Zygoma-gear appliance for intraoral upper molar distalization · grated implants, miniscrews, and...

CASE REPORT

195

aAssistant Professor, Karadeniz Technical University, Department

of Orthodontics, Trabzon, Turkey.bAssistant Professor, Karadeniz Technical University, Department

of Oral Surgery, Trabzon, Turkey.

Corresponding author: Mehmet Bayram.

Karadeniz Technical University, Department of Orthodontics,

Trabzon, Black Sea 61080, Turkey.

＋90 462 3774724; e-mail, [email protected].

Received January 26, 2010; Last Revision March 6, 2010;

Accepted March 9, 2010.

DOI:10.4041/kjod.2010.40.3.195

Zygoma-gear appliance for intraoral upper molar distalization

Metin Nur, DDS, PhD,a Mehmet Bayram, DDS, PhD,

a Alper Pampu, DDS, PhD

b

The aim of this report is to present an intraoral upper molar distalization system supported with zygomatic anchorage plates (Zygoma-gear Appliance, ZGA). This system was used for a 16-year-old female patient with a Class II molar relationship requiring molar distalization. The system consisted of bilateral zygomatic anchorage plates, an inner-bow and heavy intraoral elastics. Distalization of the upper molars was ach-ieved in 3 months and the treatment results were evaluated from lateral cephalometric radiographs. According to the results of the cephalometric analysis, the maxillary first molars showed a distalization of 4 mm, associated with a distal axial inclination of 4.5o. The results of this study show that an effective upper molar distalization without anchorage loss can be achieved in a short time using the ZGA. We sug-gest that this new system may be used in cases requiring molar distalization in place of extraoral appliances. (Korean J Orthod 2010;40(3):195-206)

Key words: Distalization, Zygomatic anchorage plate, Class II, Anchorage

INTRODUCTION

Several methods have been used for upper molar

distalization including extraoral1 and intraoral2-10 appli-

ances. The esthetic and social concerns of the use of

headgear wear and the anchorage loss that occurs with

the application of intraoral systems have stimulated

many investigators to use skeletal anchorage. To over-

come these anchorage problems, skeletal anchorage

units applied to palatal regions, for example, osteointe-

grated implants, miniscrews, and Graz type implant

were combined with these tooth and tissue supported

intraoral appliances.11-18 Although anchorage loss has

been eliminated in this way, different problems related

with the proximity between the implant and the roots

of teeth or the presence of a bulky acrylic Nance ap-

pliance behind the upper incisors may become a prob-

lem during the retraction of anterior teeth.

The zygomatic process of the maxilla is another ap-

propriate region for skeletal anchorage.19

Recently, zy-

gomatic anchorage systems have been used alternati-

vely for upper molar distalization.20,21 We designed an

intraoral upper molar distalization system supported by

the zygomatic region named as the Zygoma-Gear Ap-

pliance (ZGA). The aim of this study is to present the

use of ZGA for bilateral upper molar distalization in

a 16-year-old female with a Class II molar relationship

requiring molar distalization.

The system consists of two zygomatic anchor plates

(Multi Purpose Anchor MPI 1000, Tasarim Med, Istan-

bul, Turkey), an inner-bow, and heavy intraoral elastics

(Fig 1A). The effective distalizing force vector of the

ZGA is illustrated in Fig 1B.

The zygomatic anchor is a titanium miniplate with

three holes, which continues into a round bar. The an-

chor plates are placed at the zygomatic buttress of the

maxillae under local anesthesia (Fig 2). The zygomatic

Metin Nur, Mehmet Bayram, Alper Pampu 대치교정지 40권 3호, 2010년

196

Fig 2. The zygomatic anchor plates adapted and fixed to the zygomatic buttress.

Fig 1. Schematic illustration of components (A) and the effective distalizing force vector of theZGA (Zygoma-Gear Appliance) (B).

buttress is palpated in the labial sulcus, and a 1- to

2-cm-high vertical incision is made starting at the mu-

cogingival junction while maintaining contact with the

bone. The lower aspect of the zygomatic process of

the maxilla is totally exposed by blunt dissection. The

anchor plate is adjusted to fit the contour of the lower

face of each zygomatic process and fixed by three

bone screws (length, 7.0 mm). The body portions of

them are positioned subperiosteally. The round bars are

intraorally exposed and positioned outside the denti-

tion, so that they never disturb the distalization of the

maxillary molars. After fixation, the incision site is

closed and sutured. The free intraoral parts of the min-

iplates are bent distally into hooks.

The inner-bow is made from stainless steel wire, 1.1

mm in diameter and designed like the inner part of a

conventional facebow. Two hooks are soldered onto

the inner-bow at the lateral teeth regions, and U bends

are bent bilaterally in front of the upper first molars.

The inner-bow is adjusted to the headgear tubes on the

upper first molar bands. A distally directed force is ap-

plied to the upper molar teeth via the heavy intraoral

elastics, which are placed between the zygomatic plate

and the inner-bow hooks.

DIAGNOSIS AND ETIOLOGY

A 16-year and 8 month-old female was diagnosed

with skeletal Class II, Division 1 malocclusion. She

was referred to our department for consultation about

her unerupted upper teeth. She had a well-balanced

face and a mild convex profile (Fig 3). The dental

midlines were concordant with each other and with her

face, and no mandibular shift was detected on closure.

Intraoral examination revealed that she had a bilateral

Class II molar and canine relationship with a posterior

Vol. 40, No. 3, 2010. Korean J Orthod Zygoma-gear appliance for intraoral upper molar distalization

197

Fig 3. Pretreatment facial and intraoral photographs of the case.

crossbite on the right side. The dental cast analysis

showed 2 mm of space deficiency in the upper arch,

1.5 mm of space excess in the lower arch, 4 mm over-

jet, and 6 mm overbite (Fig 4). The maxillary lateral

incisors were small, creating a tooth size discrepancy.

Bolton’s tooth size analysis revealed a maxillary ante-

rior deficiency of 2.1 mm.

Radiographic examination showed that all teeth, in-

cluding the third molars, were present (Fig 5). Initial

panoramic radiograph revealed that both maxillary can-

ines had well developed roots, were impacted at the

level of the roof of the palate, and were mesially angu-

lated near the roots of the maxillary lateral incisors.

Further detailed radiographic investigation disclosed no

significant resorption of the roots of the maxillary lat-

eral incisors. A horizontal tube shift technique with pe-

riapical radiographs and clinical palpation confirmed

that both impacted maxillary canines were in the pala-

tal position.

Cephalometric evaluation revealed a mild skeletal

Class II pattern due to a mild mandibular retrognatia.

The pre-treatment cephalometric parameters showed

that the maxilla was normal (SNA 82o), and in centric

occlusion the mandible was in a slightly retruded posi-

tion according to the cranial base (SNB 76o). The max-

illary incisors were slightly upright, while the man-

dibular incisors were normal. The mandibular plane

was normal relative to the cranial base (SN-GoGn

34.5o).


198

Fig 4. Pretreatment diagnostic models of the case.

Fig 5. Pretreatment radiographic records of the case.

TREATMENT OBJECTIVES

Treatment objectives, based on the clinical examina-

tion and cephalometric analysis, were to:

1. Align the palatally impacted maxillary canines.

2. Correct the unilateral posterior crossbite.

3. Obtain normal overjet and overbite.

4. Establish a well-intercuspated bilateral Class I ca-

nine and molar occlusion.

5. Constitute a good aesthetic smile.

TREATMENT ALTERNATIVES

There were four treatment alternatives for this case:

(1) align the palatally impacted maxillary canines and

distalization of upper molars; (2) extraction of the im-

pacted canines and closure of the extraction space or-

thodontically; (3) extraction of the impacted canines

and prosthetic rehabilitation with implants or bridge-

work; and (4) align the palatally impacted maxillary

canines with the extraction of two upper first pre-

molars.

Considering all aspects of the case in detail, during

the treatment-planning interview, the patient was told


199

Fig 6. Intraoral occlusal views of the mechanics for erupting of the impacted canines (A), and of the erupted canines(B).

Fig 7. Application of the ZGA (Zygoma-Gear Appliance) at the beginning of distalization (A), and the views of thepatient immediately after the distalization (B).

that the impacted canines might not respond to ortho-

dontic eruption; and if this were the case, they would

need to be extracted, and prosthetic rehabilitation with

implants or bridgework would be required. She chose

orthodontic eruption of the impacted canines with the

nonextraction approach, and informed consent was tak-

en to this effect.

TREATMENT PROGRESS

Preadjusted fixed appliances (0.022 × 0.028-in, MBT

system) were placed in both arches to achieve leveling

and alignment. Intraoral cross elastics were used for

the correction of crossbite at the right first molars.

After the leveling phase, the retained primary canines

were extracted and then both palatally impacted maxil-

lary canines were surgically exposed with the help of

an envelope flap. Bondable cleats were bonded to

them, and stainless steel ligature wires were braided

from these cleats. After soft tissue healing, an auxiliary

continuous 0.016-in Australian wire including vertical

loops with terminal eyelets was applied with a 0.016-in

stainless steel main archwire (Fig 6A). In the passive

state, the eyelets faced down occlusally. Torsion was

built up in the round wire, which was secured at its

distal ends as the vertical loops were bent through 90o

to tie them to the braided ligatures from the canines.

This was done to generate eruptive forces for the bi-


200

Fig 9. The system for retraction of the incisors.

Fig 8. Lateral cephalometric radiograph of the case taken immediately after the distalization.

laterally impacted teeth. After 2.5 months of traction,

it was observed that the maxillary canines were erupt-

ed sufficiently in crossbite. An elastic chain was ap-

plied to move the canines labially (Fig 6B). Bite-rais-

ers (Guray Bite Raiser, GAC International Inc, Bohem-

ia, NY) were adjusted on the upper first molar bands

for bite-opening to avoid possible interferences be-

tween the upper canines and lower teeth during the la-

bial movement of the upper canines.

When the maxillary canines had moved into the arch,

canine brackets were then bonded and a continuous

0.016-in superelastic nickel-titanium (NiTi) wire was

placed. After leveling, we decided to accomplish the

upper molar distalization with an extraoral appliance.

However, usage of an extraoral appliance was rejected

by the patient and her parents because the patient was

concerned about her facial appearance. Therefore, the

ZGA was designed and applied for distalization of the

upper molars (Fig 7A).

Three weeks after the zygomatic plate implantation

surgery, a distalization force of 400 g per side was ap-

plied to the upper molars. The patient was instructed

to wear her appliance for at least 20 hours a day and

to change intraoral elastics every 12 hours. After 3

months of distalization, super Class I molar relation-

ships were achieved on both sides (Figs 7B and 8).

The teeth located at the anterior of the upper molars

were also distalized together with the molar teeth,

spontaneously. Then fixed appliance treatment was pro-

gressed for other alignment problems. The maxillary

premolars and canines were completely distalized by

using power chains. After the Class I canine relation-

ship was obtained, the retraction of incisors was ac-

complished by using closed coils, which were placed

between the zygomatic anchor and 0.019 × 0.025-in

stainless steel posted archwire (Fig 9).

At the end of active treatment, finishing procedures

were used for the final alignment of the teeth and de-

tailing of the occlusion. The orthodontic appliances

were removed after active treatment was completed

(Figs 10 - 12). After debonding procedures, peg shaped

maxillary lateral incisors were restored with composite

resin (Fig 13) and a maxillary removable Hawley re-

tainer and a 3-3 mandibular fixed lingual retainer were

constructed for the patient and placed.

RESULTS

After 21 months of treatment with the ZGA and full

fixed orthodontic appliances, the impacted canines

were successfully aligned and Class I molar and canine

relationships were established with satisfactory inter-


201

Fig 10. Posttreatment facial and intraoral photographs of the case.

digitation of the posterior teeth. Acceptable overjet and

overbite were also achieved and the tooth size discrep-

ancy caused by the upper lateral incisors was managed

successfully.

Table 1 shows the cephalometric changes in all

stages of the treatment. A comparison of the pre- and

post-distalization cephalometric analysis revealed that

the maxillary first molars showed a distalization of 4

mm, associated with a distal axial inclination of 4.5o.

Non-significant changes were observed in vertical an-

gles (SN/GoGn, FMA, and ANS-PNS/GoGn) (Fig 14A).

According to the analysis of the posttreatment lateral

cephalometric radiograph, SNA, ANB, Wits appraisal,

interincisal angle, overjet, and overbite were decreased

(Fig 14B).

After the completion of active treatment, the centric

relation coincided with the centric occlusion, and the

patient reported no temporomandibular joint problems.

The final panoramic radiograph showed that minimal

root resorption had occurred during treatment and that

root parallelism was satisfactory. The patient has been

in retention for more than 12 months, and the occlu-

sion has been maintained very well during this time.

DISCUSSION

Nonextraction treatment of Class II malocclusion of-

ten requires distal movement of the upper molar teeth


202

Fig 13. Intraoral photographs of the case after restoring the peg shaped upper lateral incisors.

Fig 12. Posttreatment radiographic records of the case.

Fig 11. Posttreatment dental casts of the case.

into a Class I relationship. Conventional extraoral ap-

pliances such as headgear are frequently used for this

purpose.1 Despite their efficacy in tooth movement;

these appliances have the major disadvantage of a


203

Pretreatment Before distalization After distalization Posttreatment

SNA (o) 82 81 81 80.5

SNB (o) 76 76 76.5 77

ANB (o) 6 5 4.5 3.5

SN-GoGn (o) 34.5 34 34.5 34

FMA (o) 22.5 23 23 22.5

ANS-PNS/GoGn (o) 23 23 22.5 22.5

S-Go (mm) 72.5 73 73 73

N-Me (mm) 115 115.5 115 115

ANS-Me (mm) 62 61.5 61 61.5

S-Go/N-Me (%) 63 63.2 63.4 63.4

Wits appraisal (mm) 5.5 2.5 2 2

U1-NA (mm) 2 2.5 4 3.5

U1-NA (o) 13 16 20 20.5

U1-ANS-PNS (o) 106.5 107.5 108 112

L1-NB (mm) 5 4 2.5 4

L1-NB (o) 23 20 17 23

IMPA (o) 92.5 90 88 93.5

U1-PtV (mm) 60.5 60 60 60

U6-PtV (mm) 33.5 33 29 30

U6/ANS-PNS (o) 92 90.5 85 90

Interincisal angle (o) 138 140 139.5 133.5

Overjet (mm) 4 4.5 4.5 2.5

Overbite (mm) 6 4.5 5 4

Lower lip-E line (mm) 0 0.5 0.5 1

Upper lip-E line (mm) 1.5 4 4 4

Nasolabial angle (o) 111 114 114 112

Table 1. Cephalometric measurements of the patient

heavy dependence on patient cooperation. Additionally,

many patients reject headgear wear because of social

and esthetic concerns.

The difficulty in the use of headgear wear has

stimulated many investigators to develop intraoral de-

vices and techniques for the distal movement of

molars.2-10 Intraoral maxillary molar distalization appli-

ances, such as Wilson arches,2 repelling magnets,3

Hilgers pendulum appliances,4-6

the sectional jig assem-

bly,7 the distal jet,8 the Keles slider,9 and the first class

appliance10 do not require extensive cooperation from

patients. However, they have several disadvantages

such as mesialization of the maxillary premolars, pro-

trusion of the maxillary incisors, an increase in overjet,

and relapse of molars. Relapse of molar distalization is

commonly seen as the molars are used as anchorage

during distalization and retraction of the premolars and

incisors.

To remedy these anchorage problems of noncom-

pliant appliances, intraoral distalizing mechanics com-

bined with palatal implants have attracted attention,11-16

because it has become possible to distalize the maxil-

lary molars without anchorage loss by using absolute

anchorage more efficiently than ever. Although anchor-

age loss has been eliminated in this way, an important

problem still occurs during the retraction of anterior

teeth. Because of the proximity of palatal implant to

the roots of anterior teeth or the presence of a bulky

acrylic Nance appliance behind the upper incisors, the

retraction of the anterior teeth is limited. At this stage,


204

Fig 14. Superimpositions of pre- and post-distalization (A), and pre- and post-treatment cephalometric tracings (B).

the palatal implants must be removed and the dista-

lized molars are used as part of the anchorage during

retraction of the anterior teeth. Therefore, the reinforce-

ment of molar anchorage or the use of another anchor-

age area is required to prevent the relapse of molars.

The zygomatic process of the maxilla can be used for

this purpose because zygomatic anchors can be posi-

tioned at the zygomatic buttress, at a safe distance

from the roots of the maxillary molars and allow a full

unit buccal segment distalization.20,21 Sugawara et al.20

and Kaya et al.21 described their distalization systems

supported with the zygomatic anchor plates. They re-

ported that the en-masse distalization of maxillary buc-

cal segments was successfully accomplished by their

systems.

In the current study, we used the ZGA for upper mo-

lar distalization in a 16-year-old girl. The upper molars

were efficiently distalized to Class I relationships with-

out anchorage loss in a short time. The ZGA system

has more advantages than other intraoral distalization

appliances and combines the advantages of extraoral

and intraoral appliances.

The upper molar distalization with the ZGA system

is completely different from previous intraoral molar

distalization methods. The difference in the appliance

design enables the first and second premolars to drift

distally freely with the help of the transeptal fibers.

The distalized molars are never required as part of the

anchorage during the retraction of the premolars and

the anterior teeth, because the orthodontic force can be

directly provided from the zygomatic anchor plates.

Additionally, this system is more esthetic than extra-

oral appliances and is well tolerated by the patient.

The other advantages of this system are the simple

and hygienic design, easy application, short chair time,

minimal laboratory procedures, controllable force mag-

nitude, and easy repair. The force magnitude can be

adjusted according to need to achieve treatment objec-

tives. A different amount of distalization can be ach-

ieved on each side. When needed, all parts of the ap-

pliance (molar bands, elastics, and inner-bow) can be

easily repaired or changed except the zygomatic anchor

plates. This new system also allows the use of fixed

orthodontic appliances during the molar distalization,

simultaneously. On the other hand, the minor surgical

operation to place the anchorage plates on the zygo-

matic buttress was the main disadvantage of this ap-

pliance. The necessity of a second operation for the re-

moval of these plates and additional cost appears to be

another disadvantage.

From a clinical point of view, the choice of force

system and the optimum force magnitude are the deci-

sive factors for obtaining the desired tooth movement.22

Achieving the bodily movement of molars is also an

important strategy in modern orthodontics during dis-

talization. For this purpose, an effective force vector


205

must be passed through the center of the resistance

(CR) of teeth. In our case, the vector for an effective

distalizing force was located occlusally close to the CR

of the upper first molars. The force vector of ZGA

could be adjusted to obtain bodily molar movements

by changing the level of the zygomatic anchor hooks

and the height of the inner bow hooks. Additionally,

we used heavy intra oral elastics to gain orthodontic

force. As is known, this type of force is intermittent

in character. A continuous force is desirable for pro-

viding more efficient tooth movement. Thus, the force

characteristic of the ZGA could be converted to a con-

tinuous form with the usage of NiTi closed coils in-

stead of elastics. The appliance can be modified ac-

cording to the treatment objectives. In further studies,

the effects of the ZGA on dentofacial structures could

be assessed with large samples.

CONCLUSION

In conclusion, the results demonstrated that for this

case the ZGA was an effective system to distalize up-

per molars without anchorage loss. Absolute anchorage

control was provided by using zygomatic anchorage

plates during the distalization of molars and the re-

traction of incisors. The main disadvantage of this sys-

tem was the minor surgical operations to place and re-

move the plates. We suggest that this new system can

be used in nonextraction Class II treatment in place of

extraoral and intraoral distalization appliances.

-국문 록 -

Zygoma-gear를 이용한 구치부 후방이동을 통한

비발치 치험례

Metin Nur, Mehmet Bayram, Alper Pampu

본 증례보고에서는 골격성 II 계를 보이는 16세 여자 환자에서 zygomatic-anchorage plates (Zygoma-gear Appli-ance, ZGA)를 이용하여 상악 구치를 후방 이동시킨 구내 장치를 소개하고자 한다. 이 장치는 양측성 zygomatic anchor-age plates, inner-bow와 강한 힘을 내는 구강 내 고무 로

구성되어 있다. 3개월 내에 상악 구치의 후방 이동이 이루어졌으며, 측모 두부 방사선 사진 분석 결과, 상악 구치는 4

mm 후방 이동, 4.5o 후방 경사되었다. 본 연구 결과 ZGA 장치를 이용해 고정원 소실 없이 단기간에 상악 구치의 후방

이동이 효과 으로 이루어졌음이 확인되었으며, 이를 통해 구치의 후방 견인이 요하는 증례에서 구외 장치 신 사용될

수 있을 것으로 단된다.

주요 단어: 구치 후방이동, 골격성 고정원, 2 부정교합,

비발치 치료

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