PMC5405362_01
Initial photos: frontal (a); smile frontal (b); profile (c); intraoral views: upper occlusal (d), lower occlusal (e), right (f), frontal (g), and left (h).
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The overjet was 6 mm, whereas the overbite was 80% (Figure 1).
Pretreatment panoramic radiograph: the presence of all permanent teeth including the developing third molars.
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The panoramic radiograph confirmed the presence of all permanent teeth including the developing third molars (Figure 2).
Pretreatment lateral cephalometric image.
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In the cephalometric assessment (Figure 3), the ANB value of 4.2  suggested a mild Class II skeletal pattern.
Cephalometric image after phase I (before starting Twin Block therapy): increased U1-SN angle and overjet are evident.
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Three months after the alignment phase has started, we took impression for Twin Block appliance while 0.016-inch SS wire was in the brackets (Figure 4).
Twin Block appliance: maxillary part (A): (a) modified ball clasps used instead of conventional clasps to coordinate with fixed appliance; Twin Block appliance (B): (b) block A, (c) block B, (d) labial bow, (e) C clasps, and (f) Adam's clasp; mandibular part (C); mandibular part mucosal surface (D); mandibular part occlusal surface (E); maxillary part mucosal surface (F); maxillary part occlusal surface (G).
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Twin Block that could be used with fixed appliance was given to the patient (Figure 5). The patient was then asked to wear the appliance full time except for mealtime and tooth brushing.
Cephalometric image after phase II (discontinuing Twin Block): mandibular growth is evident.
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At this stage lateral cephalometric image clearly showed mandibular growth (Figure 6).
Posttreatment photos: frontal (a); smile frontal (b); profile (c); intraoral views: upper occlusal (d), lower occlusal (e), right (f), frontal (g), and left (h).
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Crowding was relieved and Cl I relationship with desirable overjet and overbite was achieved (Figure 7).
Posttreatment cephalographic image (a); overall superimposition of pretreatment (black color) and posttreatment (red color) cephalometric radiographs (b).
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The skeletal effects and increasing of mandibular length were evident, despite the fact that some of the corrections, mainly proclination of lower incisors, were due to dental effects of Twin Block (Figure 8). Overall superimposition of the lateral cephalometric radiographs is also illustrated in Figure 8.