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 .งกวล .ออร โท.ไทย.  2 ฉบ บท  1 ..-- .. 2545 7 Treatment of Class II Division 1 Malocclusion: Asymmetric Extraction  Watana Mathurasai DDS., M.D.S.,F.I.C.D,F.A.C.D. Smorntree Viteporn DDS.,M.D.Sc., F.I.C.D. The specific characteristics of Class II division 1 malocclusion that is usual ly the major concern of a patient is severe protrusion of maxillary incisors. Compromised orthodontic treatment in the adult patient is extraction only the maxillary first bicuspids so that there are enough space for correction of the protrusion and improvemen t of facial profile if possible. In a Class II division 1 patient with acceptable profile space obtained from extraction of the two maxillary first bicuspids may be redundant thus caus- ing excessive retraction of the maxillary incisors. In this case nonextraction or extraction only one bicuspid should be the treatment of choice. Factors influence success of correction of dental protrusion in the patient with accept- able facial profile are clinical examination, space assessment, anchorage management, and bio- mechanics. Since in this case the objectives of the treatment do not concern only function but esthetics. Excessive space obtained from extrac- tion may end up with the uprighted incisor, deep overbite, and flat facial profile due to excessive retraction of the anterior teeth. Otherwise treat- ment planning as a nonextraction case may be not possible since it aggravates the protrusion. The possibility of asymmetric extraction of only one bicuspid should be evaluated according to the aforementioned factors. Clinical examination: The initial relation between the maxillary dental midline and the facial midline should be thoroughly examined to investigate the possibility to maintain or shift the maxillary dental midline towards the extraction site. The symmetric positions of the maxillary canines when smiling has to be evaluated as well. Space assessment : The occlusogram (1) of the maxillary denture should be scrutinized to determine final position of the anterior and pos- terior segments and to select type of anchorage. Original Article Abstract Compromised treatment of Class II division 1 malocclusion in the adlut patient usually re- quires extraction of the two maxillary first bicuspids so that Class I canine can be obtained.Asymmetric extraction of one bicuspid is a treatment of choice in the patient with acceptable profile and space deficiency is moderate . Success of the treatment depends upon clinical examination, space assess- ment, anchorage management and biomechanics. The article presented treatment of Class II divi- sion 1 malocclusion with lingual orthodontic mechanics by extraction one bicuspid .

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J. Lingual Ortho.Th. Vol.2 No.1 Jan.-Jun 20028

Anchorage management : Space obtained

from extraction one bicuspid is utilized for cor-

rection of protrusion by maximum retraction of the

anterior segment (Type A anchorage), retractionof the anterior segment and protraction of the

posterior segment (Type B anchorage) or pro-

traction of the posterior segment (Type C anchor-

age)(2). In lingual orthodontics, management of

anchorage is depended upon configuration of the

archwire and the amount of force.

Biomechanics : Asymmetric retraction of

the anterior segment should be a treatment of

choice if the dental protrusion cannot be

corrected by alteration of jaw relationship.

The objective of the article was to present

the Class II division 1 case treated with

asymmetric extraction by lingual orthodontic

mechanics.

Diagnosis and EtiologyA woman aged 19 years searched for cor-

rection of maxillary incisor protrusion without

changing her facial profile. Clinical examination

(figure 1) showed acceptable facial profile, nor-

mal lip position and function. The maxillary dental

midline in relation to the facial midline was shifted

to the right side 1 mm, the mandibular dental mid-

line was normal. The maxillary left posterior seg-

ment moved forward due to disto-lingual rotation

of the maxillary left canine causing severe

Figure 1 Pretreatment facial profile and occlusion

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Figure 2 Pretreatment cephalometric analysis

Figure 3 Oral features during treatment

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J. Lingual Ortho.Th. Vol.2 No.1 Jan.-Jun 200210

Class II molar and canine relationship around 4

mm. The maxillary right segment was slightly

Class II molar and canine relation 2 mm. The

overbite was normal while the overjet was 6 mm.The Bolton analysis showed maxillary

anterior teeth excess 2 mm.

Panoramic radiograph showed normal

development dentition.

Cephalometric analysis showed skeletal

Class I normal bite with maxillary incisor

protrusion and proclination, normal facial profile

(figure 2).

Hereditary factor should be a major

etiological factor.

Treatment Objectives

To correct maxillary incisor protrusion

while maintaining the facial profile.

To obtain Class I molar (right side), Class

II molar (left side) and Class I canine (both sides)

with normal overbite and overjet.

Extraction of the maxillary left first bicus-

pid was recommended to obtain space available

8 mm for correction of the maxillary left canine

rotation and incisor protrusion. Type B anchor-

age was selected to achieve the aforemen-

tioned occlusion.

Treatment Progress (figure 3)Edgewise lingual appliance was used for

the maxillary teeth and labial appliance was used

for the mandibular teeth. The .022x.028" Roth

vertical slot edgewise appliance (Ortho Organizer)

were placed. The treatment sequences were as

follows:

Upper Arch

1. Band #16, #26 Impression for bracket align-ment with TARG system

2. Indirect bonding #15, #12, #11, #21, #22, #25

leveling with .014"TMA

3. Insert .016"TMA after extraction #24,

direct bonding #23 Labial brackets and retract#23 with elastic chain 150 grams

4.Insert .016x.016" Blue elgiloy L loop closing loop

5. Insert .016" NiTi after complete space closure.

6. Insert .017x.025" TMA archwire

Lower Arch

1 Band #36, #46 direct bonding all remaining teeth

leveling with .0175" Superflex

2. Insert .014" stainless steel archwire

3. Insert .016" stainless steel archwire

4. Insert .018" stainless steel archwire

5. Insert .016x.022" stainless steel archwire

6. Insert .017x.025" TMA archwire

Final adjustment of occlusion with Class

II traction 4 oz. 1/4”

Treatment Result (figure 4,5)

Maxillary incisor protrusion and

proclination could be corrected by retraction of

the anterior teeth and protraction of the posterior

teeth so that the facial profile could be maintained.

Class I canines, Class I molar (right side) Class II

(left side) were obtained.

Discussion

Asymmetric retraction by lingual orthodon-tic mechanics was rare since the technique is

usually performed symmetrically by utilizing

the horizontal force from elastic chain or

retraction loop (3)to retract the anterior segment.

In order to achieve type B anchorage the hori-

zontal force must be higher than those required

for retraction only the six anterior teeth. The simple

mechanics likes unilateral retraction with elasticchain was not recommended as the heavy force

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Figure 4 Posttreatment cephalometric analysis

Figure 5 Posttreatment facial profile and occlusion

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J. Lingual Ortho.Th. Vol.2 No.1 Jan.-Jun 200212

References

1. Marcotte MR. The use of occlusogram in

planning orthodontic treatment. Am J Orthod.

1976;69:655-67.2. Burstone CJ. The segmented arch approach

to space closure. Am J Orthod.1982;82:361-78.

3. Alexander CM., Alexander RG., Gorman JC.

et al. Lingual orthodontics: A status report part

5 lingual mechanotherapy. J Clin Orthod

1983;17:99-115.

might cause distortion of the archwire thus ended

up with asymmetric arch form. In order to mini-

mize this side effect the L loop retraction archwire

was used with minimal attachment to the teeth of the nonextraction side. Initial retraction of the

maxillary left canine with both labial and lingual

mechanics was necessary for controlling rotation

of the canine and enabling the perfect engage-

ment of the canine slot to the retraction archwire.

Acknowledgement The authors would like to express our sincerely thanks to the patient for

her contributions as the subject of the presentation.