodontal complications. Afterthe tissues had healed, 0.014-in superelastic nickel-titanium wires were placed, and space was created forthe impacted central incisors with an open-coil spring.

Fig 3. Pretreatment dental casts of AY and UY.


Elastic thread was placed through the link of the goldchain and tied with tension to the coil, thereby applyingtraction to the impacted incisor. Once the impactedtooth became visible, an orthodontic bracket was placedideally. The impacted central incisors were moved intotheir proper positions in 9 months (Fig 9). Afterthe maxillary arches were leveled and aligned, the

mandibular arch was bonded. Treatment was finishedafter the eruption of all permanent teeth. Bilateral ClassI occlusions with ideal overjet and overbite wereachieved. Essix retainers (Dentsply, York, Pa) wereplaced in both dental arches to maintain the orthodonticcorrections. The total active treatment time was 29months.

Fig 4. Pretreatment panoramic radiographs of AY and UY.

Fig 5. Pretreatment occlusal radiographs of AY and UY.

Fig 6. Pretreatment periapical radiographs of AY and UY.


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TREATMENT RESULTS

The impacted maxillary left central incisors weresuccessfully aligned in their proper positions, andboth boys finished treatment with pleasant smiles(Fig 10). Class I molar and canine relationships, andideal overjet and overbite were achieved. In both pa-tients, the repositioned incisors had acceptable

gingival contour and width of the attached gingiva(Figs 11 and 12). The posttreatment panoramicradiographs show no root resorption or periodontalbone loss (Fig 13). Cephalometric measurementsshow that Class I skeletal relationships and normalgrowth patterns were maintained after treatment(Figs 14 and 15).

Fig 7. Pretreatment cephalometric radiographs and tracings of AY and UY.

Fig 8. The extracted mesiodentes of AY and UY.


DISCUSSION

The etiology of a mesiodens is not understood. Sev-eral theories, such as hyperactivity of the dental lam-ina,2 a phylogenetic relic of extinct ancestors,8 anda dichotomy of tooth buds,1 have been proposed to ex-plain the phenomenon. Many authors have focused onthe genetic influence, such as Brook,10 who reportedmuch higher frequencies of supernumerary teeth amongfirst-degree relatives than in the general population, sug-gesting a significant genetic component in the etiology.Similarly, Hattab et al5 suggested that supernumeraryteeth have a strong hereditary component but donot conform with a simple Mendelian pattern.

Fig 9. Orthodontic traction of impacted central incisors. Progress photos of AY and UY: A, beginning oftreatment; B, after 6 months of treatment; C, After 7 months of treatment; D, after 9 months of treatment.


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Langowska-Adamsczyk and Karmanska11 reportedsimilarly positioned supernumerary and impacted teethin monozygotic twins, and they concluded that there isa genetic influence in the etiology. Nevertheless, theysuspected environmental factors for the differences ob-served in the twins’ dentitions. Kabban et al12 investi-gated 34 pairs of twins and found a remarkablesimilarity in tooth sizes and morphologies of monozy-gotic twins, suggesting a strong inheritability factor intooth size and shape. The twins presented heredisplayed identical appearances on all radiographic,cephalometric, and intraoral images. This identical re-semblance strongly indicates a genetic origin as themain etiologic factor.

There were 3 treatment choices for these twins: re-moval of the mesiodens, removal of the mesiodens withsurgical exposure of the unerupted tooth, and removalof the supernumerary tooth with orthodontic traction ofthe unerupted tooth. Studies have shown that the delayedtooth might erupt naturally after the supernumerary is re-moved; however, eruption occurs when the arch length issufficient and root formation of the unerupted tooth hasbeen completed.13-15 These twins had inadequate spacefor the unerupted central incisor because of migration ofadjacent teeth into the space. Different treatmentmodalities might have been applied to each twin todetermine the best treatment alternative for similarpatients; however, this would have been unethical.

Fig 10. Posttreatment facial photographs of AY and UY.


Removal of the mesiodens with orthodontic traction of theunerupted central incisor seemed to be the best treatmentapproach. Patient cooperation, length of treatment,potential risk of migration of adjacent teeth into theempty space, and patient age must be considered intreatment of a mesiodens.

Some previous reports stated that spontaneouseruption occurs 18 to 24 months after removal of a mesio-dens.16,17 These twins’ impacted central incisors were

fully erupted with orthodontic traction in 9 months, andthe total treatment time was 29 months. Eruption andleveling of the permanent teeth were controlled in thenext 20 months. The eruption of the second permanentmolars was controlled at the followup appointments.

CONCLUSIONS

Monozygotic twins with identical malocclusionswere treated in the same manner. It is known that the

Fig 11. Posttreatment intraoral photographs of AY and UY.


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genotype of the monozygotic twins is the same; in thisreport, the phenotype was the same also. Environmentalfactors might affect the formation of the phenotype;

however, the identical appearance of these twin brothersstrongly suggests that the role of genetic influence on theetiology of malocclusions could be stronger than known.

Fig 12. Posttreatment dental casts of AY and UY.


Fig 13. Posttreatment panoramic radiographs of AY and UY.

Fig 14. Posttreatment cephalometric radiographs and tracings of AY and UY.


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Fig 15. Initial and final cephalometric tracings of AY and UY, superimposed on S-N at sella.

Table. Cephalometric summary

AY UY

Measurements Initial Final Initial Final

SNA (�) 78 78 78 79

SNB (�) 74 75 75 77

ANB (�) 4 3 3 2

GoGN-SN (�) 41 42 42 43

U1-SN (�) 98 104 102 104

IMPA (�) 86 89 85 84

U1-L1 (�) 135 126 129 129

U1-NA (�) 20 19 24 25

U1-NA (mm) 3 5 4,5 4

L1-NB (�) 22 25 24 23

L1-NB (mm) 3.5 4 4.5 4


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