The patient was diagnosed as a skeletal Class I jaw relation with normodivergent facial pattern, Angle’s Class I malocclusion with severe space deficiency and posterior crossbite. Treatment plan
The treatment plan included application of RME appliance at initial stage, following with non-extraction method by fixed orthodontic appliance to align the dental arch and correct the occlusion. Treatment progress
At initial stage, only the mandibular fixed appliance was bonded. The Hyrax expander was inserted on the upper arch, with 2 turns per day (0.25 mm per turn) until the expansion screw reached 10.5 mm (in 21 days). The upper central diastema could be observed (Figure 3)
. The maxillary fixed appliance was bonded after RME. The Hyrax expander was kept in situ for another 2 months for retention. Since the patient’s poor oral hygiene, the expander was removed at the 3rd
month. No further active expansion was observed during the phase of fixed appliance. After 24 months of treatment, a better overbite and overjet with good occlusion was achieved (Figure 4, 5)
. Treatment result
After a total 24 months of treatment, satisfactory dental alignment and acceptable overjet and overbite were achieved. The posterior crossbite were partially corrected (from 14 to 16) (Figure 4)
. The final radiographs indicated parallel roots, proper root alignment, and no obvious root resorption (Figure 5)
Superimposition of cephalometric tracings indicated that the sagittal relationship of basal bone was generally maintained, with slightly downward and backward rotation of the mandibular basal bone, which led to an increase in the mandibular plane angle of 2˚. We also observed a mild mandibular growth during treatment (Figure 6)
From regional superimpositions, the maxillary incisors were palatally uprighted, retroclined by 10˚; and the upper molar was extruded due to the maxillary expansion. On the mandibular arch, the lower incisors were extruded and became proclined, and the lower molar was extruded which might be caused by the mandibular growth.
PA comparisons indicated a substantial increase in skeletal width in the nasal, maxillary and inter-molar regions (Table 2)
. The skeletal expansion amount in these three regions was 2 mm, 1 mm, and 5 mm, respectively.
Posttreatment extra-oral and intra-oral photographs, and study model. View Hi-Res Image
Posttreatment lateral, PA cephalometric and panoramic radiographs. View Hi-Res Image
Superimpositions of pre-treatment (black line) and post-treatment (red line) cephalometric tracings. View Hi-Res Image
Pre-treatment and post-treatment postero-anterior radiograph transverse measurements. View Hi-Res Image