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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.