Asymmetric extractions for an asymmetric malocclusion

Christopher Lawrence Tan Soon Lee; Kirti Saxena

doi:10.4103/2393-8692.196151

CASE REPORT

Year : 2016 | Volume : 2 | Issue : 2 | Page : 110-112

Asymmetric extractions for an asymmetric malocclusion

Christopher Lawrence Tan Soon Lee, Kirti Saxena
Department of Orthodontics, Klinik Pergigian Jalan Gambut, Kuantan, Pahang, Malaysia

Date of Web Publication

19-Dec-2016

Correspondence Address:
Kirti Saxena
C1-L1-3, Pantai Hillpark Phase 1, Jalan Pantai Dalam, Bangsar South, Kuala Lumpur 59200
Malaysia

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/2393-8692.196151

Abstract

Some patients with Class II subdivision malocclusions have Class I characteristics on one side and Class II characteristics on the other. The resulting asymmetric occlusal relationship complicates orthodontic treatment. Traditionally, four premolars are extracted in such cases to achieve a bilateral Class I molar relation which needs patient compliance with the use of Class II elastics. The present case report shows one such Class II subdivision malocclusion case which was treated by asymmetric extractions. This approach is independent of the patient compliance and saved one premolar, with no compromise in dental occlusion or esthetics.

Keywords: Class II subdivision malocclusion, extraction of three premolars, midline shift

How to cite this article:
Lee CL, Saxena K. Asymmetric extractions for an asymmetric malocclusion. Indian J Oral Health Res 2016;2:110-2

How to cite this URL:
Lee CL, Saxena K. Asymmetric extractions for an asymmetric malocclusion. Indian J Oral Health Res [serial online] 2016 [cited 2023 Oct 4];2:110-2. Available from: https://www.ijohr.org/text.asp?2016/2/2/110/196151

Introduction

The studies show that Class II subdivision malocclusion is primarily caused by distal positioning of the mandibular first molar in relation to the maxillary first molar, on the Class II side. ^{[1],[2],[3],[4],[5],[6],[7]} Secondarily, it can be consequent to mesial positioning of the maxillary first molar, in relation to the mandibular first molar, on the Class II side.^[2] As a result, most Class II subdivision malocclusion patients present with mandibular dental midline displaced toward the Class II side associated with the maxillary dental midline coincident to the midsagittal plane or with a mild deviation, which requires asymmetric orthodontic approaches. ^[1],[2]

The present case report shows one such Class II subdivision malocclusion case which was treated by asymmetric extractions. First premolars were extracted in the upper arch and the first premolar on the Class I side was extracted in the lower arch. This approach is independent of patient compliance and saved one premolar along with good posttreatment occlusion and a slight improvement of the profile.

Case report

A 16-year-old Malay boy complained of corner teeth sticking out in the upper arch. Extra oral examination showed a mildly convex profile with posterior divergence, competent lips, an average nasolabial angle, and lower facial height with no gross asymmetry. Intraoral examination showed all 28 teeth present with moderate crowding in both arches and a lower midline shift to the left of midfacial axis with acceptable overjet and overbite. The molar and canine relation on the right side were in Class I occlusion, whereas on the left side were in Class II occlusion with Class II division 2 incisor relation [Figure 1]a.

Cephalometric examination showed a mild Class II skeletal relation, proclined lower incisors with average growth pattern [Table 1]. ^[8] All third molars were visible on orthopantomogram [Figure 1]b with satisfactory oral hygiene.

Figure 1: (a) Pretreatment extraoral and intraoral snaps. (b) Pretreatment orthopantomogram and cephalogram

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Table 1: Cephalometric findings

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Treatment objectives were

To align arches
To establish balanced occlusal relationship bilaterally
To maintain correct overjet and overbite
To improve the profile
To constitute a good esthetic smile with correct centerlines.

Treatment options/alternatives

Lower molar protraction (Class II side) with alignment along with all four first premolar extractions
Lower molar protraction (Class II side) with alignment along with first premolar extractions in the upper arch, the first premolar extraction on Class I side and second premolar extraction on Class II side in lower arch
Extraction of two premolars in the upper arch to correct crowding and one premolar in the lower arch on Class I side to correct midline and crowding.

The patient chose the third option as only three premolars were being extracted and was willing to accept a Class II molar relation on the left side.

Treatment progress

Anchorage reinforcement was needed to prevent mesial molar movement in the upper arch; this was achieved by cementing a Nance button [Figure 2] as the treatment involved the extraction of the first premolars in the upper arch to correct the crowding. Treatment started with the placement of 0.022½ Roth prescription brackets and molar tubes. Leveling and alignment were done using 0.012½ Ni-Ti and 0.017½ × 0.025½ Ni-Ti wires. The patient was monitored and recalled every 6 weeks to check progress. Finally, 0.017½ × 0.025" stainless steel wire in the upper arch and 0.019½ × 0.025" stainless steel archwires were placed in the lower arch.

Figure 2: Mid-treatment snaps showing a Nance button and active tiebacks

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The upper and lower anteriors were then consolidated together, and en-masse retraction was performed using active tie-backs [Figure 2]. Final space closure was done using power-chain. Once the occlusion settled, the appliance was debonded. Retention was achieved with Modified Hawley retainers in both arches.

Results

The time taken for leveling and aligning was 7 months and 11 months for space closure and settling. On the right side, the Class I molar relation was maintained, whereas on the left side, the Class II molar relation showed better intercuspation. At the end of treatment, a proper overjet and overbite were maintained with coincident midlines and a slight improvement of the profile was seen [Figure 3].

Figure 3: Posttreatment extraoral and intraoral snaps

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Discussion

Patients with Class II subdivision malocclusions have Class I characteristics on one side and Class II characteristics on the other. The resulting asymmetric occlusal relationship complicates orthodontic treatment. In most patients with Class II subdivision malocclusion, the maxillary dental midline is coincident to the midsagittal plane or has a minimal deviation whereas the mandibular dental midline is usually displaced toward the Class II side. ^[1],[2],[9] In this case, the decision of upper first premolar extraction was made to relieve the crowding and align the canines into the arch which addressed the patient's chief complaint. In the lower arch, there was an option of extracting two premolars or a single premolar. If two premolars been extracted:

Correction of center lines would need use of anterior cross elastics
Mesial movement of lower molar to a Class I relation would also require Class II elastics and the previous studies have shown that resistance to mesial movement of posterior segments is similar after extracting the first or second premolar ^[10]
More time consuming. ^[11]

In the four premolar extraction approach attaining a Class I molar relationship on the original Class II side and a consequent coincidence of the maxillary and mandibular dental midlines depends largely on patient compliance. ^{[2],[12],[13]} On the other hand, asymmetric extraction of three premolars (two maxillary premolars and one mandibular premolar on the Class I side) will produce Class I canine and molar relationships on the Class I side and Class II molar and Class I canine relationships on the Class II side, along with coincidence of the maxillary and mandibular dental midlines. ^{[1],[2],[14],[15],[16],[17]} Correcting the interdental midline deviation with this treatment is easier because it is achieved simultaneously with closing the extraction space in the mandibular arch. Many studies have concluded that occlusal long-term stability of Class II subdivision malocclusion treatment with three or four premolar extractions is similar. ^[18]

Conclusion

Comparatively lesser compliance needed from the asymmetric extraction approach seems to be superior to the alternative requirement of Class II elastics. In comparison to the extraction of four premolars, extracting three premolars are more acceptable to the patients. In the present case, we achieved the goals of profile improvement and clinically as well as functionally acceptable occlusion. Finally, a proper case selection and treatment plan are must to achieve optimum treatment results.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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