## 4 Discussion  
In coincidence with previous studies [12], the authors firmly believe that classical cephalometric analyses cannot be used as a roadmap in facial planning: analyses based on intracranial horizontal lines, such as the Sella-Nasion [13] or Frankfort plane [14], add errors due to positional variations and skull base disparities, while extracranial references such as the NHO are preferred for surgical planning. In accordance with this, some esthetic reference lines for antero-posterior maxillomandibular guide positioning have been created. The most recent and widely accepted approach was defined by [PERSON] [15] and uses a vertical line running through the subnasale point, but it will be altered in hypoplastic maxillaries and modified by surgery. On the other hand, the UI-STP or BL reference [6; 7], used in this study, constitutes a stable reference that is not modified with surgery and can be analyzed clinically in a lateral smiling picture in the NHP, without the need for any radiological examination [16]. During the past few decades, and basing the treatment plan on \"classical\" cephalometric analyses, the most common movement of the jaw when performing orthognathic surgery in class III patients used to be isolated mandibular setback, since such patients were most likely to be diagnosed with mandibular excess [3]. Nowadays, maxillary advancement or two-jaw surgery combining these procedures has become the most popular treatment option [17]. According to the authors' protocol, during 3D planning, the upper and lower jaws are placed in class I and moved forward until the upper incisor reaches the BL. Then, vertical adjustments are made. The chin is positioned appropriately according to the occlusal plane and the lower incisor position (around 90\({}^{\circ}\)). Finally, the required occlusal plane rotational movements are performed in order to obtain a true linear distance between the A and B points around 3 mm [18]. This planning is irrespective of the occlusal situation of the patient or the amount of maxilla-mandibular discrepancy. The results of this study show that, when using this reference line as an antero-posterior repositioning reference in Caucasian patients, most cases diagnosed with and treated for class III dentofacial deformities underwent forward movements of both the upper maxilla and the mandible (although the latter to a lesser extent), in order to maximize the facial esthetics, improve soft tissue support, and avoid a reduction in the upper airway volume (90.3% of all patients, \(p\) = 2.7 \(\times\) 10\({}^{-12}\) (\(p\) < 0.001)) (Figure 4). Figure 4: Same patient showing class III correction after bimaxillary advancement. With regard to mandibular setback, it only appears to be necessary in a minority of cases (7.3% of our patients), which are mostly coincident with hemimandibular elongation or hyperplasia and underlying acromegaly (three cases in our sample). In comparing the functional advantages of mandibular advancement or setback, there are several points favorable for the forward movement of the jaw. In relation to stability, it has been widely demonstrated that isolated mandibular setback, especially when large movements are performed, results in poorer outcomes than when performing two-jaw surgery with maxilla advancement and less mandibular setback [19; 20]. On the other hand, several investigators have reported the induction of sleep-related breathing disorders after mandibular setback procedures [21; 22; 23]. Mandibular setback results in the reorganization of the pharyngeal wall, and research has evidenced the postoperative narrowing of the retrolingual and hypopharyngeal airway and posteriorifer displacement of the hyoid bone and tongue. This new relationship in the upper airway may compromise the air flow and predispose the patient to OSAHS [24; 25; 26]. Lastly, setback can also entail esthetically detrimental secondary effects, since an undesired jowl may appear [1].