Dentoalveolar and Skeletal Effects of an Anterior Open Bite Treatment Protocol Using Zygomatic Anchorage

Primary aim was to analyse dentoalveolar and skeletal effects induced by an anterior open bite (AOB) treatment protocol for intrusion of maxillary buccal segment. Secondary aim was to investigate whether a subsequent change occurred in hyoid position. Study group included 28 non-growing subjects treated in academic setting for correction of AOB. All patients received same appliance that included bilateral acrylic bite-blocks covering posterior dentition. Intrusive force was applied between buccal bars of appliance and zygomatic multipurpose implants. Lateral cephalograms taken at pre-treatment (T0) and after intrusion (T1) were analysed using NemoCeph software. Eight skeletal, 9 dental, 6 soft tissue and 5 hyoid parameters were measured and evaluated statistically. Mean open bite was -3.2 ± 2.1 mm at T0. T1-T0 duration was 9.6 ± 1.9 months. Increase in SNB (1.1° ± 2.1°) and the decrease in ANB (-1.1° ± 1.3°), Y-axis (-0.5° ± 3.5°), SN-GoGn (-2.0° ± -2.5°) and lower facial height (-1.4 ± 2.1 mm) were significant, indicating mandibular counter-clockwise rotation. Overjet and open bite decreased significantly (-1.8 ± 2.3 mm and 4.2 ± 2.1 mm, respectively). Maxillary molars intruded (U6-PP: -3.1 ± 1.3 mm) and distalised (ΔU6-TVL: -1.5 ± 2.7 mm) significantly. Mean change in L6-MP was significant (0.9 ± 1.4 mm) showing mandibular molar eruption. Lower lip-true vertical line (TVL) showed significant forward movement of lower lip (-1.8 ± 2.3 mm). Mean changes in hyoid parameters were not significant. Significant maxillary buccal segment intrusion was achieved in a relatively short period. AOB was corrected while facial profile and smile aesthetics were improved. Distalisation of maxillary molar suggests that intrusive force vector can be modified to achieve simultaneous intrusion and distalisation.