Nonsurgical correction of a Class III malocclusion in …...Nonsurgical correction of a Class III malocclusion in an adult by miniscrew-assisted mandibular dentition distalization

CASE REPORT

Nonsurgical correction of a Class III malocclusionin an adult by miniscrew-assisted mandibulardentition distalization

Yan Jing,a Xianglong Han,b Yongwen Guo,a Jingyu Li,c and Ding Baid

Chengdu, Sichuan, China

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This article reports the successful use of miniscrews in the mandible to treat a 20-year-old Mongolian womanwith a chief complaint of anterior crossbite. The patient had a skeletal Class III malocclusion with a mildly pro-trusive mandible, an anterior crossbite, and a deviated midline. In light of the advantages for reconstruction ofthe occlusal plane and distal en-masse movement of the mandibular arch, we used a multiloop edgewise arch-wire in the initial stage. However, the maxillary incisors were in excessive labioversion accompanied by little re-traction of the mandibular incisors; these results were obviously not satisfying after 4 months of multiloopedgewise archwire treatment. Two miniscrews were subsequently implanted vertically in the external obliqueridge areas of the bilateral mandibular ramus as skeletal anchorage for en-masse distalization of the mandibulardentition. During treatment, the mandibular anterior teeth were retracted about 4.0 mm without negative lingualinclinations. The movement of the mandibular first molar was almost bodily translation. The maxillary incisorsmaintained good inclinations by rotating their brackets 180� along with the outstanding performance of thebeta-titanium wire. The patient received a harmonious facial balance, an attractive smile, and ideal occlusalrelationships. The outcome was stable after 1 year of retention. Our results suggest that the application ofminiscrews in the posterior area of the mandible is an effective approach for Class III camouflage treatment.This technique requires minimal compliance and is particularly useful for correcting Class III patients withmild mandibular protrusion and minor crowding. (Am J Orthod Dentofacial Orthop 2013;143:877-87)

Smile attractiveness has been regarded as a stan-dard of successful treatment by both orthodon-tists and patients. Evaluating the face in the

smiling profile is also a critical part of a completeorthodontic diagnosis.1 Maxillary incisors play animportant role in defining beauty, and thus they shouldbe angulated and positioned most favorably in theiranteroposterior and vertical relationships to all facialstructures to ensure maximum facial harmony.1-4

State Key Laboratory of Oral Diseases, Department of Orthodontics,China Hospital of Stomatology, Sichuan University, Chengdu,

an, China.raduate student.ciate professor.raduate student.ssor and chair.uthors report no commercial, proprietary, or financial interest in thects or companies described in this article.t requests to: Ding Bai, State Key Laboratory of Oral Diseases, Departmenthodontics, West China Hospital of Stomatology, Sichuan University, 14#,ction of Renmin South Road, Chengdu, Sichuan, China, 610041; e-mail,[email protected], revised and accepted, May 2012.5406/$36.00ight � 2013 by the American Association of Orthodontists./dx.doi.org/10.1016/j.ajodo.2012.05.021

Excessive labioversion of the maxillary incisors caneasily ruin a pleasing smile.

Dentoalveolar compensations (proclined maxillaryincisors and retroclined mandibular incisors) arecommon in patients with a Class III malocclusion causedby a retrognathic maxilla or a prognathic mandible.5-8

Also, moderate proclination of the maxillary incisors isindispensable in camouflage treatment of anteriorcrossbite. It is always, therefore, challenging for ortho-dontists to place the maxillary incisors in an appro-priate anteroposterior position with a harmoniouslabial inclination in Class III treatment. To preventexcessive proclination of the maxillary incisors, distalen-masse movement of the mandibular dentition isquite effective in camouflage treatment for patientswith a Class III malocclusion.9 The multiloop edgewisearchwire is considered a practical method with fewerside effects.9-12 However, the extent of occlusalenhancement that occurs in response to the multiloopedgewise archwire greatly depends on a patient'scompliance and can vary with each person. As skeletalanchorage, the application of miniscrews, which offermore simple and stable force systems, has graduallybecome popular and reliable.13-18

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Fig 1. Pretreatment photographs.

Fig 2. Pretreatment study casts.

878 Jing et al

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Fig 3. A, Pretreatment cephalogram; B, panoramic radiograph; C, cephalometric tracing.

Table. Cephalometric measurements

Measurement Pretreatment

After 4 months ofmultiloop edgewisearchwire treatment Posttreatment

SNA (�) 79.1 77.8 77.6SNB (�) 81.7 79.2 79.1ANB (�) �2.6 �1.4 �1.5SN-GoGn (�) 36.1 39.0 38.9S-Go/N-Me (%) 61.3 59.4 59.4FH-OP (�) 9.9 8.7 6.6U1-SN (�) 79.6 64.7 77.7L1-NB (�) 18.4 24.0 13.5

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In this case report, we introduce a nonsurgical treat-ment of an adult with a Class III malocclusion withminiscrew-assisted mandibular dentition distalization.At the beginning of the therapy, the multiloop

American Journal of Orthodontics and Dentofacial Orthoped

edgewise archwire technique resulted in an unsatisfy-ing smile because of the excessive proclination of themaxillary incisors. Then we stopped to vertically im-plant a pair of miniscrews in the external oblique ridgeareas of the bilateral mandibular ramus as anchoragefor the distal en-masse movement of the mandibulardentition and obtained an excellent treatment outcomeultimately.

DIAGNOSIS AND ETIOLOGY

The patient was a 20-year-old Mongolian womanwho had a Class III facial type and slight crowding witha complete Class III relationship. Her chief complaintwas an anterior crossbite. Her medical history showedno contraindication for orthodontic therapy, and noone in her direct family had skeletal Class III features.

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Fig 4. Treatment progress: A, short Class III elastics on multiloop edgewise archwire; B, nickel-titanium closed coil springs on miniscrews for distal en-masse movement of the mandibular arch.

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The photographs taken before treatment showedsymmetric facial structures (Fig 1). The patient had a con-cave facial profile, a protrusive lower lip, and an acutenasolabial angle. Her maxillary anterior teeth wereretrognathic, with inadequate display when smiling.The mandibular dental midline was deviated 2.0 mm tothe right, although the maxillary dental midline wascoincident with the facial midline. There were no signsor symptoms of temporomandibular joint dysfunction.Mandibular movements, such as maximal opening andlateral and anterior displacement, were within normallimits. No deviation and pain were discovered duringthe border movement of the mandible. The dental casts(Fig 2) showed a Class III occlusion on each side, withoutapparent crowding. Overjet was �2.0 mm, and overbitewas�4.5mm. A cephalogram (Fig 3,A) and a panoramicradiograph (Fig 3, B) were taken before treatment. Thecephalometric analysis (Table) and its tracing (Fig 3, C)showed that the mandible protruded relative to thecranial base (SNB angle, 81.7�; ANB angle, �2.6�). Thepanoramic radiograph (Fig 3, B) showed no otherabnormal signs, except that the 2 germs of the mandib-ular third molars were tipped mesially.

After the analysis of the photographs, casts, andradiographs, it was decided to approach her problemsas a skeletal Class III malocclusion with an anteriorcrossbite and a deviated midline.

TREATMENT OBJECTIVES

The treatment objectives were to (1) obtaina harmonious facial profile by decreasing the protrusion

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of the mandible; (2) improve the occlusion, includingcorrection of the anterior crossbite, establishment ofideal overjet and overbite, and achievement of Class Imolar relationships; and (3) place the dental midlinesin the middle of the patient's face.

TREATMENT ALTERNATIVES

The first alternative was combined surgical andorthodontic treatment. The anterior crossbite would becorrected with a mandibular setback, and the concaveprofile would be improved as well. However, we decidedthat her skeletal problem was not sufficiently excessiveto require orthognathic surgery.

The second alternative was orthodontic treatmentwith extraction of 4 premolars. Through the retractionof the mandibular anterior teeth and the mesialmovement of the maxillary molars, the anterior crossbiteand Class III molar relationships would be corrected, andthe concave facial profile would be camouflaged.Nevertheless, her mandibular incisors were not suitablefor much distal movement because of the thin trabecularbone in the mandibular anterior area that could damagethe periodontal tissues by gingival recession, fenestra-tion, or dehiscence.

The third alternative was to extract the mandibularthird molars and use the multiloop edgewise archwiretechnique to obtain distal en-masse movement of themandibular arch with short Class III elastics. Thereby,the anterior crossbite would be corrected, the molarrelationships would be changed into Class I, and herconcave facial profile would be camouflaged as well.

Journal of Orthodontics and Dentofacial Orthopedics

Fig 5. A andB,Photographs after 4months of multiloop edgewise archwire treatment;C, cephalogramafter 4 months of multiloop edgewise archwire treatment; D, superimposed cephalometric tracings be-fore treatment and after 4 months of multiloop edgewise archwire treatment.

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After we discussed the 3 alternatives with the patient,she chose the thirdoption andpromised to cooperate in ex-tracting the third molars and wearing the Class III elastics.

TREATMENT PROGRESS

Orthodontic treatment began on November 9, 2007.The mandibular third molars were extracted before

American Journal of Orthodontics and Dentofacial Orthoped

bonding. Preadjusted 0.022-in brackets (Shiye, Hang-zhou, China) were bonded to all teeth. Alignment andleveling with sequential nickel-titanium archwires wereachieved in 12 months, ending with 0.018 3 0.025-instainless steel wires. After that, 0.018 3 0.025-instainless steel multiloop edgewise archwires withprogressive tip-back bends were placed in both arches.

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Fig 6. A, Frontal x-ray showing the positions of the miniscrews in the mandible; B and C, the positionsof the miniscrews in the oral cavity.

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The patient was instructed to wear the short Class IIIelastics (3/16 in, 6 oz; 3M Unitek, Monrovia, Calif) for24 hours per day (Fig 4, A).

The anterior crossbite was corrected substantially4 months later. However, the maxillary incisors wereproclined remarkably. Class I molar relationships werenot completely established, although the overallocclusion was improved significantly. Thus, in the17th month, we took a set of photos (Fig 5, A andB) and a cephalogram (Fig 5, C), and made a cephalo-metric analysis (Table) to reestimate her treatment. Thesuperimposition of the cephalograms (Fig 5, D)showed that the correction of the anterior crossbitewas mostly because of the proclined maxillary incisorswithout obvious distal movement of the mandibularincisors. Also, the excessively proclined maxillaryanterior teeth made her facial profile worse, especiallywhen smiling.

To reinforce the distal en-masse movement of themandibular dentition, we modified the treatment plan.We replaced the orthodontic appliance with 0.022-inDamon III self-ligating brackets (Sybron Dental Special-ties Ormco, Orange, Calif) and used miniscrews insteadof the multiloop edgewise archwire technique. When

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rebonding, the maxillary incisor brackets were rotated180�, assisting in labial root torque at the rectangularwire stage. The miniscrews were implanted vertically inthe external oblique ridge areas of the bilateral mandib-ular ramus between the mandibular first and secondmolars, where the greatest thickness of buccolingualbone was found (Fig 6).19

After 3 months of releveling, we started to draw themandibular dentition distally using nickel-titaniumcoil springs with 300-g forces on each side. The springwas connected from the miniscrew to the hookbetween the mandibular canine and the first premolar.At the same time, 0.019 3 0.025 beta-titanium alloywire was used to control the root position of themaxillary incisors. Six months later, the anterioroverbite and overjet were improved remarkably, andthe labial inclination of maxillary teeth was alsomuch better (Fig 4, B).

The total treatment duration was 32 months. Themultiloop edgewise archwire technique was used for4 months, and it took 12 months for the distalen-masse movement of the mandibular dentition withminiscrews. The miniscrews were stable all the timeand removed under topical anesthesia.

Journal of Orthodontics and Dentofacial Orthopedics

Fig 7. A and B, Posttreatment photographs; C, photographs after 1 year of retention.

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TREATMENT RESULTS

A harmonious facial balance, a charming smile, anda well-aligned dentition were obtained (Fig 7). Theanterior crossbite was corrected, and Class I molarrelationships were achieved (Fig 8). The posttreatmentcephalogram and panoramic radiograph are shown inFigure 9. The cephalometric analysis (Table) and thesuperimposition (Fig 9, C) show that the ANB angleincreased from �2.6� to �1.5�, and the SNB angledecreased from 81.7� to 79.1�. According to thesuperimposition, the mandibular anterior teeth wereretracted about 4 mm without negative lingual inclina-tions. The movement of the mandibular first molar couldbe considered almost bodily translation because itscrown was moved 4.0 mm distally, and its roots weremoved 3.0 mm distally. The maxillary incisors weremoved labially under control with good inclination

American Journal of Orthodontics and Dentofacial Orthoped

(U1-SN, 77.7�). The SN-GoGn angle increased from36.1� to 38.9�, and S-Go/N-Me decreased from 61.3%to 59.4%, indicating that the mandible had rotatedclockwise slightly. The patient was satisfied with thetreatment results, and the outcome was stable after1 year of retention (Fig 7, C).

DISCUSSION

For this patient, the etiology of her Class III malocclu-sion was expressed through mandibular protrusion. Thechanges contributing most to the correction of her initialdental and skeletal discrepancies were dentoalveolarcompensation with distal en-masse movement of themandibular dentition: a combination of clockwiserotation of the mandible and counterclockwise rotationof the occlusal plane. Ideal overjet and overbitewere achieved with controlled labial movement of the

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Fig 8. Posttreatment study casts.

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maxillary incisors and retraction of the mandibularanterior teeth.

The anteroposterior position of the maxillary incisorsis important for the harmony of the face and the beautyof the smile. To standardize the orthodontic estheticanalysis, Andrews and Andrews20 noted the “6 elementsof orofacial harmony,” for which the patient's foreheadis used as a stable landmark to determine the anteropos-terior position of the maxillary incisors in the smilingprofile. The facial axis point of the maxillary centralincisors should touch the goal anterior limit line, whenthe teeth in each arch conform to element I (ie, archshapes and lengths are optimal).20 Either in front of orbehind the goal anterior limit line is not a favorableanteroposterior position for the maxillary centralincisors. However, the labial inclination of maxillaryincisors can vary and have remarkably different effectson facial esthetics, even if the facial axis point touchesthe goal anterior limit line and the anterior teeth havegood overbite and overjet. Furthermore, the maxillaryincisors can hardly be placed in a standard position forClass II or Class III camouflage treatment because ofthe skeletal discrepancy. Consequently, more or less

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inclination of the maxillary incisors is inevitable; thiscan greatly impact the static and dynamic beauty ofthe facial profile. Previously, we found that the maxillaryincisor that is upright or in a slight lingual inclination ispreferable.21 Labioversion of the maxillary incisors caneasily ruin a pleasing smile, especially for a patientwith a Class III facial type.2,21 Thus, identifying anefficient way to achieve maximum distal en-massemovement of the mandibular arch should be a primarygoal in Class III camouflage treatment for adults.

We used the multiloop edgewise archwire techniqueat the beginning of this treatment. However, the occlusalenhancement in response to this technique depends onthe patient's cooperation and can vary with each patient.Also, labial tipping of the maxillary incisors generallyoccurs as a negative effect of anterior anchorage lossduring molar distalization. As a result, the U1-SN was64.7�, which was 14.9� less than the initial status after4 months of multiloop edgewise archwire treatment. Ap-parently, the overproclined maxillary incisors compro-mised the pleasing smile. To minimize this side effect,we used miniscrews instead of the multiloop edgewisearchwire to reinforce the distal retraction of the

Journal of Orthodontics and Dentofacial Orthopedics

Fig 9. A, Posttreatment cephalogram; B, panoramic radiograph; C, superimposition.

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mandibular arch and create enough overjet to uprightthe labially inclined maxillary incisors. The miniscrewswere implanted vertically so that they would not blockthe way for the distal movement of the mandibulardentition. The mandibular incisors were successfullyretracted about 4.0 mm without undesirable tipping,and the movement type of the mandibular molars wasalmost bodily translation.

Enlow et al22 stated that it is critical to move theocclusal plane counterclockwise during skeletal ClassIII therapy. In this patient, the Frankfort horizontal toocclusal plane angle decreased gradually, along withan increase of the SN-GoGn angle (Table). Thesechanges demonstrated that the combination ofcounterclockwise rotation of the occlusal plane withclockwise rotation of mandible can be obtained not

American Journal of Orthodontics and Dentofacial Orthoped

only by the multiloop edgewise archwire technique,but also with miniscrew-assisted mandibular archdistalization. Multiloop edgewise archwires can recon-struct the occlusal plane by uprighting and intrudingthe posterior teeth, and extruding the mandibularincisors with short elastics.23 However, the same effectscan be obtained by miniscrews. The mandibular arch canbe rotated counterclockwise during the distal en-massemovement because the direction of the retraction forceapplied on the miniscrews is above the center ofmandibular arch resistance, leading to a flattenedocclusal plane (Fig 10). On the other hand, molardistalization, which contributed mostly to the clockwiserotation of mandible, was beneficial for alleviating thenegative overbite. With the combination of retractedmandibular incisors, the anterior crossbite could be

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Fig 10. Because the direction of the retraction forceapplied to the miniscrews is above the center of mandib-ular arch resistance, the mandibular arch can be rotatedcounterclockwise when distalized, leading to a flattenedocclual plane. On the other hand, molar distalization isbeneficial for decreasing a negative overbite. With thecombination of these 2 factors, the anterior crossbitecan be corrected, and ideal overbite and overjet can beestablished. The dotted line represents the retractionforce; the red point represents the center of mandibulararch resistance.

886 Jing et al

easily corrected, and ideal overbite and overjet were wellestablished. Compared with the multiloop edgewisearchwire technique, the application of miniscrewssignificantly simplifies the force system and reducesthe difficulty in bending wires and maintainingappropriate labial inclinations of the maxillary incisors,since the force does not directly impose on those teeth.In addition, it depends much less on the patient'scompliance. Thus, we suppose that implantingminiscrews in the posterior area of the mandible providesadvantages for the correction of an anterior crossbite bya similar mechanism as the multiloop edgewise archwiretechnique. Moreover, in conjunction with the self-ligation system, the lower frictional resistance mightgreatly contribute to the effective distal en-massemovement of the mandibular dentition.24-26

Another critical factor for the successful recovery ofmaxillary incisor inclination was that the brackets ofthese teeth were rotated 180� when we replaced allbrackets with Damon III brackets. This correctionchanged the preadjusted torque of the maxillary centralincisor from 112� to �12�, and the torque of themaxillary lateral incisors from 18� to �8�. In this way,the labial root torque could be expressed accurately,efficiently, and gently with the outstanding performanceof the 0.019 3 0.025 beta-titanium alloy wire.

CONCLUSIONS

The use of miniscrews in the posterior area of themandible is an effective approach for Class III camou-flage treatment. Not only can the occlusal plane be

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flattened in conjunction with clockwise rotation of themandible, but also it is beneficial to control the labialinclination of the maxillary incisors for the en-massemandibular arch distalization. Therefore, this techniquerequires less compliance and is particularly useful forcorrecting Class III patients with mild mandibularprotrusion and minor crowding. Identically, Class IIpatients with a mildly protrusive maxilla are alsocandidates for en-masse maxillary arch distalizationwith miniscrews implanted in the posterior area of themaxilla. The outcome of this case was stable after1 year, although more follow-up is necessary todetermine the long-term stability.

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21. Cao L, Zhang K, Bai D, Jing Y, Tian Y, Guo Y. Effect of maxillaryincisor labiolingual inclination and anteroposterior position onsmiling profile esthetics. Angle Orthod 2011;81:121-9.

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