## 3 Discussion
In addition, the combined use of SBJA and high-pull J-hook headgear caused a change in the anterior elevation of the occlusal plane, which is generally not an observed effect of BJA. It is an opposite consequence of the general BJA effect, which is the anteversion of the occlusal plane. We found, however, that when an upward force was applied to the anterior part of the SBJA by the high-pull J-hook headgear, the entire maxillary dentition being covered with a plate, which is a feature of the SBJA, led to the application of an anti-clockwise force being applied to the entire maxillary dentition. This suppressed the eruption of maxillary anterior teeth and caused anterior elevation changes to the occlusal plane due to the normal growth of the maxillary molars. In addition, we conceived that the suppression of eruption of maxillary anterior teeth improved the gummy smile. Furthermore, although BJA is generally associated with the clockwise rotation of the mandible [23], this was not observed in any of the three cases. [PERSON] et al. [24] reported that BJA generally involves a large amount of protrusion of the mandibular molars. In this study, the amount of protrusion of the mandibular molars was smaller than that of the maxillary molars in all the three cases observed, so it is possible that the clockwise rotation of the mandible was not noted. This mechanism will, however, need to be investigated in the future. Additionally, the treatment duration was long in all three cases. It took time for the effect of the appliance to appear. It is considered that long treatment duration is a demerit of the method of improving gummy smiles using SBJA and high-pull J-hook headgear. In these cases, as a result of using SBJA in combination with high-pull J-hook headgear with the aim of improving the overreruption of maxillary anterior teeth, the eruption of maxillary anterior teeth was suppressed, and led to a result similar to those reported on treatments that improved gummy smiles using orthodontic anchor screws in patients in the growth stage [13; 14]. It was thought that the method of improving gummy smiles usingSBJA and high-pull J-hook headgear, as examined in this study, may be an option for school-age patients and their parents, who may be resistant to surgically invasive treatments. When an orthodontic anchor screw is used to improve a gummy smile during the growth period, the anchor screw may be lost, and it has been reported that the dropout rate from treatment after implanting orthodontic anchor screws is high in young patients [26]. We suspect that the improvement of gummy smiles using SBJA and high-pull J-hook headgears are an alternative treatment in such situations. However, the lengthening of the treatment period must be considered. In conclusion, the combined use of SBJA with a loop attached to the labial side of maxillary anterior teeth and high-pull J-hook headgear may suppress the eruption of maxillary anterior teeth and improve gummy smiles in growth period patients with maxillary prognathism. However, this study was a case series, and therefore future studies are needed to assess the ideal treatment for specific subgroups of patients, the ideal timing and so on. Conceptualization, T.S. ([PERSON]), M.T. ([PERSON]), K.M. and S.G.; Methodology, T.S. ([PERSON]) and K.M. ; Validation, R.A.; Formal analysis, T.S. ([PERSON]) and R.A.; Investigation, T.S. ([PERSON]); Resources, S.G.; Data curation, R.A.; Writing--original draft, T.S. ([PERSON]); Writing--review & editing, M.T. ([PERSON]), M.K., T.S. ([PERSON]) and M.T. ([PERSON]); Supervision, S.G.; Project administration, T.S. ([PERSON]) and K.M. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. Informed Consent Statement: Informed consent was obtained from all subjects involved in the study. The authors declare no conflict of interest.