A 13 years old female presented in the late mixed dentition stage with a Class II division 2 incisor relationship on a moderate Class II skeletal base with average vertical proportions. The upper arch presented with mild crowding and retroclined central incisors. The lower arch was also mildly crowded with proclined labial segment. In occlusion, the overbite was deep and complete with scissor bite involving the upper and lower right 1st premolars.
overbite was deep and complete with scissor bite involving the upper and lower right 1st premolars.
The treatment consisted of an initial sectional fixed appliance involving the upper labial segment followed by a Twin Block appliance. A subsequent second phase of upper and lower pre-adjusted edgewise fixed appliances were used on a non-extraction basis for definitive alignment, levelling and occlusal detailing. Retention consisted of removable upper and lower Essix retainers.
A Class II incisor relationship is defined by the British Standards classification as being present when the lower incisor edges occlude posterior to the cingulum plateau of the upper incisors¹. In Class II division 2 cases, the upper central incisors are retroclined and the overjet usually minimal but may be increased. Treatment of class II div 2 cases of growing patients with moderate to severe skeletal discrepancy usually involves proclination of the upper labial segment, converting the incisal relationship to a Class II division I malocclusion. Then the treatment is followed by a functional appliance phase to correct the sagittal discrepancy. The initial phase of proclination of the upper labial segment is achieved by one of the following methods:
1 -Expansion and Labial Segment Alignment Appliance (ELSAA) is the most commonly used.
2 -Sectional fixed appliance treatment to the upper labial segment only.
3 -Modified twin block appliance as demonstrated by Dyer and colleagues (2001) where they incorporated an anterior screw and torquing spurs in the twin block appliance for the upper labial segment. This avoids the need for an initial upper labial segment alignment.
The success of treating Class II division 2 incisor relationship depends on the correction of the transverse, anterior- posterior and vertical discrepancies. To achieve stability of the corrected malocclusion, it is important to correct the inter-incisal angle and edge centroid relationship3. Houston (1989) stated that it is essential to reduce the inter-incisal angle towards 125 degrees, bringing the lower incisor tip anterior to the upper incisor centroid.
The Twin Block was developed by Clark (1982) and has proved a popular and clinically successful appliance. The correction of the sagittal discrepancy is possible in many patients within 6-9 months. However, it requires patient co-operation and increased daily wear. The correction of the malocclusion is achieved by mandibular skeletal and dentoalveolar changes in addition to normal growth.
A 13 year old female presented to the orthodontic department complaining of crooked upper front teeth. She was very motivated and had no medical condition contra-indicating the provision of orthodontic treatment.
Extra oral examination
The patient presented with moderate class II skeletal pattern with average Frankfort-mandibular planes angel and lower anterior face height. The lips were competent with slightly high resting lower lip line, with average upper incisor show at rest and full crown show when smiling. The labiomental fold was prominent
The poor oral hygiene resulted in generalised gingivitis and decalcification of the cervical margins of the upper labial segment. She was in the late mixed dentition stage with a Class II division 2 incisor relationship. All the permanent dentition was present except the unerupted lower second premolars and second molars with retained second deciduous molars. The upper arch presented with mild crowding and retroclined central incisors. The lower arch was also mildly crowded with proclined labial segment. In occlusion, the overbite was deep and traumatic to the upper palatal gingival tissues. There was also a scissor bite involving the upper and lower right 1st premolars. The overjet was 3 mm and upper and lower centre lines were coincident. The buccal segment relationship was class II bilaterally.
All the permenant teeth were present including the lower second premolars, lower second molars and all third molars as shown in the Dental Panoramic Tomogram (DPT). The upper standard occlusal view revealed normal morphology of the incisors roots and no supernumerary. The cephalometric analysis supports the clinical finding of a moderate Class II sagittal skeletal relationship (ANB: 7°). Vertically, the lower face height is in the lower end of the normal range (53%) and the MMPA is increased (32°). Dentally, the upper incisors are retroclined to the maxillary plane (96°) while the lower incisors are proclined to the mandibular plane (105˚). The lower incisor edges lying posteriorly to the upper root centroid (-1 mm).
Mandibular retrognathia is the main aetiological , genetically inherited, factor. It resulted in moderate Class II skeletal pattern with deep overbite. The lower lip line is slightly resting higher than normal which resulted in the retroclination of the upper central incisors.
Treatment Aims and Objectives
1- Improve the oral hygiene
2- Decompensate upper incisors by proclination
3- Improve the facial profile by orthopaedic therapy
4- Align and level the arches
5- Overbite correction
6- Overjet reduction
7- Arch coordination and occlusal detailing
8- Achieve a Class I molar relationship
10- Monitor eruption of the unerupted teeth
1- Patient referral to school of hygiene for prevention advice and oral hygiene instruction.
2- Sectional fixed Preadjusted Edgewise appliance to procline the upper labial segment
3- Twin Block appliance
4- Upper and lower Preadjusted Edgewise appliances with an MBT prescription and an 0.022” x 0.030” slot
Upper fixed sectional 3 / 3 and functional appliance therapy
To improve dento-facial aesthetics and occlusal relationships, the initial aim was to improve the sagittal skeletal discrepancy. The sectional fixed appliance encourages proclination of the upper labial segment. The principal advantage of the Twin block was to allow incisor and molar correction and upper arch expansion.
Fixed appliance therapy
A second phase of fixed appliance therapy was used to reduce the remaining overbite and to detail the occlusion. Bonding the lower second molars and the use of Class II inter-maxillary elastics were employed to facilitate overbite reduction. The increased lower incisor labial root torque of the MBT prescription will also help resist excessive proclination.
After the functional appliance stage, Cephalometric analysis shows that the sagittal skeletal relationship has improved slightly (ANB: 4). Vertically, there has been no change in the skeletal relationships. There has been significant dento-alveolar changes; the upper incisor teeth have proclined (+11°) to a normal inclination while the lower incisors have proclined but to a lesser extent (+3°; A-Po +2mm).
The patient completed the treatment aged 14 years and 7 months. The malocclusion was treated satisfactory and the treatment aims were achieved. The functional appliance phase was successful in the improvement of the facial profile, reduction of the OJ, OB and the correction of the molar relationship.
The sectional fixed appliances allowed for the decompensation of the upper labial segment by proclination which facilitated the functional appliance phase.
The patient had a favourable growth pattern which contributed to the majority of the corrected malocclusion. The fixed appliance phase was indicated to detail the occlusion and to close the remaining lateral open bite post functional.
The lower labial segment was proclined at initial presentation. This happened naturally as an attempt to compensate for the underlying moderate Class II skeletal base. The inclination of the lower labial segment was maintained at the end of the treatment and that was achieved with the use of the fixed appliances with an MBT prescription (-6° torque for the lower labial segment).
The patient was provided with upper and lower Essix retainers for full time wear initially. The patient was advised about the late lower labial segment crowding and the importance of the long-term retention.
The success of treatment of Class II div II cases with functional appliances depends on:
1- Patients co-operation with appliance wear.
2- Favourable mandibular growth.
3- Correction of the inter-incisal angle and edge centroid relationship3,4
1. British Standard Institute. Glossary of Dental Terms 1983. BS9942; BSI London.
2. Dyer, F.M, Mckeown and H.F, Sandler, P.J. (2001) Journal of Orthodontics. 28: 271-280
3. Houston, W. and Tulley, J. (1993) A textbook of orthodontics, Wright, Bristol
4. Houston, W. (1989) Incisor edge centroid relationship and overbite depth, European Journal of Orthodontics, 11: 139-143
5. Clark, W.J. (1982) The Twin Bock traction technique, European Journal of Orthodontics, 4: 129-138
by Dr. Kholood Alfoudari