## 4 Discussion
Indeed, the conventional use of intermaximillary elastics could have resulted in unwanted collateral effects, such as upper teeth extrusion and upper jaw canting. Instead, the application of skeletal anchorage and an accurate biomechanical analysis could be a very powerful tool to manage the potentially difficult orthodontic situations that can occur during a surgery-first approach. In this sense, the use of skeletal anchoring represents a real revolution in orthodontics in that it allows the clinicians to achieve desired tooth movements while minimising or completely eliminating possible side effects. TADs also greatly simplify applied orthodontic biomechanics, with considerable benefit to both clinicians and patients. These already very important advantages are even more significant considering that the use of TADs is not associated with either greater risks or greater pain reported by the patient when compared to conventional orthodontic therapy [24]. A limitation of the described protocol is the need for patient compliance. Indeed, the success of aligner therapy and the use of elastics on the TADs requires the patient's full cooperation and scrupulous attention to wearing them according to the indications provided by the clinician. Nevertheless, the described approach fully exploits the period of best collaboration and patient motivation by eliminating the initial aesthetic improvement phase and providing the patient with a large part of the set goal in the first months. This could reduce the burnout that often occurs during the long months of orthodontic preparation that characterise the classic three-step approach. It must be stressed that there are currently still conflicting views on the postoperative stability of surgery-first and surgery-early approaches in orthognathic surgery. Some systematic reviews [25; 26] reported surgery-first as an efficient alternative to conventional orthognathic protocols, with shorter total treatment duration, similar postoperative stability, and improvement in patients' perception of their quality of life immediately following the beginning of treatment. Some others [27], however, found a greater tendency toward mandibular anti-clockwise rotation after the surgery-first approach, with consequent poorer postoperative stability than in the conventional approaches. According to these findings, surgery-first patients' screening and orthodontic treatments could potentially be longer and more difficult in order to compensate for possible postoperative relapse. Indeed, most studies available currently evaluate stability just after surgery and not at the end of the orthodontic treatment. This deeply influences the external validity of the available findings and indicates the need for further studies with longer follow-up periods and similar research protocols [28]. Finally, there seems to be no consensus on whether it is best to start postoperative orthodontic treatment immediately after, soon after, or -- after surgery. In accordance with previous studies [16; 29], we applied the aligners about four weeks post-operatively (very soon), in order to align and level the teeth and resolve possible dental interferences. Further advantages of this orthodontic timing could be the benefit of the phenomena of regional acceleration and higher bone metabolism that last for 3-4 months after orthognathic surgery and possibly speed orthodontic teeth movement [13; 21; 30; 31].